Solar-Terrestrial Environment Laboratory, Nagoya University

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Director's Message

Director : Shinobu Machida
Solar-Terrestrial Environment Laboratory

The Solar-Terrestrial Environment Laboratory at Nagoya University researches the structure and dynamic fluctuations of the sun, earth, and cosmic space between them (a generic term for which is solar-terrestrial environment, or solar-terrestrial system). The Laboratory, working in fields extending over both space science and geoscience, promotes nationwide collaborative studies as an institute under Japan's inter-university collaborative system.

What kind of region is the solar-terrestrial system? Together with enormous amounts of visible light and other electromagnetic waves, the sun also releases gas (plasma) streams of electrically-charged particles. This gas stream is called the solar wind. The earth, meanwhile, is known to be a huge magnet, and the magnetic field that stretches across the space surrounding the earth prevents the solar wind from approaching the earth. The earth is thus surrounded by a vast, invisible region called the magnetosphere. 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 the earth's surface. These spaces around the earth are called geospace.

Conflict between this matter and energy from the sun and the earth's magnetic field gives rise to various interesting phenomena in geospace. The auroras that color the polar regions are one of them. The sun, however, which is the source of all our energy, fluctuates and changes on many time scales. The flares that occur on the sun's surface are short-term, explosive phenomena that cause geomagnetic storms. It is well known that high-energy particles produced during these storms have negative effects on communications and other artificial satellites. The study of these phenomena is also called space weather research. The sun also fluctuates on much longer time scales, including its cycle of about 11 years. A relation has been indicated between these fluctuations and climate fluctuations, but the mechanisms for this are unknown. It will be difficult to uncover these mechanisms with research focused only on the sun and atmosphere near the earth's surface; studies will need to include higher regions of the atmosphere.

The mission of the Solar-Terrestrial Environment Laboratory is to understand the entire solar-terrestrial domain from the sun to the earth as a single system (complex system), and to understand the basic physical and chemical elementary processes that occur in this system on various time and space scales. An example of this is the electromagnetic field structure surrounding the earth, i.e., the magnetosphere. This is a universal structure that is seen from planets such as earth and Jupiter to the heliosphere and galactic scale. The solar-terrestrial system is the closest of these structures to us, and the only region to which we can send up exploration spacecraft for close in-situ investigation. Studying this region and understanding its structure and fluctuations will contribute to the development of space and geoscience. The interests of the Laboratory, however, do not stop with the sun, earth, and cosmic space between them. Our area of research extends to the other planets and all parts of the heliosphere, as well as to planets outside this system, galactic cosmic rays, and other phenomena.

The Solar-Terrestrial Environment Laboratory is at the forefront of world research in its 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 known widely among the general public is an important role. This web site includes a "Research Divisions" section where we report our most recent results from research and educational activities, plus a "Public Outreach" section that explains some of the major concepts in this field in an understandable way for non-specialists and students. We have come to understand much about the solar-terrestrial system, but as with much of natural science, learning one thing often reveals a more essential, difficult part 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.

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