The Global Statistical Response of the Outer Radiation Belt During Geomagnetic Storms

Murphy, K. R., Watt, Clare, Mann, I. R., Rae, Jonathan, Sibeck, D. G., Boyd, A. J., Forsyth, C. F., Turner, D. L., Claudepierre, S. G., Baker, D. N., Spence, H. E., Reeves, G. D., Blake, J. B. and Fennell, J. (2018) The Global Statistical Response of the Outer Radiation Belt During Geomagnetic Storms. Geophysical Research Letters, 45 (9). pp. 3783-3792. ISSN 0094-8276

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Abstract

Using the total radiation belt electron content calculated from Van Allen Probe phase space density, the time‐dependent and global response of the outer radiation belt during storms is statistically studied. Using phase space density reduces the impacts of adiabatic changes in the main phase, allowing a separation of adiabatic and nonadiabatic effects and revealing a clear modality and repeatable sequence of events in storm time radiation belt electron dynamics. This sequence exhibits an important first adiabatic invariant (μ)‐dependent behavior in the seed (150 MeV/G), relativistic (1,000 MeV/G), and ultrarelativistic (4,000 MeV/G) populations. The outer radiation belt statistically shows an initial phase dominated by loss followed by a second phase of rapid acceleration, while the seed population shows little loss and immediate enhancement. The time sequence of the transition to the acceleration is also strongly μ dependent and occurs at low μ first, appearing to be repeatable from storm to storm.

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