An Overview of CMEs in Solar Cycles 23 and 24

Abstract:

Observations of white light CMEs now extend over the last four solar cycles (SCs), including through the maximum of SC 24. SOHO/LASCO has observed all of SC 23 and continues to obtain data through the present. In addition, since 2007 we have had near-Sun observations from the STEREO/SECCHI coronagraphs. In the heliosphere CMEs have been observed with the Solar Mass Ejection Imager (SMEI; 2003 - 2011) and SECCHI heliospheric imagers. CME rates have typically been well correlated with sunspot numbers (SSN). However, since the SC 23/24 minimum, there is evidence that the CME and SSN rates are diverging, with similar SC 24 rise and peak CME rates but much lower SSN rates. It has been suggested that this is related to the weak solar polar magnetic fields during the recent extended minimum and the rise of SC 24. The weak fields also have consequences in various CME parameters and associated effects, such as shocks, energetic particles and geo-activity. I will review these CME observations and effects.