Observations of discrete magnetosonic waves off the magnetic equator

Zhima, Zeren; Chen, Lunjin; Fu, Huishan; Cao, Jinbin; Horne, Richard B. ORCID:; Reeves, Geoff. 2015 Observations of discrete magnetosonic waves off the magnetic equator. Geophysical Research Letters, 42 (22). 9694-9701.

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Fast mode magnetosonic waves are typically confined close to the magnetic equator and exhibit harmonic structures at multiples of the local, equatorial proton cyclotron frequency. We report observations of magnetosonic waves well off the equator at geomagnetic latitudes from −16.5°to −17.9° and L shell ~2.7–4.6. The observed waves exhibit discrete spectral structures with multiple frequency spacings. The predominant frequency spacings are ~6 and 9 Hz, neither of which is equal to the local proton cyclotron frequency. Backward ray tracing simulations show that the feature of multiple frequency spacings is caused by propagation from two spatially narrow equatorial source regions located at L ≈ 4.2 and 3.7. The equatorial proton cyclotron frequencies at those two locations match the two observed frequency spacings. Our analysis provides the first observations of the harmonic nature of magnetosonic waves well away from the equatorial region and suggests that the propagation from multiple equatorial sources contributes to these off-equatorial magnetosonic emissions with varying frequency spacings.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > BAS Programmes 2015 > Space Weather and Atmosphere
ISSN: 0094-8276
Additional Keywords: magnetsonic wave, off-equatorial region, discrete structure
Date made live: 15 Feb 2016 09:58 +0 (UTC)

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