Abstract
Geomagnetic storms are primarily driven by stream interaction regions
(SIRs) and coronal mass ejections (CMEs). Since SIR and CME storms have
different solar wind and magnetic field characteristics, the
magnetospheric response may vary accordingly. Using FAST/TEAMS data, we
investigate the variation of ionospheric O+ and H+ outflow as a function
of geomagnetic storm phase during SIR and CME magnetic storms. The
effects of storm size and solar EUV flux, including solar cycle and
seasonal effects, on storm time ionospheric outflow, are also
investigated. The results show that for both CME and SIR storms, the O+
and H+ fluence peaks during the main phase, and then declines in the
recovery phase. However, for CME storms, there is also significant
increase during the initial phase. Because the outflow starts during the
initial phase in CME storms, there is time for the O+ to reach the
plasma sheet before the start of the main phase. Since plasma is
convected into the ring current from the plasma sheet during the main
phase, this may explain why more O+ is observed in the ring current
during CME storms than during SIR storms. We also find that outflow
fluence is higher for large storms than moderate storms and is higher
during solar maximum than solar minimum.