Mats Kirkaune

• Kirkaune, Mats; Wedemeyer, Sven; Marrewijk, Joshiwa van; Mroczkowski, Tony & Morris, Thomas W. (2025). Observing the Sun with the Atacama Large Aperture Submillimeter Telescope (AtLAST): Forecasting Full-disk Observations. The Open Journal of Astrophysics. 8. doi: 10.33232/001c.144106. Fulltekst i vitenarkiv Vis sammendrag

  The Atacama Large Millimeter Array (ALMA) has revolutionised the field of solar millimetre astronomy with its high angular resolution and cadence. However, with a limited field of view (FOV), targeted observations of highly dynamic phenomena such of flares are challenging. A large aperture single-dish telescope with a large FOV, such as the future Atacama Large Aperture Submillimeter Telescope (AtLAST), would prove useful in observing such phenomena, as one could scan the full solar disk on shorter timescales. We aimed to explore what FOVs, detector counts, and scan strategies are suitable for AtLAST to push the required full-disk scan times below 1 minute, enabling regular observations of dynamic solar phenomena. Utilising the maria code, we were able to simulate solar observations with AtLAST, and thoroughly explored how instrumental properties and scanning strategies affect the full-disk observations in the planned frequency bands. We find the double-circle scan pattern, currently employed at ALMA for full-disk mapping to also be an acceptable way of scanning the Sun with AtLAST. Using small to intermediately sized instruments (1000 - 50,000 detector elements), the estimated observational cadence would be less than 1 minute across AtLAST’s frequency range with a reasonable pixel spacing. Using instruments with larger FOVs ( ⪆ 0.25 ∘ , equivalent to ⪆ 1 R), we find a simple circular scan to be more efficient, achieving cadences on second time scales, but requiring more detector elements ( ⪆ 100,000). We find that a large FOV single-dish telescope such as AtLAST could provide the solar millimetre community with hitherto unachievable observations, namely full-disk observations at high cadence and adequate resolution. With cadences potentially down to seconds, such an instrument would be ideal in the study of quickly evolving solar phenomena.

• Wedemeyer, Sven; Barta, Miroslav; Brajša, Roman; Chai, Yi; Costa, Joaquim & Gary, Dale [Vis alle 38 forfattere av denne artikkelen] (2024). Science development study for the Atacama Large Aperture Submillimeter Telescope (AtLAST): Solar and stellar observations. Open Research Europe. 4. doi: 10.12688/openreseurope.17453.1. Fulltekst i vitenarkiv Vis sammendrag

  Observations at (sub-)millimeter wavelengths offer a complementary perspective on our Sun and other stars, offering significant insights into both the thermal and magnetic composition of their chromospheres. Despite the fundamental progress in (sub-)millimeter observations of the Sun, some important aspects require diagnostic capabilities that are not offered by existing observatories. In particular, simultaneously observations of the radiation continuum across an extended frequency range would facilitate the mapping of different layers and thus ultimately the 3D structure of the solar atmosphere. Mapping large regions on the Sun or even the whole solar disk at a very high temporal cadence would be crucial for systematically detecting and following the temporal evolution of flares, while synoptic observations, i.e., daily maps, over periods of years would provide an unprecedented view of the solar activity cycle in this wavelength regime. As our Sun is a fundamental reference for studying the atmospheres of active main sequence stars, observing the Sun and other stars with the same instrument would unlock the enormous diagnostic potential for understanding stellar activity and its impact on exoplanets. The Atacama Large Aperture Submillimeter Telescope (AtLAST), a single-dish telescope with 50m aperture proposed to be built in the Atacama desert in Chile, would be able to provide these observational capabilities. Equipped with a large number of detector elements for probing the radiation continuum across a wide frequency range, AtLAST would address a wide range of scientific topics including the thermal structure and heating of the solar chromosphere, flares and prominences, and the solar activity cycle. In this white paper, the key science cases and their technical requirements for AtLAST are discussed.

