Extremely Large Enhancements of the Jovian Decameter Radio Bursts Caused by the Magnetosphere-Plasmasphere Passages of Shoemaker-Levy 9 Comet Fragments-Evolution of Jovian Decametric Radiation Feature into the State of Intense Decametric Pulsar

Abstract

Observation results of the Jovian decameter wave emissions in the period of the passages of fragments of Shoemaker-Levy 9 comet through the Jovian magnetosphere indicated extremely large enhancements of Jovian decameter wave radiations (JDR), being caused by dust-plasma clouds moving across the Jovian magnetic fields. The total emission power of the decameter wave radiations was increased to the level of approximately 10 times larger than the regular maximum level of the emissions of the Jovian decameter radiation in a corresponding frequency range. The Jovian decameter wave radiations have continuously been emitted for six months, long after the passage of the fragments of Shoemaker-Levy 9 comet; the evidence suggests that the Jovian plasma environment has been completely changed by the remnants of dust clouds that were left behind the Shoemaker-Levy 9 comet fragments. IntroductionFrom 20:11 UT on July 16, 1994 to 08:05 UT on July 22, 1994 the succeeded collisions of the fragments of Shoemaker-Levy 9 had taken place. Since the prediction of the collision event, possible effects of the fragments of the Shoemaker-Levy 9 comet approaching to Jupiter on the enhancements of the Jovian decameter wave radiations (JDR) have been considered in three phases (Oya et al., private communication at the autumn meeting of the Japanese Society of Planetary Science, 1993). These are phases of the passage of fragments through the magnetosphere, the phase of the passage through the plasmasphere and the last phase of crashing into the dense Jovian atmosphere; the interaction of the fragments with the Jovian magnetic field, being surrounded by dusts and plasma, may generate the electric field whose effects can be transported down into the polar region ionosphere inducing the electric currents where some parts of the energy may be transformed into the energy of decameter radio waves. Several predictions have been published relating to the enhancements of Jovian decameter wave radiations mainly for the magnetosphere interaction of cometgenic plasma and dust (Ip and Prange, 1994;Farrell et al., 1994;Bolin and Brenning, 1994).The observations of Jovian decameter wave radiations have been made in the observation stations of the Tohoku University Jovian Decameter Radiation Observatory (TU-JDO). The system of TU-JDO have been developed during past 20 years (Oya and Morioka, 1979;Oya et al., 1984) and have been made current observations; being based on this background, special campaign activities for the event of the SL-9 comet collision with Jupiter have been carried out in a period after July 14, 1994. The present paper is purposed to report the first results of the Shoemaker-Levy 9 effects on JDR from the TU-JDO observation data which indicated extremely large enhancements of JDR in the phases of the passages of the cometary fragments through the magnetosphere and plasmasphere; and there have been continued serious remaining effects long after the collisions due to the possible passages of dust clouds through the Jovian plasma environmen...

Occurrence probability of Jovian decametric radiation observed by short baseline interferometer system in Fukui University of Technology

“…8, which corresponds to the previously-reported result (Carr et al, 1983), however, the former peak (60 • ≤ CML ≤ 180 • ) is too high relative to the latter peak (180 • ≤ CML ≤ 300 • ). In fact, the obtained result is more similar to that reported by Oya et al (1997) who pointed out the possibility the occurrence probability is influenced by the fragments of SL-9 comet. About the emissions from 60 • to 180 • in CML except for well known Io-B emissions, we calculate the dependence of occurrence probabilities on Io phase.…”

“…The technique proposed in this study is based on Fourier transform of observed interferometer data; this provides useful tool to detect the weak Jovian emission out of background noise by calculating the correlation coefficient between observed and theoretical fringe wave form of the interferometer. As the results of data analyses by using the data set obtained from 2007 to 2010, we found the similar dependence of occurrence probabilities on CML to that reported by Oya et al (1997). It is clarified that the occurrence probability of emissions detected in the non-Io-B region which is defined as sources associated with 60 to 180 degrees in CML has a clear dependence on the Io-phase around 240 degrees; we may state appearance of a new Io related source.…”

“…In addition, Oya et al (1997) showed a possibility that radiation process of DAM was influenced by the impact of SL-9 cometary fragments to Jupiter in 1994, therefore, we have paid attention to the change of DAM's occurrence probability since the impact of SL-9 fragments. In Fukui University of Technology, an interferometer system with 3 short baselines had been set up from 2000 to 2002 and the observation of occurrence probability has been carried out except for 2005.…”