| 1. |
- Eberhart, Martin, et al.
(författare)
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Atomic oxygen number densities in the mesosphere-lower thermosphere region measured by solid electrolyte sensors on WADIS-2
- 2019
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 12:4, s. 2445-2461
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Tidskriftsartikel (refereegranskat)abstract
- Absolute profiles of atomic oxygen number densities with high vertical resolution have been determined in the mesosphere-lower thermosphere (MLT) region from in situ measurements by several rocket-borne solid electrolyte sensors. The amperometric sensors were operated in both controlled and uncontrolled modes and with various orientations on the foredeck and aft deck of the payload. Calibration was based on mass spectrometry in a molecular beam containing atomic oxygen produced in a microwave discharge. The sensor signal is proportional to the number flux onto the electrodes, and the mass flow rate in the molecular beam was additionally measured to derive this quantity from the spectrometer reading. Numerical simulations provided aerodynamic correction factors to derive the atmospheric number density of atomic oxygen from the sensor data. The flight results indicate a preferable orientation of the electrode surface perpendicular to the rocket axis. While unstable during the upleg, the density profiles measured by these sensors show an excellent agreement with the atmospheric models and photometer results during the downleg of the trajectory. The high spatial resolution of the measurements allows for the identification of small-scale variations in the atomic oxygen concentration.
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| 2. |
- Ehard, Benedikt, et al.
(författare)
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Combination of Lidar and Model Data for Studying Deep Gravity Wave Propagation
- 2016
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Ingår i: Monthly Weather Review. - 0027-0644 .- 1520-0493. ; 144:1, s. 77-98
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a feasible method to complement ground-based middle atmospheric Rayleigh lidar temperature observations with numerical simulations in the lower stratosphere and troposphere to study gravity waves. Validated mesoscale numerical simulations are utilized to complement the temperature below 30-km altitude. For this purpose, high-temporal-resolution output of the numerical results was interpolated on the position of the lidar in the lee of the Scandinavian mountain range. Two wintertime cases of orographically induced gravity waves are analyzed. Wave parameters are derived using a wavelet analysis of the combined dataset throughout the entire altitude range from the troposphere to the mesosphere. Although similar in the tropospheric forcings, both cases differ in vertical propagation. The combined dataset reveals stratospheric wave breaking for one case, whereas the mountain waves in the other case could propagate up to about 40-km altitude. The lidar observations reveal an interaction of the vertically propagating gravity waves with the stratopause, leading to a stratopause descent in both cases.
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| 3. |
- Grygalashvyly, Mykhaylo, et al.
(författare)
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Atmospheric band fitting coefficients derived from a self-consistent rocket-borne experiment
- 2019
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:2, s. 1207-1220
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Tidskriftsartikel (refereegranskat)abstract
- 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 O-2 (b(1)Sigma(+)(g)) for nighttime conditions. Following McDade et al. (1986), we derived the empirical fitting coefficients, which parameterize the atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0). This allows us to derive the atomic oxygen concentration from nighttime observations of atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(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 O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(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.
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| 4. |
- Grygalashvyly, Mykhaylo, et al.
(författare)
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Nighttime O(1D) and corresponding Atmospheric Band emission (762 nm) derived from rocket-borne experiment
- 2021
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 213
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Tidskriftsartikel (refereegranskat)abstract
- Based on common volume rocket-borne measurements of temperature, densities of atomic oxygen and neutral air, we derived O(D-1) nighttime concentrations and corresponding Atmospheric band emission (762 nm). This is one of the first retrievals of the nighttime O(D-1) concentration. Recently, Kalogerakis, Sharma and co-workers have suggested a new production path of O(D-1) based on the reaction of vibrationally excited OH and O. We calculate Atmospheric band volume emission related to the population of O-2(b(1)Sigma(+)(g)) from O(D-1) and compare with total Atmospheric band emissions observed during the same rocket launch. This allows an estimation of the relative contribution of the new Kalogerakis-Sharma mechanism (KSM) to the total Atmospheric band emission. The concentration of O(D-1) due to KSM amounts to several tens cm(-3) with a peak around 95 km. The KSM gives an essential contribution to the total Atmospheric band volume emission (762 nm). Additionally, we illustrate analytically that the expressions for volume emission by the new KSM and the traditional two-step mechanism have similar functional dependences on the atmospheric concentrations of O and O-2. This causes an ambiguity, when interpreting Atmospheric band observations in terms of the one mechanism or the other.
