Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

Abstract

How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use highresolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent oppositepolarity magnetic elements very close to the larger dominant polarity. These opposite-polarity smallscale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca ii H images obtained from the Sunrise Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.

New Evidence that Magnetoconvection Drives Solar–Stellar Coronal Heating

“…We observed, as have a few other researchers (Falconer et al 1997;Chitta et al 2017), that the active region coronal loops Figure 5. A schematic drawing depicting the dependence of the coronal EUV brightness of active region coronal loops on the photospheric magnetic rooting of the loops.…”

Onset of Turbulent Fast Magnetic Reconnection Observed in the Solar Atmosphere

“…During the abrupt rise phase, v A has an upper limit of 750 km s −1 (Appendix B), when the excess turbulent flow speeds are around 80 km s −1 . The predicted FWHM of a current sheet is then roughly 2 When observed at even higher spatial resolution, the bipole may reveal magnetic sub-structures unresolved by SDO/HMI (Chitta et al 2017). These features could add further complexities to turbulence injection.…”

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

“…Watanabe et al 2011;Vissers et al 2013;Peter et al 2014;Kim et al 2015;Vissers et al 2015;Rutten et al 2015;Rezaei & Beck 2015;Nelson et al 2016;Tian et al 2016;Reid et al 2016;Rutten 2016;Nelson et al 2017;Toriumi et al 2017;Hong et al 2017;Libbrecht et al 2017;van der Voort et al 2017;Tian et al 2018;Ulyanov et al 2019;Huang et al 2019;Chen et al 2019). In addition to the above energy bursts and plasma ejections, recent observations have suggested that the cancellation of opposite polarities at the footpoints of coronal loops could be responsible for the brightening of coronal loops (Tiwari et al 2014;Chitta et al 2017b;Huang et al 2018;Chitta et al 2018;Şahin et al 2019).…”