On the Importance of Searching for Oscillations of the Jovian Inner Radiation Belt with a Quasi-Period of 40 Minutes
Experiments aboard the Ulysses spacecraft discovered quasi-periodic bursts of relativistic electrons and of radio emissions with ~40-minute period(QP-40) from the south pole of Jupiter in February 1992. Such polar QP-40 burst activities were found to correlate well with arrivals of high-speed solar winds at Jupiter. We advance the physical scenario that the inner radiation belt(IRB) within ~2-3 Jupiter's radius, where ralativistic electrons are known to be trapped via synchrotron emissions, can execute global QP-40 magnetoinertial oscillations excited by arrivals of high-speed solar winds. Modulated by such QP-40 IRB oscillations, relativistic electrons trapped in the IRB may escape from the magnetic circumpolar regions during a certain phase of each 40-min period to form circumpolar QP-40 electron bursts. Highly beamed synchrotron emissions from such QP-40 burst electrons with small pitch angles relative to Jovian magnetic field at ~30-40 Jupiter radius give rise to QP-40 radio bursts with typical frequencies <0.2MHz. We predict that the synchrotron brightness of the IRB should vary on QP-40 timescales upon arrivals of high-speed solar winds with estimated magnitudes larger than 0.1Jy, detectable by ground-based radio telescopes. Using the real-time solar wind data from the spacecraft ACE, we show here that shch QP-40 pulsations of Jupiter's polar X-ray hot spot did in fact coincide with the arrival of high-speed solar wind at Jupiter.