2013, Bekkeng, T.A., Barjatya, A., Hoppe, U.-P., Pedersen, A., Moen, J.I., Friedrich, M., Rapp, M.

Three sounding rockets were launched from Andøya Rocket Range in the ECOMA campaign in December 2010. The aim was to study the evolution of meteoric smoke particles during a major meteor shower. Of the various instruments onboard the rocket payload, this paper presents the data from a multi-Needle Langmuir Probe (m-NLP) and a charged dust detector. The payload floating potential, as observed using the m-NLP instrument, shows charging events on two of the three flights. These charging events cannot be explained using a simple charging model, and have implications towards the use of fixed bias Langmuir probes on sounding rockets investigating mesospheric altitudes. We show that for a reliable use of a single fixed bias Langmuir probe as a high spatial resolution relative density measurement, each payload should also carry an additional instrument to measure payload floating potential, and an instrument that is immune to spacecraft charging and measures absolute plasma density.

2012, Friedrich, M., Rapp, M., Blix, T., Hoppe, U.-P., Torkar, K., Robertson, S., Dickson, S., Lynch, K.

The ionosphere is always assumed to contain equal numbers of positive and negative charges in a given volume (quasineutrality). Hence fewer electrons than positive charges are an indication of negative charges other than electrons. Theories predict and in-situ mass spectrometer measurements confirmed that these negative charges are negative ions, but recent experimental results suggest that other scavengers of free electrons can also be active in the mesosphere. Outside the polar summer mesosphere this additional removal of electrons is today believed to be due to meteoric dust, which maximises in the mesosphere. Data predominantly from the recent ECOMA flights are used to test this presumption. Six sounding rockets carried different dust detectors, as well as probes for electrons and ions. With such an instrumental ensemble one can assess whether indeed the existence of meteoric dust removes more electrons than would be expected from gas phase ion chemistry alone. Other factors potentially impacting on electron removal are also discussed in the paper.

2012, Rapp, M., Plane, J.M.C., Strelnikov, B., Stober, G., Ernst, S., Hedin, J., Friedrich, M., Hoppe, U.-P.

The ECOMA sounding rocket campaign in 2010 was performed to investigate the charge state and number density of meteoric smoke particles during the Geminids meteor shower in December 2010. The ALOMAR Na lidar contributed to the campaign with measurements of sodium number density, temperature and line-of-sight wind between 80 and 110 km altitude over Andøya in northern Norway. This paper investigates a possible connection between the Geminids meteor shower and the mesospheric sodium layer. We compare with data from a meteor radar and from a rocket-borne in situ particle instrument on three days. Our main result is that the sodium column density is smaller during the Geminids meteor shower than the winter average at the same latitude. Moreover, during two of the three years considered, the sodium column density decreased steadily during these three weeks of the year. Both the observed decrease of Na column density by 30% and of meteoric smoke particle column density correlate well with a corresponding decrease of sporadic meteor echoes. We found no correlation between Geminids meteor flux rates and sodium column density, nor between sporadic meteors and Na column density (R = 0.25). In general, we found the Na column density to be at very low values for winter, between 1.8 and 2.6 × 1013 m−2. We detected two meteor trails containing sodium, on 13 December 2010 at 87.1 km and on 19 December 2010 at 84 km. From these meteor trails, we estimate a global meteoric Na flux of 121 kg d−1 and a global total meteoric influx of 20.2 t d−1.