scholarly journals Polar spacecraft based comparisons of intense electric fields and Poynting flux near and within the plasma sheet-tail lobe boundary to UVI images: An energy source for the aurora

2000 ◽  
Vol 105 (A8) ◽  
pp. 18675-18692 ◽  
Author(s):  
J. R. Wygant ◽  
A. Keiling ◽  
C. A. Cattell ◽  
M. Johnson ◽  
R. L. Lysak ◽  
...  
Keyword(s):  
Energy Source ◽  
Electric Fields ◽  
Plasma Sheet ◽  
Poynting Flux

scholarly journals Magnetic field configuration and field-aligned acceleration of energetic ions during substorm onsets

2001 ◽  
Vol 19 (9) ◽  
pp. 1089-1094 ◽  
Author(s):  
A. Korth ◽  
Z. Y. Pu
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Plasma Sheet ◽  
Field Configuration ◽  
Local Magnetic Field ◽  
Magnetospheric Configuration And Dynamics ◽  
Night Side ◽  
Field Lines ◽  
Synchronous Orbit ◽  
Substorm Onsets

Abstract. In this paper, we present an interpretation of the observed field-aligned acceleration events measured by GEOS-2 near the night-side synchronous orbit at substorm onsets (Chen et al., 2000). We show that field-aligned acceleration of ions (with pitch angle asymmetry) is closely related to strong short-lived electric fields in the Ey direction. The acceleration is associated with either rapid dipolarization or further stretching of local magnetic field lines. Theoretical analysis suggests that a centrifugal mechanism is a likely candidate for the parallel energization. Equatorward or anti-equatorward energization occurs when the tail current sheet is thinner tailward or earthward of the spacecraft, respectively. The magnetic field topology leading to anti-equatorward energization corresponds to a situation where the near-Earth tail undergoes further compression and the inner edge of the plasma sheet extends inwards as close as the night-side geosynchronous altitudes.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet; storms and sub-storms)

scholarly journals A physical mechanism producing suprathermal populations and initiating substorms in the Earth's magnetotail

2008 ◽  
Vol 26 (6) ◽  
pp. 1617-1639 ◽  
Author(s):  
D. V. Sarafopoulos
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Plasma Sheet ◽  
Physical Mechanism ◽  
Energetic Particles ◽  
Dimensional Structure ◽  
Magnetospheric Substorms ◽  
Physical Description ◽  
Fundamental Building Block ◽  
Field Lines

Abstract. We suggest a candidate physical mechanism, combining there dimensional structure and temporal development, which is potentially able to produce suprathermal populations and cross-tail current disruptions in the Earth's plasma sheet. At the core of the proposed process is the "akis" structure; in a thin current sheet (TCS) the stretched (tail-like) magnetic field lines locally terminate into a sharp tip around the tail midplane. At this sharp tip of the TCS, ions become non-adiabatic, while a percentage of electrons are accumulated and trapped: The strong and transient electrostatic electric fields established along the magnetic field lines produce suprathermal populations. In parallel, the tip structure is associated with field aligned and mutually attracted parallel filamentary currents which progressively become more intense and inevitably the structure collapses, and so does the local TCS. The mechanism is observationally based on elementary, almost autonomous and spatiotemporal entities that correspond each to a local thinning/dipolarization pair having duration of ~1 min. Energetic proton and electron populations do not occur simultaneously, and we infer that they are separately accelerated at local thinnings and dipolarizations, respectively. In one example energetic particles are accelerated without any dB/dt variation and before the substorm expansion phase onset. A particular effort is undertaken demonstrating that the proposed acceleration mechanism may explain the plasma sheet ratio Ti/Te≈7. All our inferences are checked by the highest resolution datasets obtained by the Geotail Energetic Particles and Ion Composition (EPIC) instrument. The energetic particles are used as the best diagnostics for the accelerating source. Near Earth (X≈10 RE) selected events support our basic concept. The proposed mechanism seems to reveal a fundamental building block of the substorm phenomenon and may be the basic process/structure, which is now missing, that might help explain the persistent, outstanding deficiencies in our physical description of magnetospheric substorms. The mechanism is tested, checked, and found consistent with substorm associated observations performed ~30 and 60 RE away from Earth.

