HR: 0800h
AN: SM41A-1103    [Abstracts]
TI: Correlation Between Particle Injections Observed at Geosynchronous Orbit and the Dst Index During Geomagnetic Storms
AU: Moon, G
EM: kafemoon@hanmail.net
AF: Department of Astronomy and Atmospheric Sciences, Kyungpook National University, 1370 Sankyuk-Dong, Buk-ku, Daegu, 702-701 Korea, Republic of
AU: * Ahn, B
EM: bhahn@knu.ac.kr
AF: Department of Earth Science, Kyungpook National University, 1370 Sankyuk-Dong, Buk-ku, Daegu, 702-701 Korea, Republic of
AU: Kamide, Y
EM: kamide@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Honohara 3-13, Toyokawa, 442-8507 Japan
AU: Reeves, G D
EM: reeves@lanl.gov
AF: Los Alamos National Laboratory, NIS-1 MS D-466, Los Alamos, NM 87545 United States
AB: To understand the relationship between geomagnetic storms and substorms, we examine the correlation between dispersionless proton injections observed by geosynchronous satellites and the Dst index during geomagnetic storms. We utilize geomagnetic storms occurred during the period of 1997$-$2002, categorizing them into four classes according to the minimum Dst value, Dst$_{min}$; Severe (Dst$_{min}$$ <$ $-$200 nT), intense ($-$200 nT $\leq$ Dst$_{min}$$ <$$-$100 nT), moderate ($-$100 nT $\leq$ Dst$_{min}$$ <$$-$50 nT), and weak ($-$50 nT $\leq$ Dst$_{min}$$ <$$-$30 nT) storms. We use the proton flux with the energy range from 50 keV to 670 keV observed by the LANL geosynchronous satellites located in the dark hemisphere from 1800 LT to 0600 LT. It is not possible to deduce the amount of the total energy injection into the inner magnetosphere from measurements only by one or two satellites. Nonetheless, we may obtain a quantity that is proportional to the true injection rate during magnetic storms by estimating the flux increase expressed in terms of the flux ratio (f$_{max}$/f$_{pre\_ave}$) and the number of injections, where f$_{pre\_ave}$ and f$_{max}$ represent the average flux of pre-storm level and onset level, respectively. Thus, we propose to introduce a parameter, ›r­’total energy injection parameter (TEIP)›r­_, defined by the product of the flux ratio and the number of injections, as an indicator of the energy injected into the inner magnetosphere. To determine the phase dependence of the substorm contribution to the development of geomagnetic storm, we examine this quantity for the main and recovery phases separately. Several interesting points are noted particularly for the main phase of storms. First, the number of particle injections tends to increase with the storm size. Second, the flux ratio (f$_{max}$/f$_{pre\_ave}$) also tends to increase with the storm size. The correlation coefficient between Dst$_{min}$ and the flux ratio is high, for example, 0.84 for the 50$\sim$75 keV energy channel. Third, there is also a significantly high correlation between TEIP and Dst$_{min}$. Particularly, the correlation coefficients are very high, above 0.85, for those channels of energy, 50$\sim$400 keV, which represent the typical energy range of ring current particles. These results indicate that the substorm expansion activity is higher during the main phase than the recovery phase, suggesting that the substorm expansion activity seems to be closely associated with the development of magnetic storms. Fourth, particle injections during the recovery phase of a storm tend to make the storm last longer. This tendency is particularly prominent for more intense storms.
DE: 2716 Energetic particles, precipitating
DE: 2760 Plasma convection
DE: 2778 Ring current
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting