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Titel |
Multi-spacecraft observations of quasiperiodic emissions |
VerfasserIn |
Frantisek Nemec, Jolene S. Pickett, George Hospodarsky, Ondrej Santolik, Barbora Bezdekova, Mykhaylo Hayosh, Michel Parrot, William Kurth, Craig Kletzing |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250123388
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Publikation (Nr.) |
EGU/EGU2016-2629.pdf |
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Zusammenfassung |
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. |
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