Tiny Dust Particles in the Solar System
Thursday, September 5, 2013
Science Update - A look at CfA discoveries in this month's journals


Earth, for example, collects dust in a series of patches which lie in a ring along the Earth's orbit. New measurements used radio instruments on twin interplanetary spacecraft to study nanometer-scale dust particles, or "nanodust." A grain of nanodust is smaller than a wavelength of optical light, and unlike the roughly ten times larger grains responsible for the zodiacal light, nanodust is too small to efficiently scatter sunlight and can only be detected using space instruments. When a grain of nanodust impacts a spacecraft, it creates an expanding cloud of ionized gas which can lead to a voltage pulse between a spacecraft's body and its antenna, and which can then be sensed. Nanodust can be accelerated by the interplanetary magnetic field to the speed of the solar wind -- significantly faster than the orbital speeds of heavier dust grains. Because the electrical signal induced by a dust grain depends more strongly on its impact speed than on its mass, nanodust produces a strong signal despite its being lightweight.


"Interplanetary Nanodust Detection by the Solar Terrestrial Relations Observatory/WAVES Low Frequency
Receiver," G. Le Chat, A. Zaslavsky, N. Meyer-Vernet, K. Issautier, S. Belheouane,
F. Pantellini, M. Maksimovic, I. Zouganelis, S.D. Bale, J.C. Kasper, Solar Physics, 286, 549, 2013.