Shock Drift Acceleration of Ions in an Interplanetary Shock Observed by MMS

Abstract

An interplanetary (IP) shock wave was recorded crossing the Magnetospheric Multiscale (MMS) constellation on 2018 January 8. Plasma measurements upstream of the shock indicate efficient proton acceleration in the IP shock ramp: 2-7 keV protons are observed upstream for about three minutes (~8000 km) ahead of the IP shock ramp, outrunning the upstream waves. The differential energy flux (DEF) of 2-7 keV protons decays slowly with distance from the ramp towards the upstream region (dropping by about half within 8 Earth radii from the ramp) and is lessened by a factor of about four in the downstream compared to the ramp (within a distance comparable to the gyroradius of ~keV protons). Comparison with test-particle simulations has confirmed that the mechanism accelerating the solar wind protons and injecting them upstream is classical shock drift acceleration. This example of observed proton acceleration by a low-Mach, quasi-perpendicular shock may be applicable to astrophysical contexts, such as supernova remnants or the acceleration of cosmic rays.

arXiv comment19 pages, 5 figures. To be published in the Astrophysical Journal Letters

References in corpus (8)

• Simulations of Ion Acceleration at Non-relativistic Shocks. I. Acceleration Efficiency
• Simultaneous Acceleration of Protons and Electrons at Nonrelativistic Quasiparallel Collisionless Shocks
• The dynamic quasiperpendicular shock: Cluster discoveries
• Ion acceleration in non-relativistic astrophysical shocks
• Large parallel and perpendicular electric fields on electron spatial scales in the terrestrial bow shock
• Injection to rapid diffusive shock acceleration at perpendicular shocks in partially ionized plasmas
• Supernova explosions of massive stars and cosmic rays
• Different types of ion populations upstream of the 8 October 2013 interplanetary shock

Cited by in corpus (5)

• A database of MMS bow shock crossings compiled using machine learning
• Electrostatic solitary waves in the Earth's bow shock: nature, properties, lifetimes and origin
• Backstreaming ions at a high Mach number interplanetary shock: Solar Orbiter measurements during the nominal mission phase
• Mirror mode storms observed by Solar Orbiter
• Energy Repartition and Entropy Generation across the Earth's Bow Shock: MMS Observations