Quasiperiodic Saturn Auroral Hiss Observed During a Cassini Proximal Orbit

Saturn auroral hiss is intense whistler mode emission similar in morphology to terrestrial auroral hiss, and is observed at high latitude very often in quasiperiodic episodes with a period of approximately 1 hr. Bader et al. (2019) report auroral pulsations that may be due to duskside magnetodisk reconnection. The source of the 1-hr period is not definitively known but has been purported to be due to second harmonic Alfven waves standing along near planet magnetic field lines (Yates et al., 2016). Observations of auroral hiss at high latitude along Cassini proximal orbits are often excellent, and we have focused on an event for which we have concurrent ultraviolet auroral images as well as electron flux data. A series of repeating auroral hiss episodes is observed to initiate near the magnetic field line that traverses a Saturn kilometric radiation source region in each hemisphere, with periodic episodes of hiss recurring at higher L-shells. Magnetic field lines centered on individual hiss episodes have auroral footprints that lie near and within a region of intense auroral ultraviolet emissions. These observations have a parallel in terrestrial return current electron beam-generated auroral hiss seen near magnetic field lines supporting auroral kilometric radiation source regions. Recent findings link periodic plasma injections with Saturn reconnection sites observed preferentially on the duskside. These injections may spawn Saturn kilometric radiation source regions and periodic auroral hiss emission in nearby return current regions.