Open AccessMedium‐latitude sources of plasmaspheric nonthermal continuum radiations observed close to harmonics of the electron gyrofrequency
Author(s) -
Grimald S.,
Décréau P. M. E.,
Canu P.,
Rochel A.,
Vallières X.
Publication year - 2008
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008ja013290
Subject(s) - plasmasphere , physics , magnetosphere , van allen radiation belt , equator , radiation , substorm , geophysics , electron , latitude , electromagnetic radiation , whistler , computational physics , plasma , optics , astronomy , nuclear physics
Nonthermal continuum (NTC) radiation is, with auroral kilometric radiation (AKR), one of the two electromagnetic emissions generated within the Earth's magnetosphere and radiated into space. It is generally believed that NTC is emitted in the plasmapause density gradient after conversion of intense electrostatic waves, present near the magnetic equator, into electromagnetic waves. In this paper, we present a specific type of NTC event, of infrequent occurrence, displaying a finger‐like pattern not yet reported: banded emissions peaking at exact multiples of a common frequency, df, which decrease inbound toward the plasmapause boundary layer (PPBL). Analysis is presented that indicates that the corresponding sources are nearby sites of the PPBL where the local electron gyrofrequency f ce equals df. The sources are radiating beams of limited cone angle size. The NTC sources for this event are shown to be located at about 20° magnetic latitude. This illustrates that the PPBL is active in radiating NTC waves not only near the magnetic equator but also up to the medium‐latitude range.