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Issue A&A
Volume 418, Number 1, April IV 2004
Page(s) L9 - L12
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20040104



A&A 418, L9-L12 (2004)
DOI: 10.1051/0004-6361:20040104

Letter

New insight into the blinker phenomenon and the dynamics of the solar transition region

J. G. Doyle1, I. I. Roussev2 and M. S. Madjarska3

1  Armagh Observatory, College Hill, Armagh, BT61 9DG, N. Ireland
2  Center for Space Environment Modeling, University of Michigan, 2455 Hayward St, Ann Arbor, MI 48109, USA
3  Mullard Space Science Laboratory, UCL, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK

(Received 21 January 2004 / Accepted 4 March 2004 )

Abstract
We present, for the first time, blinker phenomena being associated with brightenings in pre-existing coronal loops registered by the Extreme-ultraviolet Imaging Telescope (EIT) in Fe XII 195 Å. The brightenings occur during the emergence of new magnetic flux as registered by the Big Bear Solar Observatory (BBSO) magnetograph. The blinkers were identified using simultaneous observations obtained with the Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrograph. In light of the new observational results, we present one possible theoretical interpretation of the blinker phenomenon. We suggest that the blinker activity we observe is triggered by interchange reconnection, serving to provide topological connectivity between newly emerging flux and pre-existing flux. The EIT images show the existence of loop structures prior to the onset of the blinker activity. Based on the available spatial resolution the blinker occurs within, or nearby, an existing coronal loop. The temperature interfaces created in the reconnection process between the cool plasma of the newly emerging loop and the hot plasma of the existing loop are what we suggest to causes the observed activity seen in both the SUMER and CDS data. As the temperature interfaces propagate with the characteristic speed of a conduction front, they heat up the cool chromospheric plasma to coronal temperatures, an increasing volume of which brightens at transition region temperatures. We believe this new interpretation gives further qualitative understanding about the evolution of newly emerging flux on the Sun. This also provides new insight into the dynamic nature of the solar transition region.


Key words: Sun: atmosphere -- transition region -- evolution -- magnetic fields -- UV radiation

Offprint request: J. G. Doyle, jgd@star.arm.ac.uk or http://star.arm.ac.uk/preprints/




© ESO 2004


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