On the Kinetic Nature of Solar Wind Discontinuities

Artemyev, А. V.; Angelopoulos, V.; Vasko, I. Y.; Avanov, L. A.; Giles, B. L.; Russell, C. T.; Strangeway, R. J.

doi:10.1029/2018gl079906

Cited by 32 publications

(38 citation statements)

References 53 publications

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“…Recent observations in the magnetosphere and numerical simulations confirm the close link between plasma outflows from the near-Earth magnetotail reconnection region and generation of the field-aligned currents (e.g. Artemyev et al 2018). These results indicate "that the dominant role of the near-Earth magnetotail reconnection in the field-aligned current generation is likely responsible for their transient nature".…”

Section: Dynamics Of Magnetic Field and Electric Currents In The Flarmentioning

confidence: 68%

Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135 s Vector Magnetograms

Sharykin

Zimovets

Myshyakov

2020

ApJ

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This work is a continuation of Paper I (Sharykin et al. 2018) devoted to analysis of nonthermal electron dynamics and plasma heating in the confined M1.2 class solar flare SOL2015-03-15T22:43 revealing energy release in the highly sheared interacting magnetic loops in the low corona, above the polarity inversion line (PIL). The scope of the present work is to make the first extensive quantitative analysis of the photospheric magnetic field and photospheric vertical electric current (PVEC) dynamics in the confined flare region near the PIL using new vector magnetograms obtained with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) with high temporal resolution of 135 s. Data analysis revealed sharp changes of the magnetic structure and PVEC associated with the flare onset near the PIL. It was found that the strongest plasma heating and electron acceleration were associated with the largest increase of the magnetic reconnection rate, total PVEC and effective PVEC density in the flare ribbons. Observations and non-linear force-free field (NLFFF) extrapolations showed that the magnetic field structure around the PIL is consistent with the tether-cutting magnetic reconnection (TCMR) geometry. We gave qualitative interpretation of the observed dynamics of the flare ribbons, magnetic field and PVEC, and electron acceleration, within the TCMR scenario.

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Section: Dynamics Of Magnetic Field and Electric Currents In The Flarmentioning

confidence: 68%

Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135 s Vector Magnetograms

Sharykin

Zimovets

Myshyakov

2020

ApJ

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“…The most interesting feature of n e and T e =( T e ‖ +2 T e ⊥ )/3 variations is that they are correlated: In the first discontinuity (Figure b) an n e increase is accompanied by a T e increase, and in the second discontinuity (Figures b), an n e increase is accompanied by a T e decrease. As we will show below, the second discontinuity demonstrates a more typical pattern of n e and T e variations when n e and T e inversely correlate (see also Artemyev et al, , ).…”

Section: Data Set and Methodsmentioning

confidence: 80%

“…Figures d, e, d, and e show electron pitch‐angles for thermal (below 100 eV) and hot (100–1,000 eV) populations. There are clear changes in the thermal electron pitch‐angle distributions (see also Artemyev et al, ); that is, discontinuities separate two electron populations, and there is no significant exchange between them. Thus, electrons from the hot population likely can cross the discontinuity.…”

Section: Data Set and Methodsmentioning

confidence: 99%

“…Toward that goal, we use observations from the two Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft (Angelopoulos, ) orbiting the Moon. The spacecraft measure electron distribution functions (including the high‐energy part up to ∼25 keV) and other plasma characteristics at 4‐s cadence (see, e.g., Artemyev et al, ), thereby fully resolving the discontinuity structure. Combining the correlation analysis of magnetic field (Auster et al, ) measurements at the two spacecraft with solar wind speed measurements (McFadden et al, ) allows determination of the local discontinuity coordinate system.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Properties of Solar Wind Discontinuities at 1 AU Observed by ARTEMIS

2019

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Because solar wind plasma flow transports the entire spectrum of magnetic field fluctuations (from low-frequency inertial range to electron kinetic range), it is a natural laboratory for plasma turbulence investigation. Among the various wave modes and coherent plasma structures that contribute to this spectrum, one of the most important solar wind elements is ion-scale solar wind discontinuities. These structures, which carry very intense current, have been considered as a free energy source for plasma instabilities that contribute to solar wind heating. Investigations of such discontinuities have been mostly focused on their magnetic field signatures; much less is known about plasma kinetics around them. Using statistics of such discontinuities observed around the Earth (∼1 AU) by two spacecraft from the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission, we demonstrate that they are accompanied by density and temperature variations with a spatial scale of tens of ion inertial lengths. Inversely correlated density and temperature variations suggest the discontinuity configuration is nearly force free. The discontinuities are typified by two spatial scales, an intense current layer (>1 nA/m 2), and a much broader current layer structure enveloping them. The magnetic field rotation occurs at the large scale, whereas at the small (inner) scale the plasma pressure gradients provide the pressure balance. We find that the electron kinetic behavior around the discontinuities strongly depends on electron energy: Whereas the pitch-angle distribution of near-thermal electrons (10-30 eV) changes significantly across discontinuities, hot (100-1,000 eV) electrons retain their properties on the two sides, suggesting they are able to cross the discontinuities freely. Exploring these and other kinetic characteristics of discontinuities, we discuss possible mechanisms of formation/evolution of these structures.

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“…Note that there is little possibility to perform a cross‐calibration of MMS and ARTEMIS measurements as these two missions never probe the same plasma regions. The comparison of ARTEMIS and MMS measurements in the solar wind shows <30% difference in plasma density and temperature measured by ARTEMIS and MMS (Artemyev et al, 2019). Thus, in this study, we do not compare absolute values of plasma characteristics measured by MMS and ARTEMIS crossings of the magnetopause.…”

Section: Data Setsmentioning

confidence: 99%

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

et al. 2020

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One of the main sources of magnetospheric particles is solar wind penetration through the magnetopause-a current sheet separating the cold, dense magnetosheath from the hot, rarified magnetospheric plasmas. The mechanism responsible for magnetosheath particle transport across the magnetopause has been better investigated for the near-Earth dayside magnetopause (contrary to the nightside), where it was found that such a transport is controlled by the current sheet thickness, structure, and dynamics. Because plasma properties and magnetic field intensity in the magnetosheath significantly change as a function of radial distance from the Earth, the current sheet characteristics are different near Earth and at distant nightside magnetopause. Comparative investigations between near-Earth and distant magnetopauses, however, require statistical observations at the two locations during the same time interval, that enable control for the same upstream solar wind driving conditions. In this paper, we perform such a study using the four Magnetosheric Multiscale (MMS) and two Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) probes to compare the characteristics of magnetic field and plasma populations during magnetopause crossings, which are separated by about 50 R E. We find that the current sheet profiles is similar at two locations. We also show that the magnetopause current sheet thickness scales with the local magnetosheath ion gyroradius. A weaker magnetic field on both sides of the current sheet is correlated with smaller current density at lunar distances.

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On the Kinetic Nature of Solar Wind Discontinuities

Cited by 32 publications

References 53 publications

Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135 s Vector Magnetograms

Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135 s Vector Magnetograms

Kinetic Properties of Solar Wind Discontinuities at 1 AU Observed by ARTEMIS

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

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