The solar chromosphere
The temperature rises monotonically through the chromosphere, which is about 2500 km thick. The
increase in temperature is very rapid at the boundary between the
middle and high chromosphere and
especially at the transition region between the chromosphere and
corona. Typical transition-region models
give a thickness of only 30 km for the rapid temperature rise from 3x104K to 3x105K and 2500 km for the slower rise from
2x105K to 106K.
However, very little is known
about the transition region and the objective of the spacecraft TRACE
is to study the transition region. TRACE was launched on April 1, 1998.
Figure 1 shows a filament (prominence) in the chromosphere (in the south east part of the Sun) which disappeared on November 6, 1991 in association with a CME.
Figure 2 shows a prominence "Grand Daddy of June 4, 1946" on the solar limb.