EPSC Abstracts
Vol. 18, EPSC-DPS2025-1098, 2025, updated on 09 Jul 2025
https://doi.org/10.5194/epsc-dps2025-1098
EPSC-DPS Joint Meeting 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Characterization of South polar-winds in Neptune’s atmosphere from ALMA observations 
Raphael Moreno1, Oscar Carrión-González1,2, Emmanuel Lellouch1, Thibault Cavalié1,3, Sandrine Guerlet1,4, Gwenael Milcareck3, Aymeric Spiga4, Michael Roman5,6, and Arielle Moullet7
Raphael Moreno et al.
  • 1LIRA, Paris Observatory, France (raphael.moreno@obspm.fr)
  • 2Max Planck Institute for Astronomy, Heidelberg, Germany
  • 3LAB, University of Bordeaux, France
  • 4Laboratoire de Météorologie Dynamique, IPSL, Sorbonne université, France
  • 5Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile
  • 6School of Physics and Astronomy, University of Leicester, Leicester, United Kingdom
  • 7National Radio Astronomy Observatory, Charlottesville, VA, USA

Measurements of winds in Neptune's stratosphere obtained by ALMA Doppler spectroscopy in 2016 by [1] have shown that stratospheric zonal winds at a pressure level of 1 mbar (-180 m/s)  appear to be less intense, by a factor of two, than tropospheric winds based on cloud tracking at 1 bar from Voyager observations (-400 m/s). These data also indicate a reversal of the circulation, from retrograde to prograde, at high southern latitudes. However, the spatial resolution of these data was insufficient for a detailed characterization of the high-latitude circulation.

We present here higher spatial resolution ALMA maps of CO and HCN emission lines towards Neptune's limb to measure their Doppler shifts and derive a map of zonal winds in its stratosphere. Our observations - carried out in March-April 2025 - used the ALMA interferometer to map the CO(3-2) and HCN(5-4) rotational lines in Neptune's atmosphere at 345.796 and 354.505 GHz, respectively. These measurements were obtained using around 44 antennas of the 12m array, with an angular resolution of ~0.19'', allowing the mapping of around 12x12 independent pixels on the planetary disk (2.21").

We will present the analysis of these observations, which will include maps of the planet's zonal wind after subtraction of the planet's solid rotation, and compare these results with earlier measurements of the Doppler wind in Neptune's atmosphere [1]. Particular attention will be paid to the South Pole region, whose resolution will be improved by a factor of 2 compared with the observations of [1]. This growing ensemble of ALMA datasets opens the door to the long-term monitoring of the seasonal stability and potential variations of Neptune's stratospheric wind patterns.

Acknowledgements

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

References

[1] Carrion-Gonzalez et al. 2023 A&A 674, L3

How to cite: Moreno, R., Carrión-González, O., Lellouch, E., Cavalié, T., Guerlet, S., Milcareck, G., Spiga, A., Roman, M., and Moullet, A.: Characterization of South polar-winds in Neptune’s atmosphere from ALMA observations , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1098, https://doi.org/10.5194/epsc-dps2025-1098, 2025.