Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsm31a2074t&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SM31A-2074
Physics
[2409] Ionosphere / Current Systems, [2431] Ionosphere / Ionosphere/Magnetosphere Interactions
Scientific paper
It is well known that the nonuniform electrical conductivity in the ionosphere plays an important role in the magnetosphere-ionosphere (M-I) coupling system. The ionospheric convection pattern is affected by the spatial distribution of the ionospheric conductivity, for example, the dawn-dusk asymmetry of the ionospheric convection in the polar cap is believed to be partly attributed to the day-night ionospheric conductivity gradient. In particular, the regions around the dawn and dusk terminators are suitable to investigate an active role of the nonuniform ionosphere in the M-I coupling system, because there is a sharp conductivity gradient there. So far, there have been several reports of the sunrise effect on ULF pulsations. ULF pulsations observed at low latitudes show a drastic change in their polarization and phase across the dawn terminator. Tanaka et al. (JGR, 112, A11308, 2007) reported that while the North-South component of the low-latitude Pc 3 pulsations remains largely unchanged with the passing of dawn, the East-West component undergoes a phase shift of about 180 degrees. This horizontal phase structure is well explained by the response of a nonuniform ionosphere around dawn to incident Alfven waves, where the secondary electric field caused by charge accumulation at the dawn terminator deforms the ionospheric current pattern. In the presentation, we review the sunrise/sunset effect on ionospheric current pattern observed by the ground-based magnetometer network. In addition, we survey the sunrise/sunset effect on the ionospheric convection by analyzing data from the SuperDARN Syowa radar and show the preliminary result.
Hori Toshihiro
Sato Naoko
Tanaka Yasuhiro
Yukimatu Akira Sessai
Yumoto Kiyo
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