VLF Phase Anomalies Associated with Substorm

概要

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The substorm-associated phase anomalies are observed on the transauroral VLF signals, OMEGA ALDRA (13.6kHz), GBR (16.0kHz), OMEGA N. DAKOTA (13.6kHz) and NLK (18.6kHz) received at Inubo, Japan. The phase anomalies are caused by energetic electrons injected from the magnetotail and/or from the outer radiation belt. The energy of the precipitating electrons is estimated from the decrease in the reflection height for the VLF wave as >150keV. The precipitation of such high-energy electrons is observed at all local times, but is predominant at 0800,1630 and 2230LT. The nighttime precipitation commences almost simultaneously with the onset of the nightside magnetic bay, while the dayside precipitation is delayed by 10-100min. It is suggested that the magnetotail-originated electrons with energy >150keV are injected directly into the nightside auroral region and some of the injected electrons drift eastward and then precipitate into the morning and afternoon sectors. The drift speed deduced from the time delay of onset is 5°/min on the average.
国立極地研究所の論文