High-resolution spectroscopy of a surge in an emerging flux region

0537138 - ASÚ 2021 RIV FR eng J - Journal Article
Verma, M. - Denker, C. - Diercke, A. - Kuckein, C. - Balthasar, H. - Dineva, S. - Kontogiannis, I. - Pal, S. P. - Sobotka, Michal
High-resolution spectroscopy of a surge in an emerging flux region.
Astronomy & Astrophysics. Roč. 639, July (2020), č. článku A19. ISSN 0004-6361. E-ISSN 1432-0746
R&D Projects: GA ČR(CZ) GC18-08097J
EU Projects: European Commission(XE) 824135 - SOLARNET
Institutional support: RVO:67985815
Keywords : Sun * activity * chromosphere
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 5.803, year: 2020
Method of publishing: Limited access
https://doi.org/10.1051/0004-6361/201936762

The active region started as a bipolar region with continuous flux emergence when a new flux system emerged in the leading part during the VTT observations, resulting in two homologous surges. While flux cancellation at the base of the surges provided the energy for ejecting the cool plasma, strong proper motions of the leading pores changed the magnetic field topology making the region susceptible to surging. Despite the surge activity in the leading part, an arch filament system in the trailing part of the old flux remained stable. Thus, stable and violently expelled mass-loaded ascending magnetic structures can coexist in close proximity. Investigating the height dependence of LOS velocities revealed the existence of neighboring strong up- and downflows. However, downflows occur with a time lag. The opacity of the ejected cool plasma decreases with distance from the base of the surge, while the speed of the ejecta increases. The location at which the surge becomes invisible in H alpha corresponds to the interface where the surge brightens in HeII lambda 304 angstrom. Broad-shouldered and dual-lobed H alpha profiles suggests accelerated or decelerated and highly structured LOS plasma flows. Significantly broadened H alpha profiles imply significant heating at the base of the surges, which is also supported by bright kernels in UV and EUV images uncovered by swaying motions of dark fibrils at the base of the surges.Conclusions. The interaction of newly emerging flux with pre-existing flux concentrations of a young, diffuse active region provided suitable conditions for two homologous surges. High-resolution spectroscopy revealed broadened and dual-lobed H alpha profiles tracing accelerated or decelerated flows of cool plasma along the multi-threaded structure of the surge.
Permanent Link: http://hdl.handle.net/11104/0314889