Statistical Study of Chorus Modulations by Background Magnetic Field and Plasma Density

Abstract. The Galileo magnetometer data are used to investigate the structure of the Alfvén wing during three flybys of Europa. The presence of an induced magnetic field is shown to shrink the cross section of the Alfvén wing and offset it along the direction radial to Jupiter. Both the shrinkage and the offset depend on the strength of the induced field. The entry and exit points of the spacecraft into and out of the Alfvén wings are modeled to determine the angle between the wings and the background magnetic field. Tracing of the Alfvén characteristics in a model magnetic field consisting of Jupiter's background field and an induced field in Europa produces an offset and shrinking of the Alfvén wing consistent with the geometric modeling. Thus we believe that the Alfvén wing properties have been determined correctly. The Alfvén wing angle is directly proportional to the local Alfvén velocity, and is thus a probe for the local plasma density. We show that the inferred plasma density can be understood in terms of the electron density measured by the plasma wave experiment. When Europa is located in the Jovian plasma sheet the derived mass-per-charge exceeds the previous estimates, which is a result of increased pickup of sputtered ions near the moon. The estimated rate of O2+ pickup agrees well with the results from numerical models.

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Black hole pair production on cosmic strings in the presence of a background magnetic field

Physics Letters B ◽

10.1016/j.physletb.2021.136224 ◽

2021 ◽

Vol 816 ◽

pp. 136224

Author(s):

Amjad Ashoorioon ◽

Mohammad Bagher Jahani Poshteh

Keyword(s):

Magnetic Field ◽

Black Hole ◽

Pair Production ◽

Cosmic Strings ◽

Hole Pair ◽

Background Magnetic Field

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Plasma density accumulation on a conical surface for diffusion along a diverging magnetic field

Physics of Plasmas ◽

10.1063/1.4870758 ◽

2014 ◽

Vol 21 (4) ◽

pp. 043502 ◽

Cited By ~ 19

Author(s):

S. K. Saha ◽

S. Chowdhury ◽

M. S. Janaki ◽

A. Ghosh ◽

A. K. Hui ◽

...

Keyword(s):

Magnetic Field ◽

Plasma Density ◽

Conical Surface

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Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

Journal of Plasma Physics ◽

10.1017/s0022377800020456 ◽

1977 ◽

Vol 17 (1) ◽

pp. 93-103 ◽

Cited By ~ 7

Author(s):

N. F. Cramer

Keyword(s):

Magnetic Field ◽

Parametric Excitation ◽

Acoustic Waves ◽

Magnetic Pressure ◽

Gas Pressure ◽

Alfven Wave ◽

Fast Wave ◽

Magnetoacoustic Waves ◽

Background Magnetic Field ◽

The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

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On the existence of compressional MHD oscillations in an inhomogeneous magnetoplasma

Journal of Plasma Physics ◽

10.1017/s0022377800015233 ◽

1990 ◽

Vol 44 (2) ◽

pp. 361-375 ◽

Cited By ~ 2

Author(s):

Andrew N. Wright

Keyword(s):

Magnetic Field ◽

Wave Equation ◽

Density Distribution ◽

Cold Plasma ◽

Wave Equations ◽

Perturbation Field ◽

Plasma Density Distribution ◽

Background Magnetic Field ◽

Transverse Fields ◽

The Magnetic Field

In a cold plasma the wave equation for solely compressional magnetic field perturbations appears to decouple in any surface orthogonal to the background magnetic field. However, the compressional fields in any two of these surfaces are related to each other by the condition that the perturbation field b be divergence-free. Hence the wave equations in these surfaces are not truly decoupled from one another. If the two solutions happen to be ‘matched’ (i.e. V.b = 0) then the medium may execute a solely compressional oscillation. If the two solutions are unmatched then transverse fields must evolve. We consider two classes of compressional solutions and derive a set of criteria for when the medium will be able to support pure compressional field oscillations. These criteria relate to the geometry of the magnetic field and the plasma density distribution. We present the conditions in such a manner that it is easy to see if a given magnetoplasma is able to executive either of the compressional solutions we investigate.

