The Scale Height of Charged Particles in Jupiter’s Magnetosphere

2021 ◽  
Author(s):  
Krishan Khurana ◽  
George Hospodarsky ◽  
Chris Paranicas
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Local Time ◽  
Radial Distance ◽  
Sheet Thickness ◽  
Scale Height ◽  
Local Times ◽  
Flux Tubes ◽  
Magnetic Disc ◽  
Dusk Sector

<p>We have recently developed a new technique that uses the timings of any three consecutive current sheet crossings to determine the instantaneous motion of Jupiter’s current sheet relative to the spacecraft. Using this information on the instantaneous location of Jupiter’s current sheet, we have modeled the external field of the magnetic disc observed by Juno and Galileo spacecraft in terms of a Harris current sheet type equilibrium and obtained a map of the thickness of the Jovian current sheet over all local times and radial distances. Our modeling of Juno and Galileo magnetic field data shows that in all local times the current sheet thickness increases with radial distance. We also find that the Jovian current sheet thickness is highly asymmetric in local time, being at its thinnest in the dawn sector and the thickest in the dusk sector. The current sheet thickness on the dayside is comparable to that in the dusk sector. The nightside current sheet is intermediate in its thickness to the dawn and the dusk sectors.</p><p>In this presentation, we use the instantaneous location of the current sheet to model the electron densities measured by the plasma or plasma wave instrument. We show that overall, the scale height of electrons and the current sheet tend to be identical. However, we have encountered many cases where the electrons have a two scale-height structure where a thin plasma sheet is embedded within a thicker current sheet, the cause for which is not known. By using the magnetic field and electron density data, we have computed the plasma content of flux tubes in several local time locations in the magnetosphere. We relate the plasma content of these flux tubes to plasma rotation, plasma density and current sheet thickness. It appears that as flux tubes rotate to the dusk side, they slow down and the plasma scale height increases but the total plasma content remains constant.</p>

Factors Controlling the Thickness of the Jovian Current Sheet

2020 ◽  
Author(s):  
Krishan Khurana ◽  
Chris Paranicas ◽  
George Hospodarsky
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Local Time ◽  
Radial Distance ◽  
Sheet Thickness ◽  
Local Times ◽  
A New Technique ◽  
Open Versus ◽  
Increasing Temperature ◽  
Dusk Sector

<p>The Jovian current sheet is the main repository of Jupiter’s magnetospheric plasma. Spatial variations in its thickness and therefore its plasma content are poorly understood because thickness determination requires a knowledge of the motion of the current sheet relative to the observing spacecraft which is hard to get. Recently, we have developed a new technique that uses the timings of any three consecutive current sheet crossings to determine the instantaneous motion of Jupiter’s current sheet relative to the spacecraft. Next by using this technique and modeling the magnetic field and electron density dataset in terms of Harris current sheet type equilibria we can estimate the thickness and plasma content of the Jovian current sheet over all local times and radial distances. Our modeling of Juno and Galileo magnetic field data shows that in all local times the current sheet thickness increases with radial distance. We also find that the Jovian current sheet is highly asymmetric in local time, being at its thinnest in the dawn sector and the thickest in the dusk sector. The current sheet thickness on the dayside is comparable to that in the dusk sector. The nightside current sheet is intermediate in its thickness to the dawn and the dusk sectors.</p><p>We show that the increase in the thickness of the current sheet with radial distance can be explained in terms of the increasing temperature and therefore the plasma beta of the current sheet with radial distance. However what causes the sharp local time variations of the current sheet is not yet fully understood. We will discuss several models of plasma transport and redistribution in Jupiter’s magnetosphere that can create local time differences in the plasma content and therefore the current sheet thickness. These models have testable implications for the structure of the magnetosphere (open versus closed, convective versus diffusive transport of plasma etc.).</p>

scholarly journals Electric fields and double layers in plasmas

1987 ◽  
Vol 5 (2) ◽  
pp. 233-255 ◽  
Author(s):  
Nagendra Singh ◽  
H. Thiemann ◽  
R. W. Schunk
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Electric Fields ◽  
Sheet Thickness ◽  
High Density ◽  
Effective Length ◽  
Double Layers ◽  
Low Density ◽  
Ambient Magnetic Field ◽  
Cold Plasmas

Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamic features of the double layers are discussed. These features, as seen in simulations, laboratory experiments and theory, indicate that double layers and the currents through them undergo slow oscillations, which are determined by the ion transit time across an effective length of the system in which the double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations have been considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields (parallel to an ambient magnetic field) and double layers in an expanding plasma are discussed.

scholarly journals Magnetic turbulence and particle dynamics in the Earth’s magnetotail

2003 ◽  
Vol 21 (9) ◽  
pp. 1947-1953 ◽  
Author(s):  
G. Zimbardo ◽  
A. Greco ◽  
A. L. Taktakishvili ◽  
P. Veltri ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Sheet Thickness ◽  
Particle Dynamics ◽  
Particle Simulation ◽  
Mhd Waves ◽  
Magnetic Fluctuations ◽  
Magnetic Turbulence ◽  
Magnetospheric Configuration And Dynamics ◽  
Interplanetary Physics

Abstract. The influence of magnetic turbulence in the near-Earth magnetotail on ion motion is investigated by numerical simulation. The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field com-ponent Bn , plus a three-dimensional spectrum of magnetic fluctuations dB which represents the observed magnetic turbulence. The dawn-dusk electric field Ey is also considered. A test particle simulation is performed using different values of Bn and of the fluctuation level dB/B0. We show that when the magnetic fluctuations are taken into account, the particle dynamics is deeply affected, giving rise to an increase in the cross tail transport, ion heating, and current sheet thickness. For strong enough turbulence, the current splits in two layers, in agreement with recent Cluster observations.Key words. Magnetospheric physics (magnetospheric configuration and dynamics) – Interplanetary physics (MHD waves and turbulence) – Electromagnetics (numerical methods)

scholarly journals Quasiperiodic ULF-pulsations in Saturn's magnetosphere

2009 ◽  
Vol 27 (2) ◽  
pp. 885-894 ◽  
Author(s):  
G. Kleindienst ◽  
K.-H. Glassmeier ◽  
S. Simon ◽  
M. K. Dougherty ◽  
N. Krupp
Keyword(s):  
Magnetic Field ◽  
Local Time ◽  
Large Scale ◽  
Rotation Period ◽  
Low Frequency ◽  
Radial Distance ◽  
Main Magnetic Field ◽  
Ulf Wave ◽  
Field Investigations ◽  
Magnetosphere Of Saturn

Abstract. Recent magnetic field investigations made onboard the Cassini spacecraft in the magnetosphere of Saturn show the existence of a variety of ultra low frequency plasma waves. Their frequencies suggest that they are presumably not eigenoscillations of the entire magnetospheric system, but excitations confined to selected regions of the magnetosphere. While the main magnetic field of Saturn shows a distinct large scale modulation of approximately 2 nT with a periodicity close to Saturn's rotation period, these ULF pulsations are less obvious superimposed oscillations with an amplitude generally not larger than 3 nT and show a package-like structure. We have analyzed these wave packages and found that they are correlated to a certain extent with the large scale modulation of the main magnetic field. The spatial localization of the ULF wave activity is represented with respect to local time and Kronographic coordinates. For this purpose we introduce a method to correct the Kronographic longitude with respect to a rotation period different from its IAU definition. The observed wave packages occur in all magnetospheric regions independent of local time, elevation, or radial distance. Independent of the longitude correction applied the wave packages do not occur in an accentuated Kronographic longitude range, which implies that the waves are not excited or confined in the same selected longitude ranges at all times or that their lifetime leads to a variable phase with respect to the longitudes where they have been exited.

