Theory of ion holes in space and astrophysical plasmas

2020 ◽  
Vol 497 (1) ◽  
pp. L69-L75 ◽  
Author(s):  
Harikrishnan Aravindakshan ◽  
Peter H Yoon ◽  
Amar Kakad ◽  
Bharati Kakad
Keyword(s):  
Electric Field ◽  
Theoretical Models ◽  
Salient Point ◽  
Astrophysical Plasma ◽  
Satisfactory Explanation ◽  
Astrophysical Plasmas ◽  
Magnetospheric Multiscale ◽  
Shock Region ◽  
Earth’S Bow Shock ◽  
Electron Holes

ABSTRACT Coherent bipolar electric field structures, ubiquitously found in various space and astrophysical plasma environments, play an important role in plasma transport and particle acceleration. Most of the studies found in the literature about them pertain to bipolar structures with positive potentials interpreted in terms of electron holes. Magnetospheric Multiscale spacecraft have recently observed a series of coherent electric field structures with negative potential in the Earth’s bow shock region, which are interpreted as ion holes. The existing theoretical models of ion holes are inadequate because they entail stringent conditions on the ratio of ion to electron temperature. This letter presents a new theory that provides a satisfactory explanation to these observations. A salient point is that this letter incorporates the electron dynamics in the theoretical formalism, which removes ambiguities associated with existing theories, thus showing that the new theory for ion holes may be widely applicable for space and astrophysical plasmas.

scholarly journals Plasma Heating by Alfvén Waves - Kinetic Properties of Magnetohydrodynamic Disturbances

1985 ◽  
Vol 107 ◽  
pp. 381-389
Author(s):  
Akira Hasegawa
Keyword(s):  
Electric Field ◽  
Plasma Heating ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Kinetic Properties ◽  
Parallel Electric Field ◽  
Astrophysical Plasmas ◽  
Finite Larmor Radius ◽  
Wave Heating

Mechanisms of Alfvén wave heating in space-astrophysical plasmas are presented with particular emphasis on the parallel electric field generated in the magnetohydrodynamic perturbations due to the finite Larmor radius effects.

scholarly journals Perspectives on Space and Astrophysical Plasma Physics

1985 ◽  
Vol 107 ◽  
pp. 537-552 ◽  
Author(s):  
C. F. Kennel ◽  
J. Arons ◽  
R. Blandford ◽  
F. Coroniti ◽  
M. Israel ◽  
...  
Keyword(s):  
Plasma Physics ◽  
Research Council ◽  
National Research Council ◽  
Current Status ◽  
Future Prospects ◽  
Astrophysical Plasma ◽  
National Academy Of Sciences ◽  
Astrophysical Plasmas ◽  
Plasma Research ◽  
Academy Of Sciences

We summarize the discussion of the current status and future prospects of space and astrophysical plasma research prepared by the Panel on Space and Astrophysical plasmas, a part of the study on Physics administered by the National Research Council of the National Academy of Sciences. The Study on Physics is chaired by W. Brinkman of Bell Laboratories and will be completed in 1984.

Drifting Electron Holes Occurring During Geomagnetically Quiet Times: BD-IES Observations

2020 ◽  
Author(s):  
Zhi-Yang Liu ◽  
Qiu-Gang Zong ◽  
Hong Zou
Keyword(s):  
Quiet Time ◽  
Drift Motion ◽  
Superposed Epoch Analysis ◽  
Bursty Bulk Flow ◽  
Magnetospheric Multiscale ◽  
Substorm Activity ◽  
Ground Magnetic ◽  
Solar Wind Parameters ◽  
Epoch Analysis ◽  
Electron Holes

<p>Drifting electron holes (DEHs), manifesting as sudden but mild dropout in electron flux, are a common phenomenon seen in the Earth's magnetosphere. It manifests the change of the state of the magnetosphere. However, previous studies primarily focus on DEHs during geomagnetically active time (e.g., substorm). Not until recently have quiet time DEHs been reported. In this paper, we present a systematic study on the quiet time DEHs. BeiDa Imaging Electron Spectrometer (BD-IES) measurements from 2015 to 2017 are investigated. Twenty-two DEH events are identified. The DEHs cover the whole energy range of BD-IES (50–600 keV). Generally, the DEHs are positively dispersive with respect to energy. Time-of-flight analysis suggests the dispersion results from electron drift motion and gives the location where the DEHs originated from. Statistics reveal the DEHs primarily originated from the postmidnight magnetosphere. In addition, superposed epoch analysis applied to geomagnetic indices and solar wind parameters indicates these DEH events occurred during geomagnetically quiet time. No storm or substorm activity could be identified. However, an investigation into nightside midlatitude ground magnetic records suggests these quiet time DEHs were accompanied by Pi2 pulsations. The DEH-Pi2 connection indicates a possible DEH-bursty bulk flow (BBF) connection, since nightside midlatitude Pi2 activity is generally attributed to magnetotail BBFs. This connection is also supported by a case study of coordinated magnetotail observations from Magnetospheric Multiscale spacecraft. Therefore, we suggest the quiet time DEHs could be caused by magnetotail BBFs, similar to the substorm time DEHs.</p>

