Quasiperpendicular high Mach number shocks
File(s)
Published version
Author(s)
Type
Journal Article
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 quasiperpendicular shocks across 2 orders of magnitude in Alfvén 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 time scale of ∼0.3τc, where τc 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.
Date Issued
2015-09-18
Date Acceptance
2015-08-20
Citation
Physical Review Letters, 2015, 115
ISSN
1079-7114
Publisher
American Physical Society
Journal / Book Title
Physical Review Letters
Volume
115
Copyright Statement
© 2015 American Physical Society
Sponsor
Science and Technology Facilities Council
Science and Technology Facilities Council (STFC)
The Royal Society
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council [2006-2012]
Grant Number
ST/N002776/1
ST/K001051/1
RP140004
ST/N000692/1
ST/K001051/1
Subjects
Science & Technology
Physical Sciences
Physics, Multidisciplinary
Physics
BOW SHOCK
COLLISIONLESS SHOCK
SIMULATIONS
NONSTATIONARITY
ACCELERATION
REFORMATION
OVERSHOOTS
BEHAVIOR
WAVES
IONS
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
General Physics
Publication Status
Published
Article Number
ARTN 125001
Date Publish Online
2015-09-16