PSTEP3 Abstract Tentative Version (May 1, 2018)
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May 16
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Session 1. Keynote
13:15—13:35 K. Kusano (Nagoya Univ.)
Challenge of PSTEP
N/A
13:35—13:55 M. Ishii (NICT)
Aspect and present results of PSTEP A01 group
N/A
13:55—14:15 Y. Miyoshi (Nagoya Univ.)
Progress of geospace research in PSTEP
N/A
Session 2: Radio propagation
14:15—14:40 S. Rougerie (CNES) and V. Fabbro (ONERA)
An electromagnetic propagation tool for signal scintillation reproduction based on derterministic ionospheric medium
Recent works propose a deterministic representation of the ionosphere, such as the IRI model [1], the GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy) model, or recently an ionosphere medium bubble generator developed by [2]. It is usually assumed that the scintillations observed on signals propagating through the ionosphere are linked to the occurrence of bubbles inside the medium. Based on such medium description, the purpose of this paper is to propose an electromagnetic propagation tool able to reproduce the signal scintillation due to the ionosphere. This paper compares also the output of the propagation tool, and outputs from stochastic model of the scintillation (here STIPEE [3]). The comparison is done on several bubbles examples, and at two frequency point: 100 MHz and 1.2 GHz. The paper demonstrate similar behavior between both approach in terme of spectrums shapes (log-amplitude and phase) and scintillation indices( S4, SigmaPhi), which is a first validation step.
14:40—15:05 C. Lin, C. H. Chen, P. K. Rajesh (NCKU), and T. Matsuo (Univ. of Colorado, Boulder)
Toward ionosphere forecast using COSMIC-2
We report that assimilating ground-based and space borne GNSS observations into a coupled thermosphere-ionosphere model by using the ensemble Kalman filter (DART-TIEGCM) results in improved specification and forecast of eastward pre-reversal enhancement (PRE) electric field (E-field). Through data assimilation, not only the ionospheric plasma density, but thermospheric winds, temperature and compositions are also adjusted simultaneously according to their relationship to ionospheric plasma density. The improvement of dusk-side PRE E-field over the prior state is achieved primarily by intensification of eastward neutral wind. The improved E-field subsequently promotes a stronger plasma fountain and deepens the equatorial trough. As a result, the horizontal gradients of Pedersen conductivity and eastward wind are increased due to greater zonal electron density gradient and smaller ion drag at dusk, respectively. Such modifications provide preferable conditions and obtain a strengthened PRE magnitude closer to the observation. The adjustment of PRE E-field is enabled through self-consistent thermosphere and ionosphere coupling processes captured in the model. The assimilative outputs are further utilized to calculate the flux tube integrated Rayleigh-Taylor instability growth rate during March 2015 for investigation of global plasma bubble occurrence. Significant improvements in the calculated growth rates could be achieved because of the improved update of zonal electric field in the data assimilation forecast. As the upcoming COSMIC-2 mission is equipped with radio occultation observations of global electron density as well as in-situ ion density and velocity measurements at low latitudes, the observations will benefit the assimilation model by providing rich data and validation of plasma bubble occurrence.
PSTEP Report A02
15:25—15:50 K. Ichimoto (Kyoto Univ.)
Report from PSTEP-A02: Solar Storm Prediction
N/A
Session 2: Radio propagation
15:50—16:15 N. Maruyama, T. Fuller-Rowell, M. Fedrizzi, G. Millward, J. Schoonover, Z. Li, A. Kubaryk, H. Wang, V. Yudin, D. Fuller-Rowell (Univ. of Colorado/CIRES and NOAA/SWPC), R. Oehmke, R. Montuoro, C. DeLuca (NOAA/NESII), W. Yang, M. Iredell (NCEP/EMC), R. Akmaev, R. Viereck (NOAA/SWPC), Y. Obana (Osaka Electro-Communication Univ.), A. Shinbori, N. Nishitani (ISEE, Nagoya Univ.), K. Hashimoto (Kibi International Univ.), M. Hairston (Univ. of Texas, Dallas), and P. Richards (George Mason Univ.)
Forecasting Ionospheric Variability using WAM-IPE model
The ionosphere plays a major role in space weather forecasting owing to its impact on GPS positioning errors that compromise the integrity of aviation navigation systems. Our study aims to evaluate the impact of whole atmospheric coupling on the storm time response of the ionosphere during geomagnetically disturbed periods, which has drawn little attention. It is not yet understood whether or not the geo-effectiveness of magnetic storms could be changed when the upper atmosphere has been pre-conditioned by lower atmospheric forcing or what is the role of lower atmospheric forcing in modulating the recovery to a quiet level? To investigate the connection between terrestrial and space weather, we have recently coupled the Ionosphere-Plasmasphere-Electrodynamics (IPE) model with the Whole Atmosphere Model (WAM). Our WAM-IPE model has been running continuously at NOAA Space Weather Prediction Center in a test operational mode on the NOAA operational supercomputer since October 2017. This presentation focuses on such phenomena as the temporal and spatial evolution of Storm Enhanced Density (SED) plumes, Tongue of Ionizations (TOIs), and troughs that are responsible for large density gradients that were observed during the two St. Patricks day storms in 2013 and 2015 and a third storm in September 2017. First, the variability in the SED plumes/TOIs/trough due to the geomagnetic activity variation is quantified. Then the impact of the lower atmospheric forcing is evaluated by comparing results with and without including forcing from below. Finally, we address some challenges in validation and verification of our WAM-IPE model results to assess the predictive capability of the model.
16:15—16:35 K. Shiokawa and Y. Otsuka (ISEE, Nagoya Univ.)
Recent observations of plasma bubbles and traveling ionospheric disturbances in the equatorial and mid-latitude ionosphere by the Optical Mesosphere Thermosphere Imagers (OMTIs) related to the PSTEP project
In the PSTEP project, we operate airglow imagers and Fabry-Perot interferometers as well as GNSS receivers in the equatorial and middle latitudes in Africa and South-East Asia. The optical instruments are operated as part of the Optical Mesosphere Thermosphere Imagers (OMTIs). In this paper we show recent results on the plasma bubbles and traveling ionospheric disturbances observed by these optical instruments and GNSS receives in the African and Asian sectors.
16:35—16:55 H. Jin (NICT), Y. Miyoshi (Kyushu Univ.), H. Fujiwara (Seikei Univ.), H. Shinagawa (NICT), C. Tao (NICT), and M. Matsumura (ISEE, Nagoya Univ.)
