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Quasiperpendicular high Mach number Shocks
Journal article   Open access   Peer reviewed

Quasiperpendicular high Mach number Shocks

Ah Sulaiman, A. Masters, Mk Dougherty, D. Burgess, M. Fujimoto and Gb Hospodarsky
Physical Review Letters, Vol.115(12), 125001
09/18/2015
DOI: 10.1103/PhysRevLett.115.125001
PMID: 26430997
url
https://doi.org/10.1103/PhysRevLett.115.125001View
Published (Version of record) Open Access

Abstract

Shock waves exist throughout the universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasi-perpendicular shocks across two orders of magnitude in Alfven Mach number (MA) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ~0.3 {\tau}c, where {\tau}c is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.
 Astrophysics Physical Sciences Physics 02 Physical Sciences Earth General Physics High Energy Astrophysical Phenomena Multidisciplinary Planetary Astrophysics Science & Technology Space Physics

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