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| 2. |
- Jones, Geraint H., et al.
(författare)
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The Comet Interceptor Mission
- 2024
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Ingår i: Space Science Reviews. - : Springer Nature. - 0038-6308 .- 1572-9672. ; 220:1
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.
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| 3. |
- Nilsson, Hans, 1955-, et al.
(författare)
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Bevara kyrksalen som ett byggnadsminne
- 2024
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Annan publikation (populärvet., debatt m.m.)abstract
- Debattartikel som argumenterar för behovet att bevara den gamla Baptistkyrkan på Klostergatan 46 i Linköping, en byggnad med stort kulturhistoriskt värde.
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| 4. |
- Wang, Xiao-Dong, et al.
(författare)
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Martian global current systems and related solar wind energy transfer : hybrid simulation under nominal conditions
- 2024
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 527:4, s. 12232-12242
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Tidskriftsartikel (refereegranskat)abstract
- The magnetized solar wind drives a current system around Mars that maintains its induced magnetosphere. The solar wind also transfers its energy to the atmospheric ions, causing continuous atmospheric erosion, which has a profound impact on the planet’s evolution history. Here, we use Amitis, a Graphics Processing Unit (GPU)-based hybrid plasma model to first reproduce the global pattern of the net electric current and ion currents under an interplanetary magnetic field perpendicular to the solar wind flow direction. The resultant current distribution matches the observations and reveals more details. Using the electric field distribution characterized earlier with the same model, we calculate for the first time the spatial distribution of energy transfer rate to the plasmas in general and to different ion species at Mars. We find out that (1) the solar wind kinetic energy is the dominant energy source that drives Martian induced magnetosphere, (2) the energy flux of the shocked solar wind flows from the magnetic equatorial plane towards the plasma sheet in the induced magnetotail, (3) both the bow shock and the induced magnetospheric boundary are dynamos where plasma energy is transferred to the electromagnetic field, and (4) the planetary ions act as loads and gain energy from the electromagnetic field. The most intense load region is the planetary ion plume. The general pattern of the energy transfer rate revealed in this study is common for induced magnetospheres. Its variabilities with the upstream conditions can provide physical insight into the observed ion escape variabilities.
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| 5. |
- Williamson, Hayley N., et al.
(författare)
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Cometary ion drift energy and temperature at comet 67P/Churyumov–Gerasimeko
- 2024
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 533, s. 2980-2990
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Tidskriftsartikel (refereegranskat)abstract
- The Ion Composition Analyzer (ICA) on the Rosetta spacecraft observed both the solar wind and the cometary ionosphere around comet 67P/Churyumov–Gerasimenko for nearly two years. However, observations of low energy cometary ions were affected by a highly negative spacecraft potential, and the ICA ion density estimates were often much lower than plasma densities found by other instruments. Since the low energy cometary ions are often the highest density population in the plasma environment, it is nonetheless desirable to understand their properties. To do so, we select ICA data with densities comparable to those of Rosetta’s Langmuir Probe (LAP)/Mutual Impedance Probe (MIP) throughout the mission. We then correct the cometary ion energy distribution of each energy-angle scan for spacecraft potential and fit a drifting Maxwell–Boltzmann distribution, which gives an estimate of the drift energy and temperature for 3521 scans. The resulting drift energy is generally between 11–18 eV and the temperature between 0.5–1 eV. The drift energy shows good agreement with published ion flow speeds from LAP/MIP during the same time period and is much higher than the cometary neutral speed. We see additional higher energy cometary ions in the spectra closest to perihelion that would be well described by a second Maxwellian-like distribution. The energy and temperature are negatively correlated with heliocentric distance, with a stronger dependence on heliocentric distance for temperature. It cannot be quantitatively determined whether this trend is primarily due to heliocentric distance or spacecraft distance to the comet, which increased with decreasing heliocentric distance.
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| 6. |
- Zhang, Chi, et al.
(författare)
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The Energetic Oxygen Ion Beams in the Martian Magnetotail Current Sheets : Hints From the Comparisons Between Two Types of Current Sheets
- 2024
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 51:5
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Tidskriftsartikel (refereegranskat)abstract
- Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we explore the plasma properties of Martian magnetotail current sheets (CS), to further understand the solar wind interaction with Mars and ion escape. There are some CS exhibit energetic oxygen ions that show narrow beam structures in the energy spectrum, which primarily occurs in the hemisphere where the solar wind electric field (Esw) is directed away from the planet. On average, these CS have a higher escaping flux than that of the CS without energetic oxygen ion beams, suggesting different roles in ion escape. The CS with energetic oxygen ion beams exhibits different proton and electron properties to the CS without energetic oxygen ion beams, indicating their different origins. Our analysis suggests that the CS with energetic oxygen ion beams may result from the interaction between the penetrated solar wind and localized oxygen ion plumes.
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| 7. |
- Goetz, Charlotte, et al.
