scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Influences of the driver and ambient medium characteristics on the formation of shocks
in the solar atmosphere
Gopalswamy Nat 1 , Xie Hong 2 , Yashiro Seiji 2 , Makela Pertti 2 , Akiyama Sachiko 2
1 NASA Goddard Space Flight Center, 2 The Catholic University of America
Traveling interplanetary (IP) shocks were discovered in the early 1960s, but their solar origin has been
controversial. Early research focused on solar flares as the source of the shocks, but when coronal
mass ejections (CMEs) were discovered, it became clear that fast CMEs clearly can drive the shocks.
Type II radio bursts are excellent signatures of shocks near the Sun. The close correspondence
between type II radio bursts and solar energetic particles (SEPs) makes it clear that the same shock
accelerates ions and electrons. A recent investigation involving a large number of IP shocks revealed
that about 35% of IP shocks do not produce type II bursts or SEPs. Comparing these radio quiet (RQ)
shocks with the radio loud (RL) ones revealed some interesting results: (1) there is no evidence for
blast waves, in that all IP shocks can be attributed to CMEs, (2) a small fraction (20%) of RQ shocks
is associated with ion enhancements at the shocks when they move past the observing spacecraft, (3)
the primary difference between the RQ and RL shocks can be traced to the different kinematic
properties of the associated CMEs and the variation of the characteristic speeds of the ambient
medium, and (4) the shock properties measured at 1 AU are not too different for the RQ and RL
cases due to the interaction of the shock driver with the IP medium that seems to erase the difference.