Features of auroral breakup obtained using data of ground-based television observations: case study

Антонова, Е. Е.; Kornilov, I. A.; Корнилова, Т. А.; Kornilov, Oleg; Stepanova, M. V.

doi:10.5194/angeo-27-1413-2009

Cited by 13 publications

(9 citation statements)

References 33 publications

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“…Localization of an isolated substorm expansion onset is one of the main endeavors of the THEMIS satellite mission. Lui et al (2008) have found that the onset is localized at the geocentric distances <10 R E , confirming previous results (see also the discussion in the paper Antonova et al, 2009a).…”

Section: Introductionsupporting

confidence: 80%

High latitude magnetospheric topology and magnetospheric substorm

et al. 2009

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Abstract. This study is focused on the problem of the localization of substorm expansion onset. In this context, the high latitude topology of transverse magnetospheric currents has been analyzed. This study has included the radial distribution of plasma pressure near noon, obtained using the THEMIS-B satellite data, the daytime compression of magnetic field lines and the existence of magnetic field minima far from the equatorial plane, given by all geomagnetic field models. As a result, the dayside integral transverse currents at the geocentric distances 7-10 R E has been estimated. It is suggested, that nightside transverse currents at geocentric distances ∼7-10 R E are closed inside the magnetosphere and with dayside transverse currents form surrounding the Earth current system (cut ring current or CRC) which topologically is the high latitude continuation of ordinary ring current. A possibility of localization of substorm expansion onset at the nighside CRC region is analyzed using the experimental evidences that the onset is localized at geocentric distances <10 R E .

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Section: Introductionsupporting

confidence: 80%

High latitude magnetospheric topology and magnetospheric substorm

et al. 2009

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“…Our results are consistent with this suggested process for substorm expansion onset. Also, Antonova et al [2009] suggested that a gradual auroral enhancement as found here might lead to an electrostatic instability within the inner plasma sheet. It is also worth noting that pressure angular data (not shown) shows an enhancement of parallel pressure giving a field‐aligned anisotropy > at THE for three of the five events, and at THD for one of the five events, in association with the spatial pressure gradient enhancement.…”

Section: Summary and Discussionmentioning

confidence: 55%

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

et al. 2011

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[1] The azimuthal plasma pressure gradient in the near-Earth plasma sheet makes crucial contributions to field-aligned current (FAC) formation. Numerical simulations and statistical observations have shown that a plasma pressure peak tends to build up in the premidnight region of the near-Earth plasma sheet during the substorm growth phase owing to enhanced magnetic drift. This leads to azimuthal pressure gradients in this region. The temporal variation of the azimuthal pressure gradient may provide an indication for the FAC variations associated with the substorm growth phase and may set up a plasma sheet precondition for the substorm onset being triggered near this region. We take advantage of two of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft separated azimuthally near the orbit apogee and investigate the azimuthal plasma pressure gradient before substorm onset in the R ∼10-12 R E region. Equatorial plasma pressure is estimated by removing the curvature force effect. Five events with the spacecraft footprints mapped very close to the aurora onset region were selected. These events show substantial duskward pressure gradient enhancement 1-5 min before onset. The onset arc, which results from enhanced energetic electron precipitation, was found to intensify simultaneously with the pressure gradient enhancement before onset breakup occurs. Since the energy and energy flux of precipitating electrons reflect the upward FAC strength, these results indicate that the duskward azimuthal pressure gradient enhancement is associated with enhanced upward FAC during the late growth phase and leads to the intensification of the onset auroral arc soon before it breaks up. It is possible that this pressure gradient enhancement may lead to ballooning mode instability and thus substorm onset along the intensifying arc.Citation: Xing, X

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“…[26] The increase in the values of diffusion coefficients with the distance in the tailward direction also can help to explain why the substorm onset takes place deeply inside the magnetosphere, as confirmed by many authors [see, e.g., Samson et al, 1992aSamson et al, , 1992bFrank and Sigwarth, 2000;Lyons et al, 2002;Stepanova et al, 2002;Yahnin et al, 2002;Dubyagin et al, 2003;Antonova et al, 2009], because only the region which was stable before the onset of the substorm expansion phase can become unstable.…”

Section: Discussionmentioning

confidence: 82%

Spatial distribution of the eddy diffusion coefficients in the plasma sheet during quiet time and substorms from THEMIS satellite data

et al. 2011

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During the last decade, a number of studies have shown that turbulent processes in the plasma sheet are very important for the analysis of the formation of quasi‐stable plasma sheet configurations. The existence of this turbulence provides a self‐consistent approach to study the dynamics of the Earth's magnetosphere, including the plasma sheet stability. The turbulence can also be very important for an understanding of the location of an isolated substorm expansion phase onset. In this study the level of turbulence has been evaluated by calculating the eddy diffusion coefficients using the Time History of Events and Macroscale Interactions during Substorms satellite data. It was found that the value of the eddy diffusion coefficients may vary by at least 3 orders of magnitude, generally ranging from 103 to 106 km2/s, increasing with the distance from the Earth. The area of low eddy diffusion coefficients, less than 104 km2/s, is situated at distances below 12 RE in the tail where we found the transition region between the dipole and the tail‐like geomagnetic field configuration. This region is consistent with the location of isolated substorms, as indicated by the first auroral arc brightening situated at the equatorial edge of the auroral oval.

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Features of auroral breakup obtained using data of ground-based television observations: case study

Cited by 13 publications

References 33 publications

High latitude magnetospheric topology and magnetospheric substorm

High latitude magnetospheric topology and magnetospheric substorm

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

Spatial distribution of the eddy diffusion coefficients in the plasma sheet during quiet time and substorms from THEMIS satellite data

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