The Dynamics of a High Mach Number Quasi-perpendicular Shock: MMS Observations

Madanian, Hadi; Desai, M. I.; Schwartz, S. J.; Wilson, L. B.; Fuselier, S. A.; Burch, J. L.; Contel, Olivier Le; Turner, D. L.; Ogasawara, K.; Brosius, A. L.; Russell, C. T.; Ergun, R. E.; Ahmadi, N.; Gershman, D. J.; Lindqvist, Per‐Arne

doi:10.3847/1538-4357/abcb88

Cited by 31 publications

(44 citation statements)

References 84 publications

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“…This idea, first put forward by Feldman et al. (1983) and then developed further (Scudder, Mangeney, Lacombe, Harvey, Wu, & Anderson, 1986) and applied (Lefebvre et al., 2007; Schwartz et al., 1988) (see Scudder, 1995 for a review), is consistent with the reported electron beams seen within the shock transition and, for example, the coherent reflection of ions at quasi‐perpendicular shocks (Madanian et al., 2021; Paschmann et al., 1982). These processes point to the presence of coherent, DC fields.…”

Section: Discussionsupporting

confidence: 68%

Evaluating the deHoffmann‐Teller Cross‐Shock Potential at Real Collisionless Shocks

et al. 2021

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Shock waves are common in the heliosphere and beyond. The collisionless nature of most astrophysical plasmas allows for the energy processed by shocks to be partitioned amongst particle sub‐populations and electromagnetic fields via physical mechanisms that are not well understood. The electrostatic potential across such shocks is frame dependent. In a frame where the incident bulk velocity is parallel to the magnetic field, the deHoffmann‐Teller frame, the potential is linked directly to the ambipolar electric field established by the electron pressure gradient. Thus measuring and understanding this potential solves the electron partition problem, and gives insight into other competing shock processes. Integrating measured electric fields in space is problematic since the measurements can have offsets that change with plasma conditions. The offsets, once integrated, can be as large or larger than the shock potential. Here we exploit the high‐quality field and plasma measurements from NASA's Magnetospheric Multiscale mission to attempt this calculation. We investigate recent adaptations of the deHoffmann‐Teller frame transformation to include time variability, and conclude that in practice these face difficulties inherent in the 3D time‐dependent nature of real shocks by comparison to 1D simulations. Potential estimates based on electron fluid and kinetic analyses provide the most robust measures of the deHoffmann‐Teller potential, but with some care direct integration of the electric fields can be made to agree. These results suggest that it will be difficult to independently assess the role of other processes, such as scattering by shock turbulence, in accounting for the electron heating.

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Section: Discussionsupporting

confidence: 68%

Evaluating the deHoffmann‐Teller Cross‐Shock Potential at Real Collisionless Shocks

et al. 2021

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“…Figure 3 also shows ion velocity spectra plotted versus the shock normal (V n ) and tangential (V t2 ) velocity components (e.g., Madanian et al 2021). Note that V t2 is by definition perpendicular to the shock normal and upstream B-field vectors.…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…Meanwhile observations are most often limited by single-point observations, resulting in spatiotemporal ambiguity, and/or inadequate temporal resolution. Furthermore, theory and observations (e.g., Morse et al 1972;Krasnoselskikh et al 2002;Sundberg et al 2017;Dimmock et al 2019;Madanian et al 2021) indicate that supercritical shocks undergo periodic reformation, also known as nonstationarity, which further complicates discerning details in single-point observations of well-formed shocks. In this study, we examined fortuitous multipoint observations during a single cycle of shock reformation on the upstream edge of a foreshock transient using NASAʼs Magnetospheric Multiscale (MMS) mission upstream of Earthʼs bow shock.…”

Section: Introductionmentioning

confidence: 99%

Direct Multipoint Observations Capturing the Reformation of a Supercritical Fast Magnetosonic Shock

Turner

Wilson

Goodrich

et al. 2021

ApJL

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Using multipoint Magnetospheric Multiscale (MMS) observations in an unusual string-of-pearls configuration, we examine in detail observations of the reformation of a fast magnetosonic shock observed on the upstream edge of a foreshock transient structure upstream of Earthʼs bow shock. The four MMS spacecraft were separated by several hundred kilometers, comparable to suprathermal ion gyroradius scales or several ion inertial lengths. At least half of the shock reformation cycle was observed, with a new shock ramp rising up out of the "foot" region of the original shock ramp. Using the multipoint observations, we convert the observed time-series data into distance along the shock normal in the shockʼs rest frame. That conversion allows for a unique study of the relative spatial scales of the shockʼs various features, including the shockʼs growth rate, and how they evolve during the reformation cycle. Analysis indicates that the growth rate increases during reformation, electron-scale physics play an important role in the shock reformation, and energy conversion processes also undergo the same cyclical periodicity as reformation. Strong, thin electron-kinetic-scale current sheets and large-amplitude electrostatic and electromagnetic waves are reported. Results highlight the critical cross-scale coupling between electron-kineticand ion-kinetic-scale processes and details of the nature of nonstationarity, shock-front reformation at collisionless, fast magnetosonic shocks.

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“…One event (#1) was added during the manuscript revision from recent publication of Madanian et al. (2021). Table contains 20 crossings of Geotail spacecraft with

β > 10

.…”

Section: Assembling the Shock Statisticsmentioning

confidence: 99%

“…More recently Madanian et al. (2021) presented a shock with

β = 9

and somewhat less developed reformation signatures in MMS data. Several shock crossings with similar appearance and a high Mach number were found at Saturn (Sulaiman et al., 2015).…”

Section: Introductionmentioning

confidence: 97%

Detailed Structure of Very High‐β Earth Bow Shock

Petrukovich

Chugunova

2021

JGR Space Physics

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Observations of Earth's bow shock with high β≥10 (ratio of thermal to magnetic pressure) are rare. However, such shocks are supposed to be ubiquitous in astrophysical plasmas. We present statistics of several tens crossings with β>10 for MMS, Cluster and Geotail, 30 of which have β>30. For the latter subset, most of the crossings reveal upstream structure with the periodically emerging activations, gradually thermalizing the solar wind ion flow. One fortuitous MMS shock event allowed to study this phenomenon with unprecedented details. Each activation, in turn, consists of high‐amplitude magnetic variations with the period about 1 s, coupled with the pulses of the plasma flow. These variations have wavelengths of about 150 km, linear polarization and are almost standing in the plasma rest frame, consistent with the expectation for Weibel mode. All together, the transition interval may last 5–10 min, but corresponds to a proton cyclotron scale in the solar wind, due to very low magnetic field and very slow shock motion. The most likely physical cause of this extended upstream activity is reformation of a supercritical shock.

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The Dynamics of a High Mach Number Quasi-perpendicular Shock: MMS Observations

Cited by 31 publications

References 84 publications

Evaluating the deHoffmann‐Teller Cross‐Shock Potential at Real Collisionless Shocks

Evaluating the deHoffmann‐Teller Cross‐Shock Potential at Real Collisionless Shocks

Direct Multipoint Observations Capturing the Reformation of a Supercritical Fast Magnetosonic Shock

Detailed Structure of Very High‐β Earth Bow Shock

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