Ion distributions in the Earth's foreshock: Hybrid‐Vlasov simulation and THEMIS observations

Kempf, Yann; Pokhotelov, Dimitry; Gutynska, O.; Wilson, L. B.; Walsh, Brian M.; Alfthan, Sebastian von; Hannuksela, O. A.; Sibeck, D. G.; Palmroth, Minna

doi:10.1002/2014ja020519

Cited by 48 publications

(66 citation statements)

References 61 publications

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“…In order to more accurately and efficiently model the foreshock region, including regions where plasma density is decreased, we employ a sparse velocity space algorithm (see von Alfthan et al, 2014;Kempf et al, 2015); that is, velocity space cells are dynamically allocated or discarded when their value is above or below a given threshold, respectively. The sparsity threshold value is scaled dynamically in accordance with proton number density.…”

Section: Vlasiator Simulation Runmentioning

confidence: 99%

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

et al. 2018

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Abstract. In this paper we present the first identification of foreshock cavitons and the formation of spontaneous hot flow anomalies (SHFAs) with the Vlasiator global magnetospheric hybrid-Vlasov simulation code. In agreement with previous studies we show that cavitons evolve into SHFAs. In the presented run, this occurs very near the bow shock. We report on SHFAs surviving the shock crossing into the downstream region and show that the interaction of SHFAs with the bow shock can lead to the formation of a magnetosheath cavity, previously identified in observations and simulations. We report on the first identification of long-term local weakening and erosion of the bow shock, associated with a region of increased foreshock SHFA and caviton formation, and repeated shock crossings by them. We show that SHFAs are linked to an increase in suprathermal particle pitch-angle spreads. The realistic length scales in our simulation allow us to present a statistical study of global caviton and SHFA size distributions, and their comparable size distributions support the theory that SHFAs are formed from cavitons. Virtual spacecraft observations are shown to be in good agreement with observational studies.

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Section: Vlasiator Simulation Runmentioning

confidence: 99%

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

et al. 2018

Self Cite

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show abstract

“…In order to more accurately and efficiently model the foreshock region, including regions where plasma density is decreased, we employ a sparse velocity space algorithm (see von Alfthan et al 2014 andKempf et al 2015), that is, velocity space cells are dynamically allocated or discarded when their value is above or below a given threshold, respectively. The sparsity threshold value is scaled dynamically in accordance with proton number density.…”

Section: Vlasiator Simulation Runmentioning

confidence: 99%

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

Blanco‐Cano¹,

Battarbee²,

Turc³

et al. 2018

Preprint

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Abstract. In this paper we present the first identification of foreshock cavitons and the formation of spontaneous hot flow anomalies (SHFAs) with the Vlasiator global magnetospheric hybrid-Vlasov simulation code. In agreement with previous studies we show that cavitons evolve into SHFAs. In the presented run, this occurs very near the bow shock. We report on SHFAs surviving the shock crossing into the downstream region, and show that the interaction of SHFAs with the bow shock can lead to the formation of a magnetosheath cavity, previously identified in observations and simulations. We report on 5 the first identification of long-term local weakening and erosion of the bow shock, associated with a region of increased foreshock SHFA and caviton formation, and repeated shock crossings by them. We show that SHFAs are linked to an increase in suprathermal particle pitch-angles spreads. The realistic length scales in our simulation allow us to present a statistical study of global caviton and SHFA size distributions, and their comparable size distributions support the theory that SHFAs are formed from cavitons. Virtual spacecraft observations are shown to be in good agreement with observational studies.

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“…In the field‐aligned beam region, the velocity of the backstreaming particles increases with increasing Θ Bn . It is therefore maximum at the foreshock edge and decreases toward the central foreshock (Burgess et al, ; Kempf et al, ) .…”

Section: Introductionmentioning

confidence: 99%

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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Ion distributions in the Earth's foreshock: Hybrid‐Vlasov simulation and THEMIS observations

Cited by 48 publications

References 61 publications

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation

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

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