Observation of Linear Polarization in the Infrared Ca II Triplet Lines during Umbral Flashes

López Ariste, A.; Socas-Navarro, H.; Molodij, G.
Bibliographical reference

The Astrophysical Journal, Volume 552, Issue 2, pp. 871-876.

Advertised on:
5
2001
Number of authors
3
IAC number of authors
0
Citations
28
Refereed citations
22
Description
We report on Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires (THEMIS)2 observations of linear polarization events associated with umbral flashes observed in the Ca II infrared (IR) triplet lines. The observed signals are usually delayed in time and shifted in space when compared to the intensity and circular polarization signals from the flash. The observations are compatible with a scenario whereby flashes are produced by a perturbation propagating along the magnetic field lines as they bend out toward the penumbra. Only a fraction of the resolution element appears to be emitting flashlike profiles, as if the waves were propagating only within localized magnetic field lines. This localization, however, does not impede the apparent propagation of the perturbation horizontally within the umbra.