| 1. |
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| 2. |
- Markljung, Ellen, 1978-
(författare)
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QTL Analysis in the Pig : From the Identification of Quantitative Trait Loci to the Understanding of Molecular Mechanisms
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Domestic pigs have become very different form the wild ancestors they originate from. Selection for muscle growth and meat quality has made the pig a good model for genetic studies of muscle development.The first part of this thesis presents a genome-wide scan for quantitative trait loci (QTL) in a cross between Landrace and Hampshire pigs. Traits such as body composition, fat deposition, body length, meat quality and weight measurements of individual muscles were investigated. In total we identified 15 different QTLs that reached genome-wide significance. The three most significant QTLs were for carcass length on chromosome 17 and two overlapping QTLs on chromosome 1 for body composition and weight of M. biceps femoris, respectively. A strong candidate gene for the body composition QTL is melanocortin 4 receptor (MC4R). We also identified several QTLs for sizes of different muscles, fat deposition and meat quality traits.In a previous study using a cross between the domestic Large White and wild boar, the mutation underlying a major QTL for muscle growth and fat deposition was identified as a single nucleotide substitution (QTN) in intron 3 of the IGF2 gene. The QTN disrupts the binding of a repressor affecting IGF2 mRNA expression. In the second part of this thesis, the identification of the repressor is presented. The repressor, named ZBED6, is a previously unknown mammalian member of the BED-domain protein family. We could show that Zbed6 specifically binds the wild-type but not the mutated sequence surrounding the QTN. Further studies of silenced Zbed6 in the mouse myoblast cell line C2C12 showed that it represses transcription in a luciferase reporter assay and affects Igf2 mRNA transcription and proliferation. ZBED6 shows very high sequence conservation and has a broad tissue distribution of expression suggesting that ZBED6 also has important biological function outside the muscle cell.
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| 3. |
- Adolfsson, Annsofie, 1960-, et al.
(författare)
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Miscarriage : Evidence Based Information for the Web and Its Development Procedure
- 2015
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Ingår i: Advances in Sexual Medicine. - Irvine, USA : Scientific Research Publishing. - 2164-5191 .- 2164-5205. ; 5:4, s. 89-110
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this paper is to describe the process of developing web information on miscarriage based on scientific evidence, for women and couples in Sweden experiencing miscarriage. Method: A participatory design was used which included researchers, professional xperts and users. A participatory design was used involving researchers, professional experts and users. The information was developed in six stages: 1) identifying the needs of information; 2) identifying and constructing the main areas of information and its paths; 3) identifying and inviting experts for revision; 4) developing the text; 5) reviewing the text; 6) design and structuring for adaption to website. Results: The text of information developed gradually based on the seven steps. The final text comprised three parts: 1) what is miscarriage; 2) experiences of miscarriage; 3) processing and lanning for new pregnancy. Conclusion: Using participatory design was time and resource consuming, however it was functional for producing appropriate information for the target group. The developed evidence based facts text is assumed to be a complement to the information that is provided by the health care system.
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| 4. |
- Aikio, A T, et al.
(författare)
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On the origin of the high-altitude electric field fluctuations in the auroral zone
- 1996
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 101:A12, s. 27157-27170
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Tidskriftsartikel (refereegranskat)abstract
- Intense fluctuations in the electric field at high altitudes in the auroral zone are frequently measured by the Viking satellite. We have made an analysis of the origin of electric and magnetic fluctuations in the frequency range of 0.1 - 1 Hz by assuming four different sources for the signals: (I) spatial structures, (2) spatial structures with a parallel potential drop below the satellite, (3) traveling; shear Alfven waves, and (4) interfering shear Alfven waves. We will shaw that these different sources of the signals may produce similar amplitude ratios and phase differences between the perpendicular electric and magnetic fields. Since the different sources have different frequency dependencies, this can be used as an additional test if the signals are broadband. In other cases, additional information is needed, for example, satellite particle measurements or ground; magnetic measurements. The ideas presented in the theory were tested for one Viking eveningside pass over Scandinavia, where ground-based magnetometer and EISCAT radar measurements were available. The magnetic conditions were active during this pass and several interfering shear Alfven waves were found. Also, a spatial structure with a parallel potential drop below the satellite was identified. The magnitude of the 10-km-wide potential drop was at least 2 kV and the upward field-aligned current 26 mu A m(-2) (value mapped to the ionospheric level). The held-aligned conductance was estimated as 1.3 - 2.2x10(-8) S m(-2).
