Coronal mass ejections, type II radio bursts, and solar energetic particle events in the SOHO era

摘要

Using the extensive and uniform data on coronal mass ejections (CMEs), solarenergetic particle (SEP) events, and type II radio bursts during the SOHOera, we discuss how the CME properties such as speed, width and solar-sourcelongitude decide whether CMEs are associated with type II radio bursts andSEP events. We discuss why some radio-quiet CMEs are associated with smallSEP events while some radio-loud CMEs are not associated with SEP events. Weconclude that either some fast and wide CMEs do not drive shocks or theydrive weak shocks that do not produce significant levels of particleacceleration. We also infer that the Alfvén speed in the corona andnear-Sun interplanetary medium ranges from <200 km/s to ~1600 km/s.Radio-quiet fast and wide CMEs are also poor SEP producers and theassociation rate of type II bursts and SEP events steadily increases withCME speed and width (i.e. energy). If we consider western hemispheric CMEs,the SEP association rate increases linearly from ~30% for 800 km/sCMEs to 100% for ≥1800 km/s. Essentially all type II bursts in thedecametre-hectometric (DH) wavelength range are associated with SEP eventsonce the source location on the Sun is taken into account. This is asignificant result for space weather applications, because if a CMEoriginating from the western hemisphere is accompanied by a DH type IIburst, there is a high probability that it will produce an SEP event.