Jupiter's Auroral Radio Emissions Observed by Cassini: Rotational Versus Solar Wind Control, and Components Identification

• Published in: Journal of geophysical research. Space physics 2021-10, Vol.126 (10), p.n/a
• Main Authors: Zarka, P., Magalhães, F. P., Marques, M. S., Louis, C. K., Echer, E., Lamy, L., Cecconi, B., Prangé, R.
• Format: Article
• Language: English
• Subjects: 2736; 2756; 2784; 7534; auroral radio emissions; Flyby missions; Jupiter; Jupiter atmosphere; Jupiter radio components; Longitude; magnetospheric dynamics; Planetary magnetospheres; Radio emission; Radio observation; Rotation; rotation control; Sciences of the Universe; Solar wind; solar wind control; Wavelengths
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2021JA029780

Reanalyzing Cassini radio observations performed during Jupiter's flyby of 2000–2001, we study the internal (rotational) versus external (solar wind) control of Jupiter's radio emissions, from kilometer to decameter wavelengths, and the relations between the different auroral radio components. For that purpose, we build a database of the occurrence of Jovian auroral radio components bKOM, HOM, and DAM observed by Cassini, and then frequency‐longitude stacked plots of the polarized intensity of these radio components. Comparing the results obtained inbound and outbound, as a function of the Observer's or Sun's longitude, we find that HOM & DAM are dominantly rotation‐modulated (i.e., emitted from searchlight‐like sources fixed in Jovian longitude), whereas bKOM is modulated more strongly by the solar wind than by the rotation (i.e., emitted from sources more active within a given Local Time sector). We propose a simple analytical description of these internal and external modulations and evaluate its main parameters (the amplitude of each control) for HOM + DAM and bKOM. Comparing Cassini and Nançay Decameter Array data, we find that HOM is primarily connected to the decameter emissions originating from the dusk sector of the Jovian magnetosphere. HOM and DAM components form a complex but stable pattern in the frequency‐longitude plane. HOM also seems to be related to the “lesser arcs” identified by Voyager. bKOM consists of a main part above ∼40 kHz in antiphase with HOM occurrence, and detached patches below ∼80 kHz in phase with HOM. The frequency‐longitude patterns formed by DAM, HOM and bKOM remain to be modeled. Key Points We build synthetic frequency‐longitude maps of polarized Jovian auroral radio emissions, DAM, HOM, and bKOM Jovian HOM and DAM are dominantly rotation‐modulated, bKOM dominantly solar wind‐modulated HOM appears primarily connected to decameter sources from the dusk side of the Jovian magnetosphere