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Journal ArticleDOI

A correlation of the occurrence of simultaneous sudden magnetospheric compressions and geomagnetic bay onsets with selected geophysical indices

01 Nov 1970-Journal of Atmospheric and Solar-Terrestrial Physics (Pergamon)-Vol. 32, Iss: 11, pp 1819-1830
TL;DR: In this paper, the results of a study of the conditions that affect the occurrence of simultaneous magnetospheric compressions, as indicated by geomagnetic sudden commencements and sudden impulses, were presented.
About: This article is published in Journal of Atmospheric and Solar-Terrestrial Physics.The article was published on 1970-11-01. It has received 92 citations till now. The article focuses on the topics: Geomagnetic secular variation & Ring current.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the interplanetary energy flux is estimated on the basis of the Poynting flux and its variations with the rate of energy dissipation in terms of: (1) the ring-current particle injection, (2) Joule dissipation, and (3) auroral particle injection for 15 major geomagnetic storms.
Abstract: The interplanetary energy flux is estimated on the basis of the Poynting flux and its variations with the rate of energy dissipation in terms of: (1) the ring-current particle injection, (2) Joule dissipation in the ionosphere, and (3) auroral particle injection for 15 major geomagnetic storms. A relationship, in terms of the angle between the interplanetary magnetic field vector and the magnetospheric field vector, is defined by which the growth of geomagnetic storms is closely associated with the Poynting flux. It is found that the energy flux that enters the magnetosphere is dissipated through intramagnetospheric substorm processes. Geomagnetic storm phenomena represent the combined influence of such effects.

744 citations

Journal ArticleDOI
TL;DR: In this article, an empirical model of the near-Earth magnetotail is developed, which depends upon distance downtail (xGSM), the solar wind momentum flux (ρv2sw), and the zGSM component of the interplanetary magnetic field (IMF Bz).
Abstract: Knowledge of the average size and shape of the near-Earth magnetotail is an essential element for our understanding of the magnetospheric response to the influence of the solar wind. An empirical model of the near-Earth magnetotail has been developed, which depends upon distance downtail (xGSM), the solar wind momentum flux (ρv2sw), and the zGSM component of the interplanetary magnetic field (IMF Bz). This model has been created by using the pressure balance relation to calculate a set of flare angles for the nightside magnetopause in the region −22 RE ≤ xGSM ≤ −10 RE. Observations of the magnetic field in the lobe by ISEE 2 and simultaneous observations of the magnetic field and plasma properties of the solar wind by IMP 8 were used to determine the internal and external pressure components, respectively. Examination of calculated flare angle values reveal a dependence upon downtail distance and ρv2sw. Normalized to the median downtail distance and dynamic pressure, the angle of flare of the magnetopause is found to increase linearly with decreasing Bz when the IMF is southward, but there is little variation when the IMF is northward. The empirical function derived for the flaring angle of the magnetotail is used to determine a relation for the radius of the tail. Comparisons with previous empirical models and results are also performed. In addition, values of magnetic flux within the magnetotail are calculated for times of sudden impulse events.

289 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the probability of polar substorms by a large-scale magnetospheric compression associated with a discontinuity in the solar wind using ground magnetogram data, AE index data and satellite geomagnetic data.
Abstract: The probability of triggering of polar substorms by a large-scale magnetospheric compression associated with a discontinuity in the solar wind has been examined statistically using ground magnetogram data, AE index data and satellite geomagnetic data on 125 sudden storm commencements observed during 1967-1970. The triggering probability was found to depend on the amplitude of the sudden storm commencement and on the degree of preceding AE activity. In almost all cases the triggering occurred when the B-Z component of the interplanetary magnetic field was negative or decreasing during the 30 min before the passage of the discontinuity. Transient geomagnetic responses with a time scale of Alfven wave propagation in the polar cap also depend on interplanetary magnetic field conditions.

211 citations

Journal ArticleDOI
TL;DR: In this article, the authors used wind solar wind data and Polar UV imaging data to study the nightside magnetospheric/magnetotail responses to interplanetary shocks/pressure pulses.
Abstract: We use Wind solar wind data and Polar UV imaging data to study the nightside magnetospheric/magnetotail responses to interplanetary shocks/pressure pulses. Of 53 interplanetary shock/pressure pulse events that occurred in 1997 and 1998 at Wind, there are 18 cases where Polar near-midnight UV images are available. All of these 18 events are used in this study. The nightside auroral responses can be classified into three types: substorm expansion phase (SS) (or substorm further intensification) events, pseudobreakup (PB) events, and quiescent (QE) events. It is found that the solar wind preconditions determine the causes of the different auroral responses. A ∼1.5-hour interplanetary magnetic field (IMF) Bs “precondition” (upstream of the interplanetary shock) gives good empirical results. The upstream IMF is strongly southward prior to substorm expansion phase triggerings (44% of all events), the IMF Bz is ∼0 nT for PB triggerings (39% of all events), and the IMF is purely northward for quiescent events (17%). The evidence for IMF Bs preconditioning is interpreted in terms of a plasma sheet loading mechanism. The interplanetary shock compression effects on the near-Earth tail are discussed in light of existing substorm/PB triggering models.

