scholarly journals Helium in the Earth's foreshock: a global Vlasiator survey

2020 ◽  
Vol 38 (5) ◽  
pp. 1081-1099
Author(s):  
Markus Battarbee ◽  
Xóchitl Blanco-Cano ◽  
Lucile Turc ◽  
Primož Kajdič ◽  
Andreas Johlander ◽  
...  
Keyword(s):  
Specular Reflection ◽  
Cone Angle ◽  
Low Frequency ◽  
Velocity Distribution Function ◽  
Bow Shock ◽  
Wave Interactions ◽  
Ulf Wave ◽  
Hot Plasma ◽  
Earth’S Bow Shock ◽  
Ion Velocity Distribution Function

Abstract. The foreshock is a region of space upstream of the Earth's bow shock extending along the interplanetary magnetic field (IMF). It is permeated by shock-reflected ions and electrons, low-frequency waves, and various plasma transients. We investigate the extent of the He2+ foreshock using Vlasiator, a global hybrid-Vlasov simulation. We perform the first numerical global survey of the helium foreshock and interpret some historical foreshock observations in a global context. The foreshock edge is populated by both proton and helium field-aligned beams, with the proton foreshock extending slightly further into the solar wind than the helium foreshock and both extending well beyond the ultra-low frequency (ULF) wave foreshock. We compare our simulation results with Magnetosphere Multiscale (MMS) Hot Plasma Composition Analyzer (HPCA) measurements, showing how the gradient of suprathermal ion densities at the foreshock crossing can vary between events. Our analysis suggests that the IMF cone angle and the associated shock obliquity gradient can play a role in explaining this differing behaviour. We also investigate wave–ion interactions with wavelet analysis and show that the dynamics and heating of He2+ must result from proton-driven ULF waves. Enhancements in ion agyrotropy are found in relation to, for example, the ion foreshock boundary, the ULF foreshock boundary, and specular reflection of ions at the bow shock. We show that specular reflection can describe many of the foreshock ion velocity distribution function (VDF) enhancements. Wave–wave interactions deep in the foreshock cause de-coherence of wavefronts, allowing He2+ to be scattered less than protons.

scholarly journals Helium in the Earth’s foreshock: a global Vlasiator survey

2020 ◽  
Author(s):  
Markus Battarbee ◽  
Xochitl Blanco-Cano ◽  
Lucile Turc ◽  
Primož Kajdič ◽  
Andreas Johlander ◽  
...  
Keyword(s):  
Specular Reflection ◽  
Cone Angle ◽  
Low Frequency ◽  
Bow Shock ◽  
Wave Interactions ◽  
Global Context ◽  
Ulf Wave ◽  
Ion Interactions ◽  
Earth’S Bow Shock ◽  
Low Frequency Waves

Abstract. The foreshock is a region of space upstream of the Earth's bow shock extending along the interplanetary magnetic field. It is permeated by shock-reflected ions and electrons, low-frequency waves, and various plasma transients. We investigate the extent of the He2+ foreshock using Vlasiator, a global hybrid-Vlasov simulation. We perform the first numerical global survey of the helium foreshock, and interpret some historical foreshock observations in a global context. The foreshock edge is populated by both proton and helium field-aligned beams, with the proton foreshock extending slightly further into the solar wind than the helium foreshock, and both extend well beyond the ULF wave foreshock. We compare our simulation results with MMS HPCA measurements, showing how the gradient of suprathermal ion densities at the foreshock crossing can vary between events. Our analysis suggests that the IMF cone angle and the associated shock obliquity gradient can play a role in explaining this differing behaviour. We also investigate wave-ion-interactions with wavelet analysis and show that the dynamics and heating of He2+ must result from proton-driven ULF waves. Enhancements in ion agyrotropy are found in relation to, e.g., the ion foreshock boundary, the ULF foreshock boundary, and specular reflection of ions at the bow shock. We show that specular reflection can describe many of the foreshock ion VDF enhancements. Wave-wave-interactions deep in the foreshock cause decoherence of wavefronts, allowing He2+ the be scattered less than protons.

WIND observation of gyrating-like ion distributions and low frequency waves upstream from the Earth's bow shock

1997 ◽  
Vol 20 (4-5) ◽  
pp. 703-706 ◽  
Author(s):  
K. Meziane ◽  
C. Mazelle ◽  
C. d'Uston ◽  
H. Rème ◽  
R.P. Lin ◽  
...  
Keyword(s):  
Low Frequency ◽  
Bow Shock ◽  
Wind Observation ◽  
Ion Distributions ◽  
Earth’S Bow Shock ◽  
Low Frequency Waves

scholarly journals Magnetosheath jet properties and evolution as determined by a global hybrid-Vlasov simulation

2018 ◽  
Author(s):  
Minna Palmroth ◽  
Heli Hietala ◽  
Ferdinand Plaschke ◽  
Martin Archer ◽  
Tomas Karlsson ◽  
...  
Keyword(s):  
Observational Studies ◽  
High Speed ◽  
Dynamic Pressure ◽  
Cone Angle ◽  
Low Frequency ◽  
Bow Shock ◽  
High Dynamic ◽  
Temporal Dimensions ◽  
First Time ◽  
Geomagnetic Dipole

Abstract. We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath high-speed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that the simulation spatial and temporal dimensions can be given without scaling. Thus, for the first time, this allows investigating the magnetosheath jet properties and comparing them directly with the observed jets within the Earth's magnetosheath. In the run shown in this paper, the interplanetary magnetic field (IMF) cone angle is 30°, and a foreshock develops upstream of the quasi-parallel magnetosheath. We visually detect a structure with high dynamic pressure propagating from the bow shock towards the magnetopause. The structure is confirmed as a jet using three different criteria, which have been adopted in previous observational studies. We compare these criteria against the simulation results. We find that the magnetosheath jet is an elongated structure extending Earthward of the bow shock by ~ 2.3 RE, while its size perpendicular to the direction of propagation is ~ 0.5 RE. We also investigate the jet evolution, and find that the jet originates due to the interaction of the foreshock Ultra Low Frequency (ULF) waves with the bow shock surface. The simulation shows that magnetosheath jets can develop also under steady IMF, as inferred by observational studies.

