Physics – Plasma Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsm41b2020k&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SM41B-2020
Physics
Plasma Physics
[2134] Interplanetary Physics / Interplanetary Magnetic Fields, [7833] Space Plasma Physics / Mathematical And Numerical Techniques, [7954] Space Weather / Magnetic Storms
Scientific paper
The relative contribution of storm-time ring current development by convection driven by either potential or inductive electric fields has remained an unresolved question in geospace research. Studies have been published supporting each side of this debate, including views that ring current build-up is entirely one or the other. This study presents new insights into the relative roles of these storm main phase processes. We perform a superposed epoch study of 141 intense storms (Dst < -100 nT) using OMNI solar wind and ground-based data. Instead of using a single reference time for the superpositioning of the events, we choose 4 reference times and expand or contract each phase of every event to the average length of this phase, creating a normalized timeline for the superposed epoch analysis. Using the bootstrap method, we statistically demonstrate that timeline normalization results in better reproduction of average storm dynamics compared to conventional methods. Examination of the enhanced resolution Dst reveals an inflection point consistent with two-step main phase development, which is supported by results for the southward interplanetary magnetic field and various ground-based magnetic indices. It is determined that the first step of Dst development is due to potential convective drift, during which an initial ring current is formed. The negative feedback of this hot ion population begins to limit further ring current growth. The second step of the main phase, however, is found to be dominated by substorm activity. It is hypothesized that this is necessary to achieve intense storm Dst levels because the substorm dipolarizations are effective at breaking through the negative feedback barrier of the existing inner magnetospheric hot ion pressure peak. In addition, the plasmaspheric drainage plume could be influencing dayside reconnection rates, which would then change the convective flow in the tail and the development of the ring current.
Gallagher Dennis L.
Katus R. M.
Liemohn Michael W.
Ridley Aaron J.
Zou Shengrong
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