Technical Readiness of MeerKAT for Photo voltaic Observations and Preliminary Science Outcomes by D. Kansabanik et al. – Group of European Photo voltaic Radio Astronomers

Photo voltaic radio emissions supply distinctive diagnostic insights into the photo voltaic corona. Nonetheless, their dynamic and multiscale nature, together with variations spanning a number of orders of magnitude in depth, pose vital observational challenges. Up to now, at gigahertz frequencies, MeerKAT (Jonas & MeerKAT Staff 2016) stands out globally for its intrinsic capability to provide high-fidelity, spectroscopic snapshot photographs of the Solar. That is enabled primarily by its dense core, excessive sensitivity, and broad frequency protection. But, as a telescope initially designed for observing faint galactic and extragalactic sources, observing the Solar within the MeerKAT main beam requires personalized observing methods and calibration strategies. This work demonstrates the technical readiness of MeerKAT for photo voltaic observations within the UHF (580–1015 MHz) and L-band (900–1670 MHz) frequency ranges, together with optimized modes, a devoted calibration scheme, and a tailor-made, totally automated Stokes I calibration and imaging pipeline. We now have additionally demonstrated a number of preliminary science outcomes utilizing this new photo voltaic observing mode of MeerKAT.

Configuring MeerKAT for Photo voltaic Observations: From Observing Technique to Science-Prepared Knowledge Merchandise

At GHz frequencies, the Solar is the brightest radio supply within the sky and occupies a considerable fraction of the MeerKAT main beam. Observing such an intense, prolonged supply requires the introduction of further attenuation at applicable phases within the sign chain so as to keep it inside its optimum linear regime. We discover that attenuation ranges of roughly 32 dB within the UHF band and 35 dB in L-band are optimum for photo voltaic observations. Whereas this attenuation allows direct observations of the Solar, it renders customary astronomical flux density calibrators too faint for typical calibration. To beat this limitation, the attenuators used are  calibrated utilizing a well-characterized noise sign injected immediately on the antenna feed.

This devoted observing technique for photo voltaic observations with MeerKAT has been efficiently applied and validated. Nonetheless, calibrating and imaging knowledge acquired on this non-standard observing mode requires further processing steps past customary interferometric workflows. To streamline the evaluation and to reliably produce science-ready, spectroscopic snapshot photo voltaic photographs, we have now developed a totally automated, end-to-end calibration and imaging pipeline, MeerSOLAR, which is publicly distributed through PyPI (https://pypi.org/undertaking/meersolar). The mixture of this new observing mode and the MeerSOLAR pipeline has enabled the manufacturing of high-fidelity photo voltaic photographs at GHz frequencies with unprecedented high quality, opening a number of new avenues for photo voltaic radio science.

Demonstration of Excessive High quality Photo voltaic Imaging with MeerKAT

MeerKAT photo voltaic observations allow unprecedented spectroscopic snapshot imaging of the Solar at centimeter wavelengths. For instance the achieved picture high quality and constancy, a consultant MeerKAT photo voltaic picture is proven within the left panel of Determine 1, centered at 942 MHz with a bandwidth of fifty MHz and an integration time of quarter-hour. The radio picture is in contrast with a contemporaneous extreme-ultraviolet (EUV) photo voltaic picture from the Atmospheric Imaging Meeting onboard the Photo voltaic Dynamics Observatory, proven in the appropriate panel of Determine 1. Corresponding photo voltaic options are recognized utilizing coloured arrows which can be constant throughout each panels. A outstanding coronal gap (area 7) displays carefully matching morphology within the radio and EUV photographs, whereas a smaller coronal gap can be evident (area 10). On-disk energetic areas (areas 8 and 9) in addition to energetic areas close to the japanese limb (areas 1 and 6) are clearly detected in each bands. Further prolonged and filamentary coronal constructions are highlighted in areas 2, 3, 4, and 5, additional demonstrating the morphological consistency between the MeerKAT radio picture and EUV observations.

Determine 1: The left panel exhibits a photo voltaic picture at 942 MHz (50 MHz and quarter-hour averaging), noticed utilizing the MeerKAT pointing immediately on the Solar. A number of options are marked by numbered arrows. Corresponding options are additionally proven within the EUV picture from AIA in the appropriate panel.

Glimpses of Early Science Outcomes

Excessive-fidelity spectroscopic snapshot imaging with MeerKAT allows a variety of recent diagnostics of the photo voltaic corona, spanning phenomena from the quiescent Solar to coronal mass ejections (CMEs). We current chosen examples that illustrate these science circumstances and spotlight the broader potential of MeerKAT photo voltaic observations.

