Dust impact detection by the Cassini Langmuir probe in Saturn's E ring

Abstract:

Individual examination reveals the existence of sharp spikes in the Cassini Radio and Plasma Wave Science / Langmuir probe (RPWS/LP) I-V (current-voltage) sweeps. These spikes are characterized as a sudden increase or decrease in the probe current, with many of them appearing as one-point anomalies lasting less than a millisecond. Their occurrence generally correlates with the E ring dust density - the closer to the ring plane and Enceladus, the more frequent the appearance of spikes. These characteristics suggest that the LP spike signals are caused by dust impacts - most likely the collection of plasma produced from high velocity dust-probe impacts. Because of the low detection rate and the flexibility regarding to the spacecraft attitude, LP spikes provide an alternative way to explore the densest part of the E ring. 

Here we will present a preliminary statistical analysis of the LP spike appearance as a function of the spacecraft location, the relative dust speed, the spacecraft and probe potentials, and other relevant parameters. Comparison with measurements carried out by the High Rate Detector, a subsystem of the Cassini Cosmic Dust Analyser, will provide constraints on the dust grain size responsible for these detections. We will also examine their spatial distribution to identify features that may associate with ring dynamical effects, such as the seasonal variation or the noon-to-midnight electric field.