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| 5. |
- Hedin, Jonas, et al.
(författare)
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On the efficiency of rocket-borne particle detection in the mesosphere
- 2007
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 7:14, s. 3701-3711
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Hedin, Jonas, 1976-
(författare)
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Rocket-borne in situ measurements in the middle atmosphere
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Earth's mesosphere and lower thermosphere in the altitude range 50-130 km is a fascinating part of our atmosphere. Complex interactions between radiative, dynamical, microphysical and chemical processes give rise to several prominent phenomena, many of those centred around the mesopause region (80-100 km). These phenomena include noctilucent clouds, polar mesosphere summer echoes, the ablation and transformation of meteoric material, and the Earth’s airglow. Strong stratification and small scale interactions are common features of both these phenomena and the mesopause region in general. In order to study interactions on the relevant spatial scales, in situ measurements from sounding rockets are essential for mesospheric research.This thesis presents new measurement techniques and analysis methods for sounding rockets, thus helping to improve our understanding of this remote part of the atmosphere. Considering the need to perform measurements at typical rocket speeds of 1 km/s, particular challenges arise both from the design of selective, sensitive, well-calibrated instruments and from perturbations due to aerodynamic influences. This thesis includes a quantitative aerodynamic analysis of impact and sampling techniques for meteoric particles, revealing a distinct size discrimination due to the particle flow. Optical techniques are investigated for mesospheric ice particle populations, resulting in instrument concepts for accessing smaller particles based on Mie scattering at short ultraviolet wavelengths. Rocket-borne resonance fluorescence measurements of atomic oxygen are critically re-assessed, leading to new calibration concepts based on photometry of O2 airglow emissions.The work presented here also provides important pre-studies for the upcoming PHOCUS rocket campaign from Esrange in July 2010. PHOCUS will address the interaction between three major mesospheric players: meteoric smoke, noctilucent clouds and gas-phase chemistry.
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| 7. |
- Moeller, Steffen, et al.
(författare)
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Community-driven development for computational biology at Sprints, Hackathons and Codefests
- 2014
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Ingår i: BMC Bioinformatics. - 1471-2105. ; 15, s. S7-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Computational biology comprises a wide range of technologies and approaches. Multiple technologies can be combined to create more powerful workflows if the individuals contributing the data or providing tools for its interpretation can find mutual understanding and consensus. Much conversation and joint investigation are required in order to identify and implement the best approaches. Traditionally, scientific conferences feature talks presenting novel technologies or insights, followed up by informal discussions during coffee breaks. In multi-institution collaborations, in order to reach agreement on implementation details or to transfer deeper insights in a technology and practical skills, a representative of one group typically visits the other. However, this does not scale well when the number of technologies or research groups is large. Conferences have responded to this issue by introducing Birds-of-a-Feather (BoF) sessions, which offer an opportunity for individuals with common interests to intensify their interaction. However, parallel BoF sessions often make it hard for participants to join multiple BoFs and find common ground between the different technologies, and BoFs are generally too short to allow time for participants to program together. Results: This report summarises our experience with computational biology Codefests, Hackathons and Sprints, which are interactive developer meetings. They are structured to reduce the limitations of traditional scientific meetings described above by strengthening the interaction among peers and letting the participants determine the schedule and topics. These meetings are commonly run as loosely scheduled unconferences (self-organized identification of participants and topics for meetings) over at least two days, with early introductory talks to welcome and organize contributors, followed by intensive collaborative coding sessions. We summarise some prominent achievements of those meetings and describe differences in how these are organised, how their audience is addressed, and their outreach to their respective communities. Conclusions: Hackathons, Codefests and Sprints share a stimulating atmosphere that encourages participants to jointly brainstorm and tackle problems of shared interest in a self-driven proactive environment, as well as providing an opportunity for new participants to get involved in collaborative projects.
