  The study of fast, eruptive events in the low solar corona is one of the
science objectives of the Atmospheric Imaging Assembly (AIA) imagers on the
recently launched Solar Dynamics Observatory (SDO), which take full disk images
in ten wavelengths with arcsecond resolution and 12 sec cadence. We study with
AIA the formation of an impulsive coronal mass ejection (CME) which occurred on
June 13, 2010 and was associated with an M1.0 class flare. Specifically, we
analyze the formation of the CME EUV bubble and its initial dynamics and
thermal evolution in the low corona using AIA images in three wavelengths (171,
193 and 211 A). We derive the first ultra-high cadence measurements of the
temporal evolution of the CME bubble aspect ratio
(=bubble-height/bubble-radius). Our main result is that the CME formation
undergoes three phases: it starts with a slow self-similar expansion followed
by a fast but short-lived (~ 70 sec) period of strong lateral over-expansion
which essentially creates the CME. Then the CME undergoes another phase of
self-similar expansion until it exits the AIA field of view. During the studied
interval, the CME height-time profile shows a strong, short-lived, acceleration
followed by deceleration. The lateral overexpansion phase coincides with the
deceleration phase. The impulsive flare heating and CME acceleration are
closely coupled. However, the lateral overexpansion of the CME occurs during
the declining phase and is therefore not linked to flare reconnection. In
addition, the multi-thermal analysis of the bubble does not show significant
evidence of temperature change.
