Flowers, Nicholas James; (1998) An investigation of energetic particle injections associated with magnetospheric substorms. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Periods of southward interplanetary magnetic field load the magnetotail with energy that is subsequently unloaded into the magnetosphere by a sequence of processes collectively termed a magnetospheric substorm. The mechanism responsible for the unloading of energy and the process of particle injection into the inner magnetosphere is a source of ongoing controversy. The work presented determines boundaries for the particle injection region using drift tracing and studies the solar wind-substorm relationship. Selection of events during the CRRES epoch is based on dipolarisations seen in magnetometer data and further qualified by retaining only those with accompanying particle injections. Solar wind interaction with the magnetosphere immediately prior to onset is statistically described using superimposed epoch analyses and correlations are sought with injection attributes. Substorm rate is shown to be related to solar wind power, however only a limited connection between event magnitude and solar wind is seen. Work on the substorm trigger process indicates that northward-turning IMF is associated with many onsets although is not mandatory, and the onset mechanism is probably internal although susceptible to external factors. The morphology of substorm injections is investigated by tracing particle signatures to convergence. A relativistic guiding centre drift particle tracing methodology is developed preserving adiabatic invariants, using realistic magnetic fields fitted to magnetometer data and electric field representations. A subset of ten events is traced back to give boundaries to the eastward electron injection region. Leading edge particle tracing is found to be closely dependent on pitch angle, and hence subject to the effects of shell splitting. Pitch angles are inferred from inter-spacecraft leading edge travel times, and found to be below 70°, probably due to removal of higher pitch angles by shell splitting. Particle tracing indicates the electron injection region eastern extent varies between 0300 and 0600 LT with a mean position of 0400 LT.

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