Update of a whole atmosphere-ionosphere coupled model GAIA and comparison with observations
The origins of variations and disturbances in the Earth’s upper atmosphere do not only come from the solar atmosphere, but also from the Earth’s lower atmosphere. Whole atmospheric models are nowadays widely used for studies of vertical atmospheric coupling. As one of such models, we have developed a whole atmosphere-ionosphere coupled model called GAIA, in order to understand physics behind the observed phenomena, to analyze the origin of them, as well as to forecast upper atmospheric variations and disturbances as space weather purpose. We carried out a realistic long-term simulation over 20 years using the inputs from meteorological reanalysis data as well as F10.7 as the proxy of solar EUV intensity. The data have been used many studies such as analysis of vertical atmospheric coupling during SSW, day-to-day variation of ionosphere, interpretation of other observed phenomena, comparison with models and observations, and so on. In this talk, we discuss how the model reproduces well and poorly the variations in the thermosphere and ionosphere by comparing with the results from other models and observations, and discuss what lead to the disagreements, and introduce several improvements of the model.
16:55—17:15 M. Matsumura, K. Shiokawa, Y. Otsuka, A. Shinbori, S. Imada (ISEE, Nagoya Univ.), H. Shinagawa, H. Jin, C. Tao, T. Tsugawa (NICT), Y. Miyoshi (Kyushu Univ.), H. Fujiwara (Seikei Univ.), K. Watanabe, S. Nishimoto (National Defense Academy of Japan), T. Kawate (ISAS/JAXA), and K. S. Lee (NAOJ)
GAIA simulations of the ionospheric response to X-class solar flares on September 6, 2017: the effect of background electron and neutral densities
Solar flares enhance EUV and X-ray radiation to promote the ionization of the Earth’s atmosphere, which increases the electron density on the dayside ionosphere. Higher electron density in the ionospheric degrades the Global Navigation Satellite System (GNSS). The electron density variation depends on the wavelength spectrum and temporal variation of the flare irradiance, which vary from flare to flare. The electron density variation also depends on the background electron density, and on the atomic oxygen and molecular nitrogen densities. So, it is important to understand the various types of the ionospheric flare response. In this paper we focus on the two successive X-class flares that occurred on September 6, 2017: X2.2 peaking at 9:10 UT and X9.3 at 12:02 UT.
To understand how the ionosphere responded to the flares, we carried out numerical simulations using the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) [Jin et al., 2011]. We used the Flare Irradiance Spectral Model (FISM) [Chamberlin et al., 2007, 2008] to drive the GAIA. Model simulations showed that in the low latitudes, Total Electron Content (TEC) increased with the first flare and sustained the enhancement until the second flare. Consequently, the TEC further increased with the second flare and the decay time was longer than that for single flare. To validate the model simulation, we will compare the TEC enhancement simulated by our model with the one measured by ground GNSS receivers. To investigate the effect of background electron and neutral densities, we will also compare the simulated TEC enhancement for this event with the one for another event such as X17.2 flare on October 28, 2003, when the solar activity was higher than in 2017.
In addition, we will report another GAIA simulation with a physics-based flare irradiance model [Imada et al., 2011] instead of the FISM, an empirical model. We tuned the parameters of the physics-based irradiance model with statistical data of satellites so that the model can predict the irradiance spectra without measurements. We will compare preliminary results using the model with ones using the FISM.
17:15—17:35 H. Shinagawa, H. Jin (NICT), Y. Miyoshi (Kyushu Univ.), H. Fujiwara (Seikei Univ.), T. Yokoyama (NICT), Y. Otsuka (Nagoya Univ.), and C. Tao (NICT)
Prediction of the Equatorial Plasma Bubble Using the Linear Growth Rate of the Rayleigh-Taylor Instability Obtained with GAIA
We evaluated the linear growth rates of the R-T instability in the ionosphere using a whole atmosphere-ionosphere coupled model GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy). The effects of thermospheric dynamics driven by atmospheric waves propagating from below on the R-T growth rate were included in the model by incorporating meteorological reanalysis data in the region below 30 km altitude. The daily maximum R-T growth rates for the period of 2011-2013 were compared with the observed occurrence days of EPB determined by the Equatorial Atmosphere Radar (EAR) and Global Positioning System (GPS) in West Sumatra, Indonesia. We found that a high R-T growth rate tends to correspond to the actual EPB occurrence. Based on this result, we will discuss the predictability of EPB occurrences using GAIA.
17:35—17:55 Y. Otsuka, A. Shinbori (ISEE, Nagoya Univ.), T. Tsugawa, and M. Nishioka (NICT)
GPS Observations of Medium-Scale Traveling Ionospheric Disturbances
Medium-scale traveling ionospheric disturbance (MSTID) is a phenomenon of the plasma density perturbations in the F region. Using total electron content (TEC) data obtained from a GPS receiver network in Japan, two-dimensional structures of MSTIDs have been revealed in the maps of TEC perturbations obtained by subtracting 1-hour running average from the original TEC data for each satellite and receiver pair. We have found that characteristics of the MSTID in Japan are different between daytime and nighttime. The daytime MSTIDs frequently appear in winter, and most of them propagate southward or south-southeastward. These characteristics are consistent with an idea that the daytime MSTIDs are caused by atmospheric gravity waves. On the other hand, the nighttime MSTIDs frequently appear in summer, and most of them propagate southwestward. From these characteristics of the MSITDs, the nighttime MSTIDs are considered to be caused by the Perkins instability. In this study, we have found that the MSITD activity during nighttime increases with decreasing solar activity. This feature is consistent with solar activity dependence of the growth rate of the Perkins instability. The MSTID activity during daytime also show anti-correlation with the solar activity although difference of the daytime MSTID activity between solar minimum and maximum is smaller than that of the nighttime MSTID activity. This result indicates that amplitude of neutral wind oscillation caused by gravity waves propagating from below into the thermosphere increases with decreasing solar activity because neutral density decreases with decreasing solar activity. In this presentation, we will investigate long-term variation of propagation velocity of MSTIDs as well as the MSTID activities to discuss mechanisms causing the MSTIDs.
17:55—18:20 R. R. S. de Mendonca, C. R. Braga, A. Dal Lago, E. Echer, L. A. da Silva, L. R. Alves, C. M. de Nardin, J. E. R. Costa, F. B. Guedes, C. D. do Carmo, J. R. Cecatto, O. Mendes Junior, D. Koga, P. F. Barbosa Neto, and M. B. de Padua
Developing indexes for communicating space weather conditions related to the interplanetary medium for the general public
We introduce the concept of indexes for easy monitoring the space weather conditions in the interplanetary medium and discuss their use as a tool for nowcast geomagnetic indexes. At present time, we defined four indexes associated with the following parameters: the interplanetary magnetic field (IMF) magnitude, its southward component, the solar wind speed increase and the compression of the day-side magnetosphere position. Taking into account to more than 20 years of in situ data and the characteristics of solar and interplanetary structures associated with space weather effects, we define six levels of disturbance that help the user to obtain information about the interplanetary medium in a simply and quickly way. In addition, we show how some of the index can be used for predict the Dst and Kp indexes behavior in the near time.
