| 1. |
- 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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| 2. |
- Gobrecht, David, et al.
(författare)
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The Corundum Conundrum
- 2023
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Ingår i: Astrophysics and Space Science Proceedings. - 1570-6591 .- 1570-6605. - 9783031290022
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Konferensbidrag (refereegranskat)abstract
- Corundum corresponds to solid, crystalline aluminium oxide (i.e. alumina) with a stoichiometric formula of Al 2 O 3. Alumina is likely to be the primary dust condensate in the atmospheres of oxygen-rich evolved stars. Therefore, alumina dust grains can trigger mass loss released in stellar winds. The conundrum, or puzzling problem, consists in the formation of alumina. In particular, the nucleation of alumina, including the clustering of gas-phase molecules and the growth of nanometer-sized clusters, is challenging. We aim to address what Al:O stoichiometries are involved and what cluster size characterises the amorphous-to-crystalline transition. To tackle these questions, we employ a quantum-chemical bottom-up approach.
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| 3. |
- Pellinen-Wannberg, Asta, et al.
(författare)
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E region ionization enhancement over northern Scandinavia during the 2002 Leonids
- 2014
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Ingår i: 2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS). - : IEEE. - 9781467352253
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Konferensbidrag (refereegranskat)abstract
- Intensive E-region ionization was observed with the EISCAT UHF radar during the 2002 Leonids meteor shower. The levels of the geomagnetic disturbance were low during the event. Thus the ionization cannot be explained by intensive precipitation. The layer was 30-40 km thick, so it cannot be classified as a sporadic E-layer (often associated to ions of meteoric origin). These are typically only about km-wide. Incoherent scatter radars have never so far reported any notable meteor shower-related increases in the average background ionization. The 2002 Leonid storm flux, however, was so high that it, if any, might be able to induce such an event. Whether meteors in general can cause such an excess E-region ionization during an intensive shower is discussed. The University of Leeds CABMOD model is used to estimate deposition rates of individual meteors and to relate the results to the predicted Leonid flux values in free space and observed ionization on November 19, 2002.
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| 4. |
- Pellinen-Wannberg, Asta K., et al.
(författare)
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Strong E region ionization caused by the 1767 trail during the 2002 Leonids
- 2014
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 119:9, s. 7880-7888
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Tidskriftsartikel (refereegranskat)abstract
- Intensive E region ionization extending up to 140 km altitude and lasting for several hours was observed with the European Incoherent Scatter (EISCAT) UHF radar during the 2002 Leonids meteor shower maximum. The level of global geomagnetic disturbance as well as the local geomagnetic and auroral activity in northern Scandinavia were low during the event. Thus, the ionization cannot be explained by intensive precipitation. The layer was 30-40 km thick, so it cannot be classified as a sporadic E layer which are typically just a few kilometers wide. Incoherent scatter radars have not to date reported any notable meteor shower-related increases in the average background ionization. The 2002 Leonids storm flux, however, was so high that it might have been able to induce such an event. The Chemical Ablation Model is used to estimate deposition rates of individual meteors. The resulting electron production, arising from hyperthermal collisions of ablated atoms with atmospheric molecules, is related to the predicted Leonid flux values and observed ionization on 19 November 2002. The EISCAT Svalbard Radar (ESR) located at some 1000 km north of the UHF site did not observe any excess ionization during the same period. The high-latitude electrodynamic conditions recorded by the SuperDARN radar network show that the ESR was within a strongly drifting convection cell continuously fed by fresh plasma while the UHF radar was outside the polar convection region maintaining the ionization.
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| 5. |
- 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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| 6. |
- Plane, John M. C., et al.
(författare)
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Opinion : Recent developments and future directions in studying the mesosphere and lower thermosphere
- 2023
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 23:20, s. 13255-13282
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Forskningsöversikt (refereegranskat)abstract
- This article begins with a review of important advances in the chemistry and related physics of the mesosphere and lower thermosphere (MLT) region of the atmosphere that have occurred over the past 2 decades, since the founding of Atmospheric Chemistry and Physics. The emphasis here is on chemistry, but we also discuss recent findings on atmospheric dynamics and forcings to the extent that these are important for understanding MLT composition and chemistry. Topics that are covered include observations, with satellite, rocket and ground-based techniques; the variability and connectedness of the MLT on various length scales and timescales; airglow emissions; the cosmic dust input and meteoric metal layers; and noctilucent/polar mesospheric ice clouds. The paper then concludes with a discussion of important unanswered questions and likely future directions for the field over the next decade.
