Geoeffectiveness of the coronal mass ejections associated with solar proton events

The intensity-time profiles of solar proton events (SPEs) are grouped into three types in the present study. The Type-I means that the intensity-time profile of an SPE has one peak, which occurs shortly after the associated solar flare and coronal mass ejection (CME). The Type-II means that the SPE profile has two peaks: the first peak occurs shortly after the solar eruption, the second peak occurs at the time when the CME-driven shock reaches the Earth, and the intensity of the second peak is lower than the first one. If the intensity of the second peak is higher than the first one, or the SPE intensity increases continuously until the CME-driven shock reaches the Earth, this kind of intensity-time profile is defined as Type-III. It is found that most CMEs associated with Type-I SPEs have no geoeffectiveness and only a small part of CMEs associated with Type-I SPEs can produce minor (−50 nT ≤ Dst ≤ −30 nT) or moderate geomagnetic storms (−100 nT≤ Dst ≤ −50 nT), but never an intense geomagnetic storm (−200 nT ≤ Dst < −100 nT). However, most of the CMEs associated with Type-II and Type-III SPEs can produce intense or great geomagnetic storms (Dst ≤ −200 nT). The solar wind structures responsible for the geomagnetic storms associated with SPEs with different intensity-time profiles have also been investigated and discussed.