Effects of magnetohydrodynamic waves in Jovian decametric emission

Abstract

The flux variability of Jovian decametric radio emission (DAM) is analyzed to search for its possible modulations by magnetohydrodynamic waves of ultra-low frequencies (ULF). The ULF modulating waves are found in DAM dynamic spectra as a moving pattern (moire) on the background of Jovian millisecond radio bursts (S-bursts). Their frequency drift (∼55 MHz/s) corresponds to the wave motion to Jupiter with Alfvén velocity (∼4 × 10 4 km s −1 ). There are whistler-like drifting details in the dynamic power spectra of ULF variations of S-burst emission flux at fixed radio frequency. Their frequency drift rates are consistent with whistlers that are dispersed mainly in the Io torus. Formally our analysis of DAM reveals the specific 2s-modulation of S-burst emission corresponding to the known magnetic pulsations near gyrofrequencies of heaviest ions (SO + 2 and SO + ) in the Io torus.

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

“…Jovian decametric emission (DAM) appears mainly in the form of long (L) bursts with the time scale of ∼1 s. Such modulation is a result of emission scattered in the interplanetary medium (Genova & Leblanc 1981) and inner magnetosphere of Jupiter (Arkhypov & Rucker 2007). The terrestrial ionosphere creates DAM flux variability with quasi-periods of 10 to 70 s .…”

S-burst storms of jovian decametric emission as a test of hypotheses

“…Similar auroral cavities were suggested in and near the DAM radio sources (Zarka, 1998). (d) Modulation lanes of DAM are formed by radiation scattering on field-aligned inhomogeneities not only in the Io plasma torus, but in the lower magnetosphere of Jupiter (Arkhipov, 2004;Arkhypov and Rucker, 2007). It follows that the jovian magnetosphere in the area of Io-B radio sources is filamented.…”

“…The velocity of dispersive Alfvén waves is calculated along the magnetic tube from the effective position of the satellite Io to the jovian surface in the northern polar region. Since the average longitude of Io during the analyzed radio storms is 216°, and the average lead angle between the real and effective positions of Io is 37° ( Arkhypov and Rucker, 2007), we trace the magnetic tube from the point on the Io orbit at the longitude of k eff = 216 À 37°= 179°. Other authors have used almost the same longitude (180°; Jones and Su, 2008;Hess et al, 2010).…”

Dynamics of decametric radio-sources and standing Alfvén waves in jovian magnetosphere

“…The propagating Alfvén waves were considered as a modulator of S/NB-emissions (i.e., Arkhypov and Rucker, 2007;Hess et al, 2007b). However, the connection of such wave with the long-lived (s $ 0.5 h like in Fig.…”