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Title: Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse

Abstract

Observations of the February 4, 1983, storm sudden commencement (ssc) by the STARE and SABRE radar systems are presented. The observing stations were in the dusk sector, where the ssc was accompanied by a preliminary reverse impulse (PRI). The radar data show the PRI to be a consequence of the ssc compression wave producing an initial antisunward flow. The polarization of the ssc electric field in the ionosphere is seen to have both longitudinal and latitudinal structure. The observations are discussed in terms of the propagation of the ssc disturbance throughout the magnetosphere.

Authors:
;  [1]
  1. (Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau (West Germany))
Publication Date:
OSTI Identifier:
5962203
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research; (United States); Journal Volume: 92:A1
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MAGNETIC STORMS; SUDDEN COMMENCEMENTS; COMPRESSION; EARTH MAGNETOSPHERE; ELECTRIC FIELDS; HYDROMAGNETIC WAVES; IONOSPHERE; POLARIZATION; RADAR; EARTH ATMOSPHERE; MEASURING INSTRUMENTS; PLANETARY IONOSPHERES; RANGE FINDERS; 661320* - Auroral, Ionospheric, & Magnetospheric Phenomena- (1992-)

Citation Formats

McDiarmid, D.R., and Nielsen, E. Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse. United States: N. p., 1987. Web. doi:10.1029/JA092iA01p00159.
McDiarmid, D.R., & Nielsen, E. Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse. United States. doi:10.1029/JA092iA01p00159.
McDiarmid, D.R., and Nielsen, E. 1987. "Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse". United States. doi:10.1029/JA092iA01p00159.
@article{osti_5962203,
title = {Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse},
author = {McDiarmid, D.R. and Nielsen, E.},
abstractNote = {Observations of the February 4, 1983, storm sudden commencement (ssc) by the STARE and SABRE radar systems are presented. The observing stations were in the dusk sector, where the ssc was accompanied by a preliminary reverse impulse (PRI). The radar data show the PRI to be a consequence of the ssc compression wave producing an initial antisunward flow. The polarization of the ssc electric field in the ionosphere is seen to have both longitudinal and latitudinal structure. The observations are discussed in terms of the propagation of the ssc disturbance throughout the magnetosphere.},
doi = {10.1029/JA092iA01p00159},
journal = {Journal of Geophysical Research; (United States)},
number = ,
volume = 92:A1,
place = {United States},
year = 1987,
month = 1
}
  • Observations by GEOS 1, supported by data collected by IMP 7, IMP 8, and ATS 6 during the July 29, 1977, sudden storm commencement (SSC) have been used to derive the magnetopause's position (7.8R/sub E/ before and 6.1 R/sub E/ after the SSC), velocity (inward speed of about 95 km/s by two independent methods) and thickness (approx.500 km measured by the change in drift pattern). Particle, field and wave data from GEOS 1 have been used to establish the satellite's position with respect to the magnetopause. After the initial crossing of the magnetopause, the satellite remained in the magnetosheath formore » most of the interval considered, occasionally encountering what are interpreted as 'open magnetic field lines.' When the spacecraft was in the magnetosheath, duskward plasma flows tangential to the magnetopause are derived from our electric field measurements. The flow velocity was higher during periods when the interplanetary magnetic field assumed a southward component as compared to periods when a northward component was present. On three occasions, an environment was encountered which was neither typical magnetospheric or magnetosheath-like. It is argued that in the instances GEOS 1 either reentered the magnetosphere or encountered a 'magnetic island,' caused by a tearing mode instability at the magnetopause. The electric field dropped to zero or very small values in these instances.« less
  • Meridian scanning photometer measurements taken in the magnetic postdawn sector at Longyearbyen, Svalbard, between 0300 and 0630 UT on December 29, 1981, are analyzed in conjunction with particle and field data retrieved during two near passes of the Dynamics Explorer 2 (DE 2) satellite. The interval included a sudden storm commencement (SSC) at 0455 UT. Pre-SSC optical and particle measurements showed a system of arcs that are spaced at {approximately} 1.1{degrees} intervals in magnetic latitude, embedded within the region 1 current system and span the convection reversal. The softer particle precipitation appears to have a source near the flanks ofmore » the magnetotail while the harder, more equatorward precipitation originates closer to Earth. During the SSC period the entire sky brightened, with enhanced 630.0-nm emissions extending from the northern horizon to south of magnetic zenith; intense but spatially separated 557.7-nm emissions dominated the southern horizon. DE 2 detected more than an order of magnitude increase and near isotropization of ring current electron fluxes, enhanced precipitation from the plasma sheet and significantly decreased auroral zone convection. Region 1/region 2 currents remained, with wavelike structures superposed. A dual timescale response to the SSC is consistent with ground and satellite measurements. On few minute travel timescales for hydromagnetic waves to pass through the system, magnetospheric particles accelerate and precipitate to increase the ionospheric conductivity. Global, field-aligned currents change more slowly. To maintain similar field-aligned currents with higher ionospheric conductances requires reduced electric fields. After 0520 UT the optical emissions settled into stable, but latitudinally separated, bands of 630.0- and 557.7-nm emissions characteristic of cleft and plasma sheet precipitation, respectively. 55 refs., 10 figs.« less
  • This article develops a model to relate the appearance of storm sudden commencements (ssc) with magnetospheric substorms. They use a data set from a recorded ssc in July 1979 as a model. This events consisted of a loading phase of greater than 1.5 hrs, which was completed in three steps. Each step had the cross-tail current sheet intensify, and expand earthward. At the onset of the third step the ssc was observed to occur. Roughly five minutes later the onset of the expansion phase of the substorm was observed. The authors show from the recorded data that there was amore » gradient in the energetic ion pressure in the plasma sheet near the earth. Such a gradient is capable of supporting a ballooning instability. They develop a model around such a ballooning instability driving the expansion phase of the substorm. Other observations made at this time are consistent with the presence of such a plasma instability in the plasma sheet.« less
  • A 74-nT sudden commencement on July 13, 1982, was observed in the magnetosphere with instruments on the Dynamics Explorer 1 satellite. Inbound, near L = 4.5, the satellite was located at 1,524 magnetic local time and 20{degree} magnetic latitude. The sudden commencement established a strong, ease-west oscillation, with 100-s period, which was observed in the magnetic field, the electric field, and the plasma flow velocity records. There was also a compressional component of this 100-s oscillation and a rapidly damped 300-s compressional pulsation. The compressional oscillations may be evidence of cavity resonances, excited by the sudden commencement. The cavity wavesmore » may, in turn, couple to toroidal waves in field line resonance at the satellite location. In addition the sudden commencement caused the onset of waves with frequencies from 0.1 up to at least 0.5 Hz. The observations are compared with similar reports from earlier pulsations related to sudden commencements.« less