A New Method to Infer the Size, Number Density, and Charge of Mesospheric Dust from its in situ Collection by the DUSTY Probe

We present a new extended method of analyzing measurements of mesospheric dust
16 made with DUSTY rocket-borne Faraday cup probes. It yields the variation of fundamental
17 dust parameters through a mesospheric cloud with an unrivalled altitude resolution down to 10
18 cm or less. A DUSTY probe was the first probe which unambiguously detected charged
19 dust/aerosol particles in the Earth’s mesosphere. DUSTY excluded the ambient plasma by
20 various biased grids, which however allowed dust particles with radii above a few nanometer
21 to enter, and it measured the flux of charged dust particles. The flux measurements directly
22 yielded the total ambient dust charge density.
23 We extend the analysis of DUSTY data by using the impact currents on its main grid and the
24 bottom plate as before, together with a dust charging model and a secondary charge production
25 model, to allow the determination of fundamental parameters, such as dust radius, charge
26 number and total dust density. We demonstrate the utility of the new analysis technique by
27 considering observations made with the DUSTY probes during the MAXIDUSTY rocket
28 campaign in June-July 2016 and comparing the results with those of other instruments (Lidar
29 and photometer) also used in the campaign.