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- ItemOn the efficiency of rocket-borne particle detection in the mesosphere(München : European Geopyhsical Union, 2007) Hedin, J.; Gumbel, J.; Rapp, M.Meteoric smoke particles have been proposed as a key player in the formation and evolution of mesospheric phenomena. Despite their apparent importance still very little is known about these particles. Important questions concern the smoke number density and size distribution as a function of altitude as well as the fraction of charged particles. Sounding rockets are used to measure smoke in situ, but aerodynamics has remained a major challenge. Basically, the small smoke particles tend to follow the gas flow around the payload rather than reaching the detector if aerodynamics is not considered carefully in the detector design. So far only indirect evidence for the existence of meteoric smoke has been available from measurements of heavy charge carriers. Quantitative ways are needed that relate these measured particle population to the atmospheric particle population. This requires in particular knowledge about the size-dependent, altitude-dependent and charge-dependent detection efficiency for a given instrument. In this paper, we investigate the aerodynamics for a typical electrostatic detector design. We first quantify the flow field of the background gas, then introduce particles in the flow field and determine their trajectories around the payload structure. We use two different models to trace particles in the flow field, a Continuous motion model and a Brownian motion model. Brownian motion is shown to be of basic importance for the smallest particles. Detection efficiencies are determined for three detector designs, including two with ventilation holes to allow airflow through the detector. Results from this investigation show that rocket-borne smoke detection with conventional detectors is largely limited to altitudes above 75 km. The flow through a ventilated detector has to be relatively large in order to significantly improve the detection efficiency.
- ItemDistribution of meteoric smoke - Sensitivity to microphysical properties and atmospheric conditions(München : European Geopyhsical Union, 2006) Megner, L.; Rapp, M.; Gumbel, J.Meteoroids entering the Earth's atmosphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.
- ItemSimultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during the WADIS sounding rocket project(Göttingen : Copernicus GmbH, 2019) Strelnikov, B.; Eberhart, M.; Friedrich, M.; Hedin, J.; Khaplanov, M.; Baumgarten, G.; Williams, B.P.; Staszak, T.; Asmus, H.; Strelnikova, I.; Latteck, R.; Grygalashvyly, M.; Lübken, F.-J.; Höffner, J.; Wörl, R.; Gumbel, J.; Löhle, S.; Fasoulas, S.; Rapp, M.; Barjatya, A.; Taylor, M.J.; Pautet, P.-D.In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere-lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties. © 2019 Author(s).
- ItemAtmospheric band fitting coefficients derived from a self-consistent rocket-borne experiment(Göttingen : Copernicus GmbH, 2019) Grygalashvyly, M.; Eberhart, M.; Hedin, J.; Strelnikov, B.; Lübken, F.-J.; Rapp, M.; Löhle, S.; Fasoulas, S.; Khaplanov, M.; Gumbel, J.; Vorobeva, E.Based on self-consistent rocket-borne measurements of temperature, the densities of atomic oxygen and neutral air, and the volume emission of the atmospheric band (762 nm), we examined the one-step and two-step excitation mechanism of O2 + b16C g for nighttime conditions. Following McDade et al. (1986), we derived the empirical fitting coefficients, which parameterize the atmospheric band emission O2 + b16C g X36 g .0;0/. This allows us to derive the atomic oxygen concentration from nighttime observations of atmospheric band emission O2 + b16C g X36 g .0; 0/. The derived empirical parameters can also be utilized for atmospheric band modeling. Additionally, we derived the fit function and corresponding coefficients for the combined (one- and two-step) mechanism. The simultaneous common volume measurements of all the parameters involved in the theoretical calculation of the observed O2 + b16C g X36 g .0; 0/ emission, i.e., temperature and density of the background air, atomic oxygen density, and volume emission rate, is the novelty and the advantage of this work. © Author(s) 2019.
- ItemFirst global observations of the mesospheric potassium layer(Hoboken, NJ : Wiley-Blackwell Publishing Ltd, 2014) Dawkins, E.C.M.; Plane, J.M.C.; Chipperfield, M.P.; Feng, W.; Gumbel, J.; Hedin, J.; Höffner, J.; Friedman, J.S.Metal species, produced by meteoric ablation, act as useful tracers of upper atmosphere dynamics and chemistry. Of these meteoric metals, K is an enigma: at extratropical latitudes, limited available lidar data show that the K layer displays a semiannual seasonal variability, rather than the annual pattern seen in other metals such as Na and Fe. Here we present the first near-global K retrieval, where K atom number density profiles are derived from dayglow measurements made by the Optical Spectrograph and Infrared Imager System spectrometer on board the Odin satellite. This robust retrieval produces density profiles with typical layer peak errors of ±15% and a 2km vertical grid resolution. We demonstrate that these retrieved profiles compare well with available lidar data and show for the first time that the unusual semiannual behavior is near-global in extent. This new data set has wider applications for improving understanding of the K chemistry and of related upper atmosphere processes. Key Points First quantitative retrieval of the terrestrial K layer from space The unusual semiannual behavior of K is near global in extent.