1. Quiescent Solar plasma above the chromosphere — MeerKAT’s observing frequencies and spectroscopic imaging functionality allow distinctive probes of the photo voltaic ambiance above the chromosphere, probably together with the transition area, which stays tough to entry with present strategies. We examine noticed on-disk spectroscopic radio photographs with simulations that embrace solely coronal emission constrained by extreme-ultraviolet observations. As proven in Determine 2, the noticed spectra exhibit a steeper spectral slope (inexperienced curve) and systematically increased flux densities than the coronal-only simulations (black curve) (Kansabanik et al., 2024). This discrepancy signifies the presence of further, cooler plasma emission absent from the simulations however captured by MeerKAT. These outcomes present the primary proof that MeerKAT could also be delicate to transition-region plasma and open a brand new diagnostic avenue for characterizing its multi-thermal properties.
2. Non-thermal emission in the course of the erupting section of a CME — Throughout a science verification statement on 10 June 2024, MeerKAT captured the eruptive section of a CME, as proven in Determine 3. The observations reveal reconnection signatures within the present sheet accompanied by enhanced radio emission, within the area highlighted by the crimson field in the appropriate panel. The related radio spectra exhibit broadband non-thermal traits, in keeping with gyrosynchrotron emission. Detailed modeling of the spatially resolved spectra and their temporal evolution will allow quantitative constraints on the magnetic area construction in the course of the CME eruption.

Determine 2: Comparability of noticed and simulated on-disk radio spectra. The simulated spectrum (black) consists of solely coronal emission, whereas the noticed spectrum (inexperienced) exhibits considerably increased flux density and a steeper slope, indicating further emission from plasma under the coronal layer.

Determine 3: Left panel: CME noticed by MeerKAT on 10 June 2024. Proper panel: radio contours from a spectroscopic MeerKAT photo voltaic picture overlaid on an EUV picture from the GOES-SUVI instrument. The crimson field highlights the reconnection website and related shiny non-thermal radio emission.

Conclusion

This examine demonstrates tha$t MeerKAT is technically prepared for photo voltaic observations on the telescope boresight, overcoming key limitations of earlier approaches that relied on sidelobe observations of the Solar (Kansabanik et al., 2024). The profitable implementation of this functionality has already enabled a number of distinctive early science outcomes, highlighting its vital diagnostic potential. As soon as absolutely commissioned and made operational, this mode will unlock new alternatives for photo voltaic analysis, considerably broaden MeerKAT’s scientific portfolio, and set up a robust basis for photo voltaic observations with the mid-frequency array of the Sq. Kilometre Array Observatory, for which MeerKAT serves as a key precursor.

Additional information

Based mostly on a latest paper by Kansabanik, D. et al., 2025, Entrance. Astron. Area Sci. 12:1666743, https://doi.org/10.3389/fspas.2025.1666743

Key phrases

MEERKAT, SOLAR RADIO EMISSION, QUIET SUN, CORONAL MASS EJECTION

Full checklist of authors: Devojyoti Kansabanik^1,2, Marcel Gouws³, Deepan Patra⁴, Angelos Vourlidas², Pieter Kotzé^3,5, Divya Oberoi⁴, Shaheda Begum Shaik^6,7, Sarah Buchner³, Fernando Camilo³

1. NASA Jack Eddy Fellow, College Company for Atmospheric Analysis, Boulder, CO, United States
2. The Johns Hopkins College Utilized Physics Laboratory, Laurel, MD, United States
3. South African Radio Astronomy Observatory, Liesbeek Home, Cape City, South Africa
4. Nationwide Centre for Radio Astrophysics, Tata Institute of Elementary Analysis, S. P. Pune College Campus, Pune, India
5. Nationwide Radio Astronomy Observatory, Charlottesville, VA, United States
6. George Mason College, Fairfax, VA, United States
7. U.S. Naval Analysis Laboratory, Washington, DC, United States

References

1. Jonas, J., and MeerKAT Staff (2016). “The MeerKAT radio telescope,” in MeerKATscience: on the Pathway to the SKA, 1. doi:10.22323/1.277.0001
2. Kansabanik, D., Mondal, S., Oberoi, D., Chibueze, J. O., Engelbrecht, N. E., Strauss, R.D., et al. (2024). Spectroscopic imaging of the solar with meerkat: Opening a brand new frontierin photo voltaic physics. Astrophysical J. 961, 96. doi:10.3847/1538-4357/ad0b7f