Magnetosheath plasma stability and ULF wave occurrence as a function of location in the magnetosheath and upstream bow shock parameters. Issue 4 (24th April 2015)

• Record Type: Journal Article
• Authors: Soucek, Jan; Escoubet, C. Philippe; Grison, Benjamin
• Is Part Of: Journal of geophysical research. Volume 120:Issue 4(2015:Apr.)
• Page Start: 2838
• Page End: 2850
• Publication Date: 2015-04-24
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021087
• Languages: English
• ISSNs: 2169-9380

Abstract

<abstract abstract-type="main" id="jgra51743-abs-0001"> <title>Abstract</title> <p>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 Θ_Bn and <italic>M</italic>_{<italic>A</italic>} is identified. We analyzed a joint dependence of the same parameters on Θ_Bn 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.</p> </abstract>