| 1. |
- Enell, Carl-Fredrik, et al.
(författare)
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The Hotel Payload 2 campaign : Overview of NO, O and electron density measurements in the upper mesosphere and lower thermosphere
- 2011
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 73:14-15, s. 2228-2236
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Tidskriftsartikel (refereegranskat)abstract
- The ALOMAR eARI Hotel Payload 2 (HotPay 2) rocket campaign took place at Andoya 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 HotPay 2 measurements of upper mesospheric and lower thermospheric (UMLT) electron, atomic oxygen (O) and nitric oxide (NO) densities. [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 km, 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 the 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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| 2. |
- Espy, P. J., et al.
(författare)
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The role of the QBO in the inter-hemispheric coupling of summer mesospheric temperatures
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:2, s. 495-502
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Tidskriftsartikel (refereegranskat)abstract
- Inter-hemispheric coupling between the polar summer mesosphere and planetary-wave activity in the extra-tropical winter stratosphere has recently been inferred using Polar Mesospheric Cloud (PMC) properties as a proxy for mesospheric temperature (Karlsson et al., 2007). Here we confirm these results using a ten-year time series of July mesospheric temperatures near 60 degrees N derived from the hydroxyl (OH) nightglow. In addition, we show that the time-lagged correlation between these summer mesospheric temperatures and the ECMWF winter stratospheric temperatures displays a strong Quasi-Biennial Oscillation (QBO). The sign and phase of the correlation is consistent with the QBO modulation of the extra-tropical stratospheric dynamics in the Southern Hemisphere via the Holton-Tan mechanism (Holton and Tan, 1980). This lends strength to the identification of synoptic and planetary waves as the driver of the inter-hemispheric coupling, and results in a strong QBO modulation of the polar summer mesospheric temperatures.
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| 3. |
- Gattinger, R. L., et al.
(författare)
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H Balmer lines in terrestrial aurora : Historical record and new observations by OSIRIS on Odin
- 2010
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115, s. A09306-
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Tidskriftsartikel (refereegranskat)abstract
- The H Balmer emissions were first identified in terrestrial aurora by Vegard (1939). The earliest photographic spectral observations are reviewed. In the subsequent decade, the intensity ratios for H alpha, H beta, and H gamma were measured, and the well-known line broadening and blue shift were established. Recently, the H alpha, H gamma, H delta, and H epsilon features have been measured by OSIRIS on Odin. The Balmer components are resolved from other auroral features using sets of synthetic spectra. The measured intensity ratios are in good agreement with an extensive set of published model calculations. The presented observations are in the polar region averaged over limb tangent altitudes from 100 to 105 km, approximately perpendicular to the terrestrial magnetic field lines, for this geometry showing Doppler broadening without obvious Doppler shifts. The OSIRIS-measured full-width at half-height of the Ha feature is 2.2 nm corresponding to an H atom velocity of 500 km s(-1) and energy approximately 1.3 keV.
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| 4. |
- Gattinger, R. L., et al.
(författare)
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Vibrational populations of near-ultraviolet O-2 band systems in the night airglow
- 2012
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Ingår i: Canadian journal of physics (Print). - : Canadian Science Publishing. - 0008-4204 .- 1208-6045. ; 90:8, s. 741-751
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Tidskriftsartikel (refereegranskat)abstract
- Observations of the limb night airglow spectrum from 250 to 475 nm, emitted from the upper mesosphere and lower thermosphere, are compared with model spectra. Data from the Arizona GLO-1 imaging spectrograph and the OSIRIS spectrograph are combined to form the observed mean airglow spectrum; a tabulated version of this spectrum is included. Model spectra of the individual O-2 Herzberg I, II, and III, Chamberlain, and Slanger band systems are combined to simulate the observed mean spectrum. Franck-Condon relative band intensities are used to form a series of basis functions for the upper vibrational levels in each band system. These functions are fitted to the observed airglow spectrum with a least-squares method, the relative vibrational populations are derived and discussed.
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| 5. |
- Hedin, Jonas, 1976-, et al.
