On the relationship between the occurrence of substorm injections and interplanetary parameters during the declining phase of solar cycle 23
Abstract
We have examined the relationship between magnetospheric substorms identified by LANL particle injections and daily interplanetary parameters observed by ACE and Geotail during the second half (from July to December) of 2003, which is the declining phase of solar cycle 23. From a statistical study of the relationship between substorms and interplanetary parameters, the following observational results are obtained: (1) Substorm injection occurrence is very well associated with high-speed stream geomagnetic activity and the correlation coefficient between daily substorm injection occurrence and daily median solar wind speed is ~0.7, implying that solar wind speed itself strongly modulates substorm injection; (2) The average of negative IMF Bz is not responsible for the increase in injections with solar wind speed; and (3) There is the evidence that IMF Bz triggering might be important to substorm injection occurrence. In addition, we tested if the substorms in our study are triggered with several types of northward triggering criteria (growth phase duration time, average Bz during the growth phase, and increase value of Bz after northward turning). We found that the correlation coefficients between the tested IMF Bz triggers and substorm injection occurrence range from 0.60 to 0.80, implying that the tested types of northward turning are responsible for a large fraction of substorms and thus are a significant contributor to the increase in onsets with increasing solar wind speed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMSM43B1327H
- Keywords:
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- 2716 Energetic particles: precipitating;
- 2731 Magnetosphere: outer;
- 2784 Solar wind/magnetosphere interactions;
- 2788 Magnetic storms and substorms (7954);
- 2790 Substorms