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. 2023;7(7):856-866.
doi: 10.1038/s41550-023-01973-3. Epub 2023 May 25.

Transverse oscillations and an energy source in a strongly magnetized sunspot

Ding Yuan  1   2   3 , Libo Fu  1   2   3 , Wenda Cao  4   5 , Błażej Kuźma  1   2   3 , Michaël Geeraerts  6 , Juan C Trelles Arjona  7   8 , Kris Murawski  9 , Tom Van Doorsselaere  6 , Abhishek K Srivastava  10 , Yuhu Miao  11 , Song Feng  12 , Xueshang Feng  1   2   3 , Carlos Quintero Noda  7   8 , Basilio Ruiz Cobo  7   8 , Jiangtao Su  13   14
Affiliations

Transverse oscillations and an energy source in a strongly magnetized sunspot

Ding Yuan et al. Nat Astron. 2023.

Abstract

The solar corona is two to three orders of magnitude hotter than the underlying photosphere, and the energy loss of coronal plasma is extremely strong, requiring a heating flux of over 1,000 W m-2 to maintain its high temperature. Using the 1.6 m Goode Solar Telescope, we report a detection of ubiquitous and persistent transverse waves in umbral fibrils in the chromosphere of a strongly magnetized sunspot. The energy flux carried by these waves was estimated to be 7.52 × 106 W m-2, three to four orders of magnitude stronger than the energy loss rate of plasma in active regions. Two-fluid magnetohydrodynamic simulations reproduced the high-resolution observations and showed that these waves dissipate significant energy, which is vital for coronal heating. Such transverse oscillations and the associated strong energy flux may exist in a variety of magnetized regions on the Sun, and could be the observational target of next-generation solar telescopes.

Keywords: Solar physics.

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Conflict of interest statement

Competing interestsThe authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Oscillatory transverse motion of the dark fibril within the sunspot.
a, Atmospheric Imaging Assembly 171 Å image showing AR12384 on 14 July 2015 at 17:36:22 ut. b,c, Hα −0.20 Å images showing the sunspot in AR12384 highlighted in a. The close-up in c highlights the dark fibrils and the slit used to track inherent transverse motions. d, Time–distance plot revealing the transverse oscillations (amplitude 39.5 km, phase 0.036). The plus signs mark the fibril’s position and the red curve is the fit from a sinusoidal function and a linear trend. See Supplementary Video 1.
Fig. 2
Fig. 2. Numerical simulation of driven propagating fast magnetoacoustic wave.
a, 3D structure of the magnetic field (B) lines, the stratified sunspot atmosphere in terms of ion mass density (ρi) and the initial simulated fibril structure. b, A horizontal cut at the fibril centre revealing the transverse motion. c, The amplitude of the oscillations in the ion velocity as a function of height. See Supplementary Video 2.
Fig. 3
Fig. 3. Energy densities and fluxes carried by the fast kink wave in the simulation.
a, Kinetic (Ek), magnetic (Em) and total (Etot) energy densities as a function of height. b, Thermal (Ft), magnetic (Fm) and total (Ftot) energy fluxes in the oscillating fibril. The thermal energy flux was amplified by a factor of 1,000 for visualization purposes.
See this image and copyright information in PMC

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