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May 17
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Session 2: Radio propagation
9:40—10:00 J. E. R. Costa, C. M. Wrasse, Cosme A. O. B. Figueiredo, D. Barros, M. B. de Padua, H. Takahashi
Equatorial and low latitude Ionosphere monitoring by TEC mapping over South America
Brazilian Studies and Monitoring of Space Weather (EMBRACE) has been publishing ionospheric TEC map in the operational form, which covers almost all the South America with 10 minutes of time resolution. The spatial resolution is varying from 50 km to 500 km depending on the density of ground based GNSS receivers. It has been successful to monitor the generation and movement of the equatorial ionization anomaly (EIA), equatorial plasma bubbles (EPB) and medium scale travelling ionospheric disturbances (MSTIDs). The data analysis of TEC in 2014 and 2015 reveals that daytime MSTIDs are frequent during the period from March to September while EPBs are frequent during the period of September to march, just of opposite season each other. Characteristics of EPBs, such as inter-bubble distances and latitudinal dependency of zonal drift velocities, were obtained. Response of TECMAP during the intense geomagnetic storm was also studied. Some relevant observational results will be presented and discussed.
10:00—10:25 B. A. Carter, J. Currie (RMIT Univ.), M. Terkildsen (Space Weather Service, Bureau of Meteorology), K. Groves (Boston College), and R. Caton (Air Force Research Laboratory)
Capturing the daily variability in the occurrence of Equatorial Plasma Bubbles using global coupled ionosphere-thermosphere modelling
Equatorial Plasma Bubbles (EPBs) are a major source of ionospheric scintillations on GPS, VHF and UHF radio systems in equatorial and low-latitude regions around the world. As such, the accurate prediction of EPBs has become a focal point of research attention within the ionospheric physics community in recent years. Scintillation forecasting models typically rely on large ionospheric scintillation datasets and are thus quite successful in capturing the well-documented longitude/seasonal climatology. However, EPB occurrence typically exhibits a significant level of daily variability – i.e., EPBs observed on one night but not the next – which is difficult for statistical/empirical models to fully capture. The Generalised Rayleigh-Taylor (R-T) plasma instability is understood to be responsible for the generation of EPBs during the night-time hours. The theoretical formulation of the R-T plasma instability by Sultan (1996) enables the direct calculation of the flux-tube integrated instability linear growth rate, provided that all physical quantities within the growth rate can be obtained from observations/modelling. In this contribution, recent advances and challenges in capturing the daily variability in the EPB occurrence using the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM) are reviewed. In particular, the thresholds used to classify an EPB-day versus a non-EPB day in multiple scintillation datasets are further scrutinised, alongside the R-T growth rate thresholds used to classify a modelled EPB-day versus a non EPB-day. In addition, the results obtained from the most recent instalment of the TIEGCM will be compared to its predecessor. Collectively, the lessons learned about EPB occurrence from global coupled ionosphere-thermosphere modelling will be discussed in the context of developing a reliable EPB/scintillation prediction capability.
10:25—10:45 H. Fujiwara (Seikei Univ.), S. Nozawa (ISEE, Nagoya Univ.), Y. Ogawa, R. Kataoka (NIPR), Y. Miyoshi (Kyushu Univ.), H. Jin, H. Shinagawa, C. Tao (NICT), and H. Liu (Kyushu Univ.)
Disturbances of the dayside ionosphere during small Kp periods
We have made simultaneous observations of the dayside ionosphere with EISCAT UHF radar at Tromsø and EISCAT Svalbard radar (ESR) at Longyearbyen. Significant ionospheric disturbances were observed on the north of the ESR site even during small Kp periods when the ionosphere was quiet on the south of the ESR site. When the disturbances were observed, a strong ion flow channel was located on the north of the ESR site. In a certain small Kp case, the ion temperature showed considerable rises by more than 1000 K at the periods of the enhanced ion flow. The regions of significant ion flow or convection electric field during small Kp periods would be located at higher latitude (higher than 80 deg latitude in the dayside) than those during moderate and/or large Kp periods. In addition, the location of the flow channel was fluctuated in association with changes in solar wind/cross polar cap potential. This ion flow fluctuation would cause quasi periodic variations (about 10-30 minutes) of the ionosphere on the north of the ESR site. In order to compare the above features of the dayside ionosphere during the periods of small Kp, we will also show some examples of observations with the EISCAT radar system during periods of large Kp and simulations with a numerical model.
Session 3: Magnetosphere
10:45—11:10 D. Summers (Memorial Univ. of Newfoundland)
Limitation of Ring Current Proton Spectra by Electromagnetic Ion Cyclotron Wave Scattering
For two chosen geomagnetic storms we measure proton energy spectra using the RBSPICE-B instrument on the Van Allen Probes. Using proton precipitation data from POES spacecraft, we deduce that EMIC wave action was prevalent at the times and locations of the most intense proton spectra. Comparisons between the observed proton energy spectra and theoretical limiting spectra show reasonable agreement. We conclude that measurements of the most intense proton spectra are consistent with limitation by EMIC wave scattering.
11:10—11:35 M. Shoji, Y. Miyoshi, (ISEE, Nagoya Univ.) Y. Katoh (Tohoku Univ.), K. Keika (The Univ. of Tokyo), V. Angelopoulos (UCLA), S. Kasahara (The Univ. of Tokyo), K. Asamura (ISAS), S. Nakamura (RISH, Kyoto Univ.), and Y. Omura (RISH, Kyoto Univ.)
Nonlinear wave particle interaction analysis on the electromagnetic ion cyclotron emissions
Electromagnetic plasma waves are thought to be responsible for energy exchange between charged particles in space plasmas. Such an energy exchange process is evidenced by phase space holes identified in the ion distribution function and measurements of the dot product of the plasma wave electric field and the ion velocity. We develop a method to identify ion hole formation, taking into consideration the phase differences between the gyromotion of ions and the electromagnetic ion cyclotron (EMIC) waves. Using this method, we identify ion holes in the distribution function and the resulting nonlinear EMIC wave evolution from Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. These ion holes are key to wave growth and frequency drift by the ion currents through nonlinear wave-particle interactions, which are identified by a computer simulation in this study.
