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Title: | Intensity and velocity oscillations in a flaring active region |
Authors: | Millar, David C. L Fletcher, Lyndsay Joshi, Jayant |
Keywords: | Sun: chromosphere Sun: flares Sun: oscillations |
Issue Date: | Jan-2024 |
Publisher: | Oxford University Press on behalf of Royal Astronomical Society |
Citation: | Monthly Notices of the Royal Astronomical Society, Vol. 527, No. 3, pp. 5916–5928 |
Abstract: | Chromospheric oscillations can give us insight into the physical environment in the solar atmosphere, both in quiet Sun and flaring conditions. Many authors have reported increases in the prevalence of 3-minute oscillations which are thought to be excited by events which impact the chromosphere such as flares. In this study, we utilized the Ca II 8542 Å line to study the oscillatory behaviour of the chromosphere in an active region which underwent two B-class flares. We analysed oscillations in both intensity and velocity, and found different behaviours in both. Intensity oscillations were most prevalent over the umbrae of sunspots and magnetic pores in the active region, and the extent of the area which contained significant oscillations was found to decrease when comparing times after the flares to before. By measuring the evolution of the magnetic field, we found that this could be because the areas surrounding the umbrae were becoming more ‘penumbral’ with an increase to the magnetic field inclination. Velocity oscillations were found across the active region both before and after the flares but were observed clearly in areas which were brightened by the second flare. By comparing to EUV imaging, it was seen that strong chromospheric velocity oscillations with 3–4-minute periods occurred at the same time and location as a flare loop cooling 30 min after the second flare peak. This could be evidence of disturbances in the loop exciting a response from the chromosphere at its acoustic cut-off frequency |
Description: | Open Access This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,provided the original work is properly cited. |
URI: | http://hdl.handle.net/2248/8346 |
ISSN: | 0035-8711 |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
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Intensity and velocity oscillations in a flaring active region.pdf | 4.45 MB | Adobe PDF | View/Open |
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