Periodic bursts of Jovian non-Io decametric radio emission

Abstract

During the years 2000–2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ≈1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ∼25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

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“…in the extended Io torus. In the decameter range, Panchenko et al (2013) observed radio arcs resembling Io's in subcorotation with the same period as that observed by Steffl et al (2006) in the torus, and interpreted as the beating of the System III (internal) and IV (torus perturbations) periods. The beating originates from a peak of the hot electron population density near 290…”

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“…Kaiser 1993;Kaiser et al 1996). Panchenko et al (2013) have shown that non-Io decametric emissions exhibit periodic bursts with periods about 1.5% longer than the rotation rate of Jupiter and that are strongly correlated with solar wind pressure increases, typically occurring every ∼ 25 days. Additionally, Louarn et al (1998Louarn et al ( , 2000Louarn et al ( , 2001Louarn et al ( , 2014 have used Galileo observations of hectometric radiation, narrow- Gurnett et al (2002) band kilometric radiation, and trapped continuum radiation to study the dynamics of the magnetosphere.…”

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