Characteristics of Jovian ionospheric Alfvn resonator observed by using wave modulations of L-burst emissions

On 4 June 2008 UT, the position of the satellite Io with respect to Jupiter was the so-called Io-A, we observed Jovian decametric (DAM) radio emissions using a waveform receiver (WFR) and detected wave modulations (WMs) in the DAM emissions. WMs appeared four times at intervals of approximately 7 min for durations of 3-10 s each. We found that the WMs had fundamental frequencies of 2.5-5 Hz, and the 1st and 2nd harmonics of these frequencies were odd resonances at the fundamental frequencies. Simulations confirmed that strong Alfvn waves arrive at the polar regions of Jupiter at 5-7 min intervals when Io is located at the center of the Io plasma torus, and Io was located at that location when WMs were detected. The 7 min intervals of WMs are consistent with the characteristic periods of Alfvn waves, suggesting the existence of the ionospheric Alfvn resonator (IAR) expected in the system of Jupiter. Thus far, few observations have suggested the existence of IAR in Jupiter. In this research, we suggest the existence of IAR in Jupiter by using a WFR and the millisecond modulations of Jovian L-burst emissions.