11:35—11:55 Y. Miyoshi, S. Saito (ISEE, Nagoya Univ.), Y. Matsumoto (Chiba Univ.), and T. Amano (Univ of Tokyo)
Simulation study on the acceleration of outer belt electrons during the solar wind pressure pulse
Relativistic electron fluxes of the outer radiation belt rapidly change associated with enhancement of solar wind dynamic pressure. The solar wind pressure pulse produce the fast mode waves, and the fast mode causes the rapid accelerations of the trapped electrons. In order to investigate this process in detail, we conduct a code-coupling simulation using the GEMSIS-RB test particle simulation (Saito et al., 2010) and the GEMSIS-GM global MHD magnetosphere simulation (Matsumoto et al., 2010). Through the interactions between the fast mode waves and drifted electrons, the energy spectrum showed that the accelerations occur at wide energy range. We derive theoretically the minimum energy for the acceleration and compare with the simulation.
11:55—12:20 S. Saito, S. Kurita, and Y. Miyoshi (ISEE, Nagoya Univ.)
Numerical study on precipitation and acceleration of relativistic electrons by whistler mode chorus waves
Whistler mode chorus waves in the Earth’s magnetosphere are considered to have important roles to increase relativistic electron flux in the outer radiation belt. Kurita et al. (2016) found that whistler chorus waves responsible for flux enhancement of relativistic electrons can be a cause of precipitation of relativistic electrons. They concluded that the microbursts are a good proxy to indicate that whistler chorus activity actually causes significant variations of relativistic electrons. In order to understand physical mechanism of the causal relationship between relativistic electron flux enhancements and relativistic electron precipitation, we study flux enhancement and atmospheric precipitation of relativistic electrons associated with whistler chorus elements propagating along a magnetic field line, by using GEMSIS-RBW simulation code (RBW). The RBW is a test-particle code solving bounce motion of electrons along a field line, parallel propagating whistler mode chorus waves, and scattering of the electrons by the whistler waves. The RBW simulation can calculate scattering processes, not only scattering following quasilinear theory but also nonlinear scattering that are phase bunching and phase trapping in coherent whistler mode chorus [Saito et al. JGR 2016]. The nonlinear phase trapping leads to electron acceleration from a few hundred keV to a few MeV within a time scale of a second. Our simulations showed that both the relativistic electron flux and relativistic electron precipitation into the atmosphere are more enhanced as the whistler chorus waves propagate more away from the equator. We will discuss dependency of latitude of the whistler chorus on the flux enhancement and precipitation of relativistic electrons.
Session 3: Magnetosphere, GIC
15:40—16:05 R. Marshall, L. Wang, A. Kelly, J. Young, and M. Terkildsen (Space Weather Services, Bureau of Meteorology, Australia)
Geomagnetic induced currents in Australian power networks – recent modelling and observations
Geomagnetic induced currents (GICs) have been considered an issue for high latitude power networks for some decades. More recently GICs have been observed and studied in power networks located in lower latitude regions. This presentation presents the results of a model aimed at predicting and understanding the impact of geomagnetic storms on power networks in Australia with particular focus on the Queensland and Tasmanian networks, the lowest and highest latitude Australian networks respectively. The model incorporates a “geoelectric field” determined using a plane wave magnetic field incident on a uniform conducting Earth, and the network model developed by Lehtinen and Pirjola (1985). Model results for intense geomagnetic storms of solar cycle 24 are compared with transformer neutral monitors at four locations within the Australian power network. The model is also used to assess the impacts of the super-intense geomagnetic storm of 29-31 October 2003 on the flow of GICs within these networks. The presentation will also include the results obtained by incorporating more realistic conductivity models into the geoelectric field estimates.
16:05—16:25 T. Kikuchi (ISEE, Nagoya Univ., RISH, Kyoto Univ.), Y. Ebihara (RISH, Kyoto Univ.), K.K. Hashimoto (Kibi International Univ.), K. Kitamura (NIT, Tokuyama College), and S. Watari (NICT)
Period dependence of reproducibility of the geomagnetically induced currents
Watari et al. [SW2009], based on the GIC measurements in Hokkaido, Japan, found that the GIC is well correlated with the y-component magnetic field (By) (correlation coefficients > 0.8) and poor correlations with Bx,z and dBx,y,z/dt. The good correlation between the GIC and By would help predict the GIC if we have capabilities of reproducing the magnetosphere-ionosphere currents during space weather disturbances. To use the GIC-By relationship for the GIC prediction, we need to confirm the good correlation being valid for any period (T) of disturbances. We made correlation analyses between the GIC and By on the geomagnetic sudden commencements and pulsations (T=1-10m), substorm positive bays (30m), DP2 fluctuations (20-60m), quiet-time diurnal variations (3-12h) and geomagnetic storms (1-20h). We found that the correlation is good for short period (cc > 0.8 for T < 1 h), but poor for long periods (cc < 0.3 for T > 6 hours). To reproduce the long period GICs more accurately, we calculated the electric field induced by By, using the convolution of the dBy/dt and step response of a uniform conductor that replaces the conducting Earth. The induced electric field is found to be better correlated with the GIC for the long-period disturbances (cc > 0.9). We also found a method that reproduces impulsive disturbances like the SC more accurately (cc > 0.9) with modified step response of the conducting Earth.
16:25—16:45 S. Nakamura, Y. Ebihara, S. Fujita, T. Goto, N. Yamada, S. Watari, and Y. Omura
Time domain simulation of geomagnetically induced current (GIC) flowing in 500 kV power grid in Japan including a three-dimensional ground inhomogeneity
We performed time domain simulation of geomagnetically induced currents (GICs) flowing in the Japanese 500 kV power grid. The three-dimensional distribution of the geomagnetically induced electric field (GIE) was calculated by using the finite-difference time-domain (FDTD) method with a three-dimensional electrical conductivity model constructed from a global relief model and a global map of sediment thickness. First, we assumed a uniform current in the ionosphere. Hence, we imposed a sheet current at 100 km altitude with a sinusoidal perturbation to illuminate the influence of the structured ground conductivity. The simulation result shows that GIE exhibits localized, uneven distribution that can be attributed to charge accumulation due to the inhomogeneity below the Earth's surface. The charge accumulation becomes large when the conductivity gradient vector is parallel, or anti-parallel to the incident electric field. For given GIE, we calculated the GICs flowing in a simplified 500 kV power grid network in Japan. The influence of the structured ground conductance on GIC appears to depend on a combination of the location of substations and the direction of the source current. Uneven distribution of the power grid system gives rise to intensification of the GICs flowing in remote areas where substations/power plants are distributed sparsely. Secondly, we imposed the equivalent sheet current inferred from the ground magnetic disturbance for the magnetic storm of 27 May 2017 as a source current of the FDTD simulation. The calculated GIC agrees well with the observations at substations around Tokyo when the uneven distribution of GIE is incorporated with the simulation.
