Measurements of meteor smoke particles during the ECOMA-2006 campaign: 1. Particle detection by active photoionization |
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| Authors: | Markus Rapp Irina Strelnikova |
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| Institution: | 1. University of Alaska, Fairbanks, USA;2. Virginia Polytechnic Institute and State University, Blacksburg, USA;3. University of Rostock, Kuehlungsborn, Germany;4. University of Rostock, Kuehlungsborn, Germany;5. University of Colorado, Boulder, USA;1. Medical Physics Department, University Hospital “S. Orsola-Malpighi”, Bologna, Italy;2. Nuclear Medicine Department, University Hospital “S. Orsola-Malpighi”, Bologna, Italy;1. National Centre for Nanotechnology & Department of Metallurgy and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan;2. EMMG, Physics Division, PINSTECH, Islamabad, Pakistan;1. University of Texas at San Antonio, San Antonio, TX 78249, United States;2. Southwest Research Institute, San Antonio, TX 78238, United States |
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| Abstract: | We present a new design of an in situ detector for the study of meteor smoke particles (MSPs) in the middle atmosphere. This detector combines a classical Faraday cup with a xenon-flashlamp for the active photoionization/photodetachment of MSPs and the subsequent detection of corresponding photoelectrons. This instrument was successfully launched in September 2006 from the Andøya Rocket Range in Northern Norway. A comparison of photocurrents measured during this rocket flight and measurements performed in the laboratory proves that observed signatures are truly due to photoelectrons. In addition, the observed altitude cut-off at 60 km (i.e., no signals were observed below this altitude) is fully understood in terms of the mean free path of the photoelectrons in the ambient atmosphere. This interpretation is also proven by a corresponding laboratory experiment. Consideration of all conceivable species which can be ionized by the photons of the xenon-flashlamp demonstrates that only MSPs can quantitatively explain the measured currents below an altitude of 90 km. Above this altitude, measured photocurrents are most likely due to photoionization of nitric oxide. In conclusion, our results demonstrate that the active photoionization and subsequent detection of photoelectrons provides a promising new tool for the study of MSPs in the middle atmosphere. Importantly, this new technique does not rely on the a priori charge of the particles, neither is the accessible particle size range severely limited by aerodynamical effects. Based on the analysis described in this study, the geophysical interpretation of our measurements is presented in the companion paper by Strelnikova, I., et al. 2008. Measurements of meteor smoke particles during the ECOMA-2006 campaign: 2. results. Journal of Atmospheric and Solar-Terrestrial Physics, this issue, doi:10.1016/j.jastp.2008.07.011]. |
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