Sub-hour modulation of L-component of Io-related Jovian decametric emission^*

¹ Institute of Radio Astronomy, National Academy of Sciences of Ukraine, Chervonopraporna 4, 61002 Kharkiv, Ukraine e-mail: rai@ri.kharkov.ua
² Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria e-mail: rucker@oeaw.ac.at

Received: 3 December 2007
Accepted: 10 January 2008

Abstract

The variability of Jovian decametric emission (DAM) is studied at time scales from 1 min to 1 h with DAM records of 1991–2007 from the archive of Nancay Radio Observatory. We found that the internal structure of the Io-related radio storms has the dominating periodicity of  min on average. This estimate practically coincides with the fundamental eigenoscillations of transversal magnetic pulsations in the Io plasma torus. Our autocorrelation analysis confirms the excess of DAM variations with the time scale of the fundamental and first harmonic periods of the Io torus. Moreover, the time scale of arc pattern in DAM dynamic spectra is estimated to be 5.4 min, which corresponds to Io's Alfvén wing diameter or to the 3rd and 4th harmonics of torus proper oscillations. These results could be interpreted in terms of electron acceleration in field-aligned electric fields of standing Alfvén waves trapped in the Io torus. There is an analogous modulation of auroral kilometric radiation of the Earth by magnetic pulsations at field line resonances in the terrestrial magnetosphere (Hanasz et al. [CITE], J. Geophys. Res., 111, A03209).