Multiple bidirectional EMIC waves observed by Cluster at middle magnetic latitudes in the dayside magnetosphere
Abstract
[1] It is well accepted that the propagation of electromagnetic ion cyclotron (EMIC) waves are bidirectional near their source regions and unidirectional when away from these regions. The generally believed source region for EMIC waves is around the magnetic equatorial plane. Here we describe a series of EMIC waves in the Pc1 (0.2–5 Hz) frequency band above the local He+ cyclotron frequency observed in situ by all four Cluster spacecraft on 9 April 2005 at midmagnetic latitudes (MLAT = ~33°–49°) with L = 10.7–11.5 on the dayside (MLT = 10.3–10.4). A Poynting vector spectrum shows that the wave packets consist of multiple groups of packets propagating bidirectionally, rather than unidirectionally, away from the equator, while the local plasma conditions indicate that the spacecraft are entering into a region sufficient for local wave excitation. One possible interpretation is that, while part of the observed waves are inside their source region, the others are either close enough to the source region, or mixed with the wave packets from multiple source regions at different latitudes.
Department
Physics
Publication Date
10-1-2013
Journal Title
Journal of Geophysical Research: Space Physics
Publisher
American Geophysical Union
Digital Object Identifier (DOI)
10.1002/jgra.50600
Document Type
Article
Recommended Citation
Allen, R. C., J. -C. Zhang, L. M. Kistler, H. E. Spence, R. -L. Lin, M. W. Dunlop, and M. André (2013),Multiple bidirectional EMIC waves observed by Cluster at middle magnetic latitudes in the dayside magnetosphere, J. Geophys. Res. Space Physics, 118, 6266–6278, doi:10.1002/jgra.50600.
Rights
©2013. American Geophysical Union. All Rights Reserved.