Influence of the IMF azimuthal component on magnetospheric substorm dynamics.

Трошичев, О. А.; Kotikov, A. L.; Bolotinskaya, B. D.; Andrezen, V. G.

doi:10.5636/jgg.38.1075

Cited by 49 publications

(33 citation statements)

References 18 publications

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“…For five selected events which had no obvious IMF trigger, By was negative for two, made a negative to positive transition for one, was near zero for another, and for only one case was it positive. These observations tend to support the report of TROSCHICHEV et al (1986), that the triggering probability is enhanced in the presence of a negative By component. estimates.…”

Section: Role Of the Azimuthal Component By On Substorm Triggeringsupporting

confidence: 80%

“…In an accompanying paper by TROSCHICHEV et al (1986) it is reported that the azimuthal component of the IMF can have significant effects on the AL index. One such effect occurs during winter season and causes an enhancement of AL when By changes from positive to negative at a time of southward Bz.…”

Section: Role Of the Azimuthal Component By On Substorm Triggeringmentioning

confidence: 99%

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Solar wind triggering of substorm expansion onset.

McPherron

Terasawa

Nishida

1986

J. geomagn. geoelec

112

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Recent reports claim that the onset of the expansion phase of magnetospheric substorms is triggered by a sudden northward turning of the interplanetary magnetic field vector (IMF). We investigate this claim by studying the relation between sudden onsets of magnetic activity (AL index) and changes in the IMF (rectified electric field). Specific examples of the relation between the solar wind and magnetic activity demonstrate that sharp onsets in AL occasionally appear to be independent of changes in the solar wind, but more frequently they appear to be triggered by northward turnings. A statistical analysis of this relation for the first six months of 1978 shows that auroral zone magnetic disturbance is present during approximately 73% of all hours. Distinct substorms defined by minima in the AL index can be identified in 23% of these disturbed hours. Sharp onsets in AL occur in about 45% of the identified substorms. For the subset of substorms with sharp onsets and corresponding solar wind data, 28% occur during steady southward IMF. However, a larger fraction of the sharp onsets (44%) appears to be correlated with northward turnings of the IMF.Because a significant number of sharp substorm expansion onsets occur during steady solar wind conditions, we conclude that the onset is caused by a process internal to the magnetosphere. However, since many other sharp onsets appear to be correlated with changes in either the IMF orientation or the solar wind dynamic pressure, we conclude this internal process can be influenced by changes in solar wind stress applied to the magnetosphere.

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Section: Role Of the Azimuthal Component By On Substorm Triggeringsupporting

confidence: 80%

Section: Role Of the Azimuthal Component By On Substorm Triggeringmentioning

confidence: 99%

Solar wind triggering of substorm expansion onset.

McPherron

Terasawa

Nishida

1986

J. geomagn. geoelec

112

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“…The R2 FAC, upward at the morning side and downward at the evening side, connect to the ring current region at 4-6 Re and close through a partial ring current flowing from the morning to the evening side near equator (Iijima & Potemra, 1976a,b). The polar ionospheric convection and current systems that could affect the magnetic variations measured from ground within the central polar cap could be divided into distinct categories, DP1, DP2, DP3 (or NBZ), and DP4 (or DPY) characterized by their relation to substorm activity and interplanetary magnetic field conditions (e.g., Wilhjelm et al, 1972;Friis-Christensen & Wilhjelm, 1975;Troshichev et al, 1986;Weimer et al, 2010). Each type of convection pattern comprise field-aligned currents (FAC) and horizontal Hall and Pedersen currents.…”

Section: High-latitude Response To Solar Wind-magnetosphere Interactionsmentioning

confidence: 99%

The Polar Cap PC Indices: Relations to Solar Wind and Global Disturbances

Stauning¹

2012

Exploring the Solar Wind

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“…In general, the validity of the results of our case studies needs to be ascertained and established through analysis of a large number of carefully identified IMF-triggered substorms. Further work is also required to characterize the effects on the dayside equatorial magnetic field of substorms without any identifiable external IMF trigger [Henderson et al, 1996], substorms triggered exclusively by changes in IMF By [Troshichev et al, 1986], and substorms induced by enhancements in solar wind dynamic pressure [e.g., Kokubun et al, 1977].…”

Section: Event Of August 19 1978mentioning

confidence: 99%

Daytime equatorial geomagnetic H field response to the growth phase and expansion phase onset of isolated substorms: Case studies and their implications

Sastri¹,

Rao²,

Rao³

et al. 2001

J. Geophys. Res.

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Abstract. Observations are presented from the Indian magnetometer network (dipole latitude range 1.2øS to 13.5øN) of short-lived (<1 hr) disturbances in the daytime equatorial geomagnetic H field associated with specific phases of isolated substorms. Three well-documented substorms are examined here, of which the expansion onset of each is closely associated with sudden transitions of interplanetary magnetic field (IMF) Bz/By after a >40-min interval of southward Bz. A positive baylike perturbation is found to prevail during the substorm growth phase, followed by a negative baylike disturbance starting precisely at the onset of expansion phase activity. The amplitude of the positive as well as negative bay-type disturbance showed a clear-cut enhancement at locations inside the equatorial electrojet belt when compared with stations away from the electrojet influence, indicative of a significant contribution of ionospheric currents to the bays. This pattern of response, which is found in two out of the three events studied, constitutes the first-time evidence for the occurrence of equatorial H field perturbations related to the growth phase as well as the expansion phase onset for individual substorms. The H field perturbations are suggested to be signatures of prompt penetration by electric fields associated with rapid changes in magnetospheric convection brought about by the swift transitions in the IMF Bz, before shielding by the ring current becomes effective. In the third event, where the growth phase is weak and prolonged, there is no perceptible simultaneous disturbance in the equatorial H field, while the expansion phase onset is associated with a positive bay of very small amplitude (<4 nT).

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Influence of the IMF azimuthal component on magnetospheric substorm dynamics.

Cited by 49 publications

References 18 publications

Solar wind triggering of substorm expansion onset.

Solar wind triggering of substorm expansion onset.

The Polar Cap PC Indices: Relations to Solar Wind and Global Disturbances

Daytime equatorial geomagnetic H field response to the growth phase and expansion phase onset of isolated substorms: Case studies and their implications

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