176 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the response of the H component when the IMF is southward and found that the dayside response to solar wind pressure increases is over 25% smaller when southward than when it is northward, presumably because of the region 1 current system associated with dayside reconnection.
Abstract: When the interplanetary field is northward and the solar wind dynamic pressure suddenly increases, the increase in the H component magnetic field on the surface of the Earth at low and mid-latitudes is governed principally by the currents on the magnetopause. Currents in the tail, which act in the opposite sense to the magnetopause currents, are also enhanced. These currents have a smaller effect than the magnetopause currents and have a greater effect at night than in the daytime hours. In this study we examine the response of the H component when the IMF is southward. We find that the dayside response to solar wind pressure increases is over 25% smaller when the IMF is southward than when it is northward, presumably because of the region 1 current system associated with dayside reconnection. At night, the opposite situation ensues. Mid-latitude bays associated with triggered substorms appear to be responsible for an enhanced nighttime response. Thus the ground level response to sudden pressure changes in the solar wind is very sensitive to the direction of the interplanetary magnetic field.

126 citations

References
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Journal ArticleDOI
TL;DR: Magnetic field behavior at synchronous orbit during magnetospheric substorms, interpreting satellite observed data in terms of partial ring currents was investigated in this paper, where the magnetic field behavior was shown to behave similarly to that of the Earth's magnetic field.
Abstract: Magnetic field behavior at synchronous orbit during magnetospheric substorms, interpreting satellite observed data in terms of partial ring currents

193 citations

Journal ArticleDOI
TL;DR: Geomagnetic bays produced by neutral sheet plasma earthward movement resulting from solar wind enlargement of geomagnetic tail are generated by the expansion of the solar wind as mentioned in this paper.

151 citations

Journal ArticleDOI
TL;DR: In this article, it was found that the measurement of ionospheric absorption in arctic regions is a sensitive method of detecting low-energy cosmic rays associated with solar flares, and the normal morphology of these events is described, and details are given of the 24 such events that have been detected in the period from May 1957 through July 1959.
Abstract: As a result of the IGY riometer program, it has been found that the measurement of ionospheric absorption in arctic regions is a sensitive method of detecting low-energy cosmic rays associated with solar flares. The normal morphology of these events is described, and details are given of the 24 such events that have been detected in the period from May 1957 through July 1959. Two features have been noted: an apparent asymmetry in the distribution of cosmic-ray-producing flares across the solar disk; a pronounced degree of uniformity in the distribution of the radio-wave absorption over the terrestrial polar cap. These features are discussed, and tentative explanations are suggested.

104 citations

Journal ArticleDOI
TL;DR: Two dimensional magnetosphere with tail and neutral sheet, using Chapman-Ferraro approximation by mapping in potential plane as mentioned in this paper, using the potential plane as the starting point for the magnetosphere.
Abstract: Two dimensional magnetosphere with tail and neutral sheet, using Chapman-Ferraro approximation by mapping in potential plane

75 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the maximum rate at which the solar wind can do work on the magnetospheric plasma is much greater than is required for supplying the energy dissipated, even with convection velocities as high as about. 1 km/sec.
Abstract: The constant of proportionality between the magnetospheric convection velocity and the magnetic stressing required to produce that velocity is obtained. This constant, the drag coefficient, is independent of the mechanism that drives the convection. From the drag coefficient the rate of dissipation due to joule and viscous heating is obtained as a function of the convection velocity. The driving mechanism must supply at least as much energy as is thus dissipated. It is found that the maximum rate at which the solar wind can do work on the magnetospheric plasma is much greater than is required for supplying the energy dissipated, even with convection velocities as high as about. 1 km/sec (in the ionosphere). Given velocities as high as 1 km/sec, a number of interesting consequences follow, such as particle energization and the Ds current system. The role of viscosity in the dynamics of the ionosphere is assessed. It is found that viscous dissipation is usually not significant. The effect of neutral gas motions on the joule dissipation is considered.

26 citations