Session 4: Hazard map
16:45—17:10 I. Ferguson (Lloyd’s Japan Inc.)
Lloyd’s City Risk Index & Solar Storm Risk
N/A
17:10—17:35 A. Gonzalez-Esparza (SCIESMEX-UNAM)
Mexican Protocol for Extreme Space Weather Events
The Mexican Space Weather Service (SCiESMEX) is collaborating with the National Center for Disaster Prevention (CENAPRED) and the Mexican Space Agency (AEM) to establish a protocol for extreme space weather events. This protocole will be signed by the Interior Minister as a part of the National Civil Protection System. The motivation of creating this protocol is based on the modifications of the civil protection law in June 2014. This modifications now include space hazards and solar and geomagnetic storms as a risk of the national security. We will explain how the protocol operates and an update of the status of the revision within the Mexican goverment.
17:35—17:55 D. Shiota and M. Ishii (NICT)
Estimation of Japanese economic impact of extreme space weather
Extreme space weather due to very powerful CMEs may potentially cause high geomagnetic induced currents (GIC) and then damage electricity transmission infrastructures. The cut off electric supply can cause regional blackout, which can lead severe damage on the regional economic activities. Oughton et al. (2017) quantified such impact of an extreme space weather event on US economy and indirect losses in the global economy, applying several patterns of blackout zone due to aurora. We develop a similar model to estimate economic impact of a space weather event on Japanese economy utilizing a similar method as Oughton et al. (2017).
17:55—18:20 C. Ko, J. Choi, J. Han, and J. Lee (KSWC)
The management of the space weather risk in KOREA
The Korean Space Weather Center (KSWC) of the National Radio Research Agency (RRA) is a government agency which is the official source of space weather information for Korean Government and the primary action agency of emergency measure to severe space weather condition as the Regional Warning Center of the International Space Environment Service (ISES). KSWC's main role is providing alerts, watches, and forecasts in order to minimize the space weather impacts on both of public and commercial sectors of satellites, aviation, communications, navigations, power grids, and etc. KSWC is also in charge of monitoring the space weather condition and conducting research and development for
its main role of space weather operation in Korea.
The Korean goverment defined the role in the radio wave act to establish and implement a basic plan for the management of space weather risks in order to prepare, control and recover against disasters due to variation of space weather conditions in every 5 years.
In this study, we will introduce this basic plan and KSWC’s policy and strategy for space weather risk management.
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May 18
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Session 5: Satellite Anomaly
10:00—10:25 R. Friedel, V. Jordanova, and the SHIELDS Team Los Alamos National Laboratory
Space Hazards Induced near Earth by Large, Dynamic Storms (SHIELDS)
Predicting space weather hazards remains a big space physics challenge due to the complex multi-scale nature of the magnetosphere. SHIELDS (Space Hazards Induced Near Earth by Large Dynamic Storms) addresses this challenge.
The SHIELDS project is a large space environment modeling project that bridges macro- and micro-scale models with data assimilation tools, operating within the Space Weather Modeling Framework of the University of Michigan. This end-to-end model of the magnetosphere driven by the dynamic solar wind, that can predict one of the most harmful space weather hazards, the spacecraft surface charging environment (SCE), and assist spacecraft design and hazard mitigation.
The primary SCE source is the low-energy (10s of keV) hot plasma injected from the magnetotail into the inner magnetosphere during substorms (magnetospheric reconfiguration events). Our SHIELDS framework specifies the dynamics of the hot particles (the seed population for the radiation belts) on both macro- and micro-scale, including substorms and plasma waves that accelerate particles to relativistic energies.
New data assimilation techniques employing data from LANL instruments on Van Allen Probes and geosynchronous satellites are being applied for the first time to the global model. This research provides a framework for understanding the near-Earth space environment where operational satellites reside. The ability to reliably distinguish between various modes of failure is critically important in anomaly resolution and forensics.
10:25—10:45 K. Koga, H. Matsumoto and T. Nagatsuma
The relationship between the space environments of high energy electrons and the satellite anomaly caused by the internal charging
Spacecraft charging is still the main part of the satellite anomaly which is caused by the space environment. Coi et.al (2011) analyzed the satellite anomaly on the geostationary Earth orbit (GEO). They found a strong relationship between the anomaly and Kp index. This result suggests that the majority of anomalies are caused by high energy electrons. There are two kinds of satellite charging. One is surface charging and the other is internal charging. Surface and internal charging are caused by few keV and few MeV electrons respectively. We will report one sample case of satellite anomaly caused by the internal charging, and discuss the correlation with the observation results of high energy electrons and the Monte-Carlo simulation results about the accumulations of electrons on the material of the electrical device.
10:45—11:05 M. Nakamura, R. Kawachi, T. Teraoka (Osaka Prefecture Univ.), T. Nagatsuma, and M. Ishii (NICT)
Development of an estimation method of spacecraft surface charging for SECURES
Spacecraft anomalies are often induced by electrostatic discharge resulting from surface charging. We are developing an estimation method of spacecraft surface potential for the Space Environment Customized Risk Estimation for Spacecraft (SECURES) of the space weather forecast Project for Solar-Terrestrial Environment Prediction (PSTEP). Spacecraft charging simulation tools are commonly used to mitigate charging effects in the spacecraft design phase. They usually take a long time to calculate the surface potential and are not suitable for quick estimation. We make lookup tables of the surface potential of the target spacecraft for combinations of plasma temperatures and densities using the spacecraft charging simulation tool. By interpolation from the lookup tables, we can quickly estimate the surface potential for the observed or predicted on-orbit plasma environment.
11:05—11:25 R. H. W. Friedel, M. G. Henderson, V. K. Jordanova, S. K. Morley, G. S. Cunningham, G. D. Reeves, M. M. Cowee, M. R. Carver, R. M. Kippen, and J. P. Sullivan (LANL)
Space Weather Data Products and Modeling Capabilities at Los Alamos National Laboratory
We present an overview of space weather data products (e.g., GPS, GEO) acquired by Los Alamos National Laboratory which has been involved in measuring and monitoring the space environment for over 50 years. In addition, Los Alamos has developed a number of space weather modeling capabilities over the years. These include: DREAM (a data-assimilative code) and DREAM3D (a basic physic diffusion code), which are designed to model the evolution of the Earth's hazardous natural and artificial radiation belts; SHIELDS/RAM-SCB, which is a state-of-the-art set of coupled codes to model the ring current/surface-charging environment in the near-Earth region; and the on-going Carrington/GIC project which will extend this modeling capability down to the ground in order to understand impacts on power grid infrastructure during extreme geomagnetic storm events.
