The physics and detection of nanodust in the solar system

Abstract

The mass distribution of small bodies in the solar system extends over more than 35 orders of magnitude, from asteroids to nanodust, which bridge the gap between molecules and macroscopic submicron grains. The small size of nanograins compared to the relevant basic scales gives them peculiar properties. Some of these properties affect their electric charging and their large chargeto-mass ratio drives their acceleration to very high speeds in moving magnetised plasmas, as the solar wind and rotating planetary magnetospheres. The electric charge and/or high speed of nanograins have enabled them to be detected serendipitously in various parts of the solar system by several instruments designed to study larger dust, plasma particles, or waves, on a number of spacecraft. These discoveries have opened an emerging field of research, in which many open questions remain, in particular concerning the lower size limit of the particles.

Frequency range of dust detection in space with radio and plasma wave receivers: Theory and application to interplanetary nanodust impacts on Cassini

“…based on measurements over a much wider range of speeds [McBride and McDonnell, 1999;Lai et al, 2002] than the more recent calibrations and whose extrapolation for fast nanodust is consistent with independent results [Meyer-Vernet et al, 2015]. Beware that in (1), Q∕m is in SI units (C/kg), whereas v is in km/s.…”

“…Impact ionization yields of materials relevant for the STEREO and Cassini spacecraft have been measured recently for microdust impacting at speeds below 40 km/s [ Collette et al , ], but no useful data from laboratory calibrations or simulations are available for high‐speed nanodust. We therefore use an approximation of the empirical relation relating the postimpact free charge Q to the grain's mass m and speed v based on measurements over a much wider range of speeds [ McBride and McDonnell , ; Lai et al , ] than the more recent calibrations and whose extrapolation for fast nanodust is consistent with independent results [ Meyer‐Vernet et al , ]. Beware that in , Q / m is in SI units (C/kg), whereas v is in km/s.…”

“…The mechanism of nanodust detection with Cassini/RPWS in the solar wind is simpler than that responsible for nanodust detection on STEREO, which relies on the variation in electric potential of only one antenna boom whose photoelectron sheath is affected by the impact plasma cloud [ Pantellini et al , , ; Zaslavsky et al , ]. This STEREO mechanism requires thick antennas with an adequate implantation geometry [ Meyer‐Vernet et al , , ] so that a part of one antenna is exposed to solar radiation and close to the impacted region of the spacecraft—as is the case for the X (Z) antenna on STEREO A (B) [see Meyer‐Vernet et al , , Figure 2]. In contrast, on Cassini the geometry is very different, with electric antennas extending nearly symmetrically far from the spacecraft of rough cylindrical shape and a large high‐gain antenna.…”

“…In contrast, the pulses' risetime is much more difficult to modelize since it depends on both the impact and ambient plasmas. Contrary to the generally longer decay time, this risetime has not been analyzed previously because it is not large compared to the time resolution of the Cassini/RPWS waveform analyzer [Gurnett et al, 2004], whereas Wind/WAVES [Bougeret and et al, 1995] cannot detect pulses in spacecraft potential, and, as we noted above, STEREO/WAVES [Bougeret et al, 2008] detects nanodust impacts via a different mechanism [see, e.g., Meyer-Vernet et al, 2015].…”

Localized structures in complex plasmas in the presence of a magnetic field

“…A dusty (complex) plasma is a multicomponent system consisting of electrons, ions, charged mesoscopic particles (dust grains) and neutral atoms or molecules Shukla and Eliasson 2009;Morfill and Ivlev 2009;Meyer-Vernet et al 2015). Interest in this 'unusual' state of matter stems from the ubiquity with which it is found in the laboratory, in space, and in astrophysics, such as cometary tails, planetary rings, solar and planetary nebulae, the lower ionosphere (mesosphere), atmospheric lighting and industrial plasma processing and nanomaterials fabrication devices (Merlino 2006;Amorim et al 2015).…”