Equatorial noise emissions with quasiperiodic modulation: Investigating the source region

0491826 - ÚFA 2019 DE eng A - Abstrakt
Němec, F. - Santolík, Ondřej - Tomori, Alexander - Hospodarsky, G. B. - Pickett, J. S. - Kurth, W. S. - Kletzing, C.
Equatorial noise emissions with quasiperiodic modulation: Investigating the source region.
Geophysical Research Abstracts. Vol. 20. Göttingen: European Geosciences Union, 2018. EGU2018-4367-1. E-ISSN 1607-7962.
[EGU General Assembly 2018. 08.04.2018-13.04.2018, Vienna]
Institucionální podpora: RVO:68378289
Klíčová slova: equatorial noise * magnetosonic waves * quasiperiodic modulation * inner magnetosphere * Cluster spacecraft * Van Allen Probes spacecraft
Obor OECD: Fluids and plasma physics (including surface physics)
https://meetingorganizer.copernicus.org/EGU2018/EGU2018-4769.pdf

Equatorial noise emissions are electromagnetic waves observed routinely in the equatorial region of the inner
magnetosphere at frequencies below the lower hybrid frequency. Although they were typically considered to
be continuous in time, some of them exhibit a clear quasiperiodic modulation of the wave intensity, being
effectively composed of individual quasiperiodic elements. The emissions are generated by unstable ring-like
proton distribution functions, resulting in their fine harmonic structure which corresponds to the proton cyclotron
frequency in the source region. Employing a reasonable magnetic field model, the evaluation of the observed
harmonic structure can be thus used to determine the source radial distance. Moreover, the events for which the
spacecraft passes directly through the source region can be distinguished by the fine harmonic structure following
the locally evaluated proton cyclotron frequency. We use the data measured by the Cluster and Van Allen Probes
spacecraft to identify such time intervals, and we use the in-situ measured magnetic field and plasma parameters
to calculate the wave growth. This allows us to reveal a possible origin of the quasiperiodic modulation of the
wave intensity, and to discuss differences between time-continuous equatorial noise and equatorial noise with a
quasiperiodic modulation.
Trvalý link: http://hdl.handle.net/11104/0285442