Tail reconnection in the global magnetospheric context: Vlasiator first results

Palmroth, Minna; Hoilijoki, Sanni; Juusola, Liisa; Pulkkinen, Tuija; Hietala, Heli; Pfau‐Kempf, Yann; Ganse, Urs; Alfthan, Sebastian von; Vainio, R.; Hesse, Michael

doi:10.5194/angeo-35-1269-2017

Cited by 33 publications

(65 citation statements)

References 24 publications

(32 reference statements)

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“…Although being computationally heavy, the hybrid‐Vlasov description has the advantage of providing noiseless ion VDFs. A number of studies utilizing this model have been already published and have shown a good agreement with previous numerical and observational works (Hoilijoki et al, , ; Kempf et al, ; Palmroth et al, , ; Pfau‐Kempf et al, ).…”

Section: Introductionsupporting

confidence: 83%

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

et al. 2018

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In this paper, we present a detailed study of the effects of the interplanetary magnetic field (IMF) strength on the foreshock properties at small and large scales. Two simulation runs performed with the hybrid‐Vlasov code Vlasiator with identical setup but with different IMF strengths, namely, 5 and 10 nT, are compared. We find that the bow shock position and shape are roughly identical in both runs, due to the quasi‐radial IMF orientation, in agreement with previous magnetohydrodynamic simulations and theory. Foreshock waves develop in a broader region in the higher IMF strength run, which we attribute to the larger growth rate of the waves. The velocity of field‐aligned beams remains essentially the same, but their density is generally lower when the IMF strength increases, due to the lower Mach number. Also, we identify in the regular IMF strength run ridges of suprathermal ions which disappear at higher IMF strength. These structures may be a new signature of the foreshock compressional boundary. The foreshock wave field is structured over smaller scales in higher IMF conditions, due to both the period of the foreshock waves and the transverse extent of the wave fronts being smaller. While the foreshock is mostly permeated by monochromatic waves at typical IMF strength, we find that magnetosonic waves at different frequencies coexist in the other run. They are generated by multiple beams of suprathermal ions, while only a single beam is observed at typical IMF strength. The consequences of these differences for solar wind‐magnetosphere coupling are discussed.

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Section: Introductionsupporting

confidence: 83%

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

et al. 2018

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“…As a net effect, the flows are accelerated until ap-proximately −14 R E , after which they are decelerated (Karlsson et al, 2015). Fast flows that reach the transition region between the tail-like and dipolar magnetic field are diverted dawnward and duskward and can rebound from the strong dipole field (Birn et al, 1999;Chen and Wolf, 1999;Ohtani et al, 2009;Panov et al, 2010;Birn et al, 2011;McPherron et al, 2011;Juusola et al, 2013;Nakamura et al, 2013).…”

Section: Occurrence Of Plasma Sheet Flowsmentioning

confidence: 99%

Fast plasma sheet flows and X line motion in the Earth's magnetotail: results from a global hybrid-Vlasov simulation

et al. 2018

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Abstract. Fast plasma flows produced as outflow jets from reconnection sites or X lines are a key feature of the dynamics in the Earth's magnetosphere. We have used a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by steady southward interplanetary magnetic field and fast solar wind, to study fast plasma sheet ion flows and related magnetic field structures in the Earth's magnetotail. In the simulation, lobe reconnection starts to produce fast flows after the increasing pressure in the lobes has caused the plasma sheet to thin sufficiently. The characteristics of the earthward and tailward fast flows and embedded magnetic field structures produced by multi-point tail reconnection are in general agreement with spacecraft measurements reported in the literature. The structuring of the flows is caused by internal processes: interactions between major X points determine the earthward or tailward direction of the flow, while interactions between minor X points, associated with leading edges of magnetic islands carried by the flow, induce local minima and maxima in the flow speed. Earthward moving flows are stopped and diverted duskward in an oscillatory (bouncing) manner at the transition region between tail-like and dipolar magnetic fields. Increasing and decreasing dynamic pressure of the flows causes the transition region to shift earthward and tailward, respectively. The leading edge of the train of earthward flow bursts is associated with an earthward propagating dipolarization front, while the leading edge of the train of tailward flow bursts is associated with a tailward propagating plasmoid. The impact of the dipolarization front with the dipole field causes magnetic field variations in the Pi2 range. Major X points can move either earthward or tailward, although tailward motion is more common. They are generally not advected by the ambient flow. Instead, their velocity is better described by local parameters, such that an X point moves in the direction of increasing reconnection electric field strength. Our results indicate that ion kinetics might be sufficient to describe the behavior of plasma sheet bulk ion flows produced by tail reconnection in global near-Earth simulations. Keywords. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet) – space plasma physics (numerical simulation studies)

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“…Statistical results have demonstrated that the occurrence rate of flapping motions is similar to that of BBFs, and peak in the central part of the magnetotail (Sergeev et al, 2006). Empirical models (Petrukovich et al, 2008;Rong et al, 2010) have been constructed to describe the characteristics of flapping current sheets.…”

Section: Introductionmentioning

confidence: 99%

A possible source mechanism for magnetotail current sheet flapping

et al. 2018

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Abstract. The origin of the flapping motions of the current sheet in the Earth's magnetotail is one of the most interesting questions of magnetospheric dynamics yet to be solved. We have used a polar plane simulation from the global hybrid-Vlasov model Vlasiator to study the characteristics and source of current sheet flapping in the center of the magnetotail. The characteristics of the simulated signatures agree with observations reported in the literature. The flapping is initiated by a hemispherically asymmetric magnetopause perturbation, created by subsolar magnetopause reconnection, that is capable of displacing the tail current sheet from its nominal position. The current sheet displacement propagates downtail at the same pace as the driving magnetopause perturbation. The initial current sheet displacement launches a standing magnetosonic wave within the tail resonance cavity. The travel time of the wave within the local cavity determines the period of the subsequent flapping signatures. Compression of the tail lobes due to added flux affects the cross-sectional width of the resonance cavity as well as the magnetosonic speed within the cavity. These in turn modify the wave travel time and flapping period. The compression of the resonance cavity may also provide additional energy to the standing wave, which may lead to strengthening of the flapping signature. It may be possible that the suggested mechanism could act as a source of kink-like waves that have been observed to be emitted from the center of the tail and to propagate toward the dawn and dusk flanks.

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Tail reconnection in the global magnetospheric context: Vlasiator first results

Cited by 33 publications

References 24 publications

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

Fast plasma sheet flows and X line motion in the Earth's magnetotail: results from a global hybrid-Vlasov simulation

A possible source mechanism for magnetotail current sheet flapping

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