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• Kirkaune, Mats; Wedemeyer, Sven; Carlsson, Mats & Brunvoll, Aline Rangøy (2026). Exploring synthetic nanoflare signatures at millimetre wavelengths. Fulltekst i vitenarkiv Vis sammendrag

  Nanoflares have long been considered to be promising candidates for heating the solar corona to millions of degrees. However, their assumed small sizes, short durations, and subtle signals in accessible observables have made direct detection difficult. In the millimetre regime, the Atacama Large (sub-)Millimeter Array (ALMA) offers the capability of measuring chromospheric temperatures at very high temporal and comparatively high spatial resolution. Yet, it is not clear if the currently offered solar observing mode of ALMA is capable of detecting nanoflares. To explore possible millimetre signatures of nanoflares, the F-CHROMA grid of 1D RADYN flare models has been extended to lower total flare energies, into the nanoflare domain. These models simulate the response of a coronal loop to an electron beam inserted at its top. The new simulations were run as a combined effort to characterise nanoflare signatures at different wavelengths. The radiative transfer code RH1.5 was used to compute the millimetre signatures of the modelled nanoflares. These signatures were then degraded to the temporal and spatial resolution achievable with ALMA. The synthetic ALMA light curves indicate that, in principle, ALMA should be able to detect nanoflare signatures, especially when using wider array configurations in combination with a higher frequency band to maximise spatial resolution. This suggests that dedicated ALMA observations could, in principle, place important constraints on atmospheric heating from nanoflares.

• Kirkaune, Mats & Wedemeyer, Sven (2026). Observing the Sun with AtLAST. Fulltekst i vitenarkiv Vis sammendrag

  The Atacama Large Aperture Submillimeter Telescope (AtLAST) has great potential for solar physics. AtLAST’s unique combination of a large aperture, a wide field-of-view, fast mapping speed, and multi-pixel instrumentation could enable it to map the full solar disk across multiple frequencies at high temporal resolution, effectively mapping the thermal and magnetic structure across the chromosphere, and how these change in time. This would help address several important solar science cases. AtLAST’s capabilities would be complementary to the Atacama Large (sub-)Millimeter Array (ALMA) and to other major solar(-capable) observatories of the future, such as the Square Kilometer Array Observatory (SKAO) in South Africa and Australia, and the European Solar Telescope in Spain.

• Kirkaune, Mats; Wedemeyer, Sven; Marrewijk, Joshiwa van; Mroczkowski, Tony & Morris, Thomas (2026). Simulated solar observations with the Atacama Large Aperture Submillimetre Telescope (AtLAST). Fulltekst i vitenarkiv Vis sammendrag

  Millimetre observations offer a highly complementary view of the Sun, providing insight into the thermal and magnetic structure of the chromosphere. The field of solar millimetre astronomy has seen considerable progress since the advent of solar observations with the Atacama Large (sub-)Millimeter Array (ALMA), offering a view of the solar chromosphere at high spatial and temporal resolution. However, some highly dynamic phenomena, such as solar flares, are hard to predict, and therefore challenging to capture with ALMA’s small field of view. The proposed Atacama Large Aperture Submillimetre Telescope (AtLAST), a next-generation 50-m aperture multi-purpose facility, could greatly complement ALMA, offering diagnostic capabilities not currently provided by existing facilities. AtLAST’s large field of view, fast scan speed, and multi-band instruments could allow for mapping the solar disk at adequate spatial resolution, at several frequencies simultaneously, and at a comparatively high cadence. The utilisation of multi-pixel instruments would make AtLAST capable of completing such scans on short timescales, enabling the creation of three-dimensional maps of the solar chromosphere at high temporal resolution. This would allow for monitoring the temperature and magnetic field of the active chromosphere on a global scale, and at an unprecedentedly high cadence, going beyond the capabilities of current facilities in the (sub-)millimetre regime. It is evident that AtLAST has the potential to produce data that would prove highly useful for solar physics. In the presented study, we have therefore explored its potential capabilities by using the multi-purpose (sub-)mm telescope simulator maria. By testing different instrumental setups and scan strategies, we find that 1st generation instrumentation at AtLAST should be able to produce full-disk solar maps on sub-minute timescales across its frequency range. With a more ambitious 2nd generation instrument, it is likely that the temporal resolution could be pushed to a few seconds. The foreseen capabilities would facilitate the detection of all solar flares above AtLAST’s sensitivity threshold, as continuously scanning the solar disk is likely to capture any fast-evolving dynamic phenomena at the covered spatial and temporal scales.

