A Database of MMS Bow Shock Crossings Compiled Using Machine Learning

Lalti, Ahmad; Khotyaintsev, Yuri V.; Dimmock, A. P.; Johlander, Andreas; Graham, Daniel B.; Olshevsky, Vyacheslav

doi:10.1029/2022ja030454

Cited by 26 publications

(29 citation statements)

References 40 publications

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“…The shock crossing was observed by MMS 1 on 07 October 2015 at 12:07:10 and documented in the database (Lalti et al. 2022). The model shock normal is used (Farris & Russell 1994).…”

Section: Observational Illustrationmentioning

confidence: 89%

Role of the overshoot in the shock self-organization

et al. 2023

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A collisionless shock is a self-organized structure where fields and particle distributions are mutually adjusted to ensure a stable mass, momentum and energy transfer from the upstream to the downstream region. This adjustment may involve rippling, reformation or whatever else is needed to maintain the shock. The fields inside the shock front are produced due to the motion of charged particles, which is in turn governed by the fields. The overshoot arises due to the deceleration of the ion flow by the increasing magnetic field, so that the drop of the dynamic pressure should be compensated by the increase of the magnetic pressure. The role of the overshoot is to regulate ion reflection, thus properly adjusting the downstream ion temperature and kinetic pressure and also speeding up the collisionless relaxation and reducing the anisotropy of the eventually gyrotropized distributions.

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“…The shock crossing was observed by MMS 1 on 07 October 2015 at 12:07:10 and documented in the database (Lalti et al. 2022). The model shock normal is used (Farris & Russell 1994).…”

Section: Observational Illustrationmentioning

confidence: 89%

Role of the overshoot in the shock self-organization

et al. 2023

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“…The three selected events are quasi-perpendicular with Alfvén Mach numbers ranging from 9 to 17 which is relatively high compared to most times MMS has encountered the bow shock, cf. (Lalti et al, 2022).…”

Section: Observationsmentioning

confidence: 99%

Electron Heating Scales in Collisionless Shocks Measured by MMS

Johlander

Khotyaintsev

Dimmock

et al. 2023

Geophysical Research Letters

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Shock waves appear in a wide variety in space plasmas where they act to slow down and heat supersonic flows before the plasma can encounter an obstacle. Plasma shocks in the heliosphere and in astrophysical settings are often collisionless, meaning that heating and entropy generation takes place through interactions between the particles and the electromagnetic fields (Krall, 1997;Parks et al., 2017). Due to the collisionless nature of the shock waves, energy is not partitioned equally between the plasma species. Ions, which gain most of the dissipated energy (e.g., Schwartz et al., 1988;Vink et al., 2015), are principally heated by the instability between gyrobunched shock-reflected and the transmitted ions (Sckopke et al., 1983).Electron heating happens in an interplay between the betatron effect through an increase in magnetic field and the electric cross-shock potential (DC fields) on one hand and wave-particle interactions (AC fields) at the shock (Goodrich & Scudder, 1984;Scudder, 1995). Since electron thermal speeds in the solar wind are much greater than the bulk speed, electrons are free to move across the shock along the magnetic field in both directions. The DC fields act to adiabatically inflate the distribution in velocity space, leaving a hole in velocity space. This phase-space inflation is reversible and therefore does not produce entropy (Balikhin et al., 1993;Lindberg et al., 2022). The hole left in velocity is filled by electron scattering by AC fields, which leads to a flat-top electron distribution downstream of the shock (Feldman et al., 1983). Through which processes the non-reversible heating takes place in shocks is not fully understood but short-wavelength electrostatic waves, which likely form from the instability from the inflation of the electron distributions, have been observed at the shock with amplitudes which suggests that they can efficiently scatter electrons (e.g.,

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“…MMS crosses the Earth's bow shock from the downstream magnetosheath to the upstream solar wind. This crossing is selected from over 1000 MMS shock crossings in the database created by Lalti, Khotyaintsev, Dimmock, et al (2022). It displays one of the highest fluxes of energetic electrons, measured in the energy range 10-20 keV.…”

Section: Observationmentioning

confidence: 99%

MMS Observation of Two‐Step Electron Acceleration at Earth's Bow Shock

Lindberg,

Vaivads,

Raptis

et al. 2023

Geophysical Research Letters

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We use the Magnetospheric Multiscale mission to observe a bi‐directional electron acceleration event in the electron foreshock upstream of Earth's quasi‐perpendicular collisionless bow shock. The acceleration region is associated with a decrease in wave activity, inconsistent with common electron acceleration mechanisms such as Diffusive Shock Acceleration and Stochastic Shock Drift Acceleration. We propose a two‐step acceleration process where an electron field‐aligned beam acts as a seed population further accelerated by a shrinking magnetic bottle process, with the shock acting as the magnetic mirror(s).

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A Database of MMS Bow Shock Crossings Compiled Using Machine Learning

Cited by 26 publications

References 40 publications

Role of the overshoot in the shock self-organization

Role of the overshoot in the shock self-organization

Electron Heating Scales in Collisionless Shocks Measured by MMS

MMS Observation of Two‐Step Electron Acceleration at Earth's Bow Shock

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