11:25—11:45 J. T. Dahlin, J. F. Drake, and M. Swisdak
The Fundamental Mechanisms of Particle Acceleration during Magnetic Reconnection
Magnetic reconnection is an key driver of energetic particles in many astrophysical phenomena, including solar flares and magnetospheric storms. However, the fraction of the released magnetic energy that is imparted to a nonthermal component can vary widely in different events. We use kinetic particle-in-cell (PIC) simulations to demonstrate the important role of the guide field (the non-reconnecting component) in controlling the efficiency of electron acceleration during reconnection. In reconnection where the guide field is smaller than the reconnecting component, the dominant electron accelerator is a Fermi-type mechanism that preferentially energizes the nonthermal component. In strong guide field reconnection, however, the field-line contraction that drives the Fermi mechanism becomes weak. Instead, electric fields parallel to the magnetic field are primarily responsible for driving electron heating. These parallel electric fields are ineffective,however, in driving the energetic component of the spectrum. Three-dimensional simulations reveal that the stochastic magnetic field that develops during 3D guide field reconnection plays a vital role in both particle acceleration and transport. The Alfvenic reconnection outflows that drive the Fermi mechanism also expel accelerated electrons from energization regions. In 2D reconnection, the expelled electrons are trapped in island cores so that acceleration ceases, whereas in 3D the stochastic magnetic field enables energetic electrons to leak out of islands and freely sample regions of energy release. A finite guide field is required to break initial 2D symmetry and facilitate escape from island structures. We show that reconnection with a guide field comparable to the reconnecting field generates the greatest number of energetic electrons, a regime where both (a) the Fermi mechanism is an efficient driver and (b) energetic electrons may freely access acceleration sites. These results have important implications for electron acceleration in solar flares and reconnection-driven dissipation in turbulence.
11:45—12:10 X. Zhang (National Satellite Meteorological Center, CMA, Beijing, China) and F. He (Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China)
Dynamic Evolution of the Plasmapause: Statistics and Model
Based on the plasmaspuase datebase compiled with ISEE-1, DE-1, Akebono, CRRES, Polar, IMAGE, Cluster, THEMIS,VAP and CE-3 satellites from 1977 to 2015, The responses of the global plasmapause to solar wind and geomagnetic changes and the diurnal, seasonal, solar cycle variations of the plasmapause are statistically investigated and modelled. It is found that as the solar wind or geomagnetic conditions change from quiet to disturbed (with clear bulge trends). It is also found that the plasmapause approaches the Earth during high solar activity and expands outward during low solar activities.The newly constructed model of solar wind driven global dynamic plasmapause (NSW-GDP) can improve the forecasting accuracy and capability for the global plasmapause, compariing with previous empirical models. The NSW-GDP model can potentially be used to forecast the global plasmapause shape with upstream solar wind and IMF parameters and corresponding predicted values of Dst and AE, and can also be used as input parameters for other inner magnetospheric coupling models.
PSTEP Report A04
12:10—12:35 T. Sakurai (National Astronomical Observatory of Japan)
Solar Cycle and its Effects on Earth: Report of A04 Team
N/A
Session 6: Radiation
13:35—13:55 T. Sato (JAEA), R. Kataoka (NIPR), D. Shiota, Y. Kubo, M. Ishii (NICT), H. Yasuda (Hiroshima Univ.), S. Miyake (National Institute of Technology, Ibaraki College), I. Park (ISEE, Nagoya Univ.), and Y. Miyoshi (ISEE, Nagoya Univ.)
WASAVIES: Warning System of Aviation Exposure to Solar Energetic Particles
A physics-based warning system of aviation exposure to solar energetic particles, WASAVIES, is improved to be capable of real-time and automatic analysis. The performance of the improved WASAVIES is examined by analyzing the three major ground level enhancement events of the 21st century. The accuracy of the calculated dose rates is well validated by the reproducibility of the count rates of several neutron monitors and GOES proton fluxes.
13:55—14:20 M. Latocha and P. Beck (Seibersdorf Laboratories)
Radiation dose assessment at flight altitudes with AVIDOS
Radiation at aviation altitudes is caused mainly by Galactic Cosmic Radiation (GCR) coming from outside of our solar system, but radiation of solar origin – Solar Cosmic Radiation (SCR) – should not be neglected. Sporadic but often intense solar phenomena like solar flares (SF) or coronal mass ejections (CME) may affect the radiation environment in the Earth’s atmosphere. Due to some of these solar energetic particle (SEP) events, radiation measured on the ground can be temporarily enhanced – so-called Ground Level Enhancements (GLE).
Radiation exposure at aviation altitudes due to GCR is relatively well described by numerous measurements and various calculation codes. Some of those codes provide even a long-term forecast of GCR radiation levels and this with reasonable accuracy. Yet, the radiation dose assessment due to SCR is still a scientific challenge. First, an occurrence of SEP events is currently not predictable and not all of them hit and reach the Earth’s surface. Second, their characteristics are very dynamic and vary from one GLE event to another.
AVIDOS is an informational and educational online software for the assessment of cosmic radiation exposure at flight altitudes during quiet and extraordinary solar conditions. It estimates route doses for flights between any two locations and attempts to nowcast the exposure during solar storms. It also provides a comparison of assessed exposure with natural background radiation on the Earth. AVIDOS is a federated service provided by Seibersdorf Laboratories accessible at the European Space Agency’s (ESA) web-portal devoted to Space Weather: http://swe.ssa.esa.int/web/guest/avidos-federated.
We will present the current status of AVIDOS development. That will include a description of GCR module with radiation forecast for up to 12 months and an SCR module for nowcast of the dose during a GLE event. We will also present the user interface of AVIDOS and report on planned improvements.
14:20—15:00 M. Ishii
Discussion & Closing
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Poster (core time 14:40—15:40 on May 17)
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* Posters could be put up for 3 days
[01] D. Seki, K. Otsuji, H. Isobe, T. T. Ishii, K. Ichimoto, and K. Shibata (Kyoto Univ.)
Increasing Small-scale Motions of the Filaments as the Precursors of their Eruptions
Filaments, the dense cooler plasmas in the solar corona, often become unstable and erupt into the interplanetary space as coronal mass ejections (CMEs). The CMEs may cause geomagnetic storms that result in various societal and economical impacts such as huge blackouts[McAllister, et al., 1996], so that it is important to predict when filament eruptions will occur. From the space weather point of view, monitoring filaments as the progenitor of CMEs has a following advantage that we can monitor the eruptions from quiet regions that may also cause severe geomagnetic storms. The aim of this study is to investigate the characteristics of eruptive filaments that can be used as the precursor of eruptions.
