MMS Observations of Whistler and Lower Hybrid Drift Waves Associated with Magnetic Reconnection in the Turbulent Magnetosheath

Vörös, Z.; Yordanova, Emiliya; Graham, Daniel B.; Khotyaintsev, Yuri V.; Narita, Yasuhito

doi:10.1029/2019ja027028

Cited by 18 publications

(15 citation statements)

References 47 publications

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“…The finite plasma beta effect would reduce the maximum growth rate of electrostatic LH waves by a factor (1 + i /2) −1/2 , if T e ≪ T i and V E < v i (Davidson et al, 1977), but it does not stabilize the instability. Therefore, LH waves can survive at the magnetosheath separatrix with a finite plasma beta at ∼5.4, and LH waves under similar plasma beta conditions have been reported in the magnetosheath reconnection (Vörös et al, 2019) and in the magnetotail plasma sheet (Zhou et al, 2014).…”

Section: Discussion and Summarysupporting

confidence: 57%

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Tang

Graham

et al. 2020

Geophysical Research Letters

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Lower hybrid waves are investigated at the magnetosheath separatrix region in asymmetric guide field reconnection by using the Magnetospheric Multiscale (MMS) mission. Three of the four MMS spacecraft observe clear wave activities around the lower hybrid frequency across the magnetosheath separatrix, where a density gradient is present. The observed waves are consistent with generation by the lower hybrid drift instability. The characteristic properties of these waves include the following: (1) the waves propagate toward the x-line in the spacecraft frame due to the large out-of-plane magnetic field, which is in the same direction of the diamagnetic drift of the x-line; (2) the wave potential is about 20% of the electron temperature. These drift waves effectively produce cross-field particle diffusion, enabling the transport of magnetosheath electrons into the exhaust region. At last, we suggest that the lower hybrid waves at the magnetosheath separatrix region represent some unique features of asymmetric guide field reconnection, which is different from that widely observed at the magnetospheric side of magnetopause reconnection. Plain Language Summary Magnetic reconnection is a fundamental process of explosive energy conversion in space, and one important unresolved issue during this process is how plasma waves impact the magnetic reconnection. Different types of waves have been found and investigated during reconnection, including kinetic Alfvén waves, lower hybrid waves, whistler waves, upper hybrid waves, and parallel electrostatic waves. Among these waves, lower hybrid waves, taken as a basic feature of 3-D asymmetric reconnection, are frequently observed at the magnetospheric side. In this study, we present new observations from the Magnetospheric Multiscale (MMS) mission, showing that the lower hybrid waves can also be found at the magnetosheath separatrix in asymmetric guide field reconnection, which enable the cross-field particle diffusion from the magnetosheath to the exhaust. These results can help deepen our understanding of the roles of plasma waves in reconnection.

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Section: Discussion and Summarysupporting

confidence: 57%

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Tang

Graham

et al. 2020

Geophysical Research Letters

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“…First, the bow shock and the magnetopause influence the magnetosheath turbulence properties (Gurnett et al 1979;Rezeau & Belmont 2001;Sahraoui et al 2006;Rakhmanova et al 2018b). Second, strong temperature anisotropy generally observed in the magnetosheath can generate various instabilities under different conditions, likely the Alfvén/ ion-cyclotron instability, the mirror-mode instability, the fast magnetosonic/whistler instability, and the fire-hose instability (e.g., Southwood & Kivelson 1993;Quest & Shapiro 1996;Gary et al 1998;Hellinger & Matsumoto 2000;Guicking et al 2012;Kunz et al 2014;Verscharen et al 2016), which is verified by many studies (e.g., Anderson & Fuselier 1993;Anderson et al 1994;Schwartz et al 1996;Czaykowska et al 2001;Lucek et al 2001;Sahraoui et al 2006;Chen & Boldyrev 2017;Teh & Zenitani 2019;Vörös et al 2019;Zhao et al 2019aZhao et al , 2019b. Third, other turbulent fluctuations related to local structures, e.g., current sheets, magnetic islands, and vortices, can further complicate the magnetosheath turbulence picture (e.g., Alexandrova 2008;Karimabadi et al 2014;Huang et al 2018).…”

Section: Introductionmentioning

confidence: 72%

Evolution of the Earth’s Magnetosheath Turbulence: A Statistical Study Based on MMS Observations