scholarly journals High-latitude poynting flux from combined Iridium and SuperDARN data

2004 ◽  
Vol 22 (8) ◽  
pp. 2861-2875 ◽  
Author(s):  
C. L. Waters ◽  
B. J. Anderson ◽  
R. A. Greenwald ◽  
R. J. Barnes ◽  
J. M. Ruohoniemi
Keyword(s):  
Electric Fields ◽  
Energy Flux ◽  
High Latitude ◽  
Electromagnetic Energy ◽  
Total Power ◽  
Data Sets ◽  
Poynting Flux ◽  
Magnetic Perturbations ◽  
Magnetometer Data ◽  
A New Technique

Abstract. Field-aligned currents convey stress between the magnetosphere and ionosphere, and the associated low altitude magnetic and electric fields reflect the flow of electromagnetic energy to the polar ionosphere. We introduce a new technique to measure the global distribution of high latitude Poynting flux, S||, by combining electric field estimates from the Super Dual Auroral Radar Network (SuperDARN) with magnetic perturbations derived using magnetometer data from the Iridium satellite constellation. Spherical harmonic methods are used to merge the data sets and calculate S|| for any magnetic local time (MLT) from the pole to 60° magnetic latitude (MLAT). The effective spatial resolutions are 2° MLAT, 2h MLT, and the time resolution is about one hour due to the telemetry rate of the Iridium magnetometer data. The technique allows for the assessment of high-latitude net S|| and its spatial distribution on one hour time scales with two key advantages: (1) it yields the net S|| including the contribution of neutral winds; and (2) the results are obtained without recourse to estimates of ionosphere conductivity. We present two examples, 23 November 1999, 14:00-15:00 UT, and 11 March 2000, 16:00-17:00 UT, to test the accuracy of the technique and to illustrate the distributions of S|| that it gives. Comparisons with in-situ S|| estimates from DMSP satellites show agreement to a few mW/m2 and in the locations of S|| enhancements to within the technique's resolution. The total electromagnetic energy flux was 50GW for these events. At auroral latitudes, S|| tends to maximize in the morning and afternoon in regions less than 5° in MLAT by two hours in MLT having S||=10 to 20mW/m2 and total power up to 10GW. The power poleward of the Region 1 currents is about one-third of the total power, indicating significant energy flux over the polar cap.

scholarly journals Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux

2004 ◽  
Vol 22 (12) ◽  
pp. 4133-4142 ◽  
Author(s):  
A. Olsson ◽  
P. Janhunen ◽  
T. Karlsson ◽  
N. Ivchenko ◽  
L. G. Blomberg
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Joule Heating ◽  
Building Blocks ◽  
Auroral Zone ◽  
Power Budget ◽  
Flux Method ◽  
Poynting Flux ◽  
Background Magnetic Field ◽  
Magnetospheric Configuration And Dynamics

Abstract. We make a statistical study of ionospheric Joule heating with the Poynting flux method using six months of Astrid-2/EMMA electric and magnetic field data during 1999 (solar maximum year). For the background magnetic field we use the IGRF model. Our results are in agreement with earlier statistical satellite studies using both the ΣPE2 method and the Poynting flux method. We present a rather comprehensive set of fitted Joule heating formulas expressing the Joule heating in given magnetic local time (MLT) and invariant latitude (ILAT) range under given solar illumination conditions as a function of the Kp index, the AE index, the Akasofu epsilon parameter and the solar wind kinetic energy flux. The study thus provides improved and more detailed estimates of the statistical Joule heating. Such estimates are necessary building blocks for future quantitative studies of the power budget in the magnetosphere and in the nightside auroral region. Key words. Ionosphere (electric fields and currents; ionosphere-magnetosphere interactions) – Magnetospheric physics (magnetospheric configuration and dynamics)

