Particles with different energies produce varying contributionsto the total ring current energy density as the storm progresses.Ring current energy densities and total ring current energieswere obtained using particle data from the Polar CAMMICE/MICSinstrument during several storms observed during the years1996-1998. Four different energy ranges for particles areconsidered: total (1-200keV), low (1-20keV),medium (20-80keV) and high (80-200keV). Evolutionof contributions from particles with different energy ranges tothe total energy density of the ring current during all stormphases is followed. To model this evolution we trace protonswith arbitrary pitch angles numerically in the driftapproximation. Tracing is performed in the large-scale andsmall-scale stationary and time-dependent magnetic and electricfield models. Small-scale time-dependent electric field is givenby a Gaussian electric field pulse with an azimuthal field componentpropagating inward with a velocity dependent on radial distance.We model particle inward motion and energization by a series ofelectric field pulses representing substorm activations duringstorm events. We demonstrate that such fluctuating fields in theform of localized electromagnetic pulses can effectivelyenergize the plasma sheet particles to higher energies(>80keV) and transport them inward to closed driftshells. The contribution from these high energy particles dominatesthe total ring current energy during storm recovery phase. Weanalyse the model contributions from particles with differentenergy ranges to the total energy density of the ring currentduring all storm phases. By comparing these results withobservations we show that the formation of the ring current is acombination of large-scale convection and pulsed inward shiftand consequent energization of the ring current particles.
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