Nanodust detection near 1 AU from spectral analysis of Cassini/RPWS radio data

TL;DR

This study detects nanodust near 1 AU using spectral analysis of Cassini radio data, revealing impacts consistent with interplanetary flux models and previous observations by STEREO.

Contribution

First detection of nanodust near 1 AU through spectral analysis of Cassini data, confirming flux levels and impact velocities consistent with prior spacecraft observations.

Findings

Nanodust impacts observed at ~300 km/s.

Flux levels compatible with STEREO measurements.

Spectral signatures similar to those near Jupiter.

Abstract

Nanodust grains of a few nanometer in size are produced near the Sun by collisional break-up of larger grains and picked-up by the magnetized solar wind. They have so far been detected at 1 AU by only the two STEREO spacecraft. Here we analyze the spectra measured by the radio and plasma wave instrument onboard Cassini during the cruise phase close to Earth orbit; they exhibit bursty signatures similar to those observed by the same instrument in association to nanodust stream impacts on Cassini near Jupiter. The observed wave level and spectral shape reveal impacts of nanoparticles at about 300 km/s, with an average flux compatible with that observed by the radio and plasma wave instrument onboard STEREO and with the interplanetary flux models.