English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We use high-resolution images of the sun obtained by the SDO/AIA instrumentto study the evolution of the coronal loops in a flaring solar active region.During 15 February 2011 a X-2.2 class flare occurred in NOAA 11158, a$\beta\gamma\delta$ sunspot complex. We identify three distinct phases of thecoronal loop dynamics during this event: (i) {\it Slow rise phase}: slow risingmotion of the loop-tops prior to the flare in response to slow rise of theunderlying flux rope, (ii) {\it Collapse phase}: sudden contraction of theloop-tops with lower loops collapsing earlier than the higher loops, and (iii){\it Oscillation phase}: the loops exhibit global kink oscillations after thecollapse phase at different periods, with period decreasing with decreasingheight of the loops. The period of these loop oscillations is used to estimatethe field strength in the coronal loops of different loop lengths in thisactive region. Further, we also use SDO/HMI observations to study thephotospheric changes close to the polarity inversion line (PIL). Thelongitudinal magnetograms show step-wise permanent decrease in the magneticflux after the flare over a coherent patch along the PIL. Further, we examinethe HMI Stokes I,Q,U,V profiles over this patch and find that the Stokes-Vsignal systematically decreases while the Stokes-Q and U signal increases afterthe flare. These observations suggest that close to the PIL the fieldconfiguration became more horizontal after the flare. We also use HMI vectormagnetic field observations to quantify the changes in the field inclinationangle and found an inward collapse of the field lines towards the polarityinversion line (PIL) by $\sim$ 10$^\circ$. These observations are consistentwith the "coronal implosion" scenario and its predictions about flare relatedphotospheric field changes.

Evidence for collapsing fields in corona and photosphere during the 15 February 2011 X2.2 flare: SDO AIA and HMI Observations