scholarly journals Reflection of the strahl within the foot of the Earth's bow shock

2019 ◽  
Vol 37 (2) ◽  
pp. 243-261 ◽  
Author(s):  
Christopher A. Gurgiolo ◽  
Melvyn L. Goldstein ◽  
Adolfo Viñas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Free Energy ◽  
Physical Properties ◽  
Bow Shock ◽  
Direct Connection ◽  
Electron Reflection ◽  
Primary Determinant ◽  
Earth’S Bow Shock ◽  
Wind Distribution

Abstract. The reflection of a fraction of the solar wind at the bow shock to some extent defines the physical properties of what is known as the foreshock, the region where the interplanetary magnetic field has a direct connection to the bow shock. Both ion and electron reflection have been observed and together form a significant source of free energy that is responsible for many of the instabilities observed in this region. In this paper we concentrate on the reflection of electrons at the shock and report two significant findings: the first is that the strahl, the field-aligned component of the electron solar wind distribution, appears to be fully reflected at the bow shock; the second finding is that the reflection is observed to occur in the foot of the shock and not in the shock ramp. This latter observation implies that mirroring in these examples is not the primary determinant of the electron reflection process.

scholarly journals Total Reflection of the Strahl within the Foot of the Earth's Bow Shock

2018 ◽  
Author(s):  
Christopher A. Gurgiolo ◽  
Melvyn L. Goldstein ◽  
Adolfo Viñas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Total Reflection ◽  
Bow Shock ◽  
Minor Role ◽  
Direct Connection ◽  
Electron Reflection ◽  
Earth’S Bow Shock ◽  
A Minor ◽  
Wind Distribution

Abstract. The reflection of a fraction of the solar wind at the bow shock to some extent defines the physical properties of what is known as the foreshock, the region where the interplanetary magnetic field has a direct connection to the bow shock. Both ion and electron reflection have been observed and together form a significant source of free energy that is responsible for many of the instabilities observed in this region. In this paper we concentrate on reflection of electrons at the shock and report two significant findings: The first is that the strahl, the field aligned component of the electron solar wind distribution, is fully reflected at the bow shock; the second finding is that the reflection occurs in the foot of the shock and not in the shock ramp. The latter implies that mirroring appears to play, at most, only a minor role in the electron reflection process.

scholarly journals Scattering of field-aligned beam ions upstream of Earth's bow shock

2007 ◽  
Vol 25 (3) ◽  
pp. 785-799 ◽  
Author(s):  
A. Kis ◽  
M. Scholer ◽  
B. Klecker ◽  
H. Kucharek ◽  
E. A. Lucek ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Bow Shock ◽  
Ion Distribution ◽  
Parallel Side ◽  
Earth’S Bow Shock ◽  
High Mach ◽  
The Magnetic Field

Abstract. Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB) ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.

scholarly journals Plasma and Magnetic Field Turbulence in the Earth’s Magnetosheath at Ion Scales

2021 ◽  
Vol 7 ◽  
Author(s):  
Liudmila Rakhmanova ◽  
Maria Riazantseva ◽  
Georgy Zastenker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Wind Plasma ◽  
Bow Shock ◽  
Present Review ◽  
Wind Effects ◽  
Earth’S Bow Shock ◽  
Magnetic Field Turbulence ◽  
Plasma Measurements ◽  
Turbulent Cascade

Crossing the Earth’s bow shock is known to crucially affect solar wind plasma including changes in turbulent cascade. The present review summarizes results of more than 15 years of experimental exploration into magnetosheath turbulence. Great contributions to understanding turbulence development inside the magnetosheath was made by means of recent multi-spacecraft missions. We introduce the main results provided by them together with first observations of the turbulent cascade based on direct plasma measurements by the Spektr-R spacecraft in the magnetosheath. Recent results on solar wind effects on turbulence in the magnetosheath are also discussed.

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 A model of the magnetosheath magnetic field during magnetic clouds

2014 ◽  
Vol 32 (2) ◽  
pp. 157-173 ◽  
Author(s):  
L. Turc ◽  
D. Fontaine ◽  
P. Savoini ◽  
E. K. J. Kilpua
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Ecliptic Plane ◽  
Bow Shock ◽  
Magnetic Clouds ◽  
The Sun ◽  
Earth’S Bow Shock ◽  
D Model ◽  
The Magnetic Field ◽  
Shock Configuration

Abstract. Magnetic clouds (MCs) are huge interplanetary structures which originate from the Sun and have a paramount importance in driving magnetospheric storms. Before reaching the magnetosphere, MCs interact with the Earth's bow shock. This may alter their structure and therefore modify their expected geoeffectivity. We develop a simple 3-D model of the magnetosheath adapted to MCs conditions. This model is the first to describe the interaction of MCs with the bow shock and their propagation inside the magnetosheath. We find that when the MC encounters the Earth centrally and with its axis perpendicular to the Sun–Earth line, the MC's magnetic structure remains mostly unchanged from the solar wind to the magnetosheath. In this case, the entire dayside magnetosheath is located downstream of a quasi-perpendicular bow shock. When the MC is encountered far from its centre, or when its axis has a large tilt towards the ecliptic plane, the MC's structure downstream of the bow shock differs significantly from that upstream. Moreover, the MC's structure also differs from one region of the magnetosheath to another and these differences vary with time and space as the MC passes by. In these cases, the bow shock configuration is mainly quasi-parallel. Strong magnetic field asymmetries arise in the magnetosheath; the sign of the magnetic field north–south component may change from the solar wind to some parts of the magnetosheath. We stress the importance of the Bx component. We estimate the regions where the magnetosheath and magnetospheric magnetic fields are anti-parallel at the magnetopause (i.e. favourable to reconnection). We find that the location of anti-parallel fields varies with time as the MCs move past Earth's environment, and that they may be situated near the subsolar region even for an initially northward magnetic field upstream of the bow shock. Our results point out the major role played by the bow shock configuration in modifying or keeping the structure of the MCs unchanged. Note that this model is not restricted to MCs, it can be used to describe the magnetosheath magnetic field under an arbitrary slowly varying interplanetary magnetic field.

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