On the size distribution of collision fragments of NLC dust particles and their relevance to meteoric smoke particles
2014 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, Vol. 118, 190-198 p.Article in journal (Refereed) Published
We present the results from a new dust probe MUDD on the PHOCUS payload which was launched in July 2011. In the interior of MUDD all the incoming NLC/PMSE icy dust particles will collide, at an impact angle similar to 70 degrees to the surface normal, with a grid constructed such that no dust particles can directly hit the bottom plate of the probe. Only collision fragments will continue down towards the bottom plate. We determine an energy distribution of the charged fragments by applying a variable electric field between the impact grid and the bottom plate of MUDD. We find that similar to 30% of the charged fragments have kinetic energies less than 10 eV, similar to 20% have energies between 10 and 20 eV while similar to 50% have energies above 20 eV. The transformation of limits in kinetic energy for ice or meteoric smoke particles (MSP) to radius is dependent on many assumptions, the most crucial being fragment velocity. We find, however, that the sizes of the charged fragments most probably are in the range of 1 to 2 nm if meteoric smoke particles (MSP), and slightly higher if ice particles. The observed high charging fraction and the dominance of fragment sizes below a few nm makes it very unlikely that the fragments can consist mainly of ice but that they must be predominantly MSP as predicted by Havnes and N ae sheim (2007) and recently observed by Hervig et al. (2012). The MUDD results indicate that MSP are embedded in NLC/PMSE ice particles with a minimum volume filling factor of similar to.05% in the unlikely case that all embedded MSP are released and charged. A few % volume filling factor (Hervig et al., 2012) can easily be reached if similar to 10% of the MSP are released and that their charging probability is similar to 0.1.
Place, publisher, year, edition, pages
2014. Vol. 118, 190-198 p.
mesosphere dust, smoke particles, sizes of MSP
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:su:diva-107089DOI: 10.1016/j.jastp.2014.03.008ISI: 000340332900007OAI: oai:DiVA.org:su-107089DiVA: diva2:743986