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| 5. |
- Aikio, A. T., et al.
(författare)
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Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments
- 2004
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 22:12, s. 4089-4101
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Tidskriftsartikel (refereegranskat)abstract
- The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 R-E in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110 km in latitude and 50 km in longitude. This constellation allowed us to study the temporal evolution of plasma with a time scale of a few minutes. Ground-based instrumentation used involved two all-sky cameras, magnetometers and the EISCAT radar. The main findings were as follows. Two auroral arcs were located close to the equatorward and poleward edge of a large-scale density cavity, respectively. These arcs showed a different kind of a temporal evolution. (1) As a response to a pseudo-breakup onset, both the up- and downward field-aligned current (FAC) sheets associated with the equatorward arc widened and the total amount of FAC doubled in a time scale of 1-2 min. (2) In the poleward arc, a density cavity formed in the ionosphere in the return (downward) current region. As a result of ionospheric feedback, a strongly enhanced ionospheric southward electric field developed in the region of decreased Pedersen conductance. Furthermore, the acceleration potential of ionospheric electrons, carrying the return current, increased from 200 to 1000 eV in 70 s, and the return current region widened in order to supply a constant amount of return current to the arc current circuit. Evidence of local acceleration of the electron population by dispersive Alfven waves was obtained in the upward FAC region of the poleward arc. However, the downward accelerated suprathermal electrons must be further energised below Cluster in order to be able to produce the observed visible aurora. Both of the auroral arcs were associated with broad-band ULF/ELF (BBELF) waves, but they were highly localised in space and time. The most intense BBELF waves were confined typically to the return current regions adjacent to the visual arc, but in one case also to a weak upward FAC region. BBELF waves could appear/disappear between s/c crossings of the same arc separated by about 1 min.
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| 6. |
- Alm, Love
(författare)
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Cluster investigations of the extent and altitude distribution of the auroral density cavity
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The auroral density cavity constitutes the boundary between the cold, dense ionospheric plasma and the hot, tenuous plasma sheet plasma. The auroral density cavity is characterized by low electron density and particle populations modified by parallel electric fields. Inside the cavity the electron densities can be as much as a factor 100-1000 lower than same altitude outside the cavity.The Cluster mission's wide range of instruments, long lifetime and ability to make multi-spacecraft observations has been very successful. Over its 15 year lifespan, the Cluster satellites have gathered data on auroral density cavities over a large altitude range and throughout an entire solar cycle, providing a vast data material.The extent of the density cavity and acceleration region is large compared to the typical altitude coverage of a satellite crossing the cavity. This makes it difficult to produce a comprehensive altitude/density profile from a single crossing. In order to facilitate comparisons between data from different events, we introduce a new reference frame, pseudo altitude. Pseudo altitude describes the satellites' position relative to the acceleration region, as opposed to relative to the Earth. This pseudo altitude is constructed by dividing the parallel potential drop below the satellite with the total parallel potential drop. A pseudo altitude of 0 corresponds to the bottom of the acceleration region and a pseudo altitude of 1 to the top of the acceleration region. As expected, the pseudo altitude increases with altitude. The electron density exhibits an anti-correlation with the pseudo altitude, the density becomes lower close to the upper edge of the acceleration region. The upper edge of the acceleration region is located between a geocentric altitude of 4.375 and 5.625 RE. Above the upper edge of the acceleration region, the electron density continues to decrease for the entire range of the study, 3.0-6.5 RE. This is much further than the geocentric altitude range of 2-3 RE which is suggested by previous models. We can conclude that the auroral density cavity is not confined by the auroral acceleration region, as suggested by previous models, and may extend all the way to the plasma sheet.
