Ion Kinetics in a Hot Flow Anomaly: MMS Observations

Schwartz, S. J.; Avanov, L. A.; Turner, D. L.; Zhang, Hui; Gingell, Imogen; Eastwood, J. P.; Gershman, D. J.; Johlander, Andreas; Russell, C. T.; Burch, J. L.; Dorelli, J.; Eriksson, S.; Ergun, R. E.; Fuselier, S. A.; Giles, B. L.; Goodrich, K.; Khotyaintsev, Yuri V.; Lavraud, B.; Lindqvist, Per‐Arne; Oka, M.; Phan, T. D.; Strangeway, R. J.; Trattner, K. J.; Torbert, R. B.; Vaivads, A.; Wei, H. Y.; Wilder, F. D.

doi:10.1029/2018gl080189

Cited by 34 publications

(39 citation statements)

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“…Features in the core that have not been reported before include deep, narrow magnetic field “holes,” where the total field strength drops below 1 nT. Based on our multievent survey, these magnetic holes are found within the cores of most FBs and HFAs, including in the HFA observed by MMS reported in Schwartz et al (2018) and Turner et al (2018). MMS next entered the sheath of the FB after 12:56:43 UT, characterized by shocked plasma exhibiting a high density and magnetic field strength.…”

Section: Analysis: Case Studysupporting

confidence: 57%

“…Based on our understanding from hybrid simulations of FBs (e.g., Karimabadi et al, 2014; Omidi et al, 2010) and unlike HFAs (e.g., Schwartz et al, 2000, 2018), the downstream boundaries of FBs are the IMF discontinuity plane about which they form, generally moving with the solar wind. In reality, an IMF discontinuity is often Alfvénic and propagating at the Alfvén speed oblique to the solar wind.…”

Section: Analysis: Case Studymentioning

confidence: 99%

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Microscopic, Multipoint Characterization of Foreshock Bubbles With Magnetospheric Multiscale (MMS)

et al. 2020

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This work presents the first detailed analysis of foreshock bubbles (FBs) using high‐resolution Magnetospheric Multiscale (MMS) data. Between October 2017 and January 2019, MMS captured 10 foreshock transient events with burst resolution data that we show are consistent with FBs. One “textbook” event is examined and described in detail. Employing the multipoint nature of MMS, we demonstrate how the size and orientation, expansion speed, and distance since formation can be estimated. From all 10 events, FB sizes ranged from 1.1 to 9.9 RE (average of 4.4 RE), and expansion speeds ranged from 139 to 377 km/s (average of 257 km/s). FBs formed under a usual range of solar wind conditions between 3 and 20 RE upstream of Earth's bow shock. We also report on new features of FBs: deep and localized magnetic “holes” within the cores of FBs, where the total field strength drops to <1 nT.

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Section: Analysis: Case Studysupporting

confidence: 57%

Section: Analysis: Case Studymentioning

confidence: 99%

Microscopic, Multipoint Characterization of Foreshock Bubbles With Magnetospheric Multiscale (MMS)

et al. 2020

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“…Possibly, foreshock structures whose magnetic field signatures resemble a magnetic depletion like hot flow anomalies (e.g. Schwartz, 1995;Zhao et al, 2017), cavitons (Kajdič et al, 2013), cavities (Sibeck et al, 2002(Sibeck et al, , 2004, density holes (Parks et al, 2006) or foreshock bubbles (Turner et al, 2020) can disturb the determination occurrence rate of MHs. Therefore, a categorization of these structures is made based on their magnetic and plasma characteristics, which will lead to three kinds of structures, discussed in the following subsections.…”

Section: Categorizationmentioning

confidence: 99%

Statistical study of linear magnetic hole structures near Earth

et al. 2021

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Abstract. The Magnetospheric Multiscale mission (MMS1) data for 8 months in the winter periods of 2017–2018 and 2018–2019, when MMS had its apogee in the upstream solar wind of the Earth's bow shock, are used to study linear magnetic holes (LMHs). These LMHs are characterized by a magnetic depression of more than 50 % and a rotation of the background magnetic field of less then 10∘. A total of 406 LMHs are found and, based on their magnetoplasma characteristics, are split into three categories: cold (increase in density, little change in ion temperature), hot (increase in ion temperature, decrease in density) and sign change (at least one magnetic field component changes sign). The occurrence rate of LMHs is 2.3 per day. All LMHs are basically in pressure balance with the ambient plasma. Most of the linear magnetic holes are found in ambient plasmas that are stable against the mirror-mode generation, but only half of the holes are mirror-mode-stable inside.

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“…Upstream of Earth's quasi-parallel bow shock, the ion foreshock is characterized by backstreaming ions that have been reflected from the shock (e.g., Eastwood et al, 2005;). In the ion foreshock, many foreshock transients have been observed and simulated, such as hot flow anomalies (HFAs) (e.g., Schwartz et al, 1985Schwartz et al, , 2018Thomsen et al, 1986Thomsen et al, , 1988Thomas et al, 1991;Lin, 1997;Omidi and Sibeck, 2007;Zhang et al, 2010), spontaneous hot flow anomalies (Omidi et al, 2013;Zhang et al, 2013), foreshock bubbles (FBs) (e.g., Omidi et al, 2010;Turner et al, 2013Turner et al, , 2020Liu et al, 2015), foreshock cavities (e.g., Lin, 2003;Sibeck et al, 2002), foreshock cavitons (e.g., Blanco-Cano et al, 2011) and short large-amplitude magnetic structures (SLAMS) (e.g., Schwartz et al, 1992;. HFAs, SHFAs, and FBs are three of the most significant types of foreshock transients due to their large sizes (e.g., several RE for HFAs/SHFAs and even larger for FBs), strong perturbations, and plasma heating.…”

Section: Introductionmentioning

confidence: 99%

Magnetospheric Multiscale (MMS) Observations of Magnetic Reconnection in Foreshock Transients

Liu

Turner

et al. 2020

JGR Space Physics

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Magnetic reconnection is a fundamental process of energy conversion in plasmas between electromagnetic fields and particles. Magnetic reconnection has been observed directly in a variety of plasmas in the solar wind and Earth's magnetosphere. Most recently, electron magnetic reconnection without ion coupling was observed for the first time in the turbulent magnetosheath and within the transition region of Earth's bow shock. In the ion foreshock upstream of Earth's bow shock, there may also be magnetic reconnection especially around foreshock transients that are very turbulent and dynamic. With observations from the National Aeronautics and Space Administration's Magnetospheric Multiscale mission inside foreshock transients, we report two events of magnetic reconnection with and without a strong guide field, respectively. In both events, a super-ion-Alfvénic electron jet was observed within a current sheet with thickness less than or comparable to one ion inertial length. In both events, energy was converted from the magnetic field to electrons, manifested as an increase in electron temperature. Weak or no ion coupling was observed in either event. Results from particle-in-cell simulations of magnetic reconnection with and without a strong guide field are qualitatively consistent with observations. Our results imply that magnetic reconnection is another electron acceleration/heating process inside foreshock transients and could play an important role in shock dynamics.

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Ion Kinetics in a Hot Flow Anomaly: MMS Observations

Cited by 34 publications

References 56 publications

Microscopic, Multipoint Characterization of Foreshock Bubbles With Magnetospheric Multiscale (MMS)

Microscopic, Multipoint Characterization of Foreshock Bubbles With Magnetospheric Multiscale (MMS)

Statistical study of linear magnetic hole structures near Earth

Magnetospheric Multiscale (MMS) Observations of Magnetic Reconnection in Foreshock Transients

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