Formation of Compact Coronal Structures Associated with the Emerging Magnetic Flux

Details Formation of Compact Coronal Structures Associated with the Emerging Magnetic Flux Formation of Compact Coronal Structures Associated with the Emerging Magnetic Flux

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sh32c01r&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #SH32C-01

Physics

7507 Chromosphere, 7509 Corona, 7529 Photosphere, 7546 Transition Region

Scientific paper

We study the events associated with the emergence of magnetic flux in the photosphere occurring throughout the solar atmosphere from its surface up to the low corona using coordinated observations from Swedish Vacuum Solar Telescope (SVST) on La Palma, the TRACE satellite and the MDI instrument on SOHO. The object of the observations is a plage dominated initially (UT 08:01:03, June 10, 1999) by positive polarity elements with about 0.3 magnetic filling factor near the same polarity sunspot. High resolution MDI magnetograms are assembled in a 6-hour movie and co-aligned with TRACE Fe IX/X 171 Å images of the corona, SVST Ca II K-line images showing the low chromosphere and Hα filtergrams showing plasma motions higher in the chromosphere. To study line of sight motions, we used filtergrams taken in the +/- 350 ~mÅ (and +/- 700 ~mÅ) wings of Hα . During the first two hours, there are almost no changes (at the MDI resolution) in the initial magnetic field pattern of studied region, and the 171 Å emission above this region shows stable amorphous structures. Then a series of events lead to the formation of two opposite polarity pores in the target region and compact coronal loops above it with the following chronology. First, opposite polarity small-scale flux tubes emerge and interact with the existing plage elements. This is followed almost immediately by strong Hα surges, whose peak activity lasts about 10 minutes. After this lag, enhanced emission in 171 Å takes the form of a short-lived transient. During the next one hour (long before the pore and compact coronal loops form), there are several new Hα surges and coronal plasma jets whose activity correlates well with remarkable changes in the photospheric fluxes which eventually form pores. For a quantitative analysis we apply a theoretical model of energy transport from subsurface motions associated with the emerging magnetic flux. Strong disturbances generated in a limited surface area may propagate upward like blast waves along a cone. This in turn may cause a sequence of phenomena associated with forward and reflected shocks, whose signatures are similar to the observations. The process may last as long as significant changes in the photospheric magnetic field occur, until it is suppressed by the strong fields in the pores. Under some condition the established pore structure may be accompanied by a current drive which leads to formation of the coronal loops.

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