Evidence of Alfvénic Interactions in the Jovian Magnetosphere from the Juno Spacecraft

2020 ◽  
Author(s):  
Christopher T.S Lorch ◽  
Licia C. Ray ◽  
Clare E.J. Watt ◽  
Robert J. Wilson ◽  
Frances Bagenal ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Plasma Sheet ◽  
Energetic Particle ◽  
Magnetospheric Plasma ◽  
Thermal Velocity ◽  
Particle Detector ◽  
Plasma Sheet Boundary Layer ◽  
Dominant Mechanism ◽  
Jovian Magnetosphere

<p>New insights provided by Juno energetic particle detector measurements indicate signatures of Alfvénic acceleration are more common than previously anticipated. Studies at Earth show that Alfvén waves can substantially accelerate plasma within the magnetosphere. At Jupiter, it is now predicted that Alfvénic acceleration is the dominant mechanism for generating the planet's powerful aurora. This acceleration occurs when the plasma thermal velocity is approximately equal to the Alfvén velocity, which at Jupiter occurs around the plasma sheet boundary. Using Juno JADE and MAG data, we investigate the regions surrounding the plasma sheet boundary layer in order to identify signatures of Alfvénic activity. Our study finds correlations between inertial scale magnetic field perturbations and variations in the local plasma population. We suggest that these signatures may be linked to turbulence in the plasma disk, which could be a source of heating for magnetospheric plasma observed in other studies.</p>

scholarly journals On a nonlinear state of the electromagnetic ion/ion cyclotron instability

2000 ◽  
Vol 7 (3/4) ◽  
pp. 173-177
Author(s):  
M. Cremer ◽  
M. Scholer
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Plasma Sheet ◽  
Large Temperature ◽  
Plasma Sheet Boundary Layer ◽  
Temperature Anisotropy ◽  
Nonlinear Properties ◽  
Cyclotron Instability ◽  
Ion Cyclotron ◽  
The Waves

Abstract. We have investigated the nonlinear properties of the electromagnetic ion/ion cyclotron instability (EMIIC) by means of hybrid simulations (macroparticle ions, massless electron fluid). The instability is driven by the relative (super-Alfvénic) streaming of two field-aligned ion beams in a low beta plasma (ion thermal pressure to magnetic field pressure) and may be of importance in the plasma sheet boundary layer. As shown in previously reported simulations the waves propagate obliquely to the magnetic field and heat the ions in the perpendicular direction as the relative beam velocity decreases. By running the simulation to large times it can be shown that the large temperature anisotropy leads to the ion cyclotron instability (IC) with parallel propagating Alfvén ion cyclotron waves. This is confirmed by numerically solving the electromagnetic dispersion relation. An application of this property to the plasma sheet boundary layer is discussed.

A possible mechanism for <theta> aurora formation

1995 ◽  
Vol 13 (7) ◽  
pp. 698-703 ◽  
Author(s):  
B. V. Rezhenov ◽  
I. M. Vardavas
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Plasma Sheet ◽  
Energy Spectra ◽  
System Of Equations ◽  
The Sun ◽  
High Latitudes ◽  
Plasma Sheet Boundary Layer ◽  
Interchange Instability ◽  
Field Lines

Abstract. A mechanism for the formation of <theta> aurora connected with the development of an interchange instability on the plasma sheet boundary layer (PSBL) is suggested. The PSBL is assumed to be deep inside the region of closed magnetic field lines. A system of equations connecting currents in the ionosphere and magnetosphere is solved numerically. It is found, using realistic ionospheric and magnetospheric parameters, that in a period of 8–10 min a system of plasma bars directed to the Sun arises at high latitudes. The system of bars is about 1000 km in width and 3000 km in length and approximates the Θ aurora. The suggested mechanism allows an explanation of a number of Θ aurora features such as the appearance probability, electric field directions, energy spectra of precipitating particles, and its location.

Energetic particle beams in the plasma sheet boundary layer following substorm expansion: Simultaneous near-Earth and distant tail observations

1986 ◽  
Vol 91 (A4) ◽  
pp. 4277 ◽  
Author(s):  
M. Scholer ◽  
D. N. Baker ◽  
G. Gloeckler ◽  
B. Klecker ◽  
F. M. Ipavich ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Energetic Particle ◽  
Plasma Sheet Boundary Layer ◽  
Particle Beams

scholarly journals Magnetic field topology of the plasma sheet boundary layer

2013 ◽  
Vol 118 (7) ◽  
pp. 4059-4065 ◽  
Author(s):  
W.-L. Teh ◽  
R. Nakamura ◽  
W. Baumjohann
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Plasma Sheet ◽  
Plasma Sheet Boundary Layer ◽  
Magnetic Field Topology

scholarly journals On the problem of Plasma Sheet Boundary Layer identification from plasma moments in Earth's magnetotail

