Temporal downflows in a penumbra

¹ Astronomical Institute of the Academy of Sciences, Fričova 298, 25165 Ondřejov, Czech Republic
e-mail: jurcak@asu.cas.cz
² National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

Received: 2 April 2010
Accepted: 25 June 2010

Abstract

Aims. We analyze temporal downflow patches that are located in a penumbra and have the same polarity of the magnetic field as a sunspot umbra.

Methods. The repetitive 2′′ wide raster scans of penumbral regions that are taken with one minute cadence by the Hinode spectropolarimeter are used to detect the line-of-sight velocities in the penumbra from enhanced signals in the wings of Stokes V profiles. The lifetimes and positions within penumbra of the identified downflow patches are investigated. The plasma properties of the downflow patches are determined using the inversions of the observed Stokes profiles.

Results. The temporal downflows have lifetimes of up to fourteen minutes. Some of them are related to the disappearance or weakening of nearby upflow regions or to the chromospheric brightenings. The downflows take place in regions with stronger and more vertical magnetic fields than the upflow regions.