Chromospheric seismology above sunspot umbrae

Abstract

The acoustic resonator is an important model for explaining the three-minute oscillations in the chromosphere above sunspot umbrae. The steep temperature gradients at the photosphere and transition region provide the cavity for the acoustic resonator, which allows waves to be both partially transmitted and partially reflected. In this paper, a new method of estimating the size and temperature profile of the chromospheric cavity above a sunspot umbra is developed. The magnetic field above umbrae is modelled numerically in 1.5D with slow magnetoacoustic wave trains travelling along magnetic fieldlines. Resonances are driven by applying the random noise of three different colours---white, pink and brown---as small velocity perturbations to the upper convection zone. Energy escapes the resonating cavity and generates wave trains moving into the corona. Line of sight (LOS) integration is also performed to determine the observable spectra through SDO/AIA. The numerical results show that the gradient of the coronal spectra is directly correlated with the chromosperic temperature configuration. As the chromospheric cavity size increases, the spectral gradient becomes shallower. When LOS integrations is performed, the resulting spectra demonstrate a broadband of excited frequencies that is correlated with the chromospheric cavity size. The broadband of excited frequencies becomes narrower as the chromospheric cavity size increases. These two results provide a potentially useful diagnostic for the chromospheric temperature profile by considering coronal velocity oscillations.

References in corpus (3)

• High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph
• Multi-height observations of magnetoacoustic cut-off frequency in a sunspot atmosphere
• Evolution of fast magnetoacoustic pulses in randomly structured coronal plasmas

Cited by in corpus (10)

• Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
• An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers
• Abnormal oscillation modes in a waning light bridge
• Stochastic transients as a source of quasi-periodic processes in the solar atmosphere
• Origin of the chromospheric three-minute oscillations in sunspot umbrae
• Probing the Sunspot Atmosphere with Three-Minute Oscillations
• Signatures of sunspot oscillations and the case for chromospheric resonances
• Modelling the connection between propagating disturbances and solar spicules
• Observational signatures of a kink-unstable coronal flux rope using Hinode/EIS
• Predictions of DKIST/DL-NIRSP observations for an off-limb kink-unstable coronal loop