2012 ◽  
Vol 30 (9) ◽  
pp. 1331-1343 ◽  
Author(s):  
E. E. Grigorenko ◽  
R. Koleva ◽  
J.-A. Sauvaud
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Velocity Distribution ◽  
Plasma Sheet ◽  
Dynamic Pressure ◽  
Distribution Functions ◽  
Bulk Velocity ◽  
Plasma Sheet Boundary Layer ◽  
Plasma Parameters ◽  
Ion Velocity

Abstract. The problem of identification of the interface region between the lobe and the Plasma Sheet (PS) – the Plasma Sheet Boundary Layer (PSBL) – using ion moments and magnetic field data often arises in works devoted to statistical studies of various PSBL phenomena. Our experience in the identification of this region based on the analysis of ion velocity distribution functions demonstrated that plasma parameters, such as the ion density and bulk velocity, the plasma beta or the dynamic pressure vary widely depending on the state of magnetotail activity. For example, while field-aligned beams of accelerated ions are often observed propagating along the lobeward edge of the PSBL there are times when no signatures of these beams could be observed. In the last case, a spacecraft moving from the lobe region to the PS registers almost isotropic PS-like ion velocity distribution. Such events may be classified as observations of the outer PS region. In this paper, we attempt to identify ion parameter ranges or their combinations that result in a clear distinction between the lobe, the PSBL and the adjacent PS or the outer PS regions. For this we used 100 crossings of the lobe-PSBL-PS regions by Cluster spacecraft (s/c) made in different periods of magnetotail activity. By eye inspection of the ion distribution functions we first identify and separate the lobe, the PSBL and the adjacent PS or outer PS regions and then perform a statistical study of plasma and magnetic field parameters in these regions. We found that the best results in the identification of the lobe-PSBL boundary are reached when one uses plasma moments, namely the ion bulk velocity and density calculated not for the entire energy range, but for the energies higher than 2 keV. In addition, we demonstrate that in many cases the plasma beta fails to correctly identify and separate the PSBL and the adjacent PS or the outer PS regions.

scholarly journals Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL

1997 ◽  
Vol 15 (10) ◽  
pp. 1246-1256 ◽  
Author(s):  
D. V. Sarafopoulos ◽  
E. T. Sarris ◽  
V. Angelopoulos ◽  
T. Yamamoto ◽  
S. Kokubun
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Energetic Particle ◽  
Velocity Dispersion ◽  
Energetic Electron ◽  
Closed Field ◽  
Normal Velocity ◽  
Neutral Sheet ◽  
Plasma Sheet Boundary Layer ◽  
Energetic Electrons

Abstract. We have analyzed the onsets of energetic particle bursts detected by the ICS and STICS sensors of the EPIC instrument on board the GEOTAIL spacecraft in the deep magnetotail (i.e., at distances greater than 180 RE). Such bursts are commonly observed at the plasma-sheet boundary layer (PSBL) and are highly collimated along the magnetic field. The bursts display a normal velocity dispersion (i.e., the higher-speed particles are seen first, while the progressively lower speed particles are seen later) when observed upon entry of the spacecraft from the magnetotail lobes into the plasma sheet. Upon exit from the plasma sheet a reverse velocity dispersion is observed (i.e., lower-speed particles disappear first and higher-speed particles disappear last). Three major findings are as follows. First, the tailward-jetting energetic particle populations of the distant-tail plasma sheet display an energy layering: the energetic electrons stream along open PSBL field lines with peak fluxes at the lobes. Energetic protons occupy the next layer, and as the spacecraft moves towards the neutral sheet progressively decreasing energies are encountered systematically. These plasma-sheet layers display spatial symmetry, with the plane of symmetry the neutral sheet. Second, if we consider the same energy level of energetic particles, then the H+ layer is confined within that of the energetic electron, the He++ layer is confined within that of the proton, and the oxygen layer is confined within the alpha particle layer. Third, whenever the energetic electrons show higher fluxes inside the plasma sheet as compared to those at the boundary layer, their angular distribution is isotropic irrespective of the Earthward or tailward character of fluxes, suggesting a closed field line topology.