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Schwinger effect in an instanton background with electric and magnetic fields via holography

Modern Physics Letters A ◽

10.1142/s0217732318501444 ◽

2018 ◽

Vol 33 (25) ◽

pp. 1850144

Author(s):

Maryam Gholizadeh Arashti ◽

Majid Dehghani

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Production Rate ◽

Pair Creation ◽

Zero Temperature ◽

Expectation Value ◽

Background Magnetic Field ◽

Electric And Magnetic Fields ◽

Schwinger Effect ◽

Horizon Limit

The Schwinger effect in the presence of instantons and background magnetic field was considered to study the dependence of critical electric field on instanton density and magnetic field using AdS/CFT conjecture. The gravity side is the near horizon limit of D3[Formula: see text]D(−[Formula: see text]1) background with electric and magnetic fields on the brane. Our approach is based on the potential analysis for particle–antiparticle pair at zero and finite temperatures, where the zero temperature case is a semi-confining theory. We find that presence of instantons suppresses the pair creation effect, similar to a background magnetic field. Then, the production rate will be obtained numerically using the expectation value of circular Wilson loop. The obtained production rate in a magnetic field is in agreement with previous results.

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A large statistical study of the entry of interplanetary magnetic field Y-component into the magnetosphere

Geophysical Research Letters ◽

10.1029/95gl02261 ◽

1995 ◽

Vol 22 (16) ◽

pp. 2083-2086 ◽

Cited By ~ 51

Author(s):

S. Wing ◽

P. T. Newell ◽

D. G. Sibeck ◽

K. B. Baker

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Statistical Study

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Plasma instabilities driven by pickup ions of ring-beam velocity distributions in the outer heliosheath

10.5194/egusphere-egu21-9329 ◽

2021 ◽

Author(s):

Ameneh Mousavi ◽

Kaijun Liu ◽

Sina Sadeghzadeh

Keyword(s):

Magnetic Field ◽

Maximum Growth ◽

Dispersion Analysis ◽

Maximum Growth Rate ◽

Injection Velocity ◽

Plasma Instabilities ◽

Pickup Ions ◽

Beam Velocity ◽

Background Magnetic Field ◽

Hybrid Simulations

The stability of the pickup ions in the outer heliosheath has been studied by many researchers because of its relevance to the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer. However, previous studies are primarily limited to pickup ions of near 90&#176; pickup angles, the angle between the pickup ion injection velocity and the background, local interstellar magnetic field. Investigations on pickup ions of smaller pickup angles are still lacking. In this paper, linear kinetic dispersion analysis and hybrid simulations are carried out to examine the plasma instabilities driven by pickup ions of ring-beam velocity distributions at various pickup angles between zero and 90&#176;. Parallel propagating waves are studied in the parameter regime where the parallel thermal spread of the pickup ions falls into the Alfv&#233;n cyclotron stability gap. The linear analysis results and hybrid simulations both show that the fastest growing modes are the right-hand helicity waves propagating in the direction of the background magnetic field, and the maximum growth rate occurs at the pickup angle of 82&#176;. The simulation results further reveal that the saturation level of the fluctuating magnetic fields for pickup angles below 45&#176; is higher than that for pickup angles above 45&#176;. So, the scattering of pickup ions at near zero pickup angles is likely more pronounced than that at near 90&#176; pickup angles .

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HelioSwarm: The Nature of Turbulence in Space Plasmas

10.5194/egusphere-egu21-12092 ◽

2021 ◽

Author(s):

Harlan Spence ◽

Kristopher Klein ◽

HelioSwarm Science Team

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Large Scale ◽

Solar Wind Plasma ◽

Turbulent Energy ◽

Space Plasmas ◽

Plasma Parameters ◽

Astrophysical Plasmas ◽

Ion Distributions ◽

Background Magnetic Field

Recently selected for phase A study for NASA&#8217;s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.&#160;&#160;HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind.&#160;

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