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| 7. |
- Sanchez-Cano, Beatriz, et al.
(författare)
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Origin of the Extended Mars Radar Blackout of September 2017
- 2019
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 124:6, s. 4556-4568
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Tidskriftsartikel (refereegranskat)abstract
- The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express, which operates between 0.1 and 5.5 MHz, suffered from a complete blackout for 10 days in September 2017 when observing on the nightside (a rare occurrence). Moreover, the Shallow Radar (SHARAD) onboard the Mars Reconnaissance Orbiter, which operates at 20 MHz, also suffered a blackout for three days when operating on both dayside and nightside. We propose that these blackouts are caused by solar energetic particles of few tens of keV and above associated with an extreme space weather event between 10 and 22 September 2017, as recorded by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Numerical simulations of energetic electron precipitation predict that a lower O-2(+) nighttime ionospheric layer of magnitude similar to 10(10) m(-3) peaking at similar to 90-km altitude is produced. Consequently, such a layer would absorb radar signals at high frequencies and explain the blackouts. The peak absorption level is found to be at 70-km altitude. Plain Language Summary Several instrument operations, as well as communication systems with rovers at the surface, depend on radio signals that propagate throughout the atmosphere of Mars. This is the case also for two radars that are currently working in Mars' orbit, sounding the ionosphere, surface, and subsurface of the planet. In mid-September 2017, a powerful solar storm hit Mars, producing a large amount of energetic particle precipitation over a 10-day period. We have found that high-energy electrons ionized the atmosphere of Mars, creating a dense layer of ions and electrons at similar to 90 km on the Martian nightside. This layer attenuated radar signals continuously for 10 days, stopping the radars to receive any signal from the planetary surface. In this work, we assess the properties of this layer in order to understand the implications of this kind of phenomenon for radar performance and communications.
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| 8. |
- Yu, Bingkun, et al.
(författare)
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Comparison of middle- and low-latitude sodium layer from a ground-based lidar network, the Odin satellite, and WACCM–Na model
- 2022
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:17, s. 11485-11504
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Tidskriftsartikel (refereegranskat)abstract
- The ground-based measurements obtained from a lidar network and the 6-year OSIRIS (optical spectrograph and infrared imager system) limb-scanning radiance measurements made by the Odin satellite are used to study the climatology of the middle- and low-latitude sodium (Na) layer. Up to January 2021, four Na resonance fluorescence lidars at Beijing (40.5∘ N, 116.0∘ E), Hefei (31.8∘ N, 117.3∘ E), Wuhan (30.5∘ N, 114.4∘ E), and Haikou (19.5∘ N, 109.1∘ E) collected vertical profiles of Na density for a total of 2136 nights (19 587 h). These large datasets provide multi-year routine measurements of the Na layer with exceptionally high temporal and vertical resolution. The lidar measurements are particularly useful for filling in OSIRIS data gaps since the OSIRIS measurements were not made during the dark winter months because they utilize the solar-pumped resonance fluorescence from Na atoms. The observations of Na layers from the ground-based lidars and the satellite are comprehensively compared with a global model of meteoric Na in the atmosphere (WACCM–Na). The lidars present a unique test of OSIRIS and WACCM (Whole Atmosphere Community Climate Model), because they cover the latitude range along 120∘ E longitude in an unusual geographic location with significant gravity wave generation. In general, good agreement is found between lidar observations, satellite measurements, and WACCM simulations. On the other hand, the Na number density from OSIRIS is larger than that from the Na lidars at the four stations within one standard deviation of the OSIRIS monthly average, particularly in autumn and early winter arising from significant uncertainties in Na density retrieved from much less satellite radiance measurements. WACCM underestimates the seasonal variability of the Na layer observed at the lower latitude lidar stations (Wuhan and Haikou). This discrepancy suggests the seasonal variability of vertical constituent transport modelled in WACCM is underestimated because much of the gravity wave spectrum is not captured in the model.
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