XRT Picture of the Week (XPOW)

XRT Picture of the Week (XPOW)

XRT Home XRT Mission Ops YouTube

2012 April 03

Click for movies. Also available on YouTube

X-Points, Loop Expansions, and Cusp Loops

Taken on 2012/02/29 with a field of view of about 130x130 arcsec, the observations depicted above show images taken through XRT's thin beryllium filter on the right and AIA's 171 Å channel on the left. Starting with the still frames, we have a nice cusp loop structure in the XRT image. Cusp loops are thought to be evidence for a prior magnetic reconnection event that energized underlying loops, heating them enough to produce the x-ray emission seen here. A catalog of cusp loops can be found at the following links: XRT & SXT. You'll also notice the striking difference between the XRT image and the adjacent AIA image, which lacks the cusp structure because the 171 Å channel traces material at much lower temperatures (1M Kelvin or so, as opposed to greater than around 4M Kelvin for the thin beryllium filter).

Potential reconnection sites, or x-points, are visible a few times throughout the XRT movie (e.g. 10:30), preceding the development of the cusp structures. Loop expansions follow, sweeping toward the x-points and appearing to be evidence of inflow into the reconnection site. Cusp loops, like the one pictured, then develop shortly thereafter. And since cusp loops are thought to indicate outflow from the reconnection site, the localized succession of loop expansions and cusps suggests an interesting flip of the overall flow direction.

Keywords: Cusp, Loop Expansion, X-Point
Filters: Be_thin

(Submitted by Keiji Yoshimura)

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