[Astronomy seminar] Astronomy departmental seminar tomorrow Friday Dec 2nd - Sepideh Kianfar (SU)

[Astronomy seminar announcements]

Dear all,

The next SU astronomy departmental seminar will take place on Friday December 2nd at 10:30 in room FC 61 (AlbaNova building, 6th floor) and on zoom.

Please note this will be the final departmental seminar of the calendar year, as the next two Fridays there will be no seminar due to the supervisor's meeting and a licentiate defense. The seminars will resume on a weekly basis in January.

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Speaker: Sepideh Kianfar (SU)
Title: Physical properties and dynamics of the bright fibrils in the solar chromosphere


Abstract:

    The highly dynamic solar chromosphere gives rise to various fine structures that cover the solar surface. Bright fibrils are an example of those structures, and the main topic of my presentation. They appear as thin and elongated features packed in plage regions or around pores on the solar surface. They are relatively short-lived and undergo oscillations. So far, they have been observed mostly in single spectral lines with a spectral resolution larger than 1 Å. We used observations of bright fibrils with high spatial and spectral resolution in different chromospheric spectral lines that have been acquired simultaneously at the Swedish 1-m SolarTelescope (SST). These observations provided us with the chance to have a more consistent image of how the bright fibrils appear in different layers of the chromosphere, and more importantly, it has enabled us to infer their physical properties by using non-LTE inversion of the observations. Our studies showed that their bright appearance is because they have higher temperature than their surroundings in the chromosphere.  Most, but not all Ca II K fibrils are also visible in the Hα and Ca II 8542 Å line cores which suggests that fibrils are not only spread out horizontally, but can also be stacked vertically. Then we used the non-LTE inversion on the time series bright fibrils to retrieve their oscillations in the line-of-sight (vertical) direction in addition to the plane-of-sky (horizontal) direction. In all the cases in our sample the fibrils oscillated in both directions. The fact that in all cases in our sample, fibrils undergo oscillations in both directions, show that the transverse wave flux based on the imaging data is too low because the contribution of the oscillation in the vertical velocity. We determined the periods and velocity amplitudes of the fibril oscillations, as well as phase differences between vertical and horizontal oscillations in the fibrils. The results are consistent with the scenario where transverse waves are excited by granular buffeting at the photospheric footpoints of the fibrils. To further investigate the fibrils and their retrieved properties, we compared our results to the MuRAM simulations of the solar atmosphere. We synthesised the spectral lines that we had acquired with the observations using a simulated snapshot and ran the non-LTE inversions on fibrillar regions of the synthesised profiles.

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We look forward to seeing many of you there. Thanks!

Eliot and Kris

Upcoming Events:

09/12 - Supervisor's meeting - No Seminar
16/12 - Yutong He licentiate - No Seminar

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Topic: Astronomy Department Seminar Sepideh Kianfar
Time: Dec 2nd, 2022 10:30 AM Stockholm

Join Zoom Meeting:
https://stockholmuniversity.zoom.us/s/61002076352

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