Seray Sahin
Gather.town id
CDH11
Poster Title
Spatial and Temporal Analysis of Coronal Rain by IRIS
Institution
Northumbria University
Abstract (short summary)
The solar corona has many unsolved questions and one of the most important is how it is heated. However, the corona also hosts a cooling problem alongside the heating problem. The corona consists of large amounts of cool and dense material called coronal rain. This cool and dense plasma falling from coronal heights.
In this study, we report the SJI/IRIS observations of coronal rain at the East limb of the Sun observed on 2017 July, 2 between 07:28 UT and 12:55 UT in the 1400 Å and 2796 Å passband. We present here a spatial and temporal analysis of coronal rain. To detect coronal rain, we used the Rolling Hough Transforma (RHT) algorithm (Schad 2017). We calculated the amount of rain in both SJI channels. According to the pioneer results, much more rain was observed in SJI 2796 Å observations compared to the SJI 1400 Å.
On the other hand, we analyzed the up-flows and down-flows motion of coronal rain. Downflow motions are more dominant and this is consistent with the literature. We found 59.8 km/s and 49.3 km/s for the projected velocities in SJI 1400 Å and SJI 2796 Å, respectively. We also observed that the number of coronal rain events varies strongly with height and velocity.
In this study, we report the SJI/IRIS observations of coronal rain at the East limb of the Sun observed on 2017 July, 2 between 07:28 UT and 12:55 UT in the 1400 Å and 2796 Å passband. We present here a spatial and temporal analysis of coronal rain. To detect coronal rain, we used the Rolling Hough Transforma (RHT) algorithm (Schad 2017). We calculated the amount of rain in both SJI channels. According to the pioneer results, much more rain was observed in SJI 2796 Å observations compared to the SJI 1400 Å.
On the other hand, we analyzed the up-flows and down-flows motion of coronal rain. Downflow motions are more dominant and this is consistent with the literature. We found 59.8 km/s and 49.3 km/s for the projected velocities in SJI 1400 Å and SJI 2796 Å, respectively. We also observed that the number of coronal rain events varies strongly with height and velocity.
Plain text (extended) Summary
The solar corona is characterised by its puzzling multi-million degree component. On the other hand, observations in the last decade have shown that the corona also contains a large amount of coronal rain, 10-100 times cooler and denser than the surroundings. The properties of coronal rain are now known to be strongly linked to coronal heating properties, but its origin, dynamics, and morphology are still not well understood. In particular, the spatial and temporal occurrence of coronal rain in an active region is unknown. In this study, we carry out an imaging and spectroscopic multi-wavelength statistical study of coronal rain observed in an active region off-limb with IRIS, spanning chromospheric to transition region temperatures. We use the Rolling Hough Transform (RHT) to automatically detect and measure the properties of coronal rain clumps. The RHT method allows obtaining both spatial and temporal mean angles and these figures show that coronal rain is widespread across the active region, irrespective of the loop inclination, with minimal variation over the 4.5-hour duration of the observation. In other words, it suggesting a prevalence of thermal non-equilibrium (TNE). The rain is predominantly at chromospheric, suggesting complete catastrophic cooling, while not much difference is observed in the dynamics over the temperature range. Coronal rain dynamics are consistent with previous findings, with downward acceleration lower than free-fall, with mean projected velocities 60.31 and 53.44 km/s for the SJI 1400 and 2796, respectively. Rain in 1400 Å is observed to fall slightly faster (10-15 km/s) than that in 2796 Å, contrary to theory. On the other hand, a clear downward acceleration for each rain event (shower) is observed with ~ 10-20 min duration time. A periodic occurrence for the rain showers is observed (~10 min). However, raster the motion may contribute to this periodicity. We will be trying to estimate the fraction of coronal volume in TNE and the role of coronal rain in the mass and energy cycle in future work. The width of rain clumps and showers, and AIA 304 analysis are under investigation.
URL
seray.sahin@northumbria.ac.uk
Poster file