Horizontal magnetic fields dominate the weak-field quiet Sun in Sunrise III observations. Evidence from traditional and transformer-based inversions
Year: 2026
Type: article
Abstract: The relative prevalence of horizontal and vertical magnetic fields in the quiet-Sun remains debated, owing to the weak linear polarisation signals that make the inferred magnetic inclination distributions sensitive to observational quality and inversion methodology. We investigate the magnetic topology of the quiet-Sun in Sunrise iii observations by independently applying transformer-based and traditional inversion techniques to the same spectropolarimetric dataset. We analysed observations obtained with the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP). Transformer-based inversions (SINN), trained exclusively on synthetic Stokes profiles generated from a large radiative magnetohydrodynamic simulation, were compared with independent inversions performed using the DeSIRe code. We separated the selected pixels into weak- and strong-field populations according to their circular-polarisation amplitudes. Linear polarisation exceeding 4σ is detected in 34.6% of the field of view, enabling the magnetic topology to be constrained over a substantially larger detected population than in typical short-integration Hinode observations. Both inversion methods recover a quiet-Sun magnetic topology in which the weak fields are strongly dominated by the horizontal component, whereas strong fields exhibit a substantially more balanced topology. At łogτ=-1, the median horizontal and unsigned line-of-sight field components in the weak-field population are 63 and 7 G with DeSIRe, and 60 and 6.5 G with SINN, respectively, corresponding to a horizontal-to-line-of-sight ratio of approximately nine for both methods. The agreement between the two fundamentally different optimisation methodologies indicates that the weak-field quiet-Sun in this dataset is characterised by a substantially stronger horizontal than vertical magnetic field component. These results demonstrate that transformer-based inversions can be successfully transferred from synthetic training data to real spectropolarimetric observations, while providing inference orders of magnitude faster than traditional inversion techniques.
Source: Astronomy and Astrophysics
Authors: Ryan J. Campbell, Carlos Quintero Noda, Manuel Collados, Mihalis Mathioudakis, Andreas Lagg, Achim Gandorfer, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, Masahito Kubo, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović, Hirohisa Hara, Toshifumi Shimizu
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Aeronautics and Space Administration, Max-Planck-Förderstiftung, European Commission, Deutsches Zentrum für Luft- und Raumfahrt, Ministerio de Ciencia e Innovación, Instituto de Astrofísica de Andalucía, Science and Technology Facilities Council, Japan Society for the Promotion of Science, Japan Aerospace Exploration Agency, Agencia Estatal de Investigación
Awards: G1171257612, G2124616825, SUMMARY SUNRISE IS A BALLOON-BORNE SOLAR OBSERVATORY DEDICATED TO THE INVESTIGATION OF THE PHYSICS GOVERNING THE EVOLUTION OF THE MAGNETIC FIELD AND THE CONVECTIVE PLASMA FLOWS IN THE LOWER SOLAR ATMOSPHERE. THESE PROCESSES ARE CRUCIAL FOR OUR UNDERSTANDING OF THE MAGNETIC ACTIVITY OF THE SUN AND OF THE OUTWARD TRANSPORT OF ENERGY TO HEAT ITS OUTER ATMOSPHERE AND TO FUEL THE ERUPTIONS AND CORONAL MASS EJECTIONS I.E. PHENOMENA THAT DRIVE SPACE WEATHER. THE SUNRISE OBSERVATORY IS DESIGNED FOR OPERATION IN THE STRATOSPHERE (AT HEIGHTS AROUND 36 KM) TO AVOID THE IMAGE