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| 8. |
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| 9. |
- Rapp, Markus, et al.
(författare)
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Observations of positively charged nanoparticles in the nighttime polar mesosphere
- 2005
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 32, s. L23821-
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Tidskriftsartikel (refereegranskat)abstract
- We present results of in situ measurements of charged nanoparticles, electrons, and positive ions obtained during a sounding rocket flight in October 2004 from Kiruna, Sweden, under nighttime conditions. The particle measurement reveals positive charge signatures in the altitude range between 80 and 90 km corresponding to peak charge number densities of ∼100 e/cm3 at around 86 km. Aerodynamical analysis of the sampling efficiency of our instrument reveals that the particles must have been larger than 2 nm assuming spherical particles with a density of 3 g/cm3. The plasma environment of the observed particles is dominated by negative and positive ions, with only few free electrons. A calculation of the mean particle charge expected for particles in a plasma consisting of electrons and positive and negative ions shows that the presence of sufficiently heavy and numerous negative ions (i.e., m n > 300 amu and λ ≥ 50) can explain the observed positive particle charge.
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| 10. |
- Rapp, Markus, et al.
(författare)
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Rocket-borne in situ measurements of meteor smoke : Charging properties and implications for seasonal variation
- 2010
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115, s. D00I16-
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Tidskriftsartikel (refereegranskat)abstract
- Rocket-borne observations of meteoric smoke particles (MSPs) are presented from three campaigns at polar latitudes (69 degrees N) in September 2006, and in the summers of 2007 and 2008. MSPs are detected using a novel technique based on photoelectron emission from the particles after stimulation by UV photons emitted by a xenon flashlamp. Resulting photoelectron currents are shown to be proportional to particle volume density. September results match model predictions qualitatively at altitudes from 65 to 85 km while measurements at higher altitudes are contaminated by photoelectrons from NO and O-2((1)Delta(g)). Contamination below this altitude can be excluded based on concurrent satellite observations. The observations show a large variability from flight to flight. Part of this variability can be attributed to differences in the charging of MSPs during day and night. Finally we find that MSP volume density in summer can exceed that during September. Analyzing model simulations of the global transport and microphysics of these particles, we show that our observations are in agreement with the model predictions, even though number densities of particles with radii >1 nm, which have long been thought to be suitable condensation nuclei for mesospheric ice particles, show the opposite behavior. It is shown that this discrepancy is caused by the fact that even larger particles (similar to 3 nm) dominate the volume density and that transport affects these different particle sizes in different ways. These results reinforce previous model findings according to which seasonal MSP variability is mainly driven by the global circulation and corresponding transport.
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| 11. |
- Strelnikov, Boris, et al.
(författare)
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Simultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during the WADIS sounding rocket project
- 2019
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:17, s. 11443-11460
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Strelnikov, Boris, et al.
(författare)
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Sounding rocket project PMWE for investigation of polar mesosphere winter echoes
- 2021
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- A first sounding rocket campaign dedicated to investigate the creation mechanism of Polar Mesosphere Winter Echoes (PMWE) was conducted in April 2018 from the north Norwegian Andøya Space Center (69 °N, 16 °E). Two instrumented sounding rockets were launched on 13th and 18th of April under PMWE and non-PMWE conditions, respectively. In this paper we give an overview of the PMWE sounding rocket mission. We describe and discuss some results of combined in situ and ground-based measurements which allow to verify existing PMWE theories. Our measurements ultimately show that: a) polar winter mesosphere is abounded with meteor smoke particles (MSP) and intermittent turbulent layers, b) all PMWE observed during this campaign can be explained by neutral air turbulence, c) turbulence creates small-scale structures in all D-region constituents, including free electrons; d) MSP ultimately influence the radar volume reflectivity by distorting the turbulence spectrum of electrons, e) the influence of MSP and of background electron density is just to increase SNR.