• Wedemeyer, Sven; Kirkaune, Mats; Gunar, Stanislav; Hudson, Hugh; Mohan, Atul & Simões, Paulo [Vis alle 22 forfattere av denne artikkelen] (2025). Radio and Millimeter Observations of the Sun - Probing the Solar Origins of Space Weather. Fulltekst i vitenarkiv Vis sammendrag

  Observations at radio and millimeter wavelengths provide a unique window into the thermal and magnetic structure of the solar chromosphere and corona, where the solar drivers of space weather are rooted. The Atacama Large Millimeter/submillimeter Array (ALMA) has marked a major advance in solar observations by providing unprecedented spatial and temporal resolution. These capabilities enable detailed studies of dynamic small-scale processes that are fundamental to the mechanisms driving solar flares, coronal mass ejections, and the acceleration of solar energetic particles. Looking ahead, the proposed Atacama Large Aperture Submillimeter Telescope (AtLAST), a 50-meter single-dish facility, would deliver rapid multi-wavelength full-disk scans with cadences of one minute or less - an essential capability for capturing fast-evolving solar phenomena. The Square Kilometer Array (SKA), currently under construction, will observe at lower frequencies, thus probing the Sun’s corona. Beyond advancing fundamental physical understanding, solar observations at millimeter wavelengths hold strong potential for space weather forecasting. They provide sensitive diagnostics of chromospheric and coronal heating and dynamics, offering real-time constraints for models used in operational prediction systems. The Solaris project - designed to enable continuous, year-round observations from sites in Antarctica and the Arctic - will serve as an important demonstrator of this capability. This poster will present recent advances in solar radio/mm observations, highlight synergies with forward modeling and data-driven simulations, and outline opportunities with upcoming facilities such as AtLAST, Solaris, and SKA. Together, these developments demonstrate the growing role of millimeter observations both in unraveling the solar origins of space weather and in providing critical observational input for future forecasting frameworks.

• Kirkaune, Mats; Brunvoll, Aline Rangøy & Saberi, Maryam (2024). Avsløring av solas hemmeligheter. Fulltekst i vitenarkiv
• Kirkaune, Mats; Wedemeyer, Sven; Marrewijk, Joshiwa Van & Mroczkowski, Tony (2024). Fast On-the-Fly Scanning of the Solar Disk with AtLAST. Fulltekst i vitenarkiv
• Kirkaune, Mats; Wedemeyer, Sven; Marrewijk, Joshiwa Van; Mroczkowski, Tony & Morris, Thomas W. (2024). Simulating fast on-the-fly observations of the Sun with AtLAST. Fulltekst i vitenarkiv
• Wedemeyer, Sven; Barta, Miroslav; Brajša, Roman; Chai, Yi; Costa, Joaquim E. R & Gary, Dale [Vis alle 38 forfattere av denne artikkelen] (2024). Observing our Sun with AtLAST. Fulltekst i vitenarkiv
• Wedemeyer, Sven & Kirkaune, Mats (2024). Solar Observations with the Atacama Large Aperture Submillimeter Telescope. Fulltekst i vitenarkiv
• Wedemeyer, Sven & Kirkaune, Mats (2023). Observing the Sun with AtLAST - Prospects and Challenges. Fulltekst i vitenarkiv

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