Equatorial noise emissions with a quasi-periodic modulation observed by DEMETER at harmonics of the O+ ion gyrofrequency

0474186 - ÚFA 2018 DE eng A - Abstrakt
Parrot, M. - Němec, F. - Santolík, Ondřej - Cornilleau-Wehrlin, N.
Equatorial noise emissions with a quasi-periodic modulation observed by DEMETER at harmonics of the O+ ion gyrofrequency.
Geophysical Research Abstracts. Göttingen: European Geosciences Union, 2017. EGU2017-2357. ISSN 1607-7962.
[EGU General Assembly 2017. 23.04.2017-28.04.2017, Vienna]
Institucionální podpora: RVO:68378289
Klíčová slova: ionospheric equatorial noise * DEMETER spacecraft * fast magnetosonic waves * whistler mode
Kód oboru RIV: BL - Fyzika plazmatu a výboje v plynech
http://meetingorganizer.copernicus.org/EGU2017/EGU2017-2357.pdf

The analysis of ionospheric equatorial noise (EN) with a quasi-periodic (QP) modulation observed by the DEMETER
spacecraft is presented. These EN emissions also called whistler mode or fast magnetosonic waves play an
important role in acceleration of radiation belt electrons. A statistical analysis with 103 events shows that they occur
just after intense magnetic storms. Usually, they are generated by unstable proton ring distribution close to the
magnetic equator at harmonics of the proton gyrofrequency in the inner magnetosphere (2 < L < 8). But at lower L
values down in the ionosphere three events have been analyzed and it appears that the EN waves are at harmonics
of - or very close to - a O+ ion gyrofrequency which can be found close or slightly above the satellite. The wave
propagation analysis indicates that these emissions are coming from an area above the satellite. Concerning one
event, the EN emissions are observed on several consecutive orbits and there is a temporal coincidence with observations
performed by the CLUSTER satellites at higher altitudes in the magnetosphere. EN emissions at lower
frequencies have been also observed by the CLUSTER satellites in the same longitudinal sector as DEMETER but
at ∼5 RE. The analysis of the STAFF data onboard C1 reveals that the magnetic field spectrogram has peaks close
to harmonics of the local proton gyrofrequency as usually reported. It is shown that the DEMETER and CLUSTER
EN waves have a similar QP modulation but with slightly different period and frequency
Trvalý link: http://hdl.handle.net/11104/0271294