Ring current behaviour during corotating interaction region and high speed stream events

Sørbø, M.; Søraas, F.; Sandanger, Marit Irene; Evans, David S.

doi:10.1016/j.jastp.2008.08.012

Cited by 6 publications

(7 citation statements)

References 41 publications

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“…It is surprising that for the isotropy boundary to play a role in the LAE dynamics of the CIR‐driven storm of 11 October 2008, the isotropy boundary must be located deep inside the inner magnetosphere, suggesting that other mechanisms are responsible for the scattering of protons into the loss cone. For CIR storms, fluctuations in IMF Bz component may cause numerous small injections and fluctuations in the location of the isotropy boundary for protons [ Sørbø et al ., ]. This activity may intensify wave‐particle interactions and cause isotropization of the distribution function in the inner magnetosphere for the 11 October 2008 event.…”

Section: Discussionmentioning

confidence: 99%

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Comparative analysis of low‐altitude ENA emissions in two substorms

et al. 2013

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We report on the dynamics of low‐altitude energetic neutral atom (ENA) emissions during two substorms that occurred during the main phases of two storms: (1) a CIR‐driven storm on 11 October 2008 and (2) a coronal mass ejection (CME)‐driven storm on 5 April 2010. For both of these storms, we have complementary spacecraft and ground‐based observations. The dual‐spacecraft Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) mission obtained ENA images containing low‐altitude emissions (LAEs). Substorm dynamics is inferred from THEMIS all‐sky imagers. TWINS‐observed LAEs are compared with trapped/loss cone proton fluxes from the low‐altitude NOAA/MetOp spacecraft constellation. We find that the timing and intensity profiles of LAEs are different for the two selected events. For the 11 October 2008 event, the LAEs rise during substorm recovery phase and storm main phase. On 5 April 2010, the LAEs tend to peak near substorm onset. We argue that the different LAE behavior results from different pitch‐angle distributions (PADs) of the ion source population. Ion PADs are isotropic during substorm recovery phase for the 11 October 2008 event and have empty loss cone for the 5 April 2010 event. For both cases, LAE intensification marks the onset of activity in the magnetotail and precedes the large substorm onset. We conclude that the LAE production starts in the transition region between the magnetotail and ring current and may expand/move into the inner magnetosphere together with ring current formation.

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Section: Discussionmentioning

confidence: 99%

“…We stress that MEPED telescopes have a 30° field of view. The meped0 channel can measure a mixed population of loss cone/trapped particles [ Sørbø et al ., ]. Very low fluxes for the meped0 channel therefore indicate that not only is the loss cone empty but also that there are no particles near the loss cone.…”

Section: April 2010 Eventmentioning

confidence: 98%

Comparative analysis of low‐altitude ENA emissions in two substorms

et al. 2013

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“…In turn, enhanced levels of convection and substorm activity inject sub‐relativistic particles into the Earth's inner magnetosphere, leading to the generation of a rich variety of plasma waves [e.g., Miyoshi et al , 2007]. Energization of this plasma sheet population during HSSs contributes to the formation of an enhanced ring current [ Jordanova et al , 2009; Sørbø et al , 2009], and subsequent further energization creates enhanced fluxes in the radiation belts. Most previous studies of CIR storms have been limited to particle fluxes and magnetospheric waves observed at geosynchronous orbit or in a limited L or MLT range, but extensive coverage in the inner magnetosphere is essential to understand the evolution of particle fluxes and magnetospheric waves in the entire inner magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Evolution of chorus waves and their source electrons during storms driven by corotating interaction regions

Thorne

Bortnik

et al. 2012

J. Geophys. Res.

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[1] During Corotating Interaction Region (CIR)-driven storms, relativistic electron fluxes in the outer radiation belt decrease in the main phase, followed by a gradual increase in the recovery phase. Recent studies have shown that whistler mode chorus waves play an important role in accelerating the seed electron population to relativistic energies in the outer radiation belt. However, the evolution of chorus waves and their source electrons responsible for the wave excitation during storm various phases is not well understood. In this study we select 72 CIR-driven storm periods over the interval 2007-2011 to perform superposed epoch analysis of the evolution of chorus waves and source electrons in the L* and MLT range extensively observed by THEMIS during various phases of CIR-driven storms. The wave amplitudes and the occurrence of chorus waves substantially increase and peak in the main phase and gradually decrease in the following recovery phase at L* < $7. The phase space density of source electrons at L* < $7 also increases in the main phase followed by a gradual decay in the recovery phase, showing a remarkable consistency with the evolution of chorus waves. Importantly, the evolution of the chorus wave activity and source electron population is highly dependent on the preceding interplanetary magnetic field (IMF) B z orientation. Our results suggest that the increased activity of chorus waves and source electrons may contribute to the enhanced radiation belt electron flux in the recovery phase of CIR-driven storms, but an additional mechanism is probably required to explain the main phase dropout.

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“…Results indicate a super-hot and super-dense plasma sheet forms at the onset of a HSSdriven storm and is convected Earthwards in a period of a few hours. Energisation of this plasma sheet population during HSSs leads to formation of a enhanced ring current (Jordanova et al, 2009;Sørbø et al, 2009), which is subsequently energised leading to enhanced fluxes in the radiation belts. Fluxes within the belts may fluctuate rapidly during HSSs revealing the balance between sources and sinks, and also our ability to reproduce such fluctuations using theoretical models (Lam et al, 2009).…”

Section: High Speed Solar Wind Streams-recent Progressmentioning

confidence: 99%