An observationally-constrained model of strong magnetic reconnection in the solar chromosphere. Atmospheric stratification and estimates of heating rates

Abstract

The evolution of the photospheric magnetic field plays a key role in the energy transport into the chromosphere and the corona. In active regions, newly emerging magnetic flux interacts with the pre-existent magnetic field, which can lead to reconnection events that convert magnetic energy to thermal energy. We aim to study the heating caused by a strong reconnection event that was triggered by magnetic flux cancellation. We use imaging-spectropolarimetric data in the Fe I 6301A, Fe I 6302A, Ca II 8542A and Ca II K obtained with the CRISP and CHROMIS instruments at the Swedish 1-m Solar Telescope. This data was inverted using multi-atom, multi-line non-LTE inversions using the STiC code. The inversion yielded a three-dimensional model of the reconnection event and surrounding atmosphere, including temperature, velocity, microturbulence, magnetic file configuration, and the radiative loss rate. The model atmosphere shows the emergence of magnetic loops with a size of several arcsecs into a pre-existing predominantly unipolar field. Where the reconnection region is expected to be, we see an increase in the chromospheric temperature of roughly 2000 K as well as bidirectional flows of the order of 10 km s${}^{-1}$ emanating from the region. We see bright blobs of roughly 0.2 arcsec diameter in the Ca II K moving at a plane-of-the-sky velocity of order 100 km s${}^{-1}$ and a blueshift of 100 km s${}^{-1}$, which we interpret as plasmoids ejected from the same region. This evidence is consistent with theoretical models of reconnection and we thus conclude that reconnection is taking place. The chromospheric radiative losses at the reconnection site in our inferred model are as high as 160 kW m${}^{-2}$, providing a quantitative constraint on theoretical models that aim to simulate reconnection caused by flux emergence in the chromosphere.

arXiv comment13 pages, 12 figures, accepted for publication in A&A

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• Ultra-high resolution observations of plasmoid-mediated magnetic reconnection in the deep solar atmosphere
• Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS
• Heating of the solar chromosphere through current dissipation
• Exploring spectropolarimetric inversions using neural fields. Solar chromospheric magnetic field under the weak-field approximation
• Grow-up of a Filament Channel by Intermittent Small-scale Magnetic Reconnection
• 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
• Constraining the systematics of (acoustic) wave heating estimates in the solar chromosphere
• Chromospheric velocities in an M3.2 flare using He I 1083.0 nm and Ca II 854.2 nm
• Radiative losses in the chromosphere during a C-class flare
• The making of robust and highly performing imaging spectropolarimeters for large solar telescopes
• Chromosphere of the quiet sun -- I. Shock and current-sheet dynamics and heating
• Designing wavelength sampling for Fabry-Pérot observations. Information-based spectral sampling
• High-Resolution Observations of a Small-Scale Cancellation Nanoflare: Supporting Evidence for the Cancellation Nanoflare Model
• Modeling of Chromospheric Features and Dynamics in Solar Plage
• Spectral resolution effects on the information content in solar spectra
• Simultaneous spectropolarimetric observations in the H$\alpha$ and Ca II 8662 Å lines of an active region
• Automatic detection of Ellerman bombs using Deep Learning
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Decay of a photospheric transient filament at the boundary of a pore and the chromospheric response