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Observational Evidence for Coronal and Interplanetary Shocks: The Workshop
Michael L. Kaiser
There is a controversy surrounding solar shocks that cause type II radio
bursts. The controversy concerns the possible causal difference between
the rather ubiquitous metric wavelength type II bursts in the low corona
reported by ground-based radio observatories and the much longer wavelength
interplanetary type II bursts reported by observers using spacecraft receivers.
Some researchers propose that the metric bursts are caused primarily by
shocks associated with impulsive explosions, such as large flares, and
are not driven by material. These shocks die out relatively close
to the sun. Others would say that the metric bursts are caused by
CMEs. On the other hand, hectometric to kilometric wavelength type II bursts
at great distances from the sun (> 10 solar radii) are apparently all associated
with CME-driven shocks. The WAVES instrument on the Wind spacecraft
covers a previously poorly explored decametric to hectometric wavelength
range, between the usual spacecraft and ground-based bands. WAVES
can probe the solar altitude range down to perhaps 2 solar radii, well
into the range where impulsive and CME-driven shocks might coexist, possibly
producing two different type II bursts. We examine the ground-based
metric data and the WAVES decametric-hectometric data for the 28 workshop
events to try to determine if the type II bursts observed in the two different
wavelength regimes can be interpreted as one continuous event. Our
technique is to attempt to fit the observed drift rates and start times
with existing (or slightly modified) coronal density models.
Authors: M. L. Kaiser and M. J. Reiner
Organization: NASA/Goddard Space Flight Center
Address: Code 695
Greenbelt, MD 20771
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