Lecturer: Ingrid Mann (EISCAT)
Date: 2011-09-22 10:30
Place: Aniara

Nanodust in Interplanetary and Near-Earth Space

Ingrid Mann
Kiruna, Sweden

Nandust describes solid particles of sizes of the order of 10 nm and smaller that have distinctly different properties than the larger dust. The presence of nanodust in the interstellar medium is inferred from observations since longtime while to this date, there is no brightness observation of nanodust in the solar system. The nanodust in the solar system is instead observed with in-situ measurements from spacecraft when it hits spacecraft and detectors with high velocity and generates free ions and electrons.

In a previous seminar at IRF I have discussed the acceleration of nanodust in the solar wind. The high-velocity impacts of such accelerated nanodust are currently observed with the plasma wave experiments onboard the two STEREO spacecraft near 1 AU (cf. Meyer-Vernet et al. Solar Physics 2009).

It seems plausible that the observed nanodust forms within the interplanetary dust cloud of our solar system. The formation of nanodust in the solar system dust cloud by fragmentation of larger particles is likened to the collision evolution in the interstellar medium. Some processes possibly determine a small size limit of the fragments, but the current observations of nanodust in the solar system do not indicate the size of the smallest dust particles and this remains an open question for future studies.

Estimating the flux of nanodust in interplanetary space is hampered by our lack of knowledge of the dust mass distribution and spatial distribution inside 1 AU and by our lack of knowledge of the fragmentation process during dust collisions. At this point observations, rather than further model calculations may guide the investigations. The observations of nanodust onboard STEREO provide already valuable information to address some of the open questions.

Nanodust as a result of its large surface area compared to its small mass is important for interactions with the surrounding particles and field environment. In the interplanetary medium it possibly plays a role for the formation of pick-up ions and neutrals in the solar wind. The present observational data, however, can not be traced back convincingly to the influence of nanodust.

Created 2011-08-16 15:24:36 by Uwe Raffalski
Last changed 2011-09-15 08:29:24 by Mats Holmström