The Coronal Mass Ejection Waiting-time Distribution

The distribution of times ∆t between coronal mass ejections (CMEs) in the Large Angle and Spectrometric Coronagraph (LASCO) CME catalog for the years 1996-2001 is examined. The distribution exhibits a power-law tail ∝ (∆t) with an index γ ≈ −2.36± 0.11 for large waiting times (∆t > 10 hours). The powerlaw index of the waiting-time distribution varies with the solar cycle: for the years 1996-1998 (a period of low activity), the power-law index is γ ≈ −1.86±0.14, and for the years 1999-2001 (a period of higher activity), the index is γ ≈ −2.98±0.20. The observed CME waiting-time distribution, and its variation with the cycle, may be understood in terms of CMEs occurring as a time-dependent Poisson process. The CME waiting-time distribution is compared with that for greater than C1 class solar flares in the Geostationary Operational Environmental Satellite (GOES) catalog for the same years. The flare and CME waiting-time distributions exhibit power-law tails with very similar indices and time variation.