| During magnetic storms, which are large perturbations of the Earth's magnetic field, measured by equatorial ground magnetometers, and lasting for days, open field lines are created when the interplanetary magnetic field merges with Earth's closed field lines on the dayside at the magnetopause. The solar wind drags the open field lines to the nightside storing open flux in the magnetotail. Substorms are nature's mechanism for converting magnetic energy stored in the magnetotail when flux is returned to the dayside. A sawtooth event (STE), which is a manifestation of a substorm, is a large-amplitude increase in flux of energetic particles at geosynchronous orbit distance. This dissertation seeks to improve understanding of STEs that occur during geomagnetic storms. While STEs are generally regarded as stormtime phenomena, they were not observed during about 37% of intense storms. This dissertation shows that when the magnetopause has been pushed inside geosynchronous orbit, STEs are not observed. Most STEs occur when the magnetosphere is driven in a manner consistent with geomagnetic storm main phase dynamics. This dissertation further shows that the virial theorem does not apply to STE sequences, and that neither of the two leading models of substorms is consistent with STE observations. |
