The Hotel Payload 2 campaign: Overview of NO, O and electron density measurements in the upper mesosphere and lower thermosphere

C.-F. Enell1, J. Hedin2, J. Stegman2, G. Witt2, M. Friedrich3, W. Singer4, G. Baumgarten4, B. Kaifler4, U.-P. Hoppe5, B. Gustavsson6, U. Brändström7, Mikhail Khaplanov2, A. Kero1, Th.Ulich1, E. Turunen8

1Sodankylä Geophysical Observatory, Sodankylä, Finland,
2Dept of Meteorology, Stockholm University, Sweden,
3Graz University of Technology, Austria,
4Leibniz-Institute of Atmospheric Physics, Rostock University, Kühlungsborn, Germany,
5Norwegian Defence Research Establishment, Kjeller, Norway,
6University of Southampton, U.K.,
7Swedish Institute of Space Physics, Kiruna, Sweden,
8EISCAT Scientific Association, Kiruna, Sweden


The ALOMAR eARI Hotel Payload 2 (HotPay 2) rocket campaign took place at Andøya Rocket Range, Norway, in January 2008. The rocket was launched on January 31, 2008 at 19:14 UT, when auroral activity appeared after a long geomagnetically quiet period. In this paper we present an overview of the HotPay2 measurements of upper mesospheric and lower thermospheric (UMLT) electron, atomic oxygen (O) and nitric oxide (NO) density. [O] and [NO] were retrieved from a set of three photometers, Night-Time Emissions from the Mesosphere and Ionosphere (NEMI). Faraday rotation receivers on the rocket and the EISCAT UHF incoherent scatter radar provided simultaneous electron density profiles whereas the ALOMAR Na lidar and meteor radar measured the temperature profile and wind. The aurora was also observed with ground-based imagers.

The retrieved oxygen number density profile has a maximum at 89 kilometres, some 10 km lower than expected from earlier measurements and modelled profiles based on climatological averages (such as the MSIS model), and the retrieved NO densities are also lower than expected. Satellite measurements indicate that subsidence over the winter pole controlled the densities. Quantitative chemistry model results based on climatological average atmospheric density and temperature profiles were therefore not in good agreement with the measured profiles. The Hotel Payload 2 measurements thus confirm the importance of downward transport from the thermosphere into the winter polar vortex.

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