Relationship between multiple substorm onsets and the IMF: A case study

Cheng, C.; Russell, C. T.; Connors, Martin; J., P.

doi:10.1029/2001ja007553

Cited by 12 publications

(10 citation statements)

References 17 publications

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“…In other words, GOES 8 was orbiting from the dawn sector to the morning sector and GOES 10 was going into the dawn sector from the postmidnight sector. The magnetic field at GOES 8 and GOES 10 satellites is defined as: H p, perpendicular to the satellite orbital plane (or paral- These results are similar to those studied by Cheng et al (2002b) and confirm the formation of the substorm current wedge after onsets of two Pi2 bursts. Although GOES 8 was at the dawn sector during the time of interest, the effect of the substorm current wedge could continue from the nightside to the dayside hemisphere.…”

Section: October 8 1999supporting

confidence: 74%

Characteristics of consecutive bursts of Pi2 pulsations observed at the SMALL array: A new implication

Cheng¹,

Russell

Yumoto

et al. 2014

Earth Planet Sp

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Consecutive bursts of Pi2 pulsations are examined with magnetic field data obtained by the SMALL array in 1999. With reference to the H -component magnetic bays in the high-latitude magnetograms at CPMN, 10 events consisting of two consecutive Pi2 bursts simultaneously observed by the Beijing (BJI, L = 1.46) and Wuhan (WHN, L = 1.20) stations are identified as associated with substorm onsets. Owing to the same waveform seen by the CPMN and IGPP/LANL arrays, they are the global phenomena. Their occurrences are mostly in the 2100-2300 LT (local time) sector in which the dominant frequencies at WHN are higher than the mean frequency, but those at BJI are lower and close to the frequency of the surface wave at the plasmapause. Moreover, the LT dependence of azimuth and polarization of two consecutive Pi2 bursts at BJI and WHN are analyzed and consistent with the ULF waves theory by Itonaga and Yumoto (1998). GOES 8 and GOES 10 confirm the formation of the substorm current wedge after the onsets of two Pi2 bursts. Thus during substorm onsets, Pi2 pulsations at low latitudes may result from hydromagnetic waves driven by an impulsive source in the magnetotail which could commence in the longitude of 2230 LT and later propagate westward and eastward as well. Low-latitude Pi2 waves near the source site may be affected by several factors as they propagate by the stimulation of a surface wave at the plasmapause, by a localized field line oscillation inside the plasmapause, and by the magnetospheric/plasmaspheric cavity (resonance) mode.

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Section: October 8 1999supporting

confidence: 74%

Characteristics of consecutive bursts of Pi2 pulsations observed at the SMALL array: A new implication

Cheng¹,

Russell

Yumoto

et al. 2014

Earth Planet Sp

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“…This indicates that this substorm onset can occur when the IMF becomes strongly northward with a declining B y component. As studied by Cheng et al [2002b], the substorm onset occurs while the magnitude of IMF B y decreases. As a result, the reason why sometimes more than two consecutive Pi2 bursts occur may be attributed to the southward IMF moving back to north again and accompanied by a decreasing B y component.…”

Section: Discussionmentioning

confidence: 97%

“…Following Lyons et al [1997], Blanchard et al [2000] attempted to establish the predictability of substorm onsets followed by sharp northward turnings of the IMF and found that some prediction failures may result from an increase in the B y magnitude which presumably opposes magnetotail convection. In addition, Figure 6b in the work of Cheng et al [2002b] shows that the B y magnitude of the IMF decreases before the third onset. Thus the question arises when the IMF becomes northward, can an increase in the B y magnitude stop substorm onset, and can a decrease in the B y magnitude restart onset?…”

Section: Introductionmentioning

confidence: 93%

“…Thus during a magnetospheric substorm, there can be at least two Pi2 bursts in space as well as on the ground as the incident IMF initially becomes southward for a period time and later northward. By mapping the onset time of ground Pi2s to the IMF monitors and substorm‐like magnetic disturbances at geosynchronous satellites on the nightside of 5 May 1999, Cheng et al [2002b] found three successive onsets in a sequence of southward IMF interval followed by a northward IMF interval marked by a single cycle of tail buildup and decay. They suggested that the physical process of the first two successive onsets could be interpreted with the two‐neutral‐point model.…”

Section: Introductionmentioning

confidence: 99%

“…They suggested that the physical process of the first two successive onsets could be interpreted with the two‐neutral‐point model. As for the third onset, Cheng et al [2002b] proposed that tail reconnection might be very unsteady and could stop and restart. Thus what mechanisms let tail reconnection restart again when the IMF is strongly northward after a sequence of north to south and to north again needs further investigation.…”

