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.

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.

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

&lt;p&gt;New insights provided by Juno energetic particle detector measurements indicate signatures of Alfv&amp;#233;nic acceleration are more common than previously anticipated. Studies at Earth show that Alfv&amp;#233;n waves can substantially accelerate plasma within the magnetosphere. At Jupiter, it is now predicted that Alfv&amp;#233;nic 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 Alfv&amp;#233;n 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 Alfv&amp;#233;nic 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.&lt;/p&gt;

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.

Scales and Units

2018 ◽  
Author(s):  
Kathryn M. de Luna
Keyword(s):  
Language Change ◽  
Historical Linguistics ◽  
Bantu Languages ◽  
The North ◽  
First Case ◽  
Linguistic Evidence ◽  
River Region ◽  
History Of ◽  
Alternative Approaches

This chapter uses two case studies to explore how historians study language movement and change through comparative historical linguistics. The first case study stands as a short chapter in the larger history of the expansion of Bantu languages across eastern, central, and southern Africa. It focuses on the expansion of proto-Kafue, ca. 950–1250, from a linguistic homeland in the middle Kafue River region to lands beyond the Lukanga swamps to the north and the Zambezi River to the south. This expansion was made possible by a dramatic reconfiguration of ties of kinship. The second case study explores linguistic evidence for ridicule along the Lozi-Botatwe frontier in the mid- to late 19th century. Significantly, the units and scales of language movement and change in precolonial periods rendered visible through comparative historical linguistics bring to our attention alternative approaches to language change and movement in contemporary Africa.

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 The effect of simplifications of a numerical mesh on the results of electromagnetic analysis of the Nuclotron-type cable

2018 ◽  
Vol 177 ◽  
pp. 08004
Author(s):  
Łukasz Tomków
Keyword(s):  
Magnetic Field ◽  
Electric Current ◽  
Current Density ◽  
Electric Current Density ◽  
Electromagnetic Analysis ◽  
First Case ◽  
Single Region ◽  
The Magnetic Field

The model of a single Nuclotron-type cable is presented. The goal of this model is to assess the behaviour of the cable under different loads. Two meshes with different simplifications are applied. In the first case, the superconductor in the cable is modelled as single region. Second mesh considers individual strands of the cable. The significant differences between the distributions of the electric current density obtained with both models are observed. The magnetic field remains roughly similar.

Detection of a change in the North-South ratio of count rates of particles of high-energy cosmic rays during a change in the polarity of the magnetic field of the Sun

JETP Letters ◽  
2015 ◽  
Vol 101 (4) ◽  
pp. 228-231
Author(s):  
A. V. Karelin ◽  
O. Adriani ◽  
G. C. Barbarino ◽  
G. A. Bazilevskaya ◽  
R. Bellotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
High Energy ◽  
The Sun ◽  
High Energy Cosmic Rays ◽  
The North ◽  
The Magnetic Field

A two-dimensional analysis of the compressible flow near a reconnection site at the dayside magnetopause

2007 ◽  
Vol 73 (1) ◽  
pp. 89-115 ◽  
Author(s):  
LARS G. WESTERBERG ◽  
HANS O. ÅKERSTEDT
Keyword(s):  
Magnetic Field ◽  
Transition Layer ◽  
Alfven Wave ◽  
The North ◽  
Dayside Magnetopause ◽  
Reconnection Site ◽  
Ideal Magnetohydrodynamic ◽  
North And South ◽  
Magnetic Field Variations ◽  
The Magnetic Field

Abstract.A compressible model of the magnetosheath plasma flow is considered. Magnetic reconnection is assumed to occur in a region stretching from the sub-Solar point to the north. Two locations of the reconnection site are treated: two and four Earth radii from the sub-Solar point, respectively. By treating the transition layer as very thin, we solve the governing equations approximately using the method of matched asymptotic expansions. The behavior of the magnetic field and the plasma velocity close to a reconnection site during the transition from the magnetosheath to the magnetosphere is investigated. We also obtain the development of the transition layer thickness north and south of the reconnection point. The magnetopause transition layer is represented by a large-amplitude Alfvén wave implying that the density is approximately the same across the magnetopause boundary. In order to match the solutions we consider a compressible ideal magnetohydrodynamic model describing density, velocity and magnetic field variations along the outer magnetopause boundary. We also compare the analytical results with solutions from a numerical simulation. The compressible effects on the structure of the magnetic field and the total velocity evolution are visible but not dramatic. It is shown that the transition layer north of the reconnection point is thinner than to the south. The effect is stronger for reconnection at higher latitudes.

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