The relativistic electron response in the outer radiation belt during magnetic storms

Iles, R. H. A.; Fazakerley, A. N.; Johnstone, A. D.; Meredith, Nigel P.; Bühler, P.

doi:10.5194/angeo-20-957-2002

Cited by 74 publications

(84 citation statements)

References 29 publications

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“…Furthermore trends observed in the data were similar to trends observed in the solar wind velocity distributions (see Table 2) linking the solar wind and the outer electron belt in agreement with earlier studies which used different techniques (e.g. Blake et al, 1997, Iles et al, 2002 and references therein).…”

Section: Outer Electron Radiation Beltsupporting

confidence: 78%

Frequency distributions: from the sun to the earth

Crosby

2011

Nonlin. Processes Geophys.

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Abstract. The space environment is forever changing on all spatial and temporal scales. Energy releases are observed in numerous dynamic phenomena (e.g. solar flares, coronal mass ejections, solar energetic particle events) where measurements provide signatures of the dynamics. Parameters (e.g. peak count rate, total energy released, etc.) describing these phenomena are found to have frequency size distributions that follow power-law behavior. Natural phenomena on Earth, such as earthquakes and landslides, display similar power-law behavior. This suggests an underlying universality in nature and poses the question of whether the distribution of energy is the same for all these phenomena. Frequency distributions provide constraints for models that aim to simulate the physics and statistics observed in the individual phenomenon. The concept of self-organized criticality (SOC), also known as the "avalanche concept", was introduced by Bak et al. (1987Bak et al. ( , 1988, to characterize the behavior of dissipative systems that contain a large number of elements interacting over a short range. The systems evolve to a critical state in which a minor event starts a chain reaction that can affect any number of elements in the system. It is found that frequency distributions of the output parameters from the chain reaction taken over a period of time can be represented by power-laws. During the last decades SOC has been debated from all angles. New SOC models, as well as non-SOC models have been proposed to explain the powerlaw behavior that is observed. Furthermore, since Bak's pioneering work in 1987, people have searched for signatures of SOC everywhere. This paper will review how SOC behavior has become one way of interpreting the power-law behavior observed in natural occurring phenomenon in the Sun down to the Earth.

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Section: Outer Electron Radiation Beltsupporting

confidence: 78%

Frequency distributions: from the sun to the earth

Crosby

2011

Nonlin. Processes Geophys.

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“…Iles et al, 2002), suggesting that substorm activity may be important. Meredith et al (2001) performed a detailed statistical analysis of the plasma wave data from the CRRES spacecraft, and showed that outside of the plasmapause the chorus activity was largely substorm-dependent and all chorus emissions were enhanced when the substorm activity was enhanced.…”

Section: Resultsmentioning

confidence: 99%

Evidence for acceleration of outer zone electrons to relativistic energies by whistler mode chorus

et al. 2002

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Abstract. We use plasma wave and electron data from the Combined Release and Radiation Effects Satellite (CRRES) to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by gyroresonant interactions with whistler mode chorus. In particular, we examine the temporal evolution of the spectral response of the electrons and the waves during the 9 October 1990 geomagnetic storm. The observed hardening of the electron energy spectra over about 3 days in the recovery phase is coincident with prolonged substorm activity, as monitored by the A E index and enhanced levels of whistler mode chorus waves. The observed spectral hardening is observed to take place over a range of energies appropriate to the resonant energies associated with Doppler-shifted cyclotron resonance, as supported by the construction of realistic resonance curves and resonant diffusion surfaces. Furthermore, we show that the observed spectral hardening is not consistent with energy-independent radial diffusion models. These results provide strong circumstantial evidence for a local stochastic acceleration mechanism, involving the energisation of a seed population of electrons with energies of the order of a few hundred keV to relativistic energies, driven by wave-particle interactions involving whistler mode chorus. The results suggest that this mechanism contributes to the reformation of the relativistic outer zone population during geomagnetic storms, and is most effective when the recovery phase is characterised by prolonged substorm activity. An additional significant result of this paper is that we demonstrate that the lower energy part of the storm-time electron distribution is in steady-state balance, in accordance with the Kennel and Petschek (1966) theory of limited stably-trapped particle fluxes.

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“…This variability is caused by an imbalance between acceleration, transport, and loss processes all of which become enhanced during geomagnetic storms (Horne, 2002;Thorne et al, 2005;Horne et al, 2006;Summers et al, 2007). The ratio of post-storm to pre-storm flux was found related to the solar wind speed (Paulikas and Blake, 1979;Reeves et al, 2003) and the direction of the IMF Bz during the storm recovery phase (Iles et al, 2002). On the other hand, Ukhorskiy and Sitnov (2008) suggested that the outer belt can respond differently to similar solar wind driving.…”

Section: Introductionmentioning

confidence: 99%

Recent developments in the radiation belt environment model

Fok

Glocer

Zheng

et al. 2011

Journal of Atmospheric and Solar-Terrestrial Physics

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a b s t r a c tThe fluxes of energetic particles in the radiation belts are found to be strongly controlled by the solar wind conditions. In order to understand and predict the radiation particle intensities, we have developed a physics-based Radiation Belt Environment (RBE) model that considers the influences from the solar wind, ring current and plasmasphere. Recently, an improved calculation of wave-particle interactions has been incorporated. In particular, the model now includes cross diffusion in energy and pitch-angle. We find that the exclusion of cross diffusion could cause significant overestimation of electron flux enhancement during storm recovery. The RBE model is also connected to MHD fields so that the response of the radiation belts to fast variations in the global magnetosphere can be studied. We are able to reproduce the rapid flux increase during a substorm dipolarization on 4 September 2008. The timing is much shorter than the time scale of wave associated acceleration.Published by Elsevier Ltd.

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The relativistic electron response in the outer radiation belt during magnetic storms

Cited by 74 publications

References 29 publications

Frequency distributions: from the sun to the earth

Frequency distributions: from the sun to the earth

Evidence for acceleration of outer zone electrons to relativistic energies by whistler mode chorus

Recent developments in the radiation belt environment model

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