Synthetic observations of wave propagation in a sunspot umbra

Abstract

Spectropolarimetric temporal series from Fe I $\lambda$ 6301.5 Å and Ca II infrared triplet lines are obtained by applying the Stokes synthesis code NICOLE to a numerical simulation of wave propagation in a sunspot umbra from MANCHA code. The analysis of the phase difference between Doppler velocity and intensity core oscillations of the Fe I $\lambda$ 6301.5 Å line reveals that variations in the intensity are produced by opacity fluctuations rather than intrinsic temperature oscillations, except for frequencies between 5 and 6.5 mHz. On the other hand, the photospheric magnetic field retrieved from the weak field approximation provides the intrinsic magnetic field oscillations associated to wave propagation. Our results suggest that this is due to the low magnetic field gradient of our sunspot model. The Stokes parameters of the chromospheric Ca II infrared triplet lines show striking variations as shock waves travel through the formation height of the lines, including emission self-reversals in the line core and highly abnormal Stokes V profiles. Magnetic field oscillations inferred from the Ca II infrared lines using the weak field approximation appear to be related with the magnetic field strength variation between the photosphere and the chromosphere.

Accepted for publication in The Astrophysical Journal

References in corpus (5)

• A Substantial Amount of Hidden Magnetic Energy in the Quiet Sun
• Emergence of small-scale magnetic loops through the quiet solar atmosphere
• MHS sunspot model from deep sub-photospheric to chromospheric layers
• Spectropolarimetric observations of the Ca II 8498 A and 8542 A lines in the quiet Sun
• Growing drift-cyclotron modes in the hot solar atmosphere

Cited by in corpus (14)

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• Semi-empirical model atmospheres for the chromosphere of the sunspot penumbra and umbral flashes
• Properties of shock waves in the quiet Sun chromosphere
• Exploring source region of 3-min slow magnetoacoustic waves observed in coronal fan loops rooted in sunspot umbra
• Downflowing umbral flashes as an evidence of standing waves in sunspot umbrae
• First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash
• Inversions of synthetic umbral flashes: selection of wavelength sampling
• Limitations of the Ca II 8542 Å line for the determination of magnetic field oscillations
• Observations of umbral flashes in the resonant sunspot chromosphere
• Chromospheric and photospheric properties of sunspots as inferred from Stokes inversions under magneto-hydrostatic and non-local-thermodynamic equilibrium
• MCALF: Multi-Component Atmospheric Line Fitting