Quiet-time Pc 5 pulsations in the Earth's magnetotail: IMP-8, ISEE-1 and ISEE-3 simultaneous observations

1994 ◽  
Vol 12 (2/3) ◽  
pp. 121-138
Author(s):  
D. V. Sarafopoulos ◽  
E. T. Sarris
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Local Time ◽  
Plasma Sheet ◽  
Plasma Sheet Boundary Layer ◽  
Quiet Time ◽  
The North ◽  
First Case ◽  
The Magnetic Field

Abstract. Quasi-periodic Pc 5 pulsations have been reported inside and just outside the Earth's magnetotail during intervals of low geomagnetic activity. In order to further define their characteristics and spatial extent, we present three case studies of simultaneous magnetic field and plasma observations by IMP-8, ISEE-1 (and ISEE-2 in one case) in the Earth's magnetotail and ISEE-3 far upstream of the bow shock, during intervals in which the spacecraft were widely separated. In the first case study, similar pulsations are observed by IMP-8 at the dawn flank of the plasma sheet and by ISEE-1 near the plasma sheet boundary layer (PSBL) near midnight local time. In the second case study, simultaneous pulsations are observed by IMP-8 in the dusk magnetosheath and by ISEE-1 and 2 in the dawn plasma sheet. In the third case study, simultaneous pulsations are observed in the north plasma sheet boundary layer and the south plasma sheet. We conclude that the pulsations occur simultaneously throughout much of the nightside magnetosphere and the surrounding magnetosheath, i.e. that they have a global character. Some additional findings are the following: (a) the observed pulsations are mixed mode compressional and transverse, where the compressional character is more apparent in the close vicinity of the plane ZGSM=0; (b) the compressional pulsations of the magnetic field in the dusk magnetosheath show peaks that coincide (almost one-to-one) with similar peaks observed inside the dawn plasma sheet; (c) in the second case study the polarization sense of the magnetic field and the recurrent left-hand plasma vortices observed in the dawn plasma sheet are consistent with anti-sunward moving waves on the magneto-pause; (d) pulsation amplitudes are weaker in the PSBL(or lobe) as compared with those in the magneto-tail's flanks, suggesting a decay with distance from the magnetopause; (e) the thickness of the plasma sheet (under extremely quiet conditions) is estimated to be ~22 RE at an average location of (X, Y)GSM=(16, 17) RE, whereas at midnight local time the thickness is ~14 RE. The detected pulsations are probably due to the pressure variations (recorded by ISEE-3) in the solar wind, and/or the Kelvin Helmholtz instability in the low-latitude boundary layer or the magnetopause due to a strongly northward IMF.

Plasma Sheet Boundary Layer in Jupiter's Magnetodisk as Observed by Juno

2020 ◽  
Vol 125 (8) ◽  
Author(s):  
X.‐J. Zhang ◽  
Q. Ma ◽  
A. V. Artemyev ◽  
W. Li ◽  
W. S. Kurth ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Plasma Sheet Boundary Layer

scholarly journals On the Nature of the Plasma Sheet Boundary Layer

1991 ◽  
Vol 43 (Supplement1) ◽  
pp. 205-213
Author(s):  
E. W. HONES Jr.
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Plasma Sheet Boundary Layer

scholarly journals Dispersive O<sup>+</sup> conics observed in the plasma-sheet boundary layer with CRRES/LOMICS during a magnetic storm

1996 ◽  
Vol 14 (6) ◽  
pp. 593-607
Author(s):  
M. Wüest ◽  
D. T. Young ◽  
M. F. Thomsen ◽  
B. L. Barraclough ◽  
H. J. Singer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Pitch Angle ◽  
Radiation Effects ◽  
Low Frequency ◽  
Particle Interactions ◽  
Plasma Sheet Boundary Layer ◽  
Angle Scattering ◽  
Central Plasma ◽  
Spacecraft Spin

Abstract. We present initial results from the Low-energy magnetospheric ion composition sensor (LOMICS) on the Combined release and radiation effects satellite (CRRES) together with electron, magnetic field, and electric field wave data. LOMICS measures all important magnetospheric ion species (H+, He++, He+, O++, O+) simultaneously in the energy range 60 eV to 45 keV, as well as their pitch-angle distributions, within the time resolution afforded by the spacecraft spin period of 30 s. During the geomagnetic storm of 9 July 1991, over a period of 42 min (0734 UT to 0816 UT) the LOMICS ion mass spectrometer observed an apparent O+ conic flowing away from the southern hemisphere with a bulk velocity that decreased exponentially with time from 300 km/s to 50 km/s, while its temperature also decreased exponentially from 700 to 5 eV. At the onset of the O+ conic, intense low-frequency electromagnetic wave activity and strong pitch-angle scattering were also observed. At the time of the observations the CRRES spacecraft was inbound at L~7.5 near dusk, magnetic local time (MLT), and at a magnetic latitude of –23°. Our analysis using several CRRES instruments suggests that the spacecraft was skimming along the plasma sheet boundary layer (PSBL) when the upward-flowing ion conic arrived. The conic appears to have evolved in time, both slowing and cooling, due to wave-particle interactions. We are unable to conclude whether the conic was causally associated with spatial structures of the PSBL or the central plasma sheet.

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