Wave emissions at half electron gyroharmonics in the equatorial plasmasphere region: CLUSTER observations and statistics
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Authors
El-Lemdani Mazouz, F.
Rauch, J.L.
Décréau, P.M.E.
Trotignon, J.G.
Vallières, X.
Darrouzet, F.
Canu, P.
Suraud, X.
Discipline
Physical sciences
Subject
Cyclotrons
Frequency bands
Geomagnetism
Harmonic analysis
Hot electrons
Magnetosphere
Rockets
Diffuse aurora
Electron cyclotron harmonic waves
Emission sites
Equatorial regions
Event studies
First harmonics
Generation mechanisms
Geomagnetic activities
Geomagnetic equators
Inner magnetospheres
Observation points
Pitch angles
Plasma pauses
Plasmasphere
Spectral characteristics
Spectral signatures
Statistical studies
Time series
Time variations
Wave characteristics
Wave emissions
Wave intensities
Electrons
Audience
Scientific
Date
2009Metadata
Show full item recordDescription
Intense (n + 1/2) fce emissions are a common phenomenon observed in the terrestrial inner magnetosphere. One of their interests is their possible effect in the pitch angle scattering of plasmasheet keV-electron, leading to diffuse auroras. In this paper, we present CLUSTER's point of view about this topic, in the equatorial region of the plasmasphere, via a statistical study using 3 years of data. Spectral characteristics of these waves, which represent an important clue concerning their generation mechanism, are obtained using WHISPER data near perigee. Details on the wave spectral signature are shown in an event study, in particular their splitting in fine frequency bands. The orbit configuration of the four spacecraft offers a complete sampling on all MLT sectors. A higher occurrence rate of the emissions in the dawn sector and their confinement to the geomagnetic equator, pointed out in previous studies, are confirmed and described with additional details. The proximity of emission sites, both to the plasmapause layer and to the geomagnetic equator surface, seems to be of great importance in the behaviour of the (n + 1/2) fce wave characteristics. Our study indicates for the first time, that both the intensity of (n + 1/2) fce emissions, and the number of harmonic bands they cover, are increasing as the observation point is located further away outside from the plasmapause layer. Moreover, a study of the wave intensity in the first harmonic band (near 3/2 fce) shows higher amplitude for these emissions than previous published values, these emissions can play a role in the scattering of hot electrons. Finally, geomagnetic activity influence, studied via time series of the Dst index preceding observations, indicates that (n + 1/2) fce emission events are observed at CLUSTER position under moderate geomagnetic activity conditions, no specific Dst time variation being required. © 2008 COSPAR.
Citation
El-Lemdani Mazouz, F.; Rauch, J.L.; Décréau, P.M.E.; Trotignon, J.G.; Vallières, X.; Darrouzet, F.; Canu, P.; Suraud, X. (2009). Wave emissions at half electron gyroharmonics in the equatorial plasmasphere region: CLUSTER observations and statistics. , Advances in Space Research, Vol. 43, Issue 2, 253-264, DOI: 10.1016/j.asr.2008.06.007.Identifiers
scopus: 2-s2.0-58149234041
Type
Article
Peer-Review
Yes
Language
eng