Multi-spacecraft observations of quasiperiodic emissions

0459790 - ÚFA 2017 DE eng A - Abstrakt
Němec, F. - Pickett, J. S. - Hospodarsky, G. - Santolík, Ondřej - Bezděková, B. - Hayosh, Mykhaylo - Parrot, M. - Kurth, W. - Kletzing, C.
Multi-spacecraft observations of quasiperiodic emissions.
Geophysical Research Abstracts. Göttingen: European Geosciences Union, 2016. EGU 2016-2629-1. ISSN 1607-7962.
[EGU General Assembly 2016. 17.04.2016-22.04.2016, Vienna]
Institucionální podpora: RVO:68378289
Klíčová slova: QP emissions * inner magnetosphere
Kód oboru RIV: DG - Vědy o atmosféře, meteorologie
http://meetingorganizer.copernicus.org/EGU2016/EGU2016-2629-1.pdf

Whistler mode electromagnetic waves observed in the inner magnetosphere at frequencies of a few kilohertz sometimes
exhibit a nearly periodic modulation of the wave intensity. The modulation periods may range from several
tens of seconds up to a few minutes, and such emissions are usually called quasiperiodic (QP) emissions. The origin
of these events is still unclear, but it seems that their generation might be related to compressional ULF magnetic
field pulsations which periodically modulate resonance conditions in the source region. From an observational
point of view, single-point measurements are quite insufficient, as they do not allow us to distinguish between
spatial and temporal variations of the emissions. Multipoint observations of these events are, on the other hand,
rather rare. We present several QP wave events observed simultaneously by several different spacecraft (Cluster,
Van Allen Probes, THEMIS, DEMETER). We demonstrate that although the quasiperiodic modulation is observed
over a huge spatial region, individual spacecraft do not see the QP elements at exactly the same times. Moreover,
when an event is observed simultaneously on the dawnside and on the duskside, the modulation period observed on
the duskside is about twice larger than the modulation period observed on the dawnside. We present a qualitative
explanation of these phenomena.
Trvalý link: http://hdl.handle.net/11104/0259952