Jiang

Wang

et al. 2020

ApJL

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Composed of shocked solar wind, the Earth's magnetosheath serves as a natural laboratory to study the transition of turbulence from low Alfvén Mach number, M A , to high M A. The simultaneous observations of magnetic field and plasma moments with unprecedented high temporal resolution provided by NASA's Magnetospheric Multiscale Mission (MMS) enable us to study the magnetosheath turbulence at both magnetohydrodynamics (MHD) and sub-ion scales. Based on 1841 burst-mode segments of MMS-1 from 2015 September to 2019 June, comprehensive patterns of the spatial evolution of magnetosheath turbulence are obtained: (1) from the subsolar region to the flanks, M A increases from <1 to >5. At MHD scales, the spectral indices of the magnetic-field and velocity spectra present a positive and negative correlation with M A. However, no obvious correlations between the spectral indices and M A are found at sub-ion scales. (2) From the bow shock to the magnetopause, the turbulent sonic Mach number, M turb , generally decreases from >0.4 to <0.1. All spectra steepen at MHD scales and flatten at sub-ion scales, representing positive/negative correlations with M turb. The break frequency increases by 0.1 Hz when approaching the magnetopause for the magnetic-field and velocity spectra, while it remains at 0.3 Hz for the density spectra. (3) In spite of minor differences, similar results are found for the quasi-parallel and quasi-perpendicular magnetosheath. In addition, such spatial evolution of magnetosheath turbulence is found to be independent of the upstream solar wind conditions, e.g., the averaged Z-component of the interplanetary magnetic field and solar wind speed.

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“…The fact that PSP encounters quasi-parallel whistler waves at the boundary of the current sheet, right after the steepest variation in B L , could indicate that the spacecraft was close to the iondiffusion region on that side of the current sheet (e.g. Vörös et al 2019). We checked the trajectory of the probe in the LMN frame and found that its 2D projection in the LN plan is oblique.…”

Section: Event 3 On November 1 2018 At 18:18 Utmentioning

confidence: 99%

“…Quasi-parallel whistlers are often observed in the vicinity of reconnection regions (e.g. Wei et al 2007;Fujimoto & Sydora 2008;Graham et al 2016;Huang et al 2017;Vörös et al 2019). No such clear wave packet was observed at the leading edge.…”

Section: Event 3 On November 1 2018 At 18:18 Utmentioning

confidence: 99%

Direct evidence for magnetic reconnection at the boundaries of magnetic switchbacks with Parker Solar Probe

Froment

Krasnoselskikh

Wit

et al. 2021

A&A

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Context. The first encounters of Parker Solar Probe (PSP) with the Sun revealed the presence of ubiquitous localised magnetic deflections in the inner heliosphere; these structures, often called switchbacks, are particularly striking in solar wind streams originating from coronal holes. Aims. We report the direct piece of evidence for magnetic reconnection occurring at the boundaries of three switchbacks crossed by PSP at a distance of 45 to 48 solar radii to the Sun during its first encounter. Methods. We analyse the magnetic field and plasma parameters from the FIELDS and Solar Wind Electrons Alphas and Protons instruments. Results. The three structures analysed all show typical signatures of magnetic reconnection. The ion velocity and magnetic field are first correlated and then anti-correlated at the inbound and outbound edges of the bifurcated current sheets with a central ion flow jet. Most of the reconnection events have a strong guide field and moderate magnetic shear, but one current sheet shows indications of quasi anti-parallel reconnection in conjunction with a magnetic field magnitude decrease by 90%. Conclusions. Given the wealth of intense current sheets observed by PSP, reconnection at switchback boundaries appears to be rare. However, as the switchback boundaries accomodate currents, one can conjecture that the geometry of these boundaries offers favourable conditions for magnetic reconnection to occur. Such a mechanism would thus contribute in reconfiguring the magnetic field of the switchbacks, affecting the dynamics of the solar wind and eventually contributing to the blending of the structures with the regular wind as they propagate away from the Sun.

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MMS Observations of Whistler and Lower Hybrid Drift Waves Associated with Magnetic Reconnection in the Turbulent Magnetosheath

Cited by 18 publications

References 47 publications

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Evolution of the Earth’s Magnetosheath Turbulence: A Statistical Study Based on MMS Observations

Direct evidence for magnetic reconnection at the boundaries of magnetic switchbacks with Parker Solar Probe

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