First Detection of Nanoparticles in the Asteroid Belt from Spectral Analysis of Cassini/Rpws Radio Data

Patricia Schippers1, Nicole Meyer-Vernet1, Soraya Belheouane1, Michel Moncuquet2, Alain Lecacheux3, William S Kurth4, Donald G Mitchell5 and Ingrid Mann6, (1)CNRS, Observatoire de Paris, LESIA, Meudon, France, (2)Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, LESIA, Meudon, France, (3)Observatoire de Paris, LESIA, Meudon, France, (4)University of Iowa, Iowa City, IA, United States, (5)Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, (6)EISCAT Scientific Association, Kiruna, Sweden
Abstract:
Nanodust grains of a few nanometer in size have been detected in the interplanetary medium at 1 AU and at the vicinity of giant planets Saturn and Jupiter. These are generally formed through collisional break-up of larger grains and are then picked-up by the planetary co-rotation electric field and/or the magnetized solar wind.

Here we analyze the spectra measured by the radio and plasma wave instrument onboard Cassini during the cruise phase close to the asteroid belt (R~2.9 AU); they exhibit bursty signatures similar to those observed by the same instrument at 1 AU (Schippers et al., 2014; doi:10.1002/2014GL060566) and at Jupiter (Meyer-Vernet et al., 2009; doi:10.1029/2008GL036752). The observed wave level and spectral shape are consistent with impacts of fast nanoparticles (v~450 km/s).

We discuss the origin of the particles by comparing the measured flux with the extrapolated flux from 1) the inner heliospheric source (0.2 AU), 2) the asteroid belt, and 3) Jupiter.

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