Electron Scattering by Low-frequency Whistler Waves at Earth’s Bow Shock

2019 ◽  
Vol 886 (1) ◽  
pp. 53 ◽  
Author(s):  
M. Oka ◽  
F. Otsuka ◽  
S. Matsukiyo ◽  
L. B. Wilson ◽  
M. R. Argall ◽  
...  
Keyword(s):  
Electron Scattering ◽  
Low Frequency ◽  
Bow Shock ◽  
Whistler Waves ◽  
Earth’S Bow Shock

scholarly journals Low-frequency magnetic variations at the high-<i>β</i> Earth bow shock

2019 ◽  
Vol 37 (5) ◽  
pp. 877-889
Author(s):  
Anatoli A. Petrukovich ◽  
Olga M. Chugunova ◽  
Pavel I. Shustov
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Spatial Scales ◽  
Low Frequency ◽  
Background Field ◽  
Bow Shock ◽  
Stable Phase ◽  
Main Magnetic Field ◽  
Astrophysical Plasmas ◽  
Earth’S Bow Shock

Abstract. Observations of Earth's bow shock during high-β (ratio of thermal to magnetic pressure) solar wind streams are rare. However, such shocks are ubiquitous in astrophysical plasmas. Typical solar wind parameters related to high β (here β>10) are as follows: low speed, high density, and a very low interplanetary magnetic field of 1–2 nT. These conditions are usually quite transient and need to be verified immediately upstream of the observed shock crossings. In this report, three characteristic crossings by the Cluster project (from the 22 found) are studied using multipoint analysis, allowing us to determine spatial scales. The main magnetic field and density spatial scale of about a couple of hundred of kilometers generally corresponds to the increased proton convective gyroradius. Observed magnetic variations are different from those for supercritical shocks, with β∼1. Dominant magnetic variations in the shock transition have amplitudes much larger than the background field and have a frequency of ∼ 0.3–0.5 Hz (in some events – 1–2 Hz). The wave polarization has no stable phase and is closer to linear, which complicates the determination of the wave propagation direction. Spatial scales (wavelengths) of variations are within several tens to a couple of hundred of kilometers.

scholarly journals Cone angle control of the interaction of magnetic clouds with the Earth's bow shock

2016 ◽  
Vol 43 (10) ◽  
pp. 4781-4789 ◽  
Author(s):  
L. Turc ◽  
C. P. Escoubet ◽  
D. Fontaine ◽  
E. K. J. Kilpua ◽  
S. Enestam
Keyword(s):  
Cone Angle ◽  
Bow Shock ◽  
Magnetic Clouds ◽  
Earth’S Bow Shock

scholarly journals The Earth's bow shock velocity distribution function

2015 ◽  
Vol 120 (2) ◽  
pp. 1229-1237 ◽  
Author(s):  
K. Meziane ◽  
A. M. Hamza ◽  
M. Maksimovic ◽  
T. Y. Alrefay
Keyword(s):  
Distribution Function ◽  
Velocity Distribution ◽  
Velocity Distribution Function ◽  
Shock Velocity ◽  
Bow Shock ◽  
Earth’S Bow Shock

scholarly journals Ultra-low-frequency waves in the ion foreshock of Mercury: a global hybrid modelling study

2019 ◽  
Vol 491 (3) ◽  
pp. 4147-4161 ◽  
Author(s):  
R Jarvinen ◽  
M Alho ◽  
E Kallio ◽  
T I Pulkkinen
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Three Dimensional ◽  
Low Frequency ◽  
Bow Shock ◽  
Solar Wind Interaction ◽  
Ulf Wave ◽  
Upstream Condition ◽  
Upstream Solar Wind ◽  
The Imf

ABSTRACT We study the solar wind interaction with Mercury using a global three-dimensional hybrid model. In the analysed simulation run, we find a well-developed, dynamic Hermean ion foreshock ahead of the quasi-parallel bow shock under upstream solar wind and interplanetary magnetic field (IMF) conditions corresponding to the orbital perihelion of the planet. A portion of the incident solar wind ion flux is scattered back upstream near the quasi-parallel bow shock including both major solar wind ion species, protons and alphas. The scattered particles form the Hermean suprathermal foreshock ion population. A significant part of the suprathermal population is backstreaming with a velocity component towards the Sun in the near-foreshock at the planetocentric distance of few planetary radii in the plane of the IMF. The ion foreshock is associated with large-scale, oblique fast magnetosonic waves in the ultra-low-frequency (ULF) range convecting downstream with the solar wind. The ULF wave period is about 5 s in the analysed upstream condition case at Mercury, which corresponds to the 30-s foreshock waves at Earth when scaled by the IMF magnitude.

Sign in / Sign up

Export Citation Format

Share Document