| 1. |
- Edberg, Niklas J. T., et al.
(författare)
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Spatial distribution of low-energy plasma around comet 67P/CG from Rosetta measurements
- 2015
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 42:11, s. 4263-4269
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Tidskriftsartikel (refereegranskat)abstract
- We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be approximate to 1-210(-6), at a cometocentric distance of 10km and at 3.1AU from the Sun. A clear 6.2h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260km from the nucleus falls off with radial distance as approximate to 1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet.
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| 2. |
- Maksimovic, M., et al.
(författare)
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First observations and performance of the RPW instrument on board the Solar Orbiter mission
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656
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Tidskriftsartikel (refereegranskat)abstract
- The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is designed to measure in situ magnetic and electric fields and waves from the continuum up to several hundred kHz. The RPW also observes solar and heliospheric radio emissions up to 16 MHz. It was switched on and its antennae were successfully deployed two days after the launch of Solar Orbiter on February 10, 2020. Since then, the instrument has acquired enough data to make it possible to assess its performance and the electromagnetic disturbances it experiences. In this article, we assess its scientific performance and present the first RPW observations. In particular, we focus on a statistical analysis of the first observations of interplanetary dust by the instrument's Thermal Noise Receiver. We also review the electro-magnetic disturbances that RPW suffers, especially those which potential users of the instrument data should be aware of before starting their research work.
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| 3. |
- Maksimovic, M., et al.
(författare)
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The Solar Orbiter Radio and Plasma Waves (RPW) instrument
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 642
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Tidskriftsartikel (refereegranskat)abstract
- The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is described in this paper. This instrument is designed to measure in-situ magnetic and electric fields and waves from the continuous to a few hundreds of kHz. RPW will also observe solar radio emissions up to 16 MHz. The RPW instrument is of primary importance to the Solar Orbiter mission and science requirements since it is essential to answer three of the four mission overarching science objectives. In addition RPW will exchange on-board data with the other in-situ instruments in order to process algorithms for interplanetary shocks and type III langmuir waves detections.
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| 4. |
- André, Mats, et al.
(författare)
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Lower hybrid waves at comet 67P/Churyumov-Gerasimenko
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 469, s. S29-S38
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the generation of waves in the lower hybrid frequency range by density gradients in the near plasma environment of comet 67P/Churyumov-Gerasimenko. When the plasma is dominated by water ions from the comet, a situation with magnetized electrons and unmagnetized ions is favourable for the generation of lower hybrid waves. These waves can transfer energy between ions and electrons and reshape the plasma environment of the comet. We consider cometocentric distances out to a few hundred km. We find that when the electron motion is not significantly interrupted by collisions with neutrals, large average gradients within tens of km of the comet, as well as often observed local large density gradients at larger distances, are often likely to be favourable for the generation of lower hybrid waves. Overall, we find that waves in the lower hybrid frequency range are likely to be common in the near plasma environment.
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| 5. |
- Edberg, Niklas J. T., et al.
(författare)
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CME impact on comet 67P/Churyumov-Gerasimenko
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462, s. S45-S56
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Tidskriftsartikel (refereegranskat)abstract
- We present Rosetta observations from comet 67P/Churyumov-Gerasimenko during the impact of a coronal mass ejection (CME). The CME impacted on 2015 Oct 5-6, when Rosetta was about 800 km from the comet nucleus, and 1.4 au from the Sun. Upon impact, the plasma environment is compressed to the level that solar wind ions, not seen a few days earlier when at 1500 km, now reach Rosetta. In response to the compression, the flux of suprathermal electrons increases by a factor of 5-10 and the background magnetic field strength increases by a factor of similar to 2.5. The plasma density increases by a factor of 10 and reaches 600 cm(-3), due to increased particle impact ionization, charge exchange and the adiabatic compression of the plasma environment. We also observe unprecedentedly large magnetic field spikes at 800 km, reaching above 200 nT, which are interpreted as magnetic flux ropes. We suggest that these could possibly be formed by magnetic reconnection processes in the coma as the magnetic field across the CME changes polarity, or as a consequence of strong shears causing Kelvin-Helmholtz instabilities in the plasma flow. Due to the limited orbit of Rosetta, we are not able to observe if a tail disconnection occurs during the CME impact, which could be expected based on previous remote observations of other CME-comet interactions.
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| 6. |
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| 7. |
- Johansson, Eva, et al.
(författare)
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Evaluation of materials supply systems during product development projects
- 2004
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Ingår i: Proceedings of the Euroma Conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper discusses the process of designing materials supply systems during product development projects with focus on the evaluation part. A case study was conducted in close cooperation with a company within the automotive industry. Two performance measures for the materials supply systems evaluation were selected, namely inventory value and handling required for the materials supply. The result from the case study is an analysis of how these performance measures can be assessed early in product development projects and how they can be used in the process of materials supply systems design.
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| 8. |
- Johansson, Eva, et al.
(författare)
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Influence of shipment size on logistics costs in the ordering company
- 2000
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Ingår i: Proceedings of the 12th NOFOMA Conference, Aarhus, Denmark.
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Konferensbidrag (refereegranskat)abstract
- This paper shows the great importance of taking transportation costs into account when deciding on the shipment sizes. During the last few decades companies have tried to reduce their shipment sizes, in order to increase their inventory turnover rates. However, the transportation cost is hardly ever included as an explicit parameter in the shipment size decision. The results from a case study show that it is economically advantageous, in the perspective of the model applied, to increase the shipment sizes for many of the suppliers. These results are discussed together with the factors that act for smaller shipment sizes. One of the final conclusions is, however, that if the manufacturing and the materials flow systems were changed in order to take full advantage of smaller shipment sizes and less material in house, it would possibly be profitable to decrease the shipment sizes even more than has hitherto been done.
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| 9. |
- Johansson, Eva, et al.
(författare)
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The information gap between design engineering and materials supply systems design
- 2003
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Ingår i: Proceedings of the 17th International Conference on Production Research, Blacksburg, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper focuses on the design of materials supply systems in product development projects. In order to design the materials supply system in parallel with the product, product data must be available to the materials supply systems designers. The aim of this paper is to discuss the information quality of the required product data and to indicate how this information quality can be increased. Empirical data have been gathered through studies conducted within the Manufacturing Industry.The empirical data show many deficiencies related to information quality. In order to improve the information quality, the advantages provided by PDM-systems must be utilised. It is also essential that materials supply systems designers are able to state what product data they need as well as the form of the data. In addition, the current status of the product data must be provided, i.e. information about how much the data may change.
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| 10. |
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