Electron- and proton-scale nested magnetic cavities: Manifestation of kinetic theta-pinch equilibrium in space plasmas

2020 ◽  
Author(s):  
Jinghuan Li ◽  
Fan Yang ◽  
Xu-Zhi Zhou ◽  
Qiu-Gang Zong ◽  
Anton V. Artemyev ◽  
...  
Keyword(s):  
Electric Field ◽  
Vortex Formation ◽  
Radial Electric Field ◽  
Plasma Pressure ◽  
Astrophysical Plasmas ◽  
Particle Distributions ◽  
Theta Pinch ◽  
Energy Cascades ◽  
Laboratory Plasmas ◽  
Cavity Boundary

<p>Magnetic cavities, sometimes referred to as magnetic holes, are ubiquitous in space and astrophysical plasmas characterized by localized regions with depressed magnetic field strength, strongly anisotropic particle distributions, and enhanced plasma pressure. Typical cavity sizes range from fluid to ion and sub-ion kinetic scales, with recent observations also identifying nested cavities that may indicate cross-scale energy cascades. Although heavily investigated in space, magnetic cavities have analogs in laboratory plasmas, the classical theta-pinches. Here, we develop an equilibrium solution of the Vlasov-Maxwell equations in cylindrical coordinates (in similar format to theta-pinch models), to reconstruct the cross-scale profiles of magnetic cavities observed by the four-spacecraft MMS mission. The kinetic model uses input parameters derived from single-spacecraft measurements to successfully reproduce signatures of magnetic cavities from all observing spacecraft. The reconstructed profiles demonstrate that near the electron-scale cavity boundary, the decoupled electron and proton motions generate a radial electric field that contributes to electron vortex formation that has been previously attributed mostly to diamagnetic effects. At larger scales, the diminishing electric field implies that diamagnetic motion is solely responsible for proton vortices.</p>

scholarly journals Solar and geomagnetic activity effects on mid-latitude F-region electric fields

2008 ◽  
Vol 26 (9) ◽  
pp. 2911-2921 ◽  
Author(s):  
V. V. Kumar ◽  
M. L. Parkinson ◽  
P. L. Dyson ◽  
R. Polglase
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Geomagnetic Activity ◽  
High Speed ◽  
Theoretical Models ◽  
Solar Flux ◽  
Quiet Time ◽  
F Region ◽  
Diurnal Patterns ◽  
Ae Index

Abstract. Diurnal patterns of average F-region ionospheric drift (electric field) and their dependence on solar and geomagnetic activity have been defined using digital ionosonde Doppler measurements recorded at a southern mid-latitude station (Bundoora 145.1° E, 37.7° S geographic, 49° S magnetic). A unique database consisting of 300 907 drift velocities was compiled, mostly using one specific mode of operation throughout 1632 days of a 5-year interval (1999–2003). The velocity magnitudes were generally larger during the night than day, except during the winter months (June–August), when daytime velocities were enhanced. Of all years, the largest drifts tended to occur during the high speed solar wind streams of 2003. Diurnal patterns in the average quiet time (AE<75 nT) meridional drifts (zonal electric field) peaked at up to ~6 m s−1 poleward (0.3 mV m−1 eastward) at 03:30 LST, reversing in direction at ~08:30 LST, and gradually reaching ~10 m s−1 equatorward at ~13:30 LST. The quiet time zonal drifts (meridional electric fields) displayed a clear diurnal pattern with peak eastward flows of ~10 m s−1 (0.52 mV m−1 equatorward) at 09:30 LST and peak westward flows around midnight of ~18 m s−1 (0.95 mV m−1 poleward). As the AE index increased, the westward drifts increased in amplitude and they extended over a greater fraction of the day. The perturbation drifts changed in a similar way with decreasing Dst except the daytime equatorward flows strengthened with increasing AE index, whereas they became weak for Dst<−60 nT. The responses in all velocity components to changing solar flux values were small, but net poleward perturbations during the day were associated with large solar flux values (>192×10−22 W m−2 Hz−1). These results help to more fully quantify the response of the mid-latitude ionosphere to changing solar and geomagnetic conditions, as required to refine empirical and theoretical models of mid-latitude electric fields.