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| 13. |
- Strelnikov, Boris, et al.
(författare)
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Spatial and temporal variability in MLT turbulence inferred from in situ and ground-based observations during the WADIS-1 sounding rocket campaign
- 2017
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 35:3, s. 547-565
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Tidskriftsartikel (refereegranskat)abstract
- In summer 2013 the WADIS-1 sounding rocket campaign was conducted at the Andoya Space Center (ACS) in northern Norway (69 degrees N, 16 degrees E). Among other things, it addressed the question of the variability in mesosphere/lower thermosphere (MLT) turbulence, both in time and space. A unique feature of the WADIS project was multi-point turbulence sounding applying different measurement techniques including rocket-borne ionization gauges, VHF MAARSY radar, and VHF EISCAT radar near Tromso. This allowed for horizontal variability to be observed in the turbulence field in the MLT at scales from a few to 100 km. We found that the turbulence dissipation rate, epsilon varied in space in a wavelike manner both horizontally and in the vertical direction. This wavelike modulation reveals the same vertical wavelengths as those seen in gravity waves. We also found that the vertical mean value of radar observations of epsilon agrees reasonably with rocket-borne measurements. In this way defined value reveals clear tidal modulation and results in variation by up to 2 orders of magnitude with periods of 24 h. The value also shows 12 h and shorter (1 to a few hours) modulations resulting in one decade of variation in magnitude. The 24 h modulation appeared to be in phase with tidal change of horizontal wind observed by SAURA-MF radar. Such wavelike and, in particular, tidal modulation of the turbulence dissipation field in the MLT region inferred from our analysis is a new finding of this work.
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| 14. |
- Strelnikova, Irina, et al.
(författare)
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Measurements of meteor smoke particles during the ECOMA-2006 campaign. 2 : Results
- 2009
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 71:3-4, s. 486-496
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Tidskriftsartikel (refereegranskat)abstract
- The first sounding rocket of the European ECOMA-project (ECOMA, Existence and Charge state Of Meteoric smoke particles in the middle Atmosphere) was launched on 8 September 2006. Measurements with a new particle detector described in the companion paper by Rapp and Strelnikova [2008. Measurements of meteor smoke particles during the ECOMA-2006 campaign: 1. Particle detection by active photoionization. Journal of Atmospheric and Solar-Terrestrial Physics, this issue, doi:10.1016/j.jastp.2008.06.002] clearly showed meteor smoke particle (MSP) signatures in both data channels. The data channels measure particles directly impacting on the detector electrode and photoelectrons from the particles actively created using ionization by the UV-photons of a xenon-flashlamp. Measured photoelectron currents resemble model expectations of the shape of the MSP layer almost perfectly, whereas derived number densities in the altitude range 60–90 km are larger than model results by about a factor of 5. Given the large uncertainties inherent to both model and the analysis of our measurements (e.g., the composition of the particles is not known and must be assumed) we consider this a satisfactory agreement and proof that MSPs do extend throughout the entire mesosphere as predicted by models. The measurements of direct particle impacts revealed a confined layer of negative charge between 80 and 90 km. This limited altitude range, however, is quantitatively shown to be the consequence of the aerodynamics of the rocket flight and does not have any geophysical origin. Measured charge signatures are consistent with expectations of particle charging given our own measurements of the background ionization. Unfortunately, however, a contamination of these measurements from triboelectric charging cannot be excluded at this stage
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