Optical/particle/magnetic/SuperDARN signature associated with the negative SI

Abstract

A negative SI (Sudden Impulse) occurred on 3 August 1997. This event was examined in detail using the data obtained by all-sky TV cameras at Zhongshan in Antarctica, SuperDARN (Super Dual Auroral Radar Network) HF (High Frequency) radars over the northern and southern polar regions, magnetometer networks at IMAGE (Imager for Magnetopause-to-Aurora Global Exploration), Greenland and CANOPUS (Canadian Auroral Network for the Origin of Plasma in Earth Neighborhood Program United Study) by referring in situ satellite data located in the solar wind (WIND (Weather Information Network and Display)), magnetosheath (GEOTAIL), magnetosphere (LANL (Los Alamos National Laboratory)-1, GOES (Geostationary Operational Environmental Satellite)-8) and ionosphere (DMSP (Defense Meteorological Satellite Program)-F13, F-14). The following interesting characteristics are found: (1) sudden enhancement of an east-west-aligned discrete aurora occurred associated with the SI(-); (2) Quasi-periodic (approximately 10 minutes) variations were found in optical intensity, HF radar power and magnetic variations; (3) upward field-aligned current and inverted 'V' electron precipitation corresponded to the region of the optical aurora; (4) SuperDARN data showed that the convection reversal boundary located at approximately 80 MLAT (Magnetic Latitude) in the 16 - 18 MLT (Magnetic Local Time) sector at the SI(-) onset and the boundary moved poleward after the SI(-); and (5) spatial and temporal variations of the convection boundary were consistent with the magnetic variations at IMAGE and Greenland network. These signatures suggest that the luminosity pulsations triggered by the solar wind negative impulse are amplified not via processes of instability in the equatorial plane filling the loss cone but via dynamic coupling between the solar wind, magnetosphere, and ionosphere.

1997年8月3日にネガティブSI(-)(サドン・インパルス)が発生したが、この現象を南極の中山基地に設置された全天空TVカメラ、北極から南極までの範囲を網羅されたSuperDARN(Super Dual Auroral Radar Network)HF(高周波)レーダ、IMAGE(Imager for Magnetopause-to-Aurora Global Exploration)、グリーンランドおよびCANOPUS(Canadian Auroral Network for the Origin of Plasma in Earth Neighborhood Program United Study)の磁力計ネットワークを用い、太陽風中にあるWIND(Weather Information Network and Display)衛星、マグネトシース中のGEOTAIL衛星、磁気圏中のLANL(Los Alamos National Laboratory)-1、GOES(静止実用環境観測衛星)-8衛星および電離圏中のDMSP(米国空軍極軌道気象衛星)-F13、F14衛星などのデータを参照して検証した。それにより次のような結果を得た。(1)SI(-)に伴ってeast-west-aligned discrete auroraが急激に強くなった。(2)光学的濃度、HFレーダ出力、および磁気変動において準周期的(?10分)変動が見られた。(3)Upward field-aligned currentおよびinverted 'V'電子降下は可視オーロラ域に対応した。(4)SuperDARNデータによると対流逆転境界はインパルス発生時16?18MLT(地磁気地方時)セクタの?80MLAT(磁気緯度)の位置にあり、インパルスの終了後極方向へ移動した。(5)対流境界の空間および時間変動はIMAGEおよびグリーンランドネットワークの磁気変動と一致した。これらの特性から、太陽風のネガティブインパルスによる輝度のゆらぎは赤道面での損失円錐を満たす不安定なプロセスによるのではなく、太陽風、磁気圏および電離圏のダイナミックな結合によることを示唆している。