Volume 442, Number 2, November I 2005
|Page(s)||661 - 671|
|Published online||07 October 2005|
AFS dynamics in a short-lived active region
Dipartimento di Fisica e Astronomia - Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95125 Catania, Italy e-mail: email@example.com
2 INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95125 Catania, Italy
3 Department of Physics, University of Thessaloniki, 54124 Thessaloniki, Greece
Accepted: 5 July 2005
In the framework of the study on active region emergence, we report the results obtained from the analysis of the short-lived (7 days) active region NOAA 10407. The data used were acquired during an observational campaign carried out with the THEMIS telescope in IPM mode in July 2003, coordinated with other ground- and space-based instruments (INAF-OACT, DOT, BBSO, MDI/SOHO, EIT/SOHO, TRACE). We determined the morphological and magnetic evolution of NOAA 10407, as well as the velocity fields associated with its magnetic structures. Within the limits imposed by the spatial and temporal resolution of the images analyzed, the first evidence of the active region formation is initially observed in the transition region and lower corona, and later on (i.e. after about 7 h) in the inner layers, as found in a previous analysis concerning a long-lived, recurrent active region. The results also indicate that the AFS formed in the active region shows typical upward motion at the AFS's tops and downward motion at the footpoints. The velocity values relevant to the upward motions decrease over the evolution of the region, similarly to the case of the recurrent active region, while we notice an increasing trend in the downflow velocity during the early phases of the time interval analyzed by THEMIS. On the other hand, the AFS preceding legs show a higher downflow than the following ones, a result in contrast with that found in the long-lived active region. The chromospheric area overhanging the sunspot umbra shows an upward motion of ∼2 km s-1, while that above the pores shows a downward motion of ~4 km s-1.
Key words: Sun: activity / sunspots / Sun: magnetic fields
© ESO, 2005
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