Magnetic filed dynamics and varying plasma emission in large coronal loops

Abstract

In this study we report detailed observations of magnetic environment at four footpoints of two warm coronal loops observed on 5 May 2016 in NOAA AR 12542 (Loop I) and 17 Dec 2015 in NOAA AR 12470 (Loop II). These loops were connecting a plage region with sunspot periphery (Loop I) and a sunspot umbra (Loop II). We used Solar Dynamics Observatory (SDO) and Goode Solar Telescope (GST) data to describe the phenomenon and understand its causes. The study indicates loop brightening episodes were associated with magnetic flux emergence and cancellation processes observed in SDO's Helioseismic and Magnetic Imager (HMI) and GST's Near InfraRed Imaging Spectrapolarimeter (NIRIS) data. The observed activity was driven by magnetic reconnection between small-scale emerging dipoles and large-scale pre-existing fields, suggesting that the reconnection occurred in the lower chromosphere at the edge of an extended plage region, where the loops were rooted. We suggest that plasma, evaporated during these reconnection events, gradually filled the loops and as it cooled the visible density front propagated from one footpoint of the loop to another at a rate of 90-110 km s${}^{-1}$. This study also indicates that at least some of the bright loops seen in SDO Atmospheric Imaging Assembly images rooted in sunspot umbra may be heated due to magnetic activity taking place at the remote (non-sunspot) footpoint.

References in corpus (17)

• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance
• Numerical simulations of quiet Sun magnetism: On the contribution from a small-scale dynamo
• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• On the generation of solar spicules and Alfvénic waves
• Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
• Vigorous convection in a sunspot granular light bridge
• X-ray and EUV Observations of Simultaneous Short and Long Period Oscillations in Hot Coronal Arcade Loops
• SDO/AIA Observations of a Reflecting Longitudinal Wave in a Coronal Loop
• Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes
• The Heating of Solar Coronal Loops by Alfven Wave Turbulence
• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona
• Properties of chromospheric evaporation and plasma dynamics of a solar flare from IRIS observations
• Spectroscopic Observations of a Coronal Loop: Basic Physical Plasma Parameters Along the Full Loop Length
• Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data
• New Evidence that Magnetoconvection Drives Solar-Stellar Coronal Heating
• Chromospheric Plasma Ejections in a Light Bridge of a Sunspot
• Chromospheric signatures of small-scale flux emergence as observed with NST and Hinode instruments

Cited by in corpus (7)

• Generation of Solar Spicules and Subsequent Atmospheric Heating
• Exploring source region of 3-min slow magnetoacoustic waves observed in coronal fan loops rooted in sunspot umbra
• Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
• Implications of spicule activity on coronal loop heating and catastrophic cooling
• Inferring Line-of-Sight Velocities and Doppler Widths from Stokes Profiles of GST/NIRIS Using Stacked Deep Neural Networks
• Are the brightest coronal loops always rooted in mixed-polarity magnetic flux?
• An Observational Test of Solar Plasma Heating by Magnetic Flux Cancellation