Observatoire de Paris Institut national de recherche scientifique français Univerité Pierre et Marie Curie Université Paris Diderot - Paris 7

Causes and Consequences of nanodust in the interplanetary medium

Thursday 5 May 2011, by Ingrid Mann (Belgian Institute for Space Aeronomy BIRA/IASB, Brussels, Belgium; currently at LESIA )

Tuesday 10 May 2011 à 11h00 , Lieu : Salle de confĂ©rence du bât. 17

Fluxes of nanometric dust have been recently discovered near Earth’s orbit with electric field measurements onboard the STEREO space mission. The new measurements can be explained with nanodust that is accelerated in the solar wind after being formed during collisions of larger dust particles in the inner solar system. The momentum flux of the nanodust is small compared to that carried by the solar wind and the total cross-sectional area in a given volume in space of the nanodust population is smaller than that of the larger constituents of the interplanetary dust cloud. Hence the contribution of nanodust to the currently known dust interactions with the solar wind is small. The total mass flux observed in the nanodust is a small fraction of the mass that is destroyed by mutual collisions inside 1 AU, but the values are possibly beyond the fluxes that we calculate with dust collision and fragmentation models. The models have large uncertainties and it is quite possible that the nanodust does not form by direct fragmentation of the larger dust, but from a molten or processed phase of the dust material. Measuring the mass distribution of the nanodust in the interplanetary medium will give new insights in the fragmentation process and would allow re-considering the fragmentation models that are also applied in studies of dust evolution in the interstellar medium.