Section: Introductionmentioning

confidence: 99%

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On the relationships between double‐onset substorm, pseudobreakup, and IMF variation: The 4 September 1999 event

et al. 2005

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[1] The relationships between double-onset substorm, pseudobreakup, and IMF variation were investigated with magnetic, auroral, and particle observations from space to the ground during 0200-0600 UT on 4 September 1999. There were five consecutive bursts of Pi2 pulsations on the ground during the time of interest. The onset time of ground Pi2s maps to the same variation sequence in the IMF structure seen propagating to the Earth in multiple satellite observations in the upstream region. The comparison of auroral and energetic particle data with IMF observations shows that a sequence of two doubleonset substorms intervened by a pseudobreakup appears in two distinct cycles of southward IMF followed by a northward interval. For the first substorm, the first onset begins when the B y magnitude declines after the IMF turns southward for about 90 min, and the second onset occurs after northward turning of the IMF accompanied by an increasing B y magnitude. The pseudobreakup appears while the IMF turns southward and the B y magnitude slightly decreases. For the second substorm, the first onset commences while the IMF remains southward with a steady B y magnitude, and the second onset occurs after the IMF becomes strongly northward and the B y magnitude decreases instead. These observations can be explained with the two-neutral-point model. The first onset occurs when the IMF turns southward. Reconnection at the near-Earth neutral point first begins on closed field lines within the plasma sheet, and the second onset occurs when the IMF turns northward and reconnection at the distant neutral point ceases and reconnection at the near-Earth neutral point may reach the open flux of the tail lobes. In addition, a decrease in the B y magnitude may help reduce magnetotail convection and release all the built-up flux to allow the onset to commence after northward turning of the IMF. If the IMF remains southward, the reduction of magnetotail convection due to a decreasing B y would lead to a pseudobreakup instead. In contrast, an increasing B y magnitude would increase magnetotail convection and weaken magnetospheric substorm after the IMF turns northward. Consequently, for the occurrence of double-onset substorms and pseudobreakups, not only the first onset begins spontaneously during steady southward IMF and the second onset appears after northward turning of the IMF but the B y change also affects magnetotail convection which may evoke (or abate) the substorm-related activation while the IMF turns southward (or northward).

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Association of consecutive Pi2‐Ps6 band pulsations with earthward fast flows in the plasma sheet in response to IMF variations

2014

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On 11 March 2009, the H component had four consecutive bay-like variations accompanied by positive and negative deflections in the D component across the Atlantic like those affected by the substorm current wedge formation. A train of pulsations with a frequency range 2-10 mHz (referred to as Pi2-Ps6 band), sensed by Time History of Events and Macroscale Interactions during Substorms (THEMIS)/Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) magnetometers, had clearly three consecutive Pi2s followed by a Ps6 at low latitudes, but first Pi2 and then Ps6 at high latitudes mixed with large-amplitude Ps6 at midlatitudes. The geostationary orbit magnetometers sensed similar magnetic perturbations. THEMIS probes first observed earthward fast flows, magnetic dipolarizations, and modulated energetic particle fluxes at~XGSM À9.2 R E , then at~XGSM À7.5 R E for Pi2 and at~XGSM À18.0 R E only for Ps6. They appeared during a very quiet period for northward interplanetary magnetic field (IMF) with a clock angle variation of low to high and then low. The H spectrum shows two harmonic frequencies~2-4 mHz and~8-10 mHz but the D spectrum one dominant frequency~2-4 mHz. Pi2 can result from a combination of fast magnetospheric and plasmaspheric cavity resonances and Ps6 from a fast magnetospheric cavity resonance. The surface waves at the interface separating braking earthward fast flows from the ambient plasma convection region could lead to large-amplitude Ps6 at midlatitudes. Hence, consecutive Pi2-Ps6 band pulsations can be associated with earthward fast flows in the plasma sheet, expectedly driven by magnetotail reconnection, respectively, in the near-Earth region and the distant Earth one in response to IMF variations as in the two-neutral-point model.

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Relationship between multiple substorm onsets and the IMF: A case study

Cited by 12 publications

References 17 publications

Characteristics of consecutive bursts of Pi2 pulsations observed at the SMALL array: A new implication

Characteristics of consecutive bursts of Pi2 pulsations observed at the SMALL array: A new implication

On the relationships between double‐onset substorm, pseudobreakup, and IMF variation: The 4 September 1999 event

Association of consecutive Pi2‐Ps6 band pulsations with earthward fast flows in the plasma sheet in response to IMF variations

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