[P-EM09] Study of coupling processes in solar-terrestrial system

[PEM09-P09] Ionospheric weather in the dayside polar cap region

*Hitoshi Fujiwara¹、Satonori Nozawa²、Yasunobu Ogawa³、Ryuho Kataoka³、Yasunobu Miyoshi⁴、Hidekatsu Jin⁵、Hiroyuki Shinagawa⁵、Huixin Liu⁴ (1.Faculty of Science and Technology, Seikei University、2.Institute for Space-Earth Environment Research, Nagoya University、3.National Institute of Polar Research、4.Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University、5.National Institute of Information and Communications Technology)

キーワード：ionosphere, thermosphere, EISCAT, GCM, simulation

Using European incoherent scatter radar (EISCAT) and EISCAT Svalbard radar (ESR),
we have made simultaneous obserbations of the dayside polar cap ionosphere at
Longyearbyen and Tromso. Five year observation data show significant disturbances
in the polar cap region northward the ESR site even during geomagnetically quiet
periods. This suggests that the energy input from the magnetosphere would play
a fundamental role for dynamics and energetics in the region all the time. In
addition, some researchers suggest effects from the lower atmosphere on the
thermospheric variations in the polar region. In order to understand variations
of the polar ionosphere/thermosphere from hour to hour, we should understand
energy flows from the above (magnetosphere) and below (lower atmosphere).
Numerical simulations with a GCM are also essential to do so. In particular,
GCM simulations would reveal physical and chemical processes/mechanisms
to produce the thermoshperic variations while the thermospheric observations
are very few in the dayside.
In the present study, we overview the EISCAT and ESR observations during 2011-2016.
The recent progress of our understandings from comprehensive observations and
GCM simulations are also shown.