In Situ Observations of the Formation of Periodic Collisionless Plasma Shocks from Fast Mode Waves

Lun, Shan; Du, Aimin; Tsurutani, B. T.; Ge, Yasong; Lu, Quanming; Mazelle, C.; Huang, Can; Glaßmeier, Karl‐Heinz; Henri, Pierre

doi:10.3847/2041-8213/ab5db3

Cited by 17 publications

(16 citation statements)

References 28 publications

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“…At Earth, the foreshock region has been crossed multiple times by various spacecrafts, which facilitates extensive statistical studies of nonlinear waves (Tsurutani and Rodriguez, 1981;Schwartz et al, 1992;Giacalone et al, 1993;Mann et al, 1994;Stasiewicz et al, 2003;Behlke et al, 2004;Lucek et al, 2004). Similarly, nonlinear waves were recently studied in great detail at Mars, where the Maven mission provided high-resolution measurements of magnetic fields and particle properties (Fowler et al, 2018;Shan et al, 2020). In contrast to planetary missions, cometary missions previous to Rosetta were exclusively fast flybys or impacts, which only provided limited information on the properties of nonlinear waves for a fixed cometary activity level.…”

Section: Introductionmentioning

confidence: 99%

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

et al. 2021

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Abstract. We present a statistical survey of large-amplitude, asymmetric plasma and magnetic field enhancements detected outside the diamagnetic cavity at comet 67P/Churyumov–Gerasimenko from December 2014 to June 2016. Based on the concurrent observations of plasma and magnetic field enhancements, we interpret them to be magnetosonic waves. The aim is to provide a general overview of these waves' properties over the mission duration. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of these waves and their characteristics. In total, we identified ∼ 70 000 steepened waves in the magnetic field data by means of machine learning. We observe that the occurrence of these steepened waves is linked to the activity of the comet, where steepened waves are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressional nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual steepened waves. With increasing mass loading, the average amplitude of the waves decreases, while the skewness increases. Using a modified 1D magnetohydrodynamic (MHD) model, we investigated if the waves can be described by the combination of nonlinear and dissipative effects. By combining the model with observations of amplitude, width and skewness, we obtain an estimate of the effective plasma diffusivity in the comet–solar wind interaction region and compare it with suitable reference values as a consistency check. At 67P/Churyumov–Gerasimenko, these steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

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Section: Introductionmentioning

confidence: 99%

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

et al. 2021

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“…The fundamental physical processes of reformation in collisionless shocks are poorly understood and are far from being settled, in part due to limited in situ measurements of the processes. A few studies have shown evidence of nonstationarity and reformation at the terrestrial (Dimmock et al, 2019; Lefebvre et al, 2009; Lobzin et al, 2007; Mazelle et al, 2010; Sundberg et al, 2017), and planetary bow shocks (Shan et al, 2020; Sulaiman et al, 2015; Tiu et al, 2011). Nonstationarity can also manifest itself in the form of shock ripples formed near the shock overshoot (Johlander et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…In quasiperpendicular supercritical shocks, which are emphasized in this letter, the angle between the upstream magnetic field and the local normal vector to the shock surface ( θ bn ) is greater than 45°, and they exhibit a well‐defined and clear transition that includes a foot, ramp, and overshoot (Burgess & Scholer, 2015; Leroy et al, 1982). At quasiparallel shocks ( θ bn <45°), upstream particle dynamics, trajectories, and turbulence are very different (Shan et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Nonstationary Quasiperpendicular Shock and Ion Reflection at Mars

Madanian

Schwartz

Halekas

et al. 2020

Geophysical Research Letters

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Collisionless shocks in space plasma are regions of heating and acceleration of charged particles and dissipation of kinetic energy. These accelerated particles are the source of electromagnetic emissions from supernova remnants and other astrophysical structures. At high Mach numbers, shocks can be inherently nonstationary and exhibit modulated energy transfer and recurring plasma compression areas in the form of reformation. We use data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft to study reformation of the Martian bow shock, which has a relatively high curvature compared to that at Earth, and the upstream solar wind is often mass loaded with a population of pickup ions. We show evidence of ion reflection effects in reformation of a supercritical quasiperpendicular shock.

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“…Magnetosonic packets termed as shocklets were observed (Omidi & Winske, 1990; Tsurutani et al., 1989). Recent observations near Mars revealed periodic formations related with the pick‐up ions (Madanian et al., 2020; Shan, Du, et al., 2020; Shan, Tsurutani, et al., 2020). While specific drivers of reformation are often unclear, this topic is an active research area now.…”

Section: Introductionmentioning

confidence: 99%

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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In Situ Observations of the Formation of Periodic Collisionless Plasma Shocks from Fast Mode Waves

Cited by 17 publications

References 28 publications

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

Nonstationary Quasiperpendicular Shock and Ion Reflection at Mars

Detailed Structure of Very High‐β Earth Bow Shock

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