EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Determining the beaming of Io decametric emissions, a remote diagnostic to probe the Io-Jupiter interaction

Laurent Lamy1,2,3, Lucas Colomban4, Philippe Zarka1,2, Renée Prangé1, Manilo Marques5, Corentin Louis6, William Kurth7, Baptiste Cecconi1,2, Julien Girard1,2, Jean Mathias Griessmeier4, and Serge Yerin8,9
Laurent Lamy et al.
  • 1LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, Meudon, France
  • 2Station de Radioastronomie de Nançay, Observatoire de Paris, Université PSL, CNRS, Univ. Orléans, Orléans, France
  • 3LAM, Pythéas, Aix Marseille Université, CNRS, CNES, Marseille, France
  • 4LPC2E, CNRS, Université d’Orléans, 3A avenue de la Recherche Scientifique, Orléans, France
  • 5Departamento de Geofisica, Universidade Federal do Rio Grande do Norte, Natal, Brazil
  • 6DIAS, Dublin, Ireland
  • 7Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA
  • 8Institute of Radio Astronomy of NAS of Ukraine, Kharkiv, Ukraine
  • 9V. N. Karazin Kharkiv National University, Kharkiv, Ukraine

We investigate the beaming of 11 Io-Jupiter decametric (Io-DAM) emissions observed by Juno/Waves, the Nançay Decameter Array and NenuFAR. Using an up-to-date magnetic field model and three different methods to position the active Io Flux Tube (IFT), we accurately locate the radiosources and determined their emission angle theta from the local magnetic field vector. These methods rely on (i) updated models of the equatorial lead angle, (ii) ultraviolet (UV) images of Jupiter's aurorae from the Hubble Space Telescope simultaneous with radio data and (iii) multi-point radio measurements. The kinetic energy E(e-) of source electrons is then inferred from theta in the framework of the Cyclotron Maser Instability. The precise position of the active IFT obtained from methods (ii) or (iii), when compared to (i), can be used to test of the effective torus plasma density. Simultaneous radio and UV observations reveal that multiple Io-DAM arcs are associated with multiple UV spots and provide the first direct evidence of an Io-DAM arc associated with a trans-hemispheric beam UV spot. Multi-point radio observations alternately probe the Io-DAM sources at various altitudes, times and hemispheres. Overall, theta decreases from ~75-80° to ~70-75° over 10-40 MHz and varies both as a function of frequency (altitude) and time (longitude of Io). Its uncertainty of a few degrees is dominated by that on the longitude of the active IFT. The inferred values of E(e-), also depending on altitude and time, vary between 3 and 16 keV, in agreement with Juno in situ measurements.

How to cite: Lamy, L., Colomban, L., Zarka, P., Prangé, R., Marques, M., Louis, C., Kurth, W., Cecconi, B., Girard, J., Griessmeier, J. M., and Yerin, S.: Determining the beaming of Io decametric emissions, a remote diagnostic to probe the Io-Jupiter interaction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8637,, 2022.