Detecting the Jovian synchrotron emission at very low frequencies using NenuFAR, supplementary material

• DOI: https://doi.org/10.25935/a5hx-vx11
• Publisher: PADC
• License: CC-BY 4.0
• Citation: Girard, J. N., Louis, C. K., Zhang, X., Lamy, L., Loh, A., Zarka, P., Santos-Costa, D. & Nénon, Q. (2026). Detecting the Jovian synchrotron emission at very low frequencies using NenuFAR, supplementary material (Version 1.0) [Dataset]. PADC/MASER. https://doi.org/10.25935/a5hx-vx11

Link to data repository

• Link to the dataset

Description

Context

Jupiter is the strongest source of planetary radio emissions in the solar system. It also features a moderate continuum radio emission associated with the radiation of relativistic electrons trapped between 1 and 4 jovian radii. Above∼1 GHz, a typical synchrotron spectrum describes the emission, however, due to the fast rotation of the magnetic field and the varying relative position of Earth, short-term, long-term and spatial variability are observed. Below∼1 GHz, a spectral turnover reduces the intensity of the emission while the associated emitting electron populations also change at a larger radial distance from Jupiter. At decameter wavelengths, the lower part of the synchrotron spectrum can be detected down to 50 MHz with LOFAR (Girard et al. (2016)), but it has yet to be validated with a sensitive instrument such as NenuFAR. Below 40 MHz, the decametric emission associated with the cyclotron-MASER instability (CMI) mechanism dominates all other radio emissions at Jupiter during visibility windows. We will study the feasibility of unambiguously detecting the lowest part of the synchrotron emission down to 40 MHz when the CMI emissions are off with tentative NenuFAR imaging of the (unresolved) total intensity of the emission. Data analysis required specific processing for planets and could potentially reveal detection in the Stokes I, Q and U. Detection will give insight into the electron population that undergoes inward diffusion toward the belts and generates synchrotron emission in lower B regions.

Content

The dataset is split into two directories:

• IMAGES: containing radio images in the various frequency bands
• REGIONS: containing regions (CASA & CARTA format) that served to derive statistics for Girard et al. (2026).

The IMAGES directory contains FITS file of PSF, Image and residual images.
WSclean commands are present in each fits header.

Each image comes in

• "Image.fits" is the restored image with WSCLEAN UNIT: Jy/beam
• "psf.fits" is the observation impulse response (Point Spread Function), normalized to 1 UNIT: no unit.
• "residual.fits" is the residual map after the WSCLEAN UNIT: Jy/beam.
• Each image is 1024x1024 pixel image
• pixel size = 2 arcmin

Coverage

• Time range: 2024-02-08 15:21:00 UT to 2024-02-08 22:29:00 UT
• Spectral range: 37.5 to 84.37 MHz

Acknowledgements

Contact
Any question or request should be addressed to contact.maser@obspm.fr

References

• Girard, J. N., et al. (2016) Imaging Jupiter’s radiation belts down to 127 MHz with LOFAR. Astronomy and Astrophysics 587, A3. https://doi.org/10.1051/0004-6361/201527518
• Girard, J. N. et al. (2026). Detecting the Jovian synchrotron emission at very low frequencies using NenuFAR. Proceedings to the PREX Conference (Accepted)