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| 7. |
- Alm, L., et al.
(författare)
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Differing Properties of Two Ion-Scale Magnetopause Flux Ropes
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:1, s. 114-131
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present results from the Magnetospheric Multiscale constellation encountering two ion-scale, magnetopause flux ropes. The two flux ropes exhibit very different properties and internal structure. In the first flux rope, there are large differences in the currents observed by different satellites, indicating variations occurring over sub-d(i) spatial scales, and time scales on the order of the ion gyroperiod. In addition, there is intense wave activity and particle energization. The interface between the two flux ropes exhibits oblique whistler wave activity. In contrast, the second flux rope is mostly quiescent, exhibiting little activity throughout the encounter. Changes in the magnetic topology and field line connectivity suggest that we are observing flux rope coalescence.
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| 8. |
- Alm, L., et al.
(författare)
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EDR signatures observed by MMS in the 16 October event presented in a 2-D parametric space
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 122:3, s. 3262-3276
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for mapping the position of satellites relative to the X line using the measured B-L and B-N components of the magnetic field and apply it to the Magnetospheric multiscale (MMS) encounter with the electron diffusion region (EDR) which occurred on 13:07 UT on 16 October 2015. Mapping the data to our parametric space succeeds in capturing many of the signatures associated with magnetic reconnection and the electron diffusion region. This offers a method for determining where in the reconnection region the satellites were located. In addition, parametric mapping can also be used to present data from numerical simulations. This facilitates comparing data from simulations with data from in situ observations as one can avoid the complicated process using boundary motion analysis to determine the geometry of the reconnection region. In parametric space we can identify the EDR based on the collocation of several reconnection signatures, such as electron nongyrotropy, electron demagnetization, parallel electric fields, and energy dissipation. The EDR extends 2-3km in the normal direction and in excess of 20km in the tangential direction. It is clear that the EDR occurs on the magnetospheric side of the topological X line, which is expected in asymmetric reconnection. Furthermore, we can observe a north-south asymmetry, where the EDR occurs north of the peak in out-of-plane current, which may be due to the small but finite guide field.
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| 9. |
- Alm, Love, et al.
(författare)
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Electron density and parallel electric field distribution of the auroral density cavity
- 2015
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 120:11, s. 9428-9441
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Tidskriftsartikel (refereegranskat)abstract
- We present an event study in which Cluster satellites C1 and C3 encounters the flux tube of a stable auroral arc in the pre-midnight sector. C1 observes the mid cavity, while C3 enters the flux tube of the auroral arc at an altitude which is below the acceleration region, before crossing into the top half of the acceleration region. This allows us to study the boundary between the ionosphere and the density cavity, as well as large portion of the upper density cavity. The position of the two satellites, in relation to the acceleration region, is described using a pseudo altitude derived from the distribution of the parallel potential drop above and below the satellites.The electron density exhibits an anti-correlation with the pseudo altitude, indicating that the lowest electron densities are found near the top of the density cavity. Over the entire pseudo altitude range, the electron density distribution is similar to a planar sheath, formed out of a plasma sheet dominated electron distribution, in response to the parallel electric field of the acceleration region. This indicates that the parallel electric fields on the ionosphere-cavity boundary, as well as the mid cavity parallel electric fields, are part of one unified structure rather than two discrete entities.The results highlight the strong connection between the auroral density cavity and auroral acceleration as well as the necessity of studying them in a unified fashion.
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| 10. |
- Alm, Love, et al.
(författare)
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In situ observations of density cavities extending above the auroral acceleration region
- 2014
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 119:7, s. 5286-5294
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Tidskriftsartikel (refereegranskat)abstract
- The uppermost part of a stable potential structure in the auroral acceleration region was studied using simultaneous observations of Cluster satellites C1 and C3. Both satellites observe a monotonically decreasing electron density as they ascend through the auroral acceleration region. As C1 exits the top of the auroral acceleration region, the electron densities continue to decrease, and the minimum electron density is reached 14 km above the upper edge of the auroral acceleration region. The electron density does not return to noncavity values until the spacecraft exits the potential structure's flux tube. The data indicate that the auroral density cavity is not confined by the potential structure and may extend above the auroral acceleration region.
