Cluster survey of the high-altitude cusp properties: a three-year statistical study

Abstract. The global characteristics of the high-altitude cusp and its surrounding regions are investigated using a three-year statistical survey based on data obtained by the Cluster spacecraft. The analysis involves an elaborate orbit-sampling methodology that uses a model field and takes into account the actual solar wind conditions and level of geomagnetic activity. The spatial distribution of the magnetic field and various plasma parameters in the vicinity of the low magnetic field exterior cusp are determined and it is found that: 1) The magnetic field distribution shows the presence of an intermediate region between the magnetosheath and the magnetosphere: the exterior cusp, 2) This region is characterized by the presence of dense plasma of magnetosheath origin; a comparison with the Tsyganenko (1996) magnetic field model shows that it is diamagnetic in nature, 3) The spatial distributions show that three distinct boundaries with the lobes, the dayside plasma sheet and the magnetosheath surround the exterior cusp, 4) The external boundary with the magnetosheath has a sharp bulk velocity gradient, as well as a density decrease and temperature increase as one goes from the magnetosheath to the exterior cusp, 5) While the two inner boundaries form a funnel, the external boundary shows no clear indentation, 6) The plasma and magnetic pressure distributions suggest that the exterior cusp is in equilibrium with its surroundings in a statistical sense, and 7) A preliminary analysis of the bulk flow distributions suggests that the exterior cusp is stagnant under northward IMF conditions but convective under southward IMF conditions.

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A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

MATEC Web of Conferences ◽

10.1051/matecconf/201814503004 ◽

2018 ◽

Vol 145 ◽

pp. 03004

Author(s):

Polya Dobreva ◽

Olga Nitcheva ◽

Monio Kartalev

Keyword(s):

Magnetic Field ◽

Field Model ◽

Specific Aspect ◽

Plasma Parameters ◽

Ion Density ◽

Magnetic Field Model ◽

Wind Spacecraft ◽

The Mean ◽

The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

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An assessment of the role of the centrifugal acceleration mechanism in high altitude polar cap oxygen ion outflow

Annales Geophysicae ◽

10.5194/angeo-26-145-2008 ◽

2008 ◽

Vol 26 (1) ◽

pp. 145-157 ◽

Cited By ~ 27

Author(s):

H. Nilsson ◽

M. Waara ◽

O. Marghitu ◽

M. Yamauchi ◽

R. Lundin ◽

...

Keyword(s):

Magnetic Field ◽

High Altitude ◽

Centrifugal Acceleration ◽

Polar Cap ◽

Acceleration Mechanism ◽

Field Gradients ◽

Magnetic Field Gradients ◽

Magnetic Field Model ◽

The Magnetic Field

Abstract. The role of the centrifugal acceleration mechanism for ion outflow at high altitude above the polar cap has been investigated. Magnetometer data from the four Cluster spacecraft has been used to obtain an estimate of magnetic field gradients. This is combined with ion moment data of the convection drift and the field-aligned particle velocity. Thus all spatial terms in the expression for the centrifugal acceleration are directly obtained from observations. The temporal variation of the unit vector of the magnetic field is estimated by predicting consecutive measurement-points through the use of observed estimates of the magnetic field gradients, and subtracting this from the consecutively observed value. The calculation has been performed for observations of outflowing O+ beams in January to May for the years 2001–2003, and covers an altitude range of about 5 to 12 RE. The accumulated centrifugal acceleration during each orbit is compared with the observed parallel velocities to get an estimate of the relative role of the centrifugal acceleration. Finally the observed spatial terms (parallel and perpendicular) of the centrifugal acceleration are compared with the results obtained when the magnetic field data was taken from the Tsyganenko T89 model instead. It is found that the centrifugal acceleration mechanism is significant, and may explain a large fraction of the parallel velocities observed at high altitude above the polar cap. The magnetic field model results underestimate the centrifugal acceleration at the highest altitudes investigated and show some systematic differences as compared to the observations in the lower altitude ranges investigated. Our results indicate that for altitudes corresponding to magnetic field values of more than 50 nT a test particle model with a steady state magnetic field model, a realistic convection model and an initial velocity of about 20 k m s−1 at 5 RE should be able to reproduce the main part of our observational results.

