Correlations between SAR arc intensity and solar and geomagnetic activity

Lobzin, V. V.; Павлов, А. В.

doi:10.1007/s00585-999-0770-5

Cited by 5 publications

(4 citation statements)

References 35 publications

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“…In addition, the location of substorm onset is statistically observed more duskward during negative B y (Grocott et al, ). Even though STEVE is not associated with high geomagnetic activity, it is interesting to note that the geomagnetic conditions observed here are similar to those observed for SAR arcs (Kozyra et al, ; Lobzin & Pavlov, ; Rees & Roble, ).…”

Section: Solar Wind Conditions and Geomagnetic Activity Indicessupporting

confidence: 81%

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A Statistical Analysis of STEVE

et al. 2018

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There has been an exciting recent development in auroral research associated with the discovery of a new subauroral phenomenon called STEVE (Strong Thermal Emission Velocity Enhancement). Although STEVE has been documented by amateur night sky watchers for decades, it is as yet an unidentified upper atmosphere phenomenon. Observed first by amateur auroral photographers, STEVE appears as a narrow luminous structure across the night sky over thousands of kilometers in the east-west direction. In this paper, we present the first statistical analysis of the properties of 28 STEVE events identified using Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager and the Redline Emission Geospace Observatory (REGO) database. We find that STEVE occurs about 1 hr after substorm onset at the end of a prolonged expansion phase. On average, the AL index magnitude is larger and the expansion phase has a longer duration for STEVE events compared to subauroral ion drifts or substorms. The average duration for STEVE is about 1 hr, and its latitudinal width is~20 km, which corresponds to~¼ of the width of narrow auroral structures like streamers. STEVE typically has an equatorward displacement from its initial location of about 50 km and a longitudinal extent of 2,145 km. Plain Language Summary Strong Thermal Emission Velocity Enhancement (STEVE) is anatmospheric phenomenon that manifests across the night sky as an extremely thin yet long ribbon of vibrant purple and white hues. Although STEVE has been well documented by amateur auroral photographers for several decades, the scientific community only recently stumbled upon this phenomenon. In this paper, we report on the first statistical analysis of STEVE's optical characteristics using ground-based all-sky imagery and examined satellite data to determine the geomagnetic conditions favorable for the formation of STEVE. Our results verify that STEVE is narrow in the north-south direction, but it extends over a wider east-west region. We have also determined that STEVE displaces southward over its lifetime in most observations. More interestingly, all 28 STEVE events identified in this study were observed at the end of a prolonged substorm expansion phase. More recently, Gallardo-Lacourt et al. (2018) analyzed data from the Polar-Orbiting Environmental Satellite (POES)-17 satellite for one STEVE event identified by Time History of Events and Macroscale Interactions GALLARDO-LACOURT ET AL. 9893

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Section: Solar Wind Conditions and Geomagnetic Activity Indicessupporting

confidence: 81%

“…In section , we analyzed the solar wind conditions and geomagnetic indices during the 28 STEVE events. Even though STEVE is not associated with high geomagnetic activity, it is interesting to note that STEVE occurs under similar conditions as observed for SAR arcs (Kozyra et al, ; Lobzin & Pavlov, ; Rees & Roble, ).…”

Section: Discussionmentioning

confidence: 55%

A Statistical Analysis of STEVE

et al. 2018

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“…Intense fluxes up to 1 × 10 10 eV cm −2 s −1 are observed at Millstone Hill during the main phase of geomagnetic storms [ Evans , 1970b]. There have been some studies investigating the ionospheric response to intense electron heat flux inputs and their associated effects on SAR arc excitation [ Kozyra et al , 1997; Lobzin and Pavlov , 1999]. In this paper we keep our storm‐time top boundary electron heat fluxes from the plasmasphere the same as those during nonstorm times to avoid any unnecessary complexity in our discussion of electron temperature variations during storms.…”

Section: Simulation Toolsmentioning

confidence: 99%

A numerical study of the response of ionospheric electron temperature to geomagnetic activity

Wang¹,

Burns²,

Killeen³

2006

J. Geophys. Res.

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[1] The response of ionospheric electron temperatures to geomagnetic activity has been simulated using the Thermosphere-Ionosphere Nested Grid (TING) model. The cause of this response has been analyzed using a new postprocessor for the TING model that looks at the individual physical terms that drive the electron energy equation. It is found that (1) electron temperatures are significantly enhanced in regions of depleted electron densities, especially inside the middle-latitude electron density trough. The most pronounced electron temperature enhancement occurs at the equatorward edge of the trough; (2) this enhancement is produced by heat flux from the plasmasphere, coupled with the effect of the relatively low thermal electron gas heat capacity there and the inefficient heat conduction in the bottomside of the F region, where electron densities have almost vanished; (3) in regions of enhanced electron densities, electron temperatures are significantly decreased as a result of enhanced energy loss to the ions; this prevents the electron temperature ''morning overshoot'' from occurring in the middle and low latitudes; (4) upwelling of molecular-species-rich air from the lower thermosphere to higher altitudes during the storm increases mixing ratios of the neutral molecular species in the F region, thus enhances the relative contribution of the neutral molecular species to the overall electron cooling there; (5) ion frictional heating increases high-latitude F region ion temperatures during geomagnetic storms, causing the ions to transfer energy to the electrons and thus enhancing electron temperatures; and (6) there are no significant electron temperature increases in the E region during the storm because of the rapid energy loss from the electrons to the neutrals.Citation: Wang, W., A. G. Burns, and T. L. Killeen (2006), A numerical study of the response of ionospheric electron temperature to geomagnetic activity,

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“…In fact, storms during this phase can produce ring currents that are dominated by O* [Roeder et al, 1996; Daglis, 1997]. While the values of the magnetospheric heat input necessary to obtain a SAR arc have been quantified for solar maximum [e.g., Kozyra et al, 1990;Fok et al, 1991;Lobzin and Pavlov, 1999], the evolution and configuration of the ring current and plasmasphere that yield these values have not been investigated. A better understanding of these effects of the storm time ring current on the thermal plasma is necessary for rigorous global modeling efforts of the thermosphere, ionosphere, and plasmasphere, as well as for the interpretation of large-scale remote sensing observations from the ground or from space.…”

Section: Introductionmentioning

confidence: 99%