scholarly journals Are there current-sheet-like structures in the Earth's magnetotail as in the solar wind – results and implications from high time resolution magnetic field measurements by Cluster

2008 ◽  
Vol 26 (7) ◽  
pp. 1889-1895 ◽  
Author(s):  
G. Li ◽  
E. Lee ◽  
G. Parks
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Time Resolution ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
High Time ◽  
High Time Resolution ◽  
Mhd Turbulence ◽  
Flux Tubes

Abstract. Recent studies of solar wind MHD turbulence show that current-sheet-like structures are common in the solar wind and they are a significant source of solar wind MHD turbulence intermittency. While numerical simulations have suggested that such structures can arise from non-linear interactions of MHD turbulence, a recent study by Borovsky (2006), upon analyzing one year worth of ACE data, suggests that these structures may represent the magnetic walls of flux tubes that separate solar wind plasma into distinct bundles and these flux tubes are relic structures originating from boundaries of supergranules on the surface of the Sun. In this work, we examine whether there are such structures in the Earth's magnetotail, an environment vastly different from the solar wind. We use high time resolution magnetic field data of the FGM instrument onboard Cluster C1 spacecraft. The orbits of Cluster traverse through both the solar wind and the Earth's magnetosheath and magnetotail. This makes its dataset ideal for studying differences between solar wind MHD turbulence and that inside the Earth's magnetosphere. For comparison, we also perform the same analysis when Cluster C1 is in the solar wind. Using a data analysis procedure first introduced in Li (2007, 2008), we find that current-sheet-like structures can be clearly identified in the solar wind. However, similar structures do not exist inside the Earth's magnetotail. This result can be naturally explained if these structures have a solar origin as proposed by Borovsky (2006). With such a scenario, current analysis of solar wind MHD turbulence needs to be improved to include the effects due to these curent-sheet-like structures.

scholarly journals New plasmapause model derived from CHAMP field-aligned current signatures

2013 ◽  
Vol 31 (3) ◽  
pp. 529-539 ◽  
Author(s):  
B. Heilig ◽  
H. Lühr
Keyword(s):  
Local Time ◽  
Activity Index ◽  
Radial Distance ◽  
Local Times ◽  
Topside Ionosphere ◽  
New Model ◽  
L Value ◽  
In Situ Observations ◽  
Value Determination

Abstract. We introduce a new model for the plasmapause location in the equatorial plane. The determination of the L-shell bounding the plasmasphere is based on magnetic field observations made by the CHAMP satellite in the topside ionosphere. Related signals are medium-scale field-aligned currents (MSFAC) (some 10 km scale size). The mid-latitude boundary of these MSFACs is used for determining the plasmapause. We are presenting a procedure for detecting the MSFAC boundary. Reliable L-values are obtained on the night side, whenever the solar zenith angle is below 90°. This means, the boundary is not determined well in the 08:00 to 16:00 magnetic local time (MLT) sector. The radial distance of the boundary is closely controlled by the magnetic activity index Kp. Over the Kp range 0 to 9, the L-value varies from 6 to 2 RE. Conversely, the dependence on solar flux is insignificant. For a fixed Kp level, the obtained L-values of the boundary form a ring on an MLT dial plot with a centre somewhat offset from the geomagnetic pole. This Kp and local time dependent feature is used for predicting the location of the MSFAC boundary at all MLTs based on a single L-value determination by CHAMP. We compared the location of the MSFAC boundary during the years 2001–2002 with the L-value of the plasmapause, determined from in situ observations by the IMAGE spacecraft. The mean difference in radial distance is within a 1 RE range for all local times and Kp values. The plasmapause is generally found earthward of the FAC boundary, except for the duskside. By considering this systematic displacement and by taking into account the diurnal variation and Kp-dependence of the residuals, we are able to construct an empirical model of the plasmapause location that is based on MSFAC measurements from CHAMP. Our new model PPCH-2012 agrees with IMAGE in situ observations within a standard deviation of 0.79 RE.

