Abstract
We found evidence that heating of erupting prominence occurs at
the beginning of two events on 1992 November 5 and on 1994 February 20,
which were observed with
the Nobeyama Radioheliograph
at 17GHz.
Both of the events are eruptions of the prominence on the disk, which
are seen as the eruptions of dark filaments.
The radio images of the events show very similasr changes as follows.
Shortly after the filaments began to be accelerated rapidly and to detach
from the disk, the filaments apparently disappear.
However, when the moving filaments pass above bright plage regions,
the plage regions become dark.
These facts indicate that the brightness temperature of the dark filaments
increases to the temperature of the quiet disk at the beginning of the abrupt
eruptions, while the filaments keep their large optical thickness.
After the rapid increase, the brightness temperature does not change
significantly during the motion of the filaments.
In contrast to H alpha, the visibility of prominences in 17GHz images
are not affected by Doppler shifts.
Therefore, changes of the brightness temperature reflect changes of the
cool core of the prominences up to the transition region temperature
is most plausible to explain the observed increase of thr brightness
temperature at 17GHz.