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| 11. |
- Alm, Love, et al.
(författare)
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Pseudo altitude : A new perspective on the auroral density cavity
- 2013
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Ingår i: Journal of Geophysical Research A: Space Physics. - : American Geophysical Union (AGU). - 2169-9380. ; 118:7, s. 4341-4351
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Tidskriftsartikel (refereegranskat)abstract
- Studying the density distribution inside the auroral density cavity is complicated by the difficulties in achieving simultaneous measurements within the same flux tube at different altitudes. Comparisons between different events are complicated by variations in both the location of the density cavity and the location of the related potential structure. Describing the spacecraft's location inside the density cavity relative to the potential structure instead of the Earth offers a more practical and consistent frame of reference, a pseudo altitude. The pseudo altitude is determined by comparing the potential drop above the spacecraft, as determined from the characteristic energy of the downward electrons, with the parallel potential drop below the spacecraft, determined from the characteristic energy of the upward ions. A pseudo altitude of 0 corresponds to the bottom of the potential structure and a pseudo altitude of 1 to the top of the structure. Seven events from 2008 were selected, each of which corresponds to a Cluster crossing of a mainly quasi-static potential structure. All of the events exhibit a consistent anticorrelation between the pseudo altitude and the electron density. No upper limit of the density cavity can be observed, while all cavities have a lower limit above a pseudo altitude of 0.33. These observations show that the auroral density cavity is predominately concentrated to the upper parts of the quasi-static potential structure.
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| 12. |
- Alm, Love, et al.
(författare)
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Statistical altitude distribution of the auroral density cavity
- 2015
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:2, s. 996-1006
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Tidskriftsartikel (refereegranskat)abstract
- The statistical altitude distribution of auroral density cavities located between 3.0 and 6.5 R-E is investigated using in situ observations from flux tubes exhibiting auroral acceleration. The locations of the observations are described using a pseudo altitude derived from the distribution of the parallel potential drop above and below the satellite. The upper edge of the auroral acceleration region is observed between 4.375 and 5.625 R-E. Above 6.125 R-E, none of the events exhibit precipitating inverted V electrons, though the upward ion beam can be observed. This indicates that the satellites are located inside the same flux tube as, but above, the auroral acceleration region. The electron density decreases as we move higher into the acceleration region. The spacecraft potential continues to decrease once above the acceleration region, indicating that the density cavity extends above the acceleration region. From 3.0 to 4.375 R-E the pseudo altitude increases by 0.20 per R-E, consistent with a distributed parallel electric field. Between 4.375 and 5.625 R-E the pseudo altitude increases weakly, by 0.01 per R-E, due to an increasing number of events per altitude bin, which are occurring above the acceleration region. Above 5.625 R-E the pseudo altitude increases by 0.28 per R-E, due to a rapid increase in the number of events per altitude bin occurring above the acceleration region, indicating that the remaining parallel potential drop is concentrated in a narrow region at the upper edge of the acceleration region, rather than in a distributed parallel electric field.
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| 13. |
- Andersson, Christin, et al.
