Coronal Mass Ejection - Interplanetary CMEs

Interplanetary CMEs

CMEs typically reach Earth one to five days after the eruption from the Sun. During their propagation, CMEs interact with the solar wind and the interplanetary magnetic field (IMF). As a consequence, slow CMEs are accelerated toward the speed of the solar wind and fast CMEs are decelerated toward the speed of the solar wind. Fast CMEs (faster than about 500 km s−1) eventually drive a shock. This happens when the speed of the CME in the frame moving with the solar wind is faster than the local fast magnetosonic speed. Such shocks have been observed directly by coronagraphs in the corona and are related to type II radio bursts. They are thought to form sometimes as low as 2 R_s (solar radii). They are also closely linked with the acceleration of solar energetic particles.