scholarly journals Measurement of Stark Halfwidths of Spectral Lines of Ionized Oxygen and Silicon Emitted from T-tube Plasma

Atoms ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 8
Author(s):  
Lazar Gavanski
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Theoretical Models ◽  
Spectral Lines ◽  
Astrophysical Plasmas ◽  
T Tube ◽  
Experimental Values

The analysis of experimental Stark halfwidths of spectral lines of singly ionized oxygen and silicon and double ionized silicon is presented in this work. The considered spectral lines were emitted from plasma generated in an electromagnetically driven T-tube, with an electron temperature of 15,000 K and electron density of 1.45 × 1023 m−3. The obtained Stark halfwidths were compared to experimental values given by other authors. In addition, all experimental values were compared to theoretical values. These data are useful for diagnostics of laboratory and astrophysical plasmas as well as verifying theoretical models.

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 Non-Equilibrium Ionization X-ray Emission from Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 99-107
Author(s):  
J. Michael Shull
Keyword(s):  
Supernova Remnants ◽  
Heavy Element ◽  
Plasma Temperature ◽  
Supernova Explosion ◽  
Theoretical Models ◽  
Astrophysical Plasmas ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Elemental Abundances ◽  
Stellar Nucleosynthesis

X-ray spectra of young supernova remnants (SNR's) are perhaps the most spectacular examples of hot, line-emitting astrophysical plasmas. Heated to temperatures of 1 to 10 keV and enriched with the heavy element products of stellar nucleosynthesis, the plasma inside these SNR's emits prodigiously in lines of 0, Ne, Mg, Si, S, Ar, Ca, and Fe. Theoretical models of this emission provide measures of the plasma temperature and density, elemental abundances, and the degree of approach to ionization equilibrium. Thus, astrophysicists are offered the opportunity to test their understanding of the supernova explosion, its interaction with the interstellar medium, and the nucleo-synthetic processes which enrich our galaxy with heavy elements.

Dust Grain Detection by Solar Orbiter, Parker Solar Probe, and Magnetospheric Multiscale (MMS) Mission — Similarities and Differences

2021 ◽  
Author(s):  
Jakub Vaverka ◽  
Jiří Pavlů ◽  
Libor Nouzák ◽  
Samuel Kočiščák ◽  
Jana Šafránková ◽  
...  
Keyword(s):  
Electric Field ◽  
Dipole Antenna ◽  
Measured Signal ◽  
Impact Detection ◽  
Magnetospheric Multiscale ◽  
Dust Detection ◽  
Antenna Configuration ◽  
Similarities And Differences ◽  
Dust Grain ◽  
Established Technique

&lt;p&gt;The dust impact detection by electric field instruments is already a well-established technique. On the other hand, not all aspects of signal generation by dust impacts and its consequent detection are completely understood and explained. It has been shown that the design and configuration (monopole/dipole) of the electric field antennas/probes are very important for dust impact detection and understanding of the measured signal. Therefore, it is not straightforward to compare detected signals by various spacecraft. Most of space missions use at the same time either monopole or dipole antenna configuration. However, the MMS simultaneous monopole and dipole measurements provide us with interesting information about dust impact signals. We have analyzed individual electric field waveforms of dust impacts detected by Solar Orbiter, Parker Solar Probe, and MMS to understand similarities and differences of dust detection by various spacecraft with different antenna designs and configurations. This understanding will allow us to reliably compare obtained dust fluxes among individual missions.&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

2008 ◽  
Vol 26 (9) ◽  
pp. 2899-2910 ◽  
Author(s):  
V. V. Lobzin ◽  
V. V. Krasnoselskikh ◽  
K. Musatenko ◽  
T. Dudok de Wit
Keyword(s):  
Electric Field ◽  
Shock Front ◽  
Energetic Electron ◽  
Bow Shock ◽  
Langmuir Waves ◽  
Shock Surface ◽  
High Frequency Electric Field ◽  
Earth’S Bow Shock ◽  
Hidden Periodicities ◽  
Field Fluctuations

Abstract. A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBi<f<fBi, where fBi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

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