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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., Comment: 19 pages, 5 figures. To be published in the Astrophysical Journal Letters

Table of interplanetary shock parameters for the events in "ARTEMIS Observations of Plasma Waves in Laminar and Perturbed Interplanetary Shocks", by the same authors, submitted to the Journal of Geophysical Review: Space Physics. Parameters were calculated from WIND and ARTEMIS observations. Note that WIND is located at L1, and interplanetary shocks can evolve between L1 and the near-Earth environment, resulting in potentially values for the shock parameters. Averages for values were taken a upstream and downstream of the transition regionduring 3-5 minute intervals where values were roughly steady and not near the transition region. Analysis was done in the spacecraft frame. Further information can be found in the paper listed above (doi:10.3847/1538-4357/abf56a). Columns include the Satellite whose observations were used for the calculation for a given row (Satellite), the date of the shock event (Date), the upstream plasma beta (Beta_up), the ratio of downstream (dn) to upstream (up) average magnetic field (Bdn/Bup), ion density (Ndn/Nup), electron temperature (Tedn/Teup), and ion temperature (Tidn/Tiup), the change in velocity caused by the shock (Vdown-Vup; km/s), the shock normal in Geocentric Solar Elliptical (GSE) coordinates (Shock normal; GSE), the shock angle with respect to the background magnetic field (Theta Bn; degrees), the shock speed (Vshn_up; km/s), the Alfven (M_A), fast (M_f), and the first critical Mach numbers (M_cr), and lastly the ratio of the fast mode to the critical Mach numbers (M_f/M_cr). Error estimates are included. Calculation of parameters made use of the Rankine-Hugoniot equations. Grey highlights signify the parameters used in the accompanying paper.&nbsp

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The “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission provides a unique opportunity to study the structure of interplanetary shocks and the associated generation of plasma waves with frequencies between ∼50 and 8000 Hz due to its long duration electric and magnetic field burst waveform captures. We compare wave properties and occurrence rates at 11 quasi-perpendicular interplanetary shocks with burst data within 10 minutes (∼3200 proton gyroradii upstream, ∼1900 downstream) of the shock ramp. A perturbed shock is defined as possessing a large amplitude whistler precursor in the quasi-static magnetic field with an amplitude greater than 1/3 the difference between the upstream and downstream average magnetic field magnitudes; laminar shocks lack these large precursors and have a smooth, step function-like transition. In addition to wave modes previously observed, including ion acoustic, whistler, and electrostatic solitary waves, waves in the ion acoustic frequency range that show rapid temporal frequency change are common. Three shocks had burst captures in the ramp; of these, the two laminar shocks contained a wide range of large amplitude wave modes in the ramp whereas the one perturbed shock contained no such waves. Thus, energy dissipation through wave–particle interactions is more prominent in these two laminar shocks than in the perturbed shock. Based on observations from all 11 shocks, the wave occurrence rates for laminar shocks are higher in the transition region, especially the ramp, than downstream. In contrast, perturbed shocks have approximately 2–3 times the wave occurrence rate downstream than laminar shocks.