Emissions with a quasiperiodic modulation of the wave intensity

0465198 - ÚFA 2017 ZA eng A - Abstrakt
Němec, F. - Pickett, J. S. - Hospodarsky, G. - Santolík, Ondřej - Bezděková, B. - Hayosh, Mykhaylo - Parrot, M. - Kurth, W. S. - Kletzing, C.
Emissions with a quasiperiodic modulation of the wave intensity.
7th VERSIM-RBS: Abstracts. Hermanus: SANSA, 2016. s. 39.
[VERSIM and RadBelt 2016 /7./. 19.09.2016-24.09.2016, Hermanus]
Institucionální podpora: RVO:68378289
Klíčová slova: whistler mode electromagnetic waves * magnetosphere
Kód oboru RIV: BL - Fyzika plazmatu a výboje v plynech
https://events.sansa.org.za/images/2016/VERSIM/abstracts/VERSIM_2016_abstracts.pdf

Whistler mode electromagnetic waves observed by spacecraft and ground-based
instruments in the inner magnetosphere sometimes exhibit a nearly periodic modulation
of the wave intensity. The modulation periods are typically on the order of minutes.
Although the origin of these events is still unclear, it appears that their generation might
be related to an ULF wave which periodically modulates resonant conditions in the
generation region. The QP modulation of the wave intensity was reported both for waves
propagating quasi-parallel to the ambient magnetic field at frequencies between about
0.5 and 4 kHz, and for waves propagating nearly perpendicular to the ambient magnetic
field at frequencies below the lower hybrid frequency ("equatorial noise"). We use
simultaneous observations of the same events by multiple spacecraft (Cluster, Van Allen
Probes, THEMIS, DEMETER) to demonstrate that although the quasiperiodic modulation is
observed over a huge spatial region, individual spacecraft do not see the intensity
maxima at exactly the same times. Moreover, the modulation period of the emissions
observed on the duskside seems to be about twice larger than the modulation period of
the emissions observed at the same time on the dawnside. We present a qualitative
explanation of these phenomena. Finally, we look for events with the quasiperiodic
modulation of the wave intensity observed simultaneously for waves propagating
perpendicular to the ambient magnetic field (lower frequencies) and quasi-parallel to the
ambient magnetic field (higher frequencies).
Trvalý link: http://hdl.handle.net/11104/0263858