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Millimeter-Wavelength Observations of the Active Sun: Unveiling the Origins of Space Weather

Sven Wedemeyer, Stefaan Poedts, Stanislav Gunár, Manuela Temmer, Astrid Veronig, Valery Nakariakov, Mats Kirkaune, Claudia Cicone, Stephen White, Jasmina Magdalenić, Roman Brajša, Bart De Pontieu, Maryam Saberi, Atul Mohan, Davor Sudar, Galina Motorina, Maria Lukicheva, Paulo Simões

TL;DR

This paper argues that millimeter-wavelength observations, particularly from a full-disk, high-cadence, multi-frequency instrument like AtLAST, are essential to uncover the solar atmospheric conditions that drive space weather. It proposes tomographic 3D reconstruction of the time-dependent chromosphere and low corona by simultaneous multi-band imaging across 30–700 GHz, enabling direct measurements of temperature and magnetic fields. The work outlines the AtLAST design and its synergy with existing solar facilities to establish a path toward reliable, physics-based space-weather forecasting. The approach promises to bridge sub-photospheric processes to heliospheric outcomes, improving resilience of technology and infrastructure.

Abstract

Societal dependence on space-based services demands major advances in predicting the impacts of eruptive solar events. Millimeter-wavelength observations offer uniquely direct access to the time-dependent physical conditions in the atmospheric layers of the Sun where these events originate. A facility capable of full-disk, high-cadence, multi-frequency imaging would provide a transformative view of the Sun and its influence on the heliosphere. AtLAST is ideally suited to deliver this capability, and to establish a European leadership role in advancing the scientific foundations that will enable reliable, operational space-weather forecasting for the first time.

Millimeter-Wavelength Observations of the Active Sun: Unveiling the Origins of Space Weather

TL;DR

This paper argues that millimeter-wavelength observations, particularly from a full-disk, high-cadence, multi-frequency instrument like AtLAST, are essential to uncover the solar atmospheric conditions that drive space weather. It proposes tomographic 3D reconstruction of the time-dependent chromosphere and low corona by simultaneous multi-band imaging across 30–700 GHz, enabling direct measurements of temperature and magnetic fields. The work outlines the AtLAST design and its synergy with existing solar facilities to establish a path toward reliable, physics-based space-weather forecasting. The approach promises to bridge sub-photospheric processes to heliospheric outcomes, improving resilience of technology and infrastructure.

Abstract

Societal dependence on space-based services demands major advances in predicting the impacts of eruptive solar events. Millimeter-wavelength observations offer uniquely direct access to the time-dependent physical conditions in the atmospheric layers of the Sun where these events originate. A facility capable of full-disk, high-cadence, multi-frequency imaging would provide a transformative view of the Sun and its influence on the heliosphere. AtLAST is ideally suited to deliver this capability, and to establish a European leadership role in advancing the scientific foundations that will enable reliable, operational space-weather forecasting for the first time.

Paper Structure

This paper contains 6 sections, 3 figures.

Table of Contents

  1. Summary.
  2. Scientific Context and Open Questions
  3. The Role of Millimeter-Wavelength Solar Observations.
  4. Tomographic Reconstruction of the Time-Dependent 3D Atmospheric Structure.
  5. Key Science Goals for Space-Weather Research
  6. Technical Requirements

Figures (3)

  • Figure 1: Space weather events can severely affect modern society because many essential technologies, including satellite-based communication and navigation systems and terrestrial power grids, are highly vulnerable to their impacts. Effective mitigation requires reliable operational space weather forecasting. Achieving this necessitates a deeper understanding of the solar drivers of space weather, their underlying physical mechanisms, and potential early indicators of activity. Image: ESA/Science Office. (License: CC BY-SA 3.0 IGO.)
  • Figure 2: Simulated observations of the Sun with a single frequency (220 GHz) for a solar multi-band imager installed at AtLAST. A double-circle scan pattern with a multi-pixel detector would enable high-cadence image series of the full disk of the Sun, thereby capturing the origins of space weather, including flares 2025OJAp....8E.129K2024OJAp....7E.118V. Such an instrument would provide unprecedented data that enable the 3D tomographic reconstruction of the thermal and magnetic state of the solar atmosphere 2024ORE.....4..140W. Credits: Adapted from 2025AA...694A.142M2025OJAp....8E.129K.
  • Figure :