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Energetics of Magnetic Storms Driven by Corotating Interaction Regions: A Study of Geoeffectiveness
Physics and Astronomy Faculty Research
  • Niescja E Turner, Trinity University
  • E J Mitchell
  • D J Knipp
  • B A Emery
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We investigate the energetics of magnetic storms associated with corotating interaction regions (CIRs). We analyze 24 storms driven by CIRs and compare to 18 driven by ejecta-related events to determine how they differ in overall properties and in particular in their distribution of energy. To compare these different types of events, we look at events with comparable input parameters such as the epsilon parameter and note the properties of the resulting storms. We estimate the energy output by looking at the ring current energy along with ionospheric Joule heating derived from the PC and Dst indices. We also include the energy of auroral precipitation, estimated from NOAA/TIROS and DMSP observations. In general, ejecta-driven storms produce more intense events, as parameterized by Dst*, but they are usually not as long lasting, and in most cases deposit less energy. This is observed even for events that have similar input quantities, such as epsilon. This may be related to the high speed of the solar wind, in that an increased magnetosonic Mach number may influence the reconnection rate and therefore the coupling. Additionally, we find the efficiency of the coupling varies greatly from CIR-driven to ejecta-driven storms, with the CIRdriven storms coupling substantially more efficiently, particularly in the recovery phase. The efficiency of coupling (output energy divided by input energy) for CIRdriven storms in recovery phase was double that of ejecta-driven storms.

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Turner, N. E., Mitchell, E. J., Knipp, D. J. and Emery, B. A. (2006) Energetics of Magnetic Storms Driven by Corotating Interaction Regions: A Study of Geoeffectiveness, in Recurrent Magnetic Storms: Corotating Solar Wind Streams (eds B. Tsurutani, R. McPherron, G. Lu, J. H. A. Sobral and N. Gopalswamy), American Geophysical Union, Washington, D. C.. doi: 10.1029/167GM11