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What Density of Magnetosheath Sodium Ions Can Provide the Observed Decrease in the Magnetic Field of the “Double Magnetopause” during the First MESSENGER Flyby?

Symmetry ◽

10.3390/sym13071168 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1168

Author(s):

Elena Belenkaya ◽

Ivan Pensionerov

Keyword(s):

Magnetic Field ◽

Analytical Approach ◽

Field Structure ◽

Sodium Ions ◽

Plasma Parameters ◽

Calculation Results ◽

Magnetizing Current ◽

The Magnetic Field ◽

Density Excess

On 14 January 2008, the MESSENGER spacecraft, during its first flyby around Mercury, recorded the magnetic field structure, which was later called the “double magnetopause”. The role of sodium ions penetrating into the Hermean magnetosphere from the magnetosheath in generation of this structure has been discussed since then. The violation of the symmetry of the plasma parameters at the magnetopause is the cause of the magnetizing current generation. Here, we consider whether the change in the density of sodium ions on both sides of the Hermean magnetopause could be the cause of a wide diamagnetic current in the magnetosphere at its dawn-side boundary observed during the first MESSENGER flyby. In the present paper, we propose an analytical approach that made it possible to determine the magnetosheath Na+ density excess providing the best agreement between the calculation results and the observed magnetic field in the double magnetopause.

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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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HALL AND MAGNETORESISTANCE EFFECTS OBTAINED FROM SIMULTANEOUS MEASUREMENTS OF LIQUID METALS AND SEMICONDUCTORS

International Journal of Modern Physics B ◽

10.1142/s0217979204027153 ◽

2004 ◽

Vol 18 (27n29) ◽

pp. 3625-3628

Author(s):

M. OGITA ◽

T. ITO ◽

M. ISAI ◽

I. MOGI ◽

S. AWAJI ◽

...

Keyword(s):

Magnetic Field ◽

Liquid Metals ◽

Simultaneous Methods ◽

Hall Measurements ◽

Hall Effects ◽

Galvanomagnetic Effects ◽

Liquid States ◽

Low Magnetic Field ◽

The Magnetic Field ◽

Solid And Liquid States

Hall measurements of liquid metals, using two-frequency, ac-dc and simultaneous methods are described. The Hall effect has been measured in Hg and Ga metals, in both solid and liquid states. The magnetoresistance and Hall effects have also been measured in an InSb single crystal, which exhibited magnetoresistance even in low magnetic field, and in Si , which did not exhibit magnetoresistance in low magnetic field. In order to investigate the magnetic field dependence of the observed galvanomagnetic effects for solid and liquid state metals, and for semiconductors, Hall measurements in high magnetic field, up to ±9 T, were also performed.

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Correlation Between the Magnetic Field and Plasma Parameters at 1 AU

Earth-affecting Solar Transients ◽

10.1007/978-94-024-1570-4_29 ◽

2018 ◽

pp. 621-633

Author(s):

Zicai Yang ◽

Fang Shen ◽

Jie Zhang ◽

Yi Yang ◽

Xueshang Feng ◽

...

Keyword(s):

Magnetic Field ◽

Plasma Parameters ◽

The Magnetic Field

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Retrieving lithospheric magnetisation distribution from magnetic field models

Geophysical Journal International ◽

10.1093/gji/ggz471 ◽

2019 ◽

Cited By ~ 1

Author(s):

V Lesur ◽

F Vervelidou

Keyword(s):