For this purpose, we analyzed the solar full disk images captured by Solar Dynamics Doppler Imager (SDDI) installed on Solar Magnetic Activity Research Telescope(SMART) at Hida Observatory, Kyoto University[Ichimoto, et al. 2017]. SDDI can obtain solar full disk images in 73 wavelengths between Hα center – 9 \AA and Hα center + 9 \AA per 0.25 \AA with the time resolution of about 15 seconds. Therefore this instrument can observe unprecedented detailed line-of-sight velocities of filaments. Focusing on this feature, in our previous work we calculated the line-of-sight velocities of the filament observed on 2016 November 5 by utilizing Beckers’ cloud model[Beckers, 1964] from before the eruption and tracked the standard deviation of the line-of-sight velocities inside the filament. As a result, we found an increase of the standard deviation, that is, an increase in the amplitude of line-of-sight velocity of the small-scale motions in the filament about 1 hour before the onset of the eruption[Seki, et al. 2017].
In this work, we newly found 6 events that showed the increase in the standard deviation of the line-of-sight velocities inside filaments before eruption. The features were seen 1.7 hours before their eruptions on average (standard deviation: 0.75 hours). We concluded that this result can support utilizing the increase of small-scale motions in a solar filament as the precursor of a filament eruption.
[02] N. Nishizuka, K. Sugiura, Y. Kubo, M. Den, and M. Ishii (NICT)
Solar Flare Prediction using Machine-learning
Solar flares are an origin of space weather phenomena. By predicting solar flares, we can increase the lead-time of space weather forecast. Here we developed a solar flare prediction model using machine learning (deep neural networks), named Deep Flare Net (DeFN). It is optimized to predict the maximum class of flares occurring in the following 24 hr. We used solar observation data during the period 2010–2015, such as vector magnetograms, ultraviolet (UV) emission, and soft X-ray emission taken by SDO and GOES. We detected active regions (ARs) from the full-disk magnetogram, from which 79 features were extracted. We adopted the features used in Nishizuka et al. (2017) and added some features for operational prediction: coronal hot brightening at 131 Å (T >10^7 K) and the X-ray and 131 Å intensity data 1 and 2 hr before an image. For operational evaluation, we divided the database into two for training and testing: the data set in 2010–2014 for training, and the one in 2015 for testing. The DeFN model consists of deep multilayer neural networks formed by adapting skip connections and batch normalizations. To statistically predict flares, the DeFN model was trained to optimize the skill score, i.e., the true skill statistic (TSS). As a result, we succeeded in predicting flares with TSS=0.80 for ≧M-class flares and TSS=0.63 for ≧C-class flares, which is higher than that for human forecasts.
[02] S. Toriumi
Numerical Modeling of Flare-productive Active Regions
Solar flares, especially the strong ones, occur in and around the complex active regions (ARs). As a part of the PSTEP project, we have been conducting the observational and numerical analysis on such flare-productive ARs. In this presentation, we report on the recent progress on the modeling of flaring ARs. In particular, we show the preliminary results from the modeling and analysis of AR NOAA 12673, which produced the series of strongest flares in this solar cycle in September 2017.
[03] K. Hirose, K. Ichimoto and K. Otsuji (Kwasan and Hida Observatories, Kyoto Univ.)
A statistical study of small blue shifted event observed with SDDI/SMART at Hida Observatory
Solar Dynamics Doppler Imager (SDDI) which is equipped with the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory observed many small-scale plasma motions. We present a statistical study of these events, such as the occurrence frequency or the place where the events often observed in the solar surface.
[04] D. Shiota (NICT) and S. Yashiro (NASA/Catholic Univ.)
Development of real-time prediction system of CME arrival and magnetic field with SUSANOO-CME MHD simulation
Southward-pointing interplanetry magnetic field brought by CMES can cause various disturbance in the magnetosphere of the Earth.
Recently we have been developing a system to predict CME arrival and magnetic field brought by CME internal magnetic flux rope utilizing real-time solar observations and an inner heliosphere MHD simulation (SUSANOO-CME, Shiota & Kataoka 2016). We will introduce the advantage of our system and report the current status of its development.
[05] K. Iwai (ISEE, Nagoya Univ.), D. Shiota (NICT), M. Tokumaru, K. Fujiki (ISEE, Nagoya Univ.), M. Den, and Y. Kubo (NICT)
Development of space weather forecast system using interplanetary scintillation (IPS) observations
The solar wind and coronal mass ejections (CMEs) sometimes cause disturbances of the geospace which are closely related our life such as radio telecommunications, spacecraft and airplanes operations, GPS navigations, and so on. Therefore, forecasting of CMEs and high-speed solar winds has become more and more important. The interplanetary scintillation (IPS) observation at the UHF radio frequency range detects CMEs and high-speed solar winds from the continuous ground-based observations. Institute for Space–Earth Environmental Research (ISEE), Nagoya University has operated radio telescopes dedicated to the IPS observation since 1980s. We have begun a development of IPS data driven MHD simulation system under a joint research between ISEE and NICT with a support from the PSTEP project. The MHD simulation of NICT can estimate CME propagations in the interplanetary space using the initial condition derived from white-light coronagraph images. On the other hand, IPS observations can observe locations and speeds of CMEs in the interplanetary space. In our IPS data driven MHD simulation system, an IPS amplitude of each radio source is calculated using the 3D electron density variation derived from the MHD simulation. Then, the calculated IPS is compared with the observed IPS to evaluate the accuracy of the MHD simulation.
[06] K. Watanabe, S. Nishimoto (NDA), S. Imada (ISEE, Nagoya Univ.), T. Kawate (ISAS/JAXA), and K.-S. Lee (NAOJ)
Derivation of Solar Flare Total Spectra from Flare Geometrical Features
Solar flares and related phenomena sometimes affect to the solar-terrestrial environment. To identify the relationship between solar flare phenomena and influence to the solar-terrestrial environment, we need to understand the full spectrum of solar flares. For the purpose of obtaining the time evolution of total solar flare spectra, we are performing statistical analysis of the electromagnetic data of solar flares. In this study, we select solar flare events larger than M-class from the Hinode flare catalogue (Watanabe et al., 2012). First, we focus on the EUV emission observed by the SDO/EVE. We examined the intensities and time evolutions of five EUV lines of 55 flare events. As a result, we found positive correlation between the “soft X-ray flux” and the “EUV peak flux” for all EUV lines. Moreover, we found that hot lines peaked earlier than cool lines of the EUV light curves. We also examined the hard X-ray data obtained by RHESSI. When we analyzed 163 events, we found good correlation between the “hard X-ray intensity” and the “soft X-ray flux”. Because it seems that the geometrical features of solar flares effect to those time evolutions, we also looked into flare ribbons observed by SDO/AIA. We examined 21 flare events, and found positive correlation between the “GOES duration” and the “ribbon length”. We also found positive correlation between the “ribbon length” and the “ribbon distance”, however, there was no remarkable correlation of the “ribbon width”. To understand physical process of flare emission, we performed numerical simulation (Imada et al., 2015), and compared with the observational flare model. We also discuss the flare numerical model which can be fitted to the observational flare model.