Geotail observations of spiky electric fields and low-frequency waves in the plasma sheet and plasma sheet boundary

1994 ◽  
Vol 21 (25) ◽  
pp. 2987-2990 ◽  
Author(s):  
C. Cattell ◽  
F. Mozer ◽  
K. Tsuruda ◽  
H. Hayakawa ◽  
M. Nakamura ◽  
...  
Keyword(s):  
Electric Fields ◽  
Plasma Sheet ◽  
Low Frequency ◽  
Low Frequency Waves

scholarly journals Cluster EDI convection measurements across the high-latitude plasma sheet boundary at midnight

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1669-1681 ◽  
Author(s):  
J. M. Quinn ◽  
G. Paschmann ◽  
R. B. Torbert ◽  
H. Vaith ◽  
C. E. McIlwain ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Latitude ◽  
Plasma Sheet ◽  
Boundary Region ◽  
Electron Drift ◽  
Polar Cap ◽  
Static Structure ◽  
Boundary Crossings ◽  
Instruments And Techniques ◽  
Using Data

Abstract. We examine two crossings of three Cluster satellites from the polar cap into the high-latitude plasma sheet at midnight local time, using data from the Electron Drift Instrument (EDI). EDI measures the full electron drift velocity in the plane perpendicular to the magnetic field for any field and drift directions. The context of the measured convection velocities is established by their relation to the intense enhancements in 1 keV electrons, also measured by EDI, as the satellites move from the polar cap into the plasma sheet boundary. In both cases presented here, the cross B convection in the polar cap is anti-sunward (toward the nightside plasma sheet) with a small duskward component. As the satellites enter the plasma sheet boundary region, the dawn-dusk convective flow component reverses its sign, and the flow in the meridianal plane (toward the center of the plasma sheet) drops substantially. The relatively stable convection in the polar cap becomes highly variable as the PSBL is encountered. The timing and sequence of the boundary crossings by the Cluster satellites are consistent with a relatively static structure on a time scale of the few minutes in satellite separations. In one of the two events, the plasma sheet boundary has a spatially separate structure that is crossed by the satellites before entering the plasma sheet.Key words. Magnetospheric physics (electric fields; magnetopause, cusp and boundary layers; instruments and techniques)

scholarly journals <i>Introduction</i>: The Equator-S mission

1999 ◽  
Vol 17 (12) ◽  
pp. 1499-1502 ◽  
Author(s):  
G. Haerendel ◽  
R. B. Torbert ◽  
H. Höfner
Keyword(s):  
Electric Fields ◽  
Plasma Sheet ◽  
Electron Beams ◽  
Plasma Environment ◽  
Outer Magnetosphere ◽  
Morning Sector ◽  
Hot Plasma ◽  
Operational Life ◽  
Successful Testing

Abstract. In spite of its short operational life of only five months, the major goals of the Equator-S mission were fulfilled, except that its contribution to the ISTP science is restricted to the morning sector of the outer magnetosphere. A set of twelve papers following this introduction is a first documentation of the achievements. They span from the successful testing and operation of the most advanced and complex way of measuring electric fields in a hot plasma environment by means of electron beams, to various investigations at or near the equatorial magnetopause and in the plasma sheet.

scholarly journals Properties of large electric fields in the plasma sheet at 4-7REmeasured with Polar

2001 ◽  
Vol 106 (A4) ◽  
pp. 5779-5798 ◽  
Author(s):  
A. Keiling ◽  
J. R. Wygant ◽  
C. Cattell ◽  
M. Johnson ◽  
M. Temerin ◽  
...  
Keyword(s):  
Electric Fields ◽  
Plasma Sheet
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