Eruption and acceleration of flare‐associated coronal mass ejection loops in the low corona

Abstract

Observations made by the EUV imaging telescope (EIT) and the Large‐Angle Spectrometric Coronagraph (LASCO) on board the Solar Heliospheric Observatory (SOHO) have been used to characterize the eruption and acceleration of flare‐associated coronal mass ejections (CMEs) in the low corona. For three well‐observed limb events we tracked CME loops back to preexisting but faint EUV‐emitting loops at heights of 100–250 Mm that initially brightened slowly and possibly increased slowly in height, apparently in response to filament activity and eruption in the associated active regions. Subsequent CME acceleration coincided with a rapid rise of the soft X‐ray flux, occurred between 100 and 350 Mm above the surface, and may have been as high as 0.5 km s−1 s−1, consistent with an impulsive acceleration of the CME to the speeds observed in subsequent white‐light observations. The existence of a delay of up to 30 min observed between initial filament eruption in H alpha and subsequent high acceleration of the CME in one event implies that there may have been two separate phases of magnetic reconnection, with the initial filament activity acting as a trigger for subsequent CME and energetic particle acceleration in the impulsive stage of the flare. The presence or absence of this impulsive phase may provide a basis for the two types of CMEs that have been discussed in the literature.