Henriques, V. M. J.; Mathioudakis, M.; Socas-Navarro, H.; de la Cruz Rodríguez, J.
Referencia bibliográfica
The Astrophysical Journal, Volume 845, Issue 2, article id. 102, 12 pp. (2017).
Fecha de publicación:
8
2017
Revista
Número de citas
31
Número de citas referidas
31
Descripción
We perform non-LTE inversions in a large set of umbral flashes,
including the dark fibrils visible within them, and in the quiescent
umbra by using the inversion code NICOLE on a set of full Stokes
high-resolution Ca ii λ8542 observations of a sunspot at disk
center. We find that the dark structures have Stokes profiles that are
distinct from those of the quiescent and flashed regions. They are best
reproduced by atmospheres that are more similar to the flashed
atmosphere in terms of velocities, even if with reduced amplitudes. We
also find two sets of solutions that finely fit the flashed profiles: a
set that is upflowing, featuring a transition region that is deeper than
in the quiescent case and preceded by a slight dip in temperature, and a
second solution with a hotter atmosphere in the chromosphere but
featuring downflows close to the speed of sound at such heights. Such
downflows may be related, or even dependent, on the presence of coronal
loops, rooted in the umbra of sunspots, as is the case in the region
analyzed. Similar loops have been recently observed to have supersonic
downflows in the transition region and are consistent with the earlier
“sunspot plumes,” which were invariably found to display
strong downflows in sunspots. Finally, we find, on average, a magnetic
field reduction in the flashed areas, suggesting that the shock pressure
is moving field lines in the upper layers.
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