The distribution function of diffuse ions and the magnetic field power spectrum upstream of Earth's bow shock

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.

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Jump conditions for pressure anisotropy and comparison with the Earth's bow shock

Nonlinear Processes in Geophysics ◽

10.5194/npg-8-167-2001 ◽

2001 ◽

Vol 8 (3) ◽

pp. 167-174 ◽

Cited By ~ 11

Author(s):

D. F. Vogl ◽

H. K. Biernat ◽

N. V. Erkaev ◽

C. J. Farrugia ◽

S. Mühlbachler

Keyword(s):

Magnetic Field ◽

Tangential Component ◽

Bow Shock ◽

Jump Conditions ◽

Plasma Parameters ◽

Pressure Anisotropy ◽

Threshold Conditions ◽

Wind Spacecraft ◽

Earth’S Bow Shock ◽

The Magnetic Field

Abstract. Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a) the perpendicular shock and b) the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy p \\perp /p\\parrallel > 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy p \\perp /p\\parrallel < 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.

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A model of the magnetosheath magnetic field during magnetic clouds

Annales Geophysicae ◽

10.5194/angeo-32-157-2014 ◽

2014 ◽

Vol 32 (2) ◽

pp. 157-173 ◽

Cited By ~ 8

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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Experimental and numerical investigation of plasma parameters in the magnetosheath

MATEC Web of Conferences ◽

10.1051/matecconf/201814503003 ◽

2018 ◽

Vol 145 ◽

pp. 03003

Author(s):

Polya Dobreva ◽

Monio Kartalev ◽

Olga Nitcheva ◽

Natalia Borodkova ◽

Georgy Zastenker

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Numerical Investigation ◽

Euler Equations ◽

Ideal Gas ◽

Bow Shock ◽

Plasma Parameters ◽

Wind Spacecraft ◽

The Magnetic Field ◽

Good Agreement

We investigate the behaviour of the plasma parameters in the magnetosheath in a case when Interball-1 satellite stayed in the magnetosheath, crossing the tail magnetopause. In our analysis we apply the numerical magnetosheath-magnetosphere model as a theoretical tool. The bow shock and the magnetopause are self-consistently determined in the process of the solution. The flow in the magnetosheath is governed by the Euler equations of compressible ideal gas. The magnetic field in the magnetosphere is calculated by a variant of the Tsyganenko model, modified to account for an asymmetric magnetopause. Also, the magnetopause currents in Tsyganenko model are replaced by numericaly calulated ones. Measurements from WIND spacecraft are used as a solar wind monitor. The results demonstrate a good agreement between the model-calculated and measured values of the parameters under investigation.

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Ogo 5 magnetic-field data near the Earth's bow shock: A correlation with theory

Journal of Geophysical Research Atmospheres ◽

10.1029/ja077i004p00604 ◽

1972 ◽

Vol 77 (4) ◽

pp. 604-610 ◽

Cited By ~ 19

Author(s):

J. K. Guha ◽

D. L. Judge ◽

J. H. Marburger

Keyword(s):

Magnetic Field ◽

Field Data ◽

Bow Shock ◽

Magnetic Field Data ◽

Earth’S Bow Shock

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

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2020.616635 ◽

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.

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ANALYTICAL MODEL OF THE PLANETARY BOW SHOCK FOR VARIOUS MAGNETIC FIELD DIRECTIONS BASED ON MHD CALCULATIONS

Solnechno-Zemnaya Fizika ◽

10.12737/szf-64202007 ◽

2020 ◽

Vol 6 (4) ◽

pp. 51-58

Author(s):

Galina Kotova ◽

Mikhail Verigin ◽

Tamash Gomboshi ◽

Konstantin Kabin

Keyword(s):

Magnetic Field ◽

Computer Time ◽

Bow Shock ◽

Radius Of Curvature ◽

Dynamic Flow ◽

Physical Processes ◽

Downstream Slope ◽

Mach Numbers ◽

Semi Empirical ◽

The Magnetic Field

Study of physical processes in plasma near planets often requires knowledge of the position and shape of the planetary bow shock. Empirical models are usually used since theoretical MHD and kinetic models consume too much computer time and cannot be used to track fast processes. M.I. Verigin proposed a semi-empirical approach based on the use of exact theoretical expressions with a small number of parameters, which have a clear physical meaning. These parameters are estimated by fitting experimental data or detailed MHD calculations. A model of the bow shock near an arbitrary-shaped obstacle has previously been developed for a gas-dynamic flow. This model can be applied to any sonic Mach numbers and large values of the Alfven Mach number. In addition, the asymptotic Mach cone — the angle of inclination of the shock wave at an infinite distance from the planet — has been calculated analytically in the MHD approximation. In this paper, we propose a model of the bow shock for any direction of the magnetic field with respect to the upcoming flow and for any Mach numbers. Parameters of the model are the distance of the nose point from the obstacle, radius of curvature and bluntness of the bow shock at the nose point, a parameter related to the transition to the asymptotic downstream slope of the shock, and a skewing angle appearing when the interplanetary magnetic field is directed at an angle to the solar wind velocity.