Magnetic Field ◽

Cost Function ◽

Spherical Harmonic ◽

Field Model ◽

Harmonic Model ◽

Whole Process ◽

Magnetic Field Model ◽

The Cost ◽

Spherical Harmonic Model ◽

The Magnetic Field

Summary We investigate to which extent the radially averaged magnetisation of the lithosphere can be recovered from the information content of a spherical harmonic model of the generated magnetic field when combined with few simple hypotheses. The results obtained show firstly that a hypothesis of magnetisation induced by a field of internal origin, even over a localised area, is not sufficient to recover uniquely the radially averaged magnetisation and, secondly, that this magnetisation can be recovered when a constant magnetisation direction is assumed. An algorithm to recover the magnetisation direction and distribution is then described and tested over a synthetic example. It requires to introduce a cost function that vanishes when estimated in a system of coordinates with its Z axis aligned with the magnetisation direction. Failing to find a vanishingly small value for the cost function is an indication that a constant magnetisation direction is not a valid hypothesis for the studied magnetic field model. The range of magnetisation directions that are compatible with the magnetic field model and a given noise level, can also be estimated. The whole process is illustrated by analysing a local, isolated maximum of the Martian magnetic field.

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Velocity-Magnetic Field Correlation of Pulsars

International Astronomical Union Colloquium ◽

10.1017/s0252921100040999 ◽

1996 ◽

Vol 160 ◽

pp. 49-50

Author(s):

Naoki Itoh ◽

Takemi Kotouda

Keyword(s):

Magnetic Field ◽

Constant Magnetic Field ◽

Field Model ◽

Transverse Velocity ◽

Distribution Model ◽

Recent Measurement ◽

Apparent Correlation ◽

Magnetic Field Model ◽

Field Correlation ◽

The Magnetic Field

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.

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Magnetic field effect on laser-induced breakdown spectroscopy and surface modifications of germanium at various fluences

Laser and Particle Beams ◽

10.1017/s0263034617000039 ◽

2017 ◽

Vol 35 (1) ◽

pp. 159-169 ◽

Cited By ~ 11

Author(s):

H. Iftikhar ◽

S. Bashir ◽

A. Dawood ◽

M. Akram ◽

A. Hayat ◽

...

Keyword(s):

Magnetic Field ◽

Electron Temperature ◽

Surface Modifications ◽

Laser Induced Breakdown Spectroscopy ◽

Excitation Temperature ◽

Number Density ◽

Plasma Parameters ◽

Breakdown Spectroscopy ◽

Laser Induced Breakdown ◽

The Magnetic Field

AbstractThe effect of the transverse magnetic field on laser-induced breakdown spectroscopy and surface modifications of germanium (Ge) has been investigated at various fluences. Ge targets were exposed to Nd: YAG laser pulses (1064 nm, 10 ns, 1 Hz) at different fluences ranging from 3 to 25.6 J/cm2 to generate Ge plasma under argon environment at a pressure of 50 Torr. The magnetic field of strength 0.45 Tesla perpendicular to the direction of plasma expansion was employed by using two permanent magnets. The emission spectra of laser-induced Ge plasma was detected by the laser-induced breakdown spectroscopy system. The electron temperature and number density of Ge plasma are evaluated by using the Boltzmann plot and stark broadening methods, respectively. The variations in emission intensity, electron temperature (Te), and number density (ne) of Germanium plasma are explored at various fluences, with and without employment of the magnetic field. It is observed that the magnetic field is responsible for significant enhancement of both excitation temperature and number density at all fluences. It is revealed that an excitation temperature increases from Te,max,without B = 16,190 to Te,max,with B = 20,123 K. Similarly, the two times enhancement in the electron density is observed from ne,max,without B = 2 × 1018 to ne,max,with B = 4 × 1018 cm−3. The overall enhancement in Ge plasma parameters in the presence of the magnetic field is attributed to the Joule heating effect and adiabatic compression. With increasing fluence both plasma parameters increase and achieve their maxima at a fluence of 12.8 J/cm2 and then decrease. In order to correlate the plasma parameters with surface modification, scanning electron microscope analysis of irradiated Ge was performed. Droplets and cones are formed for both cases. However, the growth of ridges and distinctness of features is more pronounced in case of the absence of the magnetic field; whereas surface structures become more diffusive in the presence of 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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