[07] A. Nakamizo (NICT), A. Yoshikawa, and T. Tanaka (Faculty of Science / ICSWSE, Kyushu Univ.)
Effects of Ionospheric Polarization on Magnetosphere Convection and Dynamics in Global MHD Simulation
The present study examines the effects of ionospheric polarization on magnetospheric convection and dynamics by using an MHD code. We perform simulations for some pairs of ionospheric conductance and solar wind/IMF. It was found that the large-scale structure, near-earth convection field (including the Harang Reversal), and formation of NENL are largely changed by the conductance distribution, more specifically, Hall conductance non-uniformity. The results indicate that ionosphere polarization has a significant role in determining the rate and path of plasma transport from the near-earth plasma sheet to geosynchronous region.
[08] J. Kim, W. Yi, K.-I. Jang (KMA, Korea), and W. Tobiska (SET, USA)
Verification of the Radiation Exposure Assessment Models with Aircraft-based Dose Measurements
Radiation exposures of air crew and the public should be accurately monitored and properly informed for protecting their health from the adverse effect of the ionizing radiation. In general the radiation exposures originated from galactic cosmic rays (GCR) or energetic solar particles (SEP) are assessed by numerical estimation models because every commercial aircraft could not embed an instrument for measuring the radiation dose rate. In this study the radiation doses of aircraft crew and passengers are assessed by three model calculation, NAIRAS (Nowcast of Atmospheric Ionizing Radiation for Aviation Safety) system, CARI-7, and KREAM (Korean Radiation Exposure Assessment Model for aviation route dose). And the assessment results from each model are verified by the ARMAS (Automated Radiation Measurements for Aerospace Safety) system that measures the ambient radiation environment at commercial aircraft altitudes. And the characteristics of model errors are statistically analyzed. The total effective dose values of 214 flights during September 2015 to October 2017 over both hemispheres are used for the model verification. The study period corresponds to the end of descending phase of the solar cycle 24. In general all models tend to underestimate the total effective doses although some modeled doses overestimate when the total dose is small. The larger the total doses are, the greater model errors are estimated. The correlation coefficient between the assessment models and ARMAS measurement is ordered by CARI-7 (0.96), KREAM (0.92), and NAIRAS (0.88). The RMSE (root mean square error) in uSv is ordered by NAIRAS (11.2), KREAM (14.1), and CARI-7 (15.3). The result of this study implies that the model errors in cases of actually large doses should be checked and improved because the underestimated assessment gives crew and the public a reduced awareness of dangers arising from ionizing radiation.
[09] C. Tao, H. Jin, H. Shinagawa (NICT), H. Fujiwara (Seikei Univ.), Y. Miyoshi (Kyushu Univ.), and M. Matsumura (ISEE, Nagoya Univ.)
Improvement of high-latitude electric field and particle model in GAIA and its application to the September 2017 event
GAIA (Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy) solves physical and chemical dynamics of the whole atmosphere region from the troposphere to the exosphere under interactions with the ionosphere. Input from the polar region dramatically varies with the solar wind and magnetospheric conditions, which affects thermosphere and ionosphere globally, while the current GAIA does not include this effect. We are conducting improvements to input (1) polar electric field and (2) atmospheric ionization due to auroral precipitation into the GAIA. For the former, we refer to an empirical Weimer model which varies as a function of solar wind parameters. We will report the development and initial results applying to the solar wind disturbance triggered by X-class solar flares in September 2017 in this presentation.
[10] K. Hozumi, T. Kondo (NICT), S. Saito (ENRI), H. Nakata (Chiba Univ.), T. Tsugawa, and M. Ishii (NICT)
LASER (Low-cost Amateur receiver System Employing RTL-SDR)
To allow user to control the HF receiver operation remotely via software, a digital receiver, LASER (Low-cost Amateur receiver System Employing RTL-SDR), has been developed based on RTL-SDR (https://www.rtl-sdr.com) that is cheap open-source hardware, and GNU Radio (http://gnuradio.org/) that is open-source software toolkit. Development of HF receiver for ionospheric research by using RTL-SDR has never been reported. This paper proposes a development of low cost HF receiver system, namely LASER, for HF-START field campaign.
[11] T. Yokoyama (NICT)
High Resolution Plasma Bubble Modeling
Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionospheric F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPB from a space weather point of view. In order to simulate the instability in the equatorial ionosphere, a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 200 m has been developed. Once EPB penetrates into the topside ionosphere, turbulent internal structures become very significant. From the preliminary spectral analysis, we obtain power law characteristics of turbulent structures of the simulated EPBs. There are two power law components with a break point at around a few km wavelengths. The power law characteristics are consistent with past in situ observations such as the C/NOFS satellite to some extent.
[12] T. Tsugawa, M. Nishioka, K. Hozumi, H. Ishibashi, T. Kondo, C. Tao, and M. Ishii (NICT)
NICT ionospheric observations and researches for social uses
National Institute of Information and Communications Technology (NICT) has been observing ionosphere by ionosondes and GNSS receiver networks in Japan and in the Southeast Asia for monitoring ionospheric condition and researching ionospheric disturbances. Domestic ionosondes have been replaced with Vertical Incidence Pulsed Ionospheric Radar 2 (VIPIR2) ionosondes which can separate the O- and X-modes of ionospheric echoes which have improved the availability of automatic scaling of the ionogram. Now the O- and X-modes separated ionograms are available online. We have tried to detect arrival directions of ionospheric echo using the 8ch receiving antenna array of the VIPIR2.
In addition to ionosonde observations, we are providing high-resolution two-dimensional maps of absolute TEC, detrended TEC, rate of TEC change index (ROTI), and loss-of-lock on GPS signal over Japan using the dense GNSS network, GEONET, on realtime basis. To expand TEC observation area and spatial resolution, we have tried to use multi-GNSS data including GPS and QZSS for routine data collection and processing.
In Southeast Asia, we has developed the Southeast Asia low-latitude ionospheric network (SEALION) for the purpose of monitoring and researching severe ionospheric disturbances, such as plasma bubble. SEALION mainly consists of five FMCW ionosondes in four countries in Southeast Asia. We are now developing a new FMCW ionosonde system which is GNU Radio based software defined system. We have an on-going project to install a VHF radar at Chumphon and multi-GNSS receivers at equatorial SEALION stations to study plasma bubbles and their effects on precise GNSS positioning. In this presentation, we will introduce NICT ionospheric observations and researches for social uses.