Pope, S.A. orcid.org/0000-0001-8130-4222 (2020) A survey of Venus shock crossings dominated by kinematic relaxation. Journal of Geophysical Research: Space Physics, 125 (11).
Abstract
Collisionless shocks are one of the most effective particle accelerators in the known universe. Even low Mach number shocks could have a significant role in particle heating and acceleration. Theory suggests that kinematic collisionless relaxation, the process whereby a downstream nongyroptopic ion population becomes thermalized through collisionless gyrophase mixing, is the dominant energy redistribution mechanism in quasi‐perpendicular, low Mach number, and low β shocks. However, there have only been a limited number of observations of these shocks using in situ measurements at Venus, Earth and in interplanetary space. This paper presents the results of the first detailed study using in situ measurements, of the effect of fundamental parameters on the formation of these shocks. All low Mach number shocks occurring during the magnetic cloud phase of an interplanetary coronal mass ejection are identified in Venus Express magnetic field data over the duration of the mission. From the 92 shock crossings identified, 38 show clear evidence of kinematic relaxation. It is shown that kinematic relaxation is dominant at Venus when the angle between the local shock normal and upstream magnetic field is greater 50° and the Alfvén Mach number is less than 1.4. These shocks are also observed across a range of solar‐zenith‐angles indicating that it is likely that any location on the Venus bow shock could form such a structure. Venus Express plasma measurements are used to verify the parameters estimated from the magnetic field and indicate the importance of heavy ions, including potential pickup O+.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Automatic Control and Systems Engineering (Sheffield) |
Funding Information: | Funder Grant number Science and Technology Facilities Council ST/R000697/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 11 Dec 2020 07:33 |
Last Modified: | 11 Dec 2020 07:33 |
Status: | Published |
Publisher: | American Geophysical Union (AGU) |
Refereed: | Yes |
Identification Number: | 10.1029/2020ja028256 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:168789 |