From Director

Director Shinobu Machida
Director Shinobu Machida

Institute for Space-Earth Environmental Research at Nagoya University conducts studies to clarify the mechanisms and relationships that exist between the Earth, the Sun, and cosmic space, treating them as a seamless system, to contribute to solving Earth's current environmental issues and to expand human activity out into space. The institute, working in fields extending over both space science and geoscience, promotes nationwide collaborative studies as an institute under Japan's inter-university collaborative system.

The Earth rotates around the Sun, and the Sun supplies most of the energy that is needed to drive our terrestrial system. Along with enormous amounts of visible light and other electromagnetic waves, the Sun also releases gas (plasma) streams of electrically charged particles. Meanwhile, the Sun's activity varies over various time scales. A solar flare or a coronal mass ejection (CME) that occurs explosively for a short time on the Sun's surface is intimately related to electromagnetic phenomena that occur on Earth. For example, such solar variations cause geomagnetic storms on Earth and may result in spacecraft malfunctions or exposure of astronauts to hazardous radiation particles generated in association with the Sun's explosive variations. The Sun also fluctuates on much longer time scales than the Earth, including the approximately 11-year solar cycle. With respect to the latter, it is known that the Earth experienced a small ice age in the 17th century for approximately 70 years due to the quenching of this solar activity; this interval is called the Maunder Minimum. To determine the activity of the Sun, it is useful to investigate the amount of carbon isotopes (14C) in tree rings. In addition, a dedicated telescope aboard a spacecraft is a powerful tool for monitoring the status of the Sun. Furthermore, numerical simulations by means of high performance supercomputers are helpful for understanding occurrences in the interior of the Sun as well as for understanding the terrestrial atmosphere and climate. By fine-tuning the performance of such numerical simulations with state-of-the-art technology to reconstruct the past and current status of the sun and terrestrial climate, it is possible to accurately forecast the Sun's activity and the terrestrial climate. We are contributing to our society by carrying out such activities. The long history of the Earth from its creation to approximately several million years ago can be studied by applying a new dating method to rocks, namely, the CHIME age calculation program. Studies can also apply 14C and CHIME dating methods to various events, archaeological samples, cultural assets, and modern relics, thereby revealing their various chronological histories, including the Earth's history of over 46 billion years. We can expand our research area by stretching the spatial axis from the Earth to the Sun and to cosmic space, and by adding another axis, time, through the use of age dating.

The gas stream emanating from the sun is called the solar wind. When the solar wind approaches the Earth, the magnetosphere is formed by the solar wind streams around it, by confining and stretching the magnetic field lines that originate from Earth across space. There are many plasma particles with various energies in the magnetosphere. Among them, particles surrounding the Earth with very high energies are called radiation belt particles. A radiation belt develops when either a solar flare or CME takes place, in most cases, with the enhancement of auroral activity. The development of a radiation belt also enhances the possibility of malfunctions of spacecraft and the risk of irradiation of crew and passengers aboard airplanes. We are working to predict the occurrence of such solar flares, CMEs, magnetic storms, and the development of radiation belts so that we might take appropriate action in advance.

The ionosphere, ozone layer, and other layers in the Earth's upper and middle atmosphere absorb ultraviolet radiation, X-rays, and other harmful irradiation from the sun and prevent them from reaching Earth's surface. The visible light and ultraviolet radiation with long wavelengths are also absorbed or reflected by atmospheric layers, but may at times reach the Earth's surface. This process is closely related to the greenhouse effect, and is quite important to our understanding of the energy budget around Earth's surface. The effects of greenhouse gases such as carbon dioxide, and the effects of aerosols and the formation of clouds that develop around aerosols as nuclei are significant. Moreover, the formation of clouds induces precipitation, which significantly affects terrestrial vegetation and the oceanic ecosystem. Terrestrial vegetation and the oceanic ecosystem in turn control terrestrial weather and climate. In some locations, water-related disasters, such as torrential rains, typhoons, or floods, occur frequently. It has been noted that the global circulation of water is changing in association with recent climate change, therefore it is important to study global water circulation. We are also conducting inter-disciplinary studies on Earth's atmosphere, land, and oceans by means of observations on the ground and from space, and by advancing numerical simulations.

It has been noted that cosmic rays may play an important role in cloud formation. In this context, we should study not only occurrences around the Earth, but also occurrences farther away from us in the universe, and this is a significant theme of the institute. Thus, our primary mission is to understand the mechanisms and mutual relationships occurring between the Earth, the Sun, and cosmic space, treating them as a seamless system, to understand the basic physical and chemical processes with various temporal and spatial scales that are invoked in such phenomena, and to contribute to solving Earth's current environmental issues. The research areas covered by this institute are not limited to the Earth, the Sun, and interplanetary space, but are expanded to include other planets in the solar system, the heliosphere, and extrasolar planets, and galaxies, etc.

Institute for Space-Earth Environmental Research is at the forefront of world research in this field, and the results of our research become part of the common intellectual property that is shared by all people. Our most recent results have been used as teaching materials in educational settings, and making our findings widely known among the general public is an important role. This website includes a section where we report our most recent results from research and educational activities, as well as a section that explains some of the major concepts in this field in a way that is accessible for non-specialists and students. We have come to understand much about space and the Earth's environmental system, but as with much of natural science, learning one thing often reveals a more essential, difficult piece of the puzzle, and much more research will be needed before we have a complete picture.

We invite you to visit our site often, and hope this will lead to your growing interest in our research.