Observation and Modeling of Chromospheric Evaporation in a Coronal Loop Related to Active Region Transient Brightening

Abstract

Using the observations recorded by Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO), the Interface Region Imaging Spectrograph (IRIS) and the Extreme-ultraviolet Imaging Spectrometer (EIS) and X-Ray Telescope (XRT) both on-board Hinode, we present the evidence of chromospheric evaporation in a coronal loop after the occurrence of two active region transient brightenings (ARTBs) at the two footpoints. The chromospheric evaporation started nearly simultaneously in all the three hot channels of AIA such as 131 Å, 94 Å and 335 Å, which was observed to be temperature dependent, being fastest in the highest temperature channel. The whole loop became fully brightened following the ARTBs after ≈ 25 s in 131 Å, ≈ 40 s in 94 Å, and ≈ 6.5 min in 335 Å. The DEM measurements at the two footpoints (i.e., of two ARTBs) and the loop-top suggest that the plasma attained a maximum temperature of ∼10 MK at all these locations. The spectroscopic observations from IRIS revealed the presence of redshifted emission of ∼20 km s −1 in cooler lines like C II and Si IV during the ARTBs that was co-temporal with the evaporation flow at the footpoint of the loop. During the ARTBs, the line width of C II and Si IV increased nearly by a factor of two during the peak emission. Moreover, enhancement in the line width preceded that in the Doppler shift which again preceded enhancement in the intensity. The observed results were qualitatively reproduced by 1-D hydrodynamic simulations where energy was deposited at both the footpoints of a monolithic coronal loop that mimicked the ARTBs identified in the observations.

ALMA observations of transient heating in a solar active region

“…6), which is best seen at the high cadence of the ALMA observations. Interestingly, we do not observe any cospatial 1600 Å emission in the hot loops in either of the events, unlike, for example, in the FAFs reported in Vissers et al (2015) or the transient brightenings in Pariat et al (2009) and Gupta et al (2018), which suggests that the bulk of the plasma is not at temperatures between log T ∼ 4.2−5.1 K to which AIA 1600 Å would be sensitive (Simões et al 2019).…”

Nature of the energy source powering solar coronal loops driven by nanoflares

“…Further observational analysis is required to build statistics on the presence (or lack) of these near-simultaneous footpoint brightenings in association with brightenings of hot coronal loops (e.g. Gupta et al 2018). In addition, it would be interesting to conduct numerical experiments to investigate the role of footpoint reconnection and the local energy deposition in the generation of a nearsimultaneous signal at both footpoints.…”

Solar Ultraviolet Bursts

“…It is not clear if this peak arises from the event as the GOES flux is an average over the entire solar disk, but if it is then the energy of an A-class flare is implied. This event has been studied in more detail in a recent paper of Gupta et al (2018).…”