Variabilities and coupling processes in the middle
and upper atmosphere in the polar regions
Detection of signals of
over the Antarctic
Application of novel radioand optical remote-sensing techniques
The mesopause around 90 km above the ground is the coldest region over the globe, where the minimum temperature reaches - 150ºC in the polar region. Although the altitude of ordinary clouds is not more than 10 km, even the very little water vapor existing in the mesopause region can be frozen under such extremely cold conditions in the summer polar region, and PMC (polar mesospheric clouds) can be observed. The frequency of such PMCs is reported to be increasing in the current century, and its relationship to global warming is attracting special interest. The polar middle and upper atmosphere is highly variable and sensitive to atmospheric waves from below as well as substantial/ particle input and solar activities from space. Therefore, precise observation of this region will give us clues about how our global atmosphere will change in the future. We are analyzing variations of this region through observations made with state-of-the-art radio and optical instruments that we have originally developed.
Interhemispheric conjugacies of the polar ionospheric and magnetospheric responses to solar wind energy input
Mystery of auroras
in both polar regions
Toward a better understanding of auroras
At the time of aurora phenomena, energetic electrons and protons produced in the night-side magnetosphere precipitate into both polar regions along magnetic field lines and illuminate the polar atmosphere. Therefore, auroras observed at both ends of a magnetic field line are expected to be symmetric. This pair of auroras is called "Conjugate aurora"and the ends,"geomagnetic conjugate points." However, conjugate auroras are actually not so symmetric. Related phenomena such as electromagnetic waves, ionospheric electric fields and currents also show considerable differences at the conjugate point, although general features are similar. We can obtain valuable information from these differences, and detailed analysis will lead to a better understanding of the auroral processes. We are seeking to obtain a comprehensive view of auroral conjugacy for a wide range of latitudes and longitudes by setting up observation networks in both polar regions, centered at Syowa Station and Iceland, to be operated with the SuperDARN radar and unmanned observation network in Antarctica.
International collaborative studies on the arctic upper and middle atmosphere based on the EISCAT radar and ground-based observations
Challenging key questions on upper/middle
using the EISCAT radars
Sounding high into the Earth's atmosphere
The National Institute of Polar Research joined the European Incoherent Scatter (EISCAT) Scientific Association in 1996 as a representative of the user community in Japan to promote international collaborative studies with powerful incoherent scatter radars in northern Scandinavia and Svalbard. The EISCAT radars make it possible to explore the Earth's upper atmosphere with precision from 60 km up to 1,000 km in altitude. The main purpose of this study is to clarify physical processes causing variation of the upper atmosphere with use of meteor radars and optical imagers in addition to EISCAT radars. Specific interest is focused on entry/dissipation processes and responses caused by solar energy input to the magnetosphere/ionosphere/thermosphere and middle atmosphere in the current several years (solar maximum). We have been actively promoting the EISCAT_3D project, which will upgrade the current EISCAT mainland radars into a next-generation radar system with several score times higher capability in order to study the vertical coupling and three- dimensional meso/micro-scale structures of the upper atmosphere.