Jupiter’s auroral radio emissions observed by Cassini: rotational versus
solar wind control, and components identification
Abstract
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, that remains to be modelled. HOM also seems
to be related to the so-called ‘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 occurrence.