scholarly journals Cluster as current sheet surveyor in the magnetotail

2013 ◽  
Vol 31 (9) ◽  
pp. 1605-1610 ◽  
Author(s):  
Y. Narita ◽  
R. Nakamura ◽  
W. Baumjohann
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Time Series Data ◽  
Sheet Thickness ◽  
Dynamical Evolution ◽  
Field Measurements ◽  
Three Dimensions ◽  
Series Data ◽  
Time Step ◽  
Analysis Technique

Abstract. A novel analysis technique is presented to estimate the current sheet thickness unambiguously and directly, without associating time series data with spatial structure. The technique is a combination of eigenvalue analysis and minimum variance estimator adapted to Harris current sheet geometry, and needs one-time, four-point magnetic field data as provided by the Cluster spacecraft. Two current sheet parameters, thickness and distance to the spacecraft, can be determined at each time step of the magnetic field measurements. An example is shown from a Cluster magnetotail crossing under quiet magnetospheric conditions, yielding the result that the current sheet thickness is on the scale of the proton gyroradius. The analysis technique can also be used to track the dynamical evolution of the current sheet structure in three dimensions.

scholarly journals Magnetic Stress in Solar System Plasmas

1999 ◽  
Vol 52 (4) ◽  
pp. 733 ◽  
Author(s):  
C. T. Russell
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Current Sheet ◽  
Giant Cells ◽  
The Sun ◽  
Flux Tubes ◽  
Reconnection Region ◽  
Wide Range ◽  
Varying Environments ◽  
The Magnetic Field

Magnetic stresses play an important role in the dynamics of geophysical systems, from deep inside the Earth to the tenuous plasmas of deep space. In the magnetic dynamos inside the sun and the planets, the magnetic stresses of necessity rival the interior mechanical stresses. In solar system plasmas, magnetic stresses play critical roles in the transfer of mass, momentum and energy from one region to another. Coronal mass ejections are rapidly expelled from the sun and their interplanetary manifestations plough through the pre-existing solar wind. Some of these structures resemble flux ropes, bundles of magnetic field wrapped around a central core, and some of these appear to be almost force-free. These structures and similar ones in planetary magnetospheres appear to be created by the mechanism of magnetic reconnection. Solar system plasmas generally organise themselves in giant cells in which the properties are rather uniform, separated by thin current layers across which the properties change rapidly. When the magnetic field on the two sides of one of these current layers changes direction significantly (by over 90°), the magnetic field on opposite sides of the boundary may become linked across the current sheet. If the resulting magnetic stress can accelerate the plasma out of the reconnection region, the process will continue uninterrupted. If not, the process will shut itself off. Such continuous reconnection can occur at the Earth’s magnetopause and those of the magnetised planets. Reconnection in the terrestrial magnetotail current sheet and the jovian current sheet occurs in a setting in which the flow can be blocked on one side, causing reconnection to be inherently time-varying. At Jupiter, this mechanism also separates heavy ions from magnetospheric flux tubes so that the ions can escape but Jupiter can retain its magnetic field. Despite the very wide range of parameters and scales encountered in heliospheric plasmas, there is surprising coherence in the mechanisms in these varying environments.

scholarly journals Representations of hermite processes using local time of intersecting stationary stable regenerative sets

2020 ◽  
Vol 57 (4) ◽  
pp. 1234-1251
Author(s):  
Shuyang Bai
Keyword(s):  
Long Range ◽  
Local Time ◽  
Limit Theorems ◽  
Local Times ◽  
Long Range Dependence ◽  
Random Interval ◽  
Stationary Increments ◽  
Self Similar ◽  
Regenerative Sets

AbstractHermite processes are a class of self-similar processes with stationary increments. They often arise in limit theorems under long-range dependence. We derive new representations of Hermite processes with multiple Wiener–Itô integrals, whose integrands involve the local time of intersecting stationary stable regenerative sets. The proof relies on an approximation of regenerative sets and local times based on a scheme of random interval covering.

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