A rectified response of daytime radio wave absorption to southward and northward excursions during northward interplanetary magnetic field: A case study

概要

論文の詳細を見る
An example of daytime radio wave absorption at 30 MHz observed by the Imaging Riometer at Ny-Alesund (75.5°MLAT) is presented. Its characteristic feature is a type of slowly varying absorption (SVA) in the morning-prenoon sector during the northward interplanetary magnetic field (IMF). Furthermore a unique feature is that fluctuating variation superimposed upon the SVA showed a "rectified response" to alternate northward/southward IMF excursions, in particular, a pronounced response in the southern (low-latitude) part in the riometer field of view. From simultaneous F-region backscatter echoes observed by Finnish HF radar and electron fluxes by the DMSP-satellite it is concluded that the daytime absorption is likely caused by precipitation of eastward drifting auroral electrons generated by substorms in the midnight region. The rectified response is interpreted as follows: The boundary of the open-closed field line moves to the poleward/equatorward during the northward/southward IMF excursions, respectively, due to the magnetic reconnections at the low-latitude boundary layer (LLBL)/cleft, and associated field-aligned currents (FAC) are intensified during the both IMF excursions. The precipitation of auroral electrons carried by upward FAC produces the absorption in the low-latitude (〜75°MLAT) of Ny-Alesund.
国立極地研究所の論文