(författare)
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Lifestyle Factors and Subjective Cognitive Impairment in Patients Seeking Help at a Memory Disorder Clinic : The Role of Negative Life Events
- 2019
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Ingår i: Dementia and Geriatric Cognitive Disorders. - : S. Karger. - 1420-8008 .- 1421-9824. ; 48:3-4, s. 196-206
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Tidskriftsartikel (refereegranskat)abstract
- Background/Aims: A large proportion of patients at memory disorders clinics are classified as having subjective cognitive impairment (SCI). Previous research has investigated whether particular lifestyle factors known to affect cognition can be useful in differentiating patients who do not show objective evidence of memory decline. There may also exist subgroups of patients with respect to lifestyle factors that could help clinicians to understand the patient group that presents to memory clinics. These may differ in diagnostic outcome. Very little is known about potential subgroups; however, but such information may help guide interventions and potentially eliminate unnecessary diagnostic procedures. The current study investigated patterns of lifestyle-related variables, including stress, sleep, sensory sensitivity, depression, and negative life events in patients presenting to a memory disorders clinic. The aim was to determine whether subgroups existed and whether it was possible to distinguish those with objectively impaired cognition. Methods: One hundred and seventy-eight patients (mean age 58 years) from a University Hospital Memory Disorders Clinic. Results: Cluster analysis identified three groups of lifestyle-related variables. Strong determinants of clusters were negative life events and age. Patients with a high number of negative life events also tended to have highest self-reported memory complaint, higher levels of stress, depression, and sensory sensitivity. However, they did not perform the worst on memory testing. In contrast, individuals who performed the worst on memory tests were older, tended to have the least memory complaints, and less negative lifestyle factors; this group also included the highest proportion of patients with mild cognitive impairment and had the lowest median amyloid A-beta 42 (A beta 42). The group with the best cognitive performance were younger, included the highest proportion of patients with SCI and the highest median A beta 42. On lifestyle variables, their ratings fell in between the other groups. Conclusions: Lifestyle subgroups of patients were determined by stress, emotional problems, and age. The groups were significantly associated with A beta 42 and diagnostic outcome. This pattern may confound the differentiation between objective and subjective memory problems. Asking about lifestyle variables, in conjunction with neuropsychological testing, could potentially identify individuals who are not likely to have objective memory impairment and guide interventions.
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| 14. |
- André, Mats, et al.
(författare)
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Magnetic reconnection and modification of the Hall physics due to cold ions at the magnetopause
- 2016
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Ingår i: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 43:13, s. 6705-6712
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Tidskriftsartikel (refereegranskat)abstract
- Observations by the four Magnetospheric Multiscale spacecraft are used to investigate the Hall physics of a magnetopause magnetic reconnection separatrix layer. Inside this layer of currents and strong normal electric fields, cold (eV) ions of ionospheric origin can remain frozen-in together with the electrons. The cold ions reduce the Hall current. Using a generalized Ohm's law, the electric field is balanced by the sum of the terms corresponding to the Hall current, the vxB drifting cold ions, and the divergence of the electron pressure tensor. A mixture of hot and cold ions is common at the subsolar magnetopause. A mixture of length scales caused by a mixture of ion temperatures has significant effects on the Hall physics of magnetic reconnection.
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| 15. |
- Archer, Jenny, et al.
(författare)
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Dynamics and characteristics of black aurora as observed by high resolution ground-based imagers and radar
- 2011
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 0143-1161 .- 1366-5901. ; 32:11, s. 2973-2985
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution, multi-spectral data from the ground-based low-light auroral imager ASK (Auroral Structure and Kinetics) are used to characterize the fine structure of black aurora. Sixteen events comprising sheared and unsheared black arcs, as well as black patches and rings, constitute the analysed dataset. Simultaneous measurements of emissions caused by high- and low-energy precipitation make it possible to relate the characteristics of different black structures to the energy of the precipitating electrons. The reductions of high-energy particles versus low-energy particles in the black regions compared to the diffuse background are investigated for the different forms of black aurora. Two separate mechanisms have been suggested to cause black aurora. The larger reduction of high-energy precipitation within the fine-scale black structures discussed here favours a magnetospheric mechanism that blocks high-energy electrons from being scattered into the loss cone. European Incoherent SCATter radar (EISCAT) electron density profiles are available for one of the nights, and are compared to the optical measurements.
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| 16. |
- Barabash, Stas, et al.
