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Wave form analysis of the continuum radiation observed by GEOTAIL
Author(s) -
Nagano I.,
Yagitani S.,
Kojima H.,
Kakehi Y.,
Shiozaki T.,
Matsumoto H.,
Hashimoto K.,
Okada T.,
Kokubun S.,
Yamamoto T.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl02108
Subject(s) - magnetosheath , physics , plasma sheet , cyclotron , earth's magnetic field , van allen probes , atomic physics , plasma , astrophysics , magnetosphere , incoherent scatter , computational physics , geophysics , magnetic field , van allen radiation belt , magnetopause , ionosphere , quantum mechanics
The Plasma Wave Instrument (PWI) onboard the GEOTAIL spacecraft has frequently observed Continuum Radiation (CR) throughout the geomagnetic tail region, including the Magnetosheath (MS), the Lobe, the Plasma Sheet Boundary Layer (PSBL), and the Plasma Sheet (PS). In addition to the usual Escaping CR (from 10 kHz to 30 kHz) and the Trapped CR (from about 5 kHz to 10 kHz), CR with the frequency structure extending down to 1 kHz (the local plasma frequency) has often been observed in the Lobe region. Waveforms of the electric field in the frequency range less than 4 kHz, which is acquired by Wave Form Capture in the PWI, are used to analyze in detail the frequency‐time structure of such low‐frequency CR near the lower cutoff. Two distinct cutoff frequencies modulated by the antenna spinning indicates that the CR in the Lobe region propagates both in the O mode and in the X mode almost perpendicular to the earthward geomagnetic field line. The CR in the Lobe region, especially in the vicinity of the PSBL, is sometimes accompanied by intense electrostatic electron‐cyclotron‐harmonic (ECH) ( n + 1/2) waves. These suggest that such a low‐frequency CR in the distant tail region is most likely to be generated from the ECH waves near the PSBL, and trapped within the Lobe between the PSBL and the MS.