On chromospheric heating during flux emergence in the solar atmosphere

Abstract

Context. The radiative losses in the solar chromosphere vary from 4~kW~m${}^{-2}$ in the quiet Sun, to 20~kW~m${}^{-2}$ in active regions. The mechanisms that transport non-thermal energy to and deposit it in the chromosphere are still not understood. Aims. We aim to investigate the atmospheric structure and heating of the solar chromosphere in an emerging flux region. Methods. We use observations taken with the CHROMIS and CRISP instruments on the Swedish 1-m Solar Telescope in the Ca II K, Ca II 854.2 nm, H$\alpha$, and Fe I 630.1 nm and 630.2 nm lines. We analyse the various line profiles and in addition perform multi-line, multi-species, non-Local Thermodynamic Equilibrium (non-LTE) inversions to estimate the spatial and temporal variation of the chromospheric structure. Results. We investigate which spectral features of Ca II K contribute to the frequency-integrated Ca II K brightness, which we use as a tracer of chromospheric radiative losses. The majority of the radiative losses are not associated with localized high-Ca II K-brightness events, but instead with a more gentle, spatially extended, and persistent heating. The frequency-integrated Ca II K brightness correlates strongly with the total linear polarization in the Ca II 854.2 nm line, while the Ca II K profile shapes indicate that the bulk of the radiative losses occur in the lower chromosphere. Non-LTE inversions indicate a transition from heating concentrated around photospheric magnetic elements below $\log {\tau }_{500}=-3$ to a more space-filling and time-persistent heating above $\log {\tau }_{500}=-4$. The inferred gas temperature at $\log {\tau }_{500}=-3.8$ correlates strongly with the total linear polarization in the Ca II 854.2 nm line, suggesting that that the heating rate correlates with the strength of the horizontal magnetic field in the low chromosphere.

Accepted for publication by A&A

References in corpus (15)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Hot Explosions in the Cool Atmosphere of the Sun
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• Twisted flux tube emergence from the convection zone to the corona
• Bombs and flares at the surface and lower atmosphere of the Sun
• Non-LTE inversions of the Mg II h&k and UV triplet lines
• Three-dimensional modeling of the Ca II H&K lines in the solar atmosphere
• Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere
• Twisted flux tube emergence from the convection zone to the corona II: Later states
• Simulating Ellerman bomb-like event
• Sparse inversion of Stokes profiles. I. Two-dimensional Milne-Eddington inversions
• Various Local Heating Events in the Earliest Phase of Flux Emergence
• The Hanle and Zeeman polarization signals of the solar Ca II 8542 Å line
• Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)
• Chromospheric polarimetry through multi-line observations of the 850 nm spectral region II: A magnetic flux tube scenario

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• A method for global inversion of multi-resolution solar data
• Three-dimensional modeling of chromospheric spectral lines in a simulated active region
• Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations
• An observationally-constrained model of strong magnetic reconnection in the solar chromosphere. Atmospheric stratification and estimates of heating rates
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• A Magnetic Reconnection model for Hot Explosions in the Cool Atmosphere of the Sun
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• Spatio-temporal analysis of chromospheric heating in a plage region
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• Three-dimensional magnetic field structure of a flux emerging region in the solar atmosphere
• Characterization of chromospheric activity based on Sun-as-a-star spectral and disk-resolved activity indices
• Plausibility of ultraviolet burst generation in the low solar chromosphere
• Observations of solar chromospheric heating at sub-arcsec spatial resolution
• Exploring spectropolarimetric inversions using neural fields. Solar chromospheric magnetic field under the weak-field approximation
• Design and Performance Analysis of a Highly Efficient Polychromatic Full-Stokes Polarization Modulator for the CRISP Imaging Spectrometer
• Small-scale magnetic flux emergence preceding a chain of energetic solar atmospheric events
• High flow speeds and transition-region like temperatures in the solar chromosphere during flux emergence
• Chromospheric polarimetry through multi-line observations of the 850 nm spectral region III: Chromospheric jets driven by twisted magnetic fields
• The Ellerman bomb and Ultraviolet burst triggered successively by an emerging magnetic flux rope
• Radiative losses in the chromosphere during a C-class flare
• Modeling of Chromospheric Features and Dynamics in Solar Plage
• Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere
• The magnetic sensitivity of the Ca II H and K lines