(författare)
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Solar Wind Protons in the Diamagnetic Cavity at Comet 67P/Churyumov-Gerasimenko
- 2023
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 128:4
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Tidskriftsartikel (refereegranskat)abstract
- The plasma environment at a comet can be divided into different regions with distinct plasma characteristics. Two such regions are the solar wind ion cavity, which refers to the part of the outer coma that does not contain any solar wind ions anymore; and the diamagnetic cavity, which is the region of unmagnetized plasma in the innermost coma. From theory and previous observations, it was thought that under usual circumstances no solar wind ion should be observable near or inside of the diamagnetic cavity. For the first time, we report on five observations that show that protons near solar wind energies can also be found inside the diamagnetic cavity. We characterize these proton signatures, where and when they occur, and discuss possible mechanisms that could lead to protons penetrating the inner coma and traversing the diamagnetic cavity boundary. By understanding these observations, we hope to better understand the interaction region of the comet with the solar wind under nonstandard conditions. The protons detected inside the diamagnetic cavity have directions and energies consistent with protons of solar wind origin. The five events occur only at intermediate gas production rates and low cometocentric distances. Charge transfer reactions, high solar wind dynamic pressure and a neutral gas outburst can be ruled out as causes. We suggest that the anomalous appearance of protons in the diamagnetic cavity is due to a specific solar wind configuration where the solar wind velocity is parallel to the interplanetary magnetic field, thus inhibiting mass-loading and deflection.
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| 8. |
- Gunell, Herbert, et al.
(författare)
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Magnetosheath jets at Mars
- 2023
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 9:22
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Tidskriftsartikel (refereegranskat)abstract
- Plasma entities, known as magnetosheath jets, with higher dynamic pressure than the surrounding plasma, are often seen at Earth. They generate waves and contribute to energy transfer in the magnetosheath. Affecting the magnetopause, they cause surface waves and transfer energy into the magnetosphere, causing throat auroras and magnetic signatures detectable on the ground. We show that jets exist also beyond Earth's environment in the magnetosheath of Mars, using data obtained by the MAVEN spacecraft. Thus, jets can be created also at Mars, which differs from Earth by its smaller bow shock, and they are associated with an increased level of magnetic field fluctuations. Jets couple large and small scales in magnetosheaths in the solar system and can play a similar part in astrophysical plasmas.
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| 9. |
- Moeslinger, Anja, et al.
(författare)
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Indirect observations of electric fields at comet 67P
- 2023
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 128:9
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Tidskriftsartikel (refereegranskat)abstract
- No spacecraft visiting a comet has been equipped with instruments to directly measure the static electric field. However, the electric field can occasionally be estimated indirectly by observing its effects on the ion velocity distribution. We present such observations made by the Rosetta spacecraft on 19 April 2016, 35 km from the nucleus. At this time comet 67P was at a low outgassing rate and the plasma environment was relatively stable. The ion velocity distributions show the cometary ions on the first half of their gyration. We estimate the bulk drift velocity and the gyration speed from the distributions. By using the local measured magnetic field and assuming an E × B drift of the gyrocentre, we get an estimate for the average electric field driving this ion motion. We analyze a period of 13 hr, during which the plasma environment does not change drastically. We find that the average strength of the perpendicular electric field component is 0.21 mV/m. The direction of the electric field is mostly anti-sunward. This is in agreement with previous results based on different methods.
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| 10. |
- Nilsson, Hans, et al.
(författare)
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Provtagningsmetoder av akvatiska resurser med 3R i fokus
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flertalet av de övervakningsmetoder av fisk- och skaldjur som idag används globalt är dödande eller invasiva. Under 2020 hanterade SLU Aqua över 9 miljoner individer av fisk under fiskerioberoende provtagning. I Sverige, till skillnad från övriga Europa, räknas även de fiskar som fångas i provfiske till försöksdjur och regeringen har anmodat att myndigheter som använder försöksdjur bör upprätta strategier för sitt arbete med frågor som rör 3R, dvs. Replace (ersätta), Reduce (minska) och Refine (förfina). I syfte att undersöka möjligheterna att implementera 3R i SLU Aquas övervakning av fiskbestånd, redovisas i denna rapport möjliga metoder för att:Ersätta – Genom fiskeriberoende provtagning i syfte att ta fram förvaltningsunderlag för bedömning av beståndsstatus för Vänerns gösbestånd och kartlägga effekter av fiske på gös i Vänern (Kapitel 5)Minska – Genom studier av hydroakustisk frekvensrespons hos fisk och/eller användandet av trålmonterad stereovideo se på möjligen att reducera behovet av trålning under hydroakustiska trålundersökningar (Kapitel 2 och 3). Genom att komplettera nätprovfiske med hydroakustik, elfiske och eDNA reducera mängden dödad fisk i denna undersökningstyp (Kapitel 4).Förfina – Genom att kombinera olika metoder öka mängden kunskap varje provtagen individ ger samt hela ekosystem (Kapitel 3 och 4).
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