Abstract
Basing on Yohkoh/SXT images, v. Svestka et al. (1995) and v. Svestka
(1996) described a
number of giant post-flare arches rising sometimes with a constant speed
of 1.1--2.4 km/s during
more than 24 hours up to altitudes of mbox{(250--300)} times 10^{3} km
above the solar limb.
As a rule, these arches are associated with gradual long-duration soft
X-ray events (LDE) being
a signature of coronal mass ejections (CME). An analysis of
the Nobeyama
Radioheliograph
(NRH)
images at 17 GHz reveals the microwave counterparts of such soft
X-ray arches. Some
so-called coronal millimeter wave sources (CMMS) appear to belong to the
same phenomenon
(e.g., Urpo, Pohjolainen, and Kruger, 1994).
We used high-spatial-resolution (~10^{' '}) NRH data to study the
dynamics of a number of
such radio arches. The analysis shows that their evolution is rather
complex reflecting particularly
a three-dimensional character of these structures. In the course of
their development, the
microwave arches are extended also along the solar limb. They change
their internal structure and
location of individual components. Some of these components seem to
remain approximately at
fixed altitudes. However, the leading front and the brightest part of
some microwave arches rises,
especially during the initial phase of the events, with a characteristic
speed of 1--4 km/s that
coincides with that of soft X-ray arches. At some restricted time
intervals, lifting of the arches in
the microwave and soft X-ray ranges display a good correspondence. The
radio arches at 17 GHz
rise to altitudes of at least about 140 times 10^{3} km.
It should be added, that according to the modeling of Hanaoka (1994),
the observed microwave
emission and spatial structure of the arches corresponds as a whole to
thermal free-free radiation
of optically thin plasma at 17 GHz with temperature and emission measure
derived from the
Yohkoh/SXT images, although some differences take place due to the
multi-temperature plasma
in the arches and different emission conditions in the microwave and
soft X-ray ranges.