(författare)
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Mars Orbiting Plasma Surveyor (MOPS)
- 2006
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Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions. ; , s. 227-232
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mars Orbiting Plasma Surveyor (MOPS) is a microsatellite mission focused on studies of the near -Mars environment and the planet - solar wind interaction. The recent findings by the ESA Mars Express mission further highlighted the complexity of the processes taking place at the planet resulting from the solar wind interaction that strongly affect the planet's atmosphere. However, despite many previous Martian missions carrying different types of space plasma experiments, a comprehensive investigation including simultaneous measurements of particles, fields, and waves has never been performed. We consider a spinning spacecraft of a wet mass of 76.1 kg with a 9.7 kg payload, which can “hitchhike” on another platform until Mars orbit insertion, and then be released into a suitable orbit. The spacecraft design is based on the experience gained in very successful Swedish space plasma missions, Viking, Freja, Astrid-1, and Astrid-2. In the present mission design, the MOPS spacecraft is equipped with its own 1m high gain antenna for direct communication with the Earth. The payload includes a wave experiment with wire booms, magnetometer with a rigid boom, Langmuir probes, electron and ion energy spectrometers and an ion mass analyzer. An energetic neutral atom imager and an UV photometer may complete the core payload. One of the proposed scenarios is piggy - backing on the Russian Phobos - Grunt mission to be launched to Mars in 2011.
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| 17. |
- Barnes, Brian R, et al.
(författare)
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The 5'-AMP-activated protein kinase gamma3 isoform has a key role in carbohydrate and lipid metabolism in glycolytic skeletal muscle
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:37, s. 38441-38447
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Tidskriftsartikel (refereegranskat)abstract
- 5'-AMP-activated protein kinase (AMPK) is a metabolic stress sensor present in all eukaryotes. A dominant missense mutation (R225Q) in pig PRKAG3, encoding the muscle-specific gamma3 isoform, causes a marked increase in glycogen content. To determine the functional role of the AMPK gamma3 isoform, we generated transgenic mice with skeletal muscle-specific expression of wild type or mutant (225Q) mouse gamma3 as well as Prkag3 knockout mice. Glycogen resynthesis after exercise was impaired in AMPK gamma3 knock-out mice and markedly enhanced in transgenic mutant mice. An AMPK activator failed to increase skeletal muscle glucose uptake in AMPK gamma3 knock-out mice, whereas contraction effects were preserved. When placed on a high fat diet, transgenic mutant mice but not knock-out mice were protected against excessive triglyceride accumulation and insulin resistance in skeletal muscle. Transfection experiments reveal the R225Q mutation is associated with higher basal AMPK activity and diminished AMP dependence. Our results validate the muscle-specific AMPK gamma3 isoform as a therapeutic target for prevention and treatment of insulin resistance.
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| 18. |
- Benner, Mats, et al.
(författare)
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Foundations and the new renewal of research
- 2022
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Ingår i: Smart Policies for Societies in Transition : The Innovation Challenge of Inclusion, Resilience and Sustainability - The Innovation Challenge of Inclusion, Resilience and Sustainability. ; , s. 213-227
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Bokkapitel (refereegranskat)
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| 19. |
- Berthomier, M., et al.
(författare)
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Alfven : magnetosphere-ionosphere connection explorers
- 2012
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Ingår i: Experimental astronomy. - Dordrecht : Springer. - 0922-6435 .- 1572-9508. ; 33:2-3, s. 445-489
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Tidskriftsartikel (refereegranskat)abstract
- The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth's atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The "ideal magnetohydrodynamics" description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfv,n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Blomberg, Lars, et al.
(författare)
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Atrid-2 : An advanced auroral microprobe
- 1999
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Astri-2 is an advanced auroral microprobe with dual primary mission objectives; to do high-quality in situ measurements of the physical processes behind the aurora, and to demonstrate the usefulness of microspacecraft as advanced research tools. Mission success will open up entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space. This long-desired kind of in situ measurements are the next major step forward in experimental space physics. Astrid-2 has platform dimensions of 45×45×30 cm, a total mass of just below 30 kg, and carries scientific instruments for measuring local electric and magnetic fields, plasma density and density fluctuations, ions and electrons, as well as photometers for remote imaging of auroral emissions. Attitude determination is provided by a high-precision star imager. Some 250 Mbytes' worth of scientific data will be received each day at the two ground stations. Astrid-2 will be launched as a piggy-back on a Russian Kosmos-3M launcher into an 83 deg inclination circular orbit at 1000 km altitude. Nodal regression will give complete coverage of all local time sectors every 3.5 months. © 1999 Elsevier B.V. All rights reserved.
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