Bibcode
Beck, C.; Collados, M. Vera; Khomenko, E.; Rezaei, R.
Bibliographical reference
"12th European Solar Physics Meeting, Freiburg, Germany, held September, 8-12, 2008. Online at http://espm.kis.uni-freiburg.de/, p.2.14"
Advertised on:
9
2008
Citations
0
Refereed citations
0
Description
The chromospheric temperature rise to values above the photospheric
temperature cannot be due to radiative energy transport alone. We will
outline different possibilities for the additional energy transport in
the solar atmosphere by processes that require (or exclude) the presence
of magnetic fields. We will discuss which of them could be identified
and studied in detail using current data. To find the signature of the
different heating processes and derive quantitative estimates of their
efficiency, we analyzed simultaneous spectropolarimetric observations of
photospheric magnetic fields (@630 nm) and intensity spectra of the
chromospheric Ca II H line (396 nm). The mechanical energy flux at
several height layers was derived from the velocity amplitudes of
propagating acoustic waves seen in different spectral lines. The
enhancement of chromospheric (radiation) temperature above the radiative
equilibrium values was taken from an inversion of the Ca II H spectra
with the SIR code assuming local thermal equilibrium (LTE) and complete
redistribution (CRD). We compare the obtained energy values with each
other and with the energy requirements demanded by
theoretical/semi-empirical atmospheric models.
We find that the most important agent of chromospheric heating are
propagating (magneto-)acoustic waves, which suffice to explain the
brightenings in Ca II H spectra and their corresponding temperature
enhancements. The energy contained in these intensity variations of the
Ca II H line, however, is found to be insufficient to maintain a
full-time and full-volume "hot" chromosphere. Additional energy
transport mechanisms without a signature in the Ca II H spectra are thus
necessary. Finally, we will outline which improvements are to be
expected with future observations of higher quality (spatial resolution,
enhanced polarimetric sensitivity, temporal cadence, other spectral
lines) to be achieved with new ground-based telescopes like GREGOR or
EST.