(författare)
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Observations of NO in the upper mesosphere and lower thermosphere during ECOMA 2010
- 2012
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 30:11, s. 1611-1621
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Tidskriftsartikel (refereegranskat)abstract
- In December 2010 the last campaign of the German-Norwegian sounding rocket project ECOMA (Existence and Charge state Of Meteoric smoke particles in the middle Atmosphere) was conducted from Andøya Rocket Range in northern Norway (69° N, 16° E) in connection with the Geminid meteor shower. The main instrument on board the rocket payloads was the ECOMA detector for studying meteoric smoke particles (MSPs) by active photoionization and subsequent detection of the produced charges (particles and photoelectrons). In addition to photoionizing MSPs, the energy of the emitted photons from the ECOMA flash-lamp is high enough to also photoionize nitric oxide (NO). Thus, around the peak of the NO layer, at and above the main MSP layer, photoelectrons produced by the photoionization of NO are expected to contribute to, or even dominate above the main MSP-layer, the total measured photoelectron current. Among the other instruments on board was a set of two photometers to study the O2(b1Σg+−X3Σg-) Atmospheric band and NO2 continuum nightglow emissions. In the absence of auroral emissions, these two nightglow features can be used together to infer NO number densities. This will provide a way to quantify the contribution of NO photoelectrons to the photoelectron current measured by the ECOMA instrument and, above the MSP layer, a simultaneous measurement of NO with two different and independent techniques. This work is still on-going due to the uncertainties, especially in the effort to quantitatively infer NO densities from the ECOMA photoelectron current, and the lack of simultaneous measurements of temperature and density for the photometric study. In this paper we describe these two techniques to infer NO densities and discuss the uncertainties. The peak NO number density inferred from the two photometers on ascent was 3.9 × 108 cm−3 at an altitude of about 99 km, while the concentration inferred from the ECOMA photoelectron measurement at this altitude was a factor of 5 smaller.
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| 6. |
- Hedin, Jonas, et al.
(författare)
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The MAGIC meteoric smoke particle sampler
- 2014
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 118, s. 127-144
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Tidskriftsartikel (refereegranskat)abstract
- Between a few tons to several hundred tons of meteoric material enters the Earth's atmosphere each day, and most of this material is ablated and vaporized in the 70-120 km altitude region. The subsequent chemical conversion, re-condensation and coagulation of this evaporated material are thought to form nanometre sized meteoric smoke particles (MSPs). These smoke particles are then subject to further coagulation, sedimentation and global transport by the mesospheric circulation. MSPs have been proposed as a key player in the formation and evolution of ice particle layers around the mesopause region, i.e. noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE). MSPs have also been implicated in mesospheric heterogeneous chemistry to influence the mesospheric odd oxygen/odd hydrogen (O-x/HOx) chemistry, to play an important role in the mesospheric charge balance, and to be a significant component of stratospheric aerosol and enhance the depletion of O-3. Despite their apparent importance, little is known about the properties of MSPs and none of the hypotheses can be verified without direct evidence of the existence, altitude and size distribution, shape and elemental composition. The aim of the MAGIC project (Mesospheric Aerosol - Genesis, Interaction and Composition) was to develop an instrument and analysis techniques to sample for the first time MSPs in the mesosphere and return them to the ground for detailed analysis in the laboratory. MAGIC meteoric smoke particle samplers have been flown on several sounding rocket payloads between 2005 and 2011. Several of these flights concerned non-summer mesosphere conditions when pure MSP populations can be expected. Other flights concerned high latitude summer conditions when MSPs are expected to be contained in ice particles in the upper mesosphere. In this paper we present the MAGIC project and describe the MAGIC MSP sampler, the measurement procedure and laboratory analysis. We also present the attempts to retrieve MSPs from these flights, the challenges inherent to the sampling of nanometre sized particles and the subsequent analysis of the sampled material, and thoughts for the future. Despite substantial experimental efforts, the MAGIC project has so far failed to provide conclusive results. While particles with elemental composition similar to what is to be expected from MSPs have been found, the analysis has been compromised by challenges with different types of contamination and uncertainties in the sticking efficiency of the particles on the sampling surfaces.
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| 7. |
- Hultgren, Kristoffer, et al.
(författare)
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First simultaneous retrievals of horizontal and vertical structures of Polar Mesospheric Clouds from Odin/OSIRIS tomography
- 2013
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 104, s. 213-223
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Tidskriftsartikel (refereegranskat)abstract
- Limb-scanning satellites can provide global information about the vertical structure of Polar Mesospheric Clouds. However, information about horizontal structures usually remains limited. In eighteen days during the northern hemisphere summers of 2010 and 2011, the Odin satellite was operated in a special mesospheric mode with short limb scans limited to the altitude range of Polar Mesospheric Clouds. For Odin's Optical Spectrograph and InfraRed Imager System (OSIRIS) this provides multiple views through a given cloud volume, which forms a basis for tomographic analyses of the vertical/horizontal cloud structures. Here we present an algorithm for a tomographic analysis of mesospheric clouds based on maximum probability techniques. We also present the first simultaneously retrieved vertical and horizontal Polar Mesospheric Cloud structures. The findings show that the tomographic algorithm is able to locate detailed structures such as tilts, stratifications, or holes that cannot be analyzed by other limb, nadir, or ground-based measurements. We find a mean peak altitude of the clouds to be 83.6 km. We identify horizontal patches down to sizes of 300 km, which corresponds to a horizontal resolution that is limited by the available number of limb scans.