DEGRADATION DUE TO TURBULENCE IN THE EARTH S LOWER ATMOSPHERE AND TO GAIN ACCESS TO THE UV WAVELENGTHS DOWN TO 200NM. A 1-M-DIAMETER TELESCOPE (THE LARGEST SOLAR TELESCOPE FLOWN TO-DATE) FEEDS AN UV IMAGER AND AN IMAGING FILTER MAGNETOGRAPH. SUNRISE WAS FLOWN TWICE IN JUNE 2009 AND JUNE 2013 DURING PERIODS OF VERY LOW AND HIGH SOLAR ACTIVITY RESPECTIVELY AND THE OBSERVATIONS RESULTED IN OVER 60 PEERREVIEWED PUBLICATIONS SO FAR. THE 3RD FLIGHT PROPOSED HERE WILL INCLUDE SUBSTANTIAL IMPROVEMENTS IN THE SUNRISE INSTRUMENTATION A NEW HIGHLY STABLE GONDOLA AND A SET OF STRONG SCIENCE OBJECTIVES TO ADDRESS ALL THREE OF NASA S HELIOPHYSICS SCIENCE GOALS IN THE 2014 SCIENCE PLAN. OBJECTIVES THE FIRST TWO SCIENCE FLIGHTS OF SUNRISE HAVE BEEN HIGHLY SUCCESSFUL. HOWEVER THESE RESULTS HAVE BEEN MAINLY RESTRICTED TO THE SOLAR PHOTOSPHERE AND BEG THE QUESTION OF WHAT INFLUENCE THE DYNAMICAL AND MAGNETIC PHENOMENA STUDIED IN THE EARLIER SUNRISE FLIGHTS HAVE ON THE HIGHER ATMOSPHERE IN PARTICULAR THE CHROMOSPHERE. THIS WILL CHANGE WITH THE THIRD SUNRISE FLIGHT WHICH WILL CARRY INSTRUMENTS TO SAMPLE THE CHROMOSPHERE IN A MULTITUDE OF SPECTRAL LINES OVER A BROAD WAVELENGTH RANGE (300 860 NM). THE INVESTIGATION WILL FOCUS ON THE FOLLOWING SCIENCE OBJECTIVES: WHAT IS THE STRUCTURE OF THE CHROMOSPHERIC MAGNETIC FIELD IN DIFFERENT TYPES OF SOLAR REGIONS? HOW WELL IS THIS MAGNETIC STRUCTURE REPRODUCED BY FORCE-FREE EXTRAPOLATIONS FROM THE PHOTOSPHERE? WHICH IS MORE IMPORTANT FOR HEATING THE SUN'S UPPER ATMOSPHERE FIELD LINE BRAIDING OR (MAGNETOHYDRODYNAMIC) WAVE FLUX? HOW IS MAGNETIC FLUX REMOVED FROM THE SURFACE OF THE SUN? HOW IMPORTANT IS MAGNETIC RECONNECTION IN THIS RESPECT? METHODOLOGY FOR ITS THIRD FLIGHT SUNRISE WILL CARRY TWO NEW INSTRUMENTS AND A MAJOR UPGRADE OF ONE OF ITS CURRENT INSTRUMENTS. THE NEW INSTRUMENTS ARE A NOVEL UV SPECTROPOLARIMETER (TO BE BUILT BY MPS) TO EXPLORE AND EXPLOIT THE EXCITING BUT DUE TO ITS POOR ACCESSIBILITY FROM THE GROUND VERY POORLY STUDIED SPECTRAL RANGE BETWEEN 300 AND 420 NM AND A VISIBLE-INFRARED SPECTROPOLARIMETER TO BE BUILT JOINTLY BY NAOJ AND ISAS IN JAPAN MPS AND IAA IN SPAIN. THE IMAGING MAGNETOGRAPH IMAX WILL BE UPGRADED TO GREATLY INCREASE ITS SPEED AND TO ALLOW IT TO ACCESS MULTIPLE SPECTRAL LINES (COMPARED WITH A SINGLE ONE SO FAR). THE BALLOON WILL BE LAUNCHED FROM ESRANGE SPACE CENTER IN KIRUNA SWEDEN WITH EXPECTED FLIGHT DURATION OF 7 DAYS AROUND THE SUMMER SOLSTICE IN 2020. THE MISSION IS A COLLABORATION BETWEEN APL (USA) MPS (GERMANY) NAOJ (JAPAN) AND IAA (SPAIN). THIS PROPOSAL WILL FUND THE USA CONTRIBUTION TO THE SUNRISE COLLABORATION. THIS CONTRIBUTION INCLUDES: BUILDING AND FLYING THE STABLE OBSERVING PLATFORM (THE GONDOLA AND ALL ITS SUBSYSTEMS) PROVIDE COORDINATION FOR A JOINT OBSERVING CAMPAIGN WITH THE 4-M APERTURE DKIST GROUND BASED SOLAR TELESCOPE AND THE USA PARTICIPATION IN SCIENCE OBJECTIVES DEFINITIONS AND OBSERVATIONS PLANNING AS WELL AS POST FLIGHT DATA ANALYSIS INTERPRETATION AND RESULTS PUBLICATIONS., G3696727022, G3874399491, G3975875632, G4212819517, G463062595, Integrating High Resolution Solar Physics, G5455020569, G5748749482, G5881647929, G5894067328, High Precision Polarimetric Observation by a Balloon-Borne Solar Telescope: Revealing Conversion Processes of Magnetic Energy in the Stellar Atmosphere, G6880300208, G7434936867, Queen's University Belfast Consolidated Grant in Solar Physics and Solar System Studies 2023 - 2026, G7518687652, G8524849061, G856857239, Revealing the fundamental processes of magnetic energy thermalization through the SUNRISE balloon observation, G939699906
OpenAlex ID: W7172516889