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Influence of the magnetic field of stellar wind on hot jupiter’s envelopes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000083 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 268-279

Author(s):

Dmitry V. Bisikalo ◽

Andrey G. Zhilkin

Keyword(s):

Magnetic Field ◽

Plasma Flow ◽

Coronal Mass Ejections ◽

Stellar Wind ◽

Roche Lobe ◽

Bow Shock ◽

Hot Jupiters ◽

The Magnetic Field ◽

Alfven Velocity ◽

Hot Jupiter

AbstractHot Jupiters have extended gaseous (ionospheric) envelopes, which extend far beyond the Roche lobe. The envelopes are loosely bound to the planet and, therefore, are strongly influenced by fluctuations of the stellar wind. We show that, since hot Jupiters are close to the parent stars, magnetic field of the stellar wind is an important factor defining the structure of their magnetospheres. For a typical hot Jupiter, velocity of the stellar wind plasma flow around the atmosphere is close to the Alfvén velocity. As a result stellar wind fluctuations, such as coronal mass ejections, can affect the conditions for the formation of a bow shock around a hot Jupiter. This effect can affect observational manifestations of hot Jupiters.

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Solitary potential structures observed in the magnetosheath by the Cluster spacecraft

Nonlinear Processes in Geophysics ◽

10.5194/npg-10-3-2003 ◽

2003 ◽

Vol 10 (1/2) ◽

pp. 3-11 ◽

Cited By ~ 67

Author(s):

J. S. Pickett ◽

J. D. Menietti ◽

D. A. Gurnett ◽

B. Tsurutani ◽

P. M. Kintner ◽

...

Keyword(s):

Magnetic Field ◽

Time Series Data ◽

Broad Band ◽

Low Frequency ◽

Bow Shock ◽

Local Magnetic Field ◽

Series Data ◽

The Individual ◽

Almost All ◽

The Magnetic Field

Abstract. Bipolar pulses of ~ 25-100 µs in duration have been observed in the wave electric field data obtained by the Wideband plasma wave instrument on the Cluster spacecraft in the dayside magnetosheath. These pulses are similar in almost all respects to those observed on several spacecraft over the last few years. They represent solitary potential structures, and in this case, electron phase space holes. When the time series data containing the bipolar pulses on Cluster are transformed to the frequency domain by a windowed FFT, the pulses appear as typical broad-band features, extending from the low-frequency cutoff of the bandpass filter, ~ 1 kHz, up to as great as 20-40 kHz in some cases, with decreasing intensity as the frequency increases. The upper frequency cutoff of the broad band is an indication of the individual pulse durations (1/f). The solitary potential structures are detected when the local magnetic field is contained primarily in the spin plane, indicating that they propagate along the magnetic field. Their frequency extent and intensity seem to increase as the angle between the directions of the magnetic field and the plasma flow decreases from 90°. Of major significance is the finding that the overall profile of the broad-band features observed simultaneously by two Cluster spacecraft, separated by a distance of over 750 km, are strikingly similar in terms of onset times, frequency extent, intensity, and termination. This implies that the generation region of the solitary potential structures observed in the magnetosheath near the bow shock is very large and may be located at or near the bow shock, or be connected with the bow shock in some way.

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Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

Annales Geophysicae ◽

10.5194/angeo-32-1247-2014 ◽

2014 ◽

Vol 32 (10) ◽

pp. 1247-1261 ◽

Cited By ~ 7

Author(s):

L. Turc ◽

D. Fontaine ◽

P. Savoini ◽

E. K. J. Kilpua

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Fields ◽

Bow Shock ◽

Field Direction ◽

Magnetic Clouds ◽

Magnetic Field Direction ◽

Field Orientation ◽

The Impact ◽

The Magnetic Field

Abstract. Magnetic clouds (MCs) are large-scale magnetic flux ropes ejected from the Sun into the interplanetary space. They play a central role in solar–terrestrial relations as they can efficiently drive magnetic activity in the near-Earth environment. Their impact on the Earth's magnetosphere is often attributed to the presence of southward magnetic fields inside the MC, as observed in the upstream solar wind. However, when they arrive in the vicinity of the Earth, MCs first encounter the bow shock, which is expected to modify their properties, including their magnetic field strength and direction. If these changes are significant, they can in turn affect the interaction of the MC with the magnetosphere. In this paper, we use data from the Cluster and Geotail spacecraft inside the magnetosheath and from the Advanced Composition Explorer (ACE) upstream of the Earth's environment to investigate the impact of the bow shock's crossing on the magnetic structure of MCs. Through four example MCs, we show that the evolution of the MC's structure from the solar wind to the magnetosheath differs largely from one event to another. The smooth rotation of the MC can either be preserved inside the magnetosheath, be modified, i.e. the magnetic field still rotates slowly but at different angles, or even disappear. The alteration of the magnetic field orientation across the bow shock can vary with time during the MC's passage and with the location inside the magnetosheath. We examine the conditions encountered at the bow shock from direct observations, when Cluster or Geotail cross it, or indirectly by applying a magnetosheath model. We obtain a good agreement between the observed and modelled magnetic field direction and shock configuration, which varies from quasi-perpendicular to quasi-parallel in our study. We find that the variations in the angle between the magnetic fields in the solar wind and in the magnetosheath are anti-correlated with the variations in the shock obliquity. When the shock is in a quasi-parallel regime, the magnetic field direction varies significantly from the solar wind to the magnetosheath. In such cases, the magnetic field reaching the magnetopause cannot be approximated by the upstream magnetic field. Therefore, it is important to take into account the conditions at the bow shock when estimating the impact of an MC with the Earth's environment because these conditions are crucial in determining the magnetosheath magnetic field, which then interacts with the magnetosphere.

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