N. Gopalswamy et al., Radio signatures of coronal mass ejection interaction: Coronal mass ejection cannibalism?, ASTROPHYS J, 548(1), 2001, pp. L91-L94
We report the first detection at long radio wavelengths of interaction betw
een coronal mass ejections (CMEs) in the interplanetary medium. The radio s
ignature is in the form of intense continuum-like radio emission following
an interplanetary type II burst. At the time of the radio enhancement, coro
nagraphic images show a fast CME overtaking a slow CME. We interpret the ra
dio enhancement as a consequence of shock strengthening when the shock ahea
d of the fast CME plows through the core of the preceding slow CME. The dur
ation of the radio enhancement is consistent with the transit time of the C
ME-driven shock through the core of the slow CME. As a consequence of the i
nteraction, the core of the slow CME changed its trajectory significantly.
Based on the emission characteristics of the radio enhancement, we estimate
the density of the core of the slow CME to be similar to4 x 10(4) cm(-3).
The CME interaction has important implications for space weather prediction
based on halo CMEs: some of the false alarms could be accounted for by CME
interactions. The observed CME interaction could also explain some of the
complex ejecta at 1 AU, which have unusual composition.