Magnetosheath plasma stability and ULF wave occurrence as a function of location in the magnetosheath and upstream bow shock parameters

We present the results of a statistical study of the distribution of mirror and Alfvén‐ion cyclotron (AIC) waves in the magnetosheath together with plasma parameters important for the stability of ULF waves, specifically ion temperature anisotropy and ion beta. Magnetosheath crossings registered by...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2015-04, Vol.120 (4), p.2838-2850
Main Authors: Soucek, Jan, Escoubet, C. Philippe, Grison, Benjamin
Format: Article
Language:English
Subjects:
Anisotropy
Cluster spacecraft
Cyclotrons
Instability
Ion cyclotron waves
Ion temperature
Ions
Magnetic properties
Magnetopause
Magnetosheath
mirror modes
Parameter identification
Plasma
plasma waves
Plasmas (physics)
Position (location)
Spacecraft
Spatial distribution
Stability
ULF waves
Upstream
Waves
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Summary:We present the results of a statistical study of the distribution of mirror and Alfvén‐ion cyclotron (AIC) waves in the magnetosheath together with plasma parameters important for the stability of ULF waves, specifically ion temperature anisotropy and ion beta. Magnetosheath crossings registered by Cluster spacecraft over the course of 2 years served as a basis for the statistics. For each observation we used bow shock, magnetopause, and magnetosheath flow models to identify the relative position of the spacecraft with respect to magnetosheath boundaries and local properties of the upstream shock crossing. A strong dependence of both plasma parameters and mirror/AIC wave occurrence on upstream ΘBn and MA is identified. We analyzed a joint dependence of the same parameters on ΘBn and fractional distance between shock and magnetopause, zenith angle, and length of the flow line. Finally, the occurrence of mirror and AIC modes was compared against the respective instability thresholds. We noted that AIC waves occurred nearly exclusively under mirror stable conditions. This is interpreted in terms of different characters of nonlinear saturation of the two modes. Key Points Spatial distribution of mirror and AIC waves in the magnetosheath Dependence of magnetosheath occurrence mirror and AIC waves on shock parameters Competition of mirror and ion cyclotron instabilities in the magnetosheath
ISSN:2169-9380
2169-9402
DOI:10.1002/2015JA021087