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| 8. |
- Pautet, P. -D, et al.
(författare)
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Analysis of gravity waves structures visible in noctilucent cloud images
- 2011
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 73:14-15, s. 2082-2090
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Tidskriftsartikel (refereegranskat)abstract
- The noctilucent clouds (NLC) are high-altitude bright cloud formations visible under certain conditions from high-latitude places during the summer months. Even if the exact nature of these clouds still remains a mystery, they are an efficient tracer of the dynamic processes at their level, particularly the gravity waves propagating from the stratosphere through the mesopause layer. In this paper, we describe a technique developed to analyze the structures visible in the NLC images taken every summer night since 2004 from Stockholm, Sweden (59.4 degrees N). The parameters of 30 short-period gravity wave events have been measured and compared with older datasets obtained mostly from low and mid-latitude sites, using airglow imaging techniques. The horizontal wavelengths are in good agreement with previous results while the observed horizontal phase speeds exhibit smaller values than for other sites. The directionality of the waves presents strong poleward preference, traditionally observed during the summer season. This anisotropy and the difference in the phase speed distribution cannot be explained by the filtering due to the background wind field but more probably by the position of the gravity waves sources, located to the south of the observation site.
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| 9. |
- Plane, John M. C., et al.
(författare)
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A combined rocket-borne and ground-based study of the sodium layer and charged dust in the upper mesosphere
- 2014
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 118, s. 151-160
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Tidskriftsartikel (refereegranskat)abstract
- The Hotel Payload 2 rocket was launched on January 31st 2008 at 20.14 LT from the Andoya Rocket Range in northern Norway (69.31 degrees N, 16.01 degrees E). Measurements in the 75-105 km region of atomic O, negatively-charged dust, positive ions and electrons with a suite of instruments on the payload were complemented by lidar measurements of atomic Na and temperature from the nearby ALOMAR observatory. The payload passed within 2.58 km of the lidar at an altitude of 90 km. A series of coupled models is used to explore the observations, leading to two significant conclusions. First, the atomic Na layer and the vertical profiles of negatively-charged dust (assumed to be meteoric smoke particles), electrons and positive ions, can be modelled using a self-consistent meteoric input flux. Second, electronic structure calculations and Rice-Ramsperger-Kassel-Markus theory are used to show that even small Fe-Mg-silicates are able to attach electrons rapidly and form stable negatively-charged particles, compared with electron attachment to O-2 and O-3. This explains the substantial electron depletion between 80 and 90 km, where the presence of atomic O at concentrations in excess of 10(10) cm(-3) prevents the formation of stable negative ions.
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| 10. |
- Reisin, E. R., et al.
(författare)
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Traveling planetary wave activity from mesopause region airglow temperatures determined by the Network for the Detection of Mesospheric Change (NDMC)
- 2014
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 119, s. 71-82
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Tidskriftsartikel (refereegranskat)abstract
- The global distribution of traveling planetary wave (PW) activity in the mesopause region is estimated for the first time from ground-based airglow measurements. Monthly and total mean climatologies of PW power are determined from rotational temperatures measured at 19 sites from 78 degrees N to 76 degrees S which contribute to the Network for the Detection of Mesospheric Change (NDMC). Wave power is expressed as the standard deviation of nocturnal mean temperature around the seasonal temperature variation. The results from 20 degrees N confirm the SABER traveling PW proxy by Offermann et al. (2009, J. Geophys. Res. 114, D06110) at two altitudes. Most sites between 69 degrees S and 69 degrees N show total mean traveling PW activity of about 6 K, and only some high latitude sites have considerably higher activity levels. At the two tropical sites, there is practically no seasonal variation of PW activity. At 70% of the midlatitude sites, the seasonal variation is moderate for most of the year, but it is quite appreciable at all high latitude sites. Results about traveling PW activity at 87 km and 95 km available from several sites signal similar behavior at both altitudes. The total mean climatological results here obtained have further been used to separate the traveling PW contribution from the superposition of wave types contained in OH rotational temperature fluctuations measured by the SCIAMACHY instrument on Envisat. A narrow equatorial wave activity maximum is probably caused by gravity waves, while a tendency towards greater activity at higher northern latitudes may be due to stationary planetary waves.
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