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- Trotignon, J. G., et al.
(författare)
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Active measurement of the thermal electron density and temperature on the Mercury Magnetospheric Orbiter of the BepiColombo mission
- 2006
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Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 38:4, s. 686-692
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Tidskriftsartikel (refereegranskat)abstract
- The thermal component of Mercury's electron population has never been measured. One scientific objective of the Plasma Wave Investigation consortium, PWI, is to determine the influence of the thermal plasma upon the formation and dynamics of the planetary magnetosphere, as a function of solar activity. The Active Measurement of Mercury's Plasma experiment, AM(2)p, has been proposed as part of PWI, to monitor the density and temperature of the thermal electron population, during the whole mission of the Mercury Magnetospheric Orbiter of BepiColombo. These two physical parameters will be deduced from the measurements of the self- and mutual-impedances of the MEFISTO (Mercury Electric Field In Situ Tool) double-sphere antenna, in a frequency range comprising the expected plasma frequency. The in situ measurement of the antenna impedance is also essential for calibrating the electric antenna which measures the natural waves; it will allow, in particular, the effective length of the antenna to be calculated as a function of frequency and plasma conditions. The purpose of this paper is to define the scientific objectives of AM(2)p, to explain the principle of the measurement, to describe the electronic device, and to show the ability of AM 2p to make reliable and accurate measurements of the thermal plasma density and temperature in the Hermean magnetosphere, as well as in the solar wind at heliocentric distances of 0.31-0.47 AU. The potential performance of this instrument has been evaluated using both an analytical approach and numerical simulations.
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- Pedersen, A., et al.
(författare)
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Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions
- 2008
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 113:A7
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Tidskriftsartikel (refereegranskat)abstract
- Spacecraft potential measurements by the EFW electric field experiment on the Cluster satellites can be used to obtain plasma density estimates in regions barely accessible to other type of plasma experiments. Direct calibrations of the plasma density as a function of the measured potential difference between the spacecraft and the probes can be carried out in the solar wind, the magnetosheath, and the plasmashere by the use of CIS ion density and WHISPER electron density measurements. The spacecraft photoelectron characteristic ( photoelectrons escaping to the plasma in current balance with collected ambient electrons) can be calculated from knowledge of the electron current to the spacecraft based on plasma density and electron temperature data from the above mentioned experiments and can be extended to more positive spacecraft potentials by CIS ion and the PEACE electron experiments in the plasma sheet. This characteristic enables determination of the electron density as a function of spacecraft potential over the polar caps and in the lobes of the magnetosphere, regions where other experiments on Cluster have intrinsic limitations. Data from 2001 to 2006 reveal that the photoelectron characteristics of the Cluster spacecraft as well as the electric field probes vary with the solar cycle and solar activity. The consequences for plasma density measurements are addressed. Typical examples are presented to demonstrate the use of this technique in a polar cap/lobe plasma.
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| 7. |
- Pedersen, A., et al.
(författare)
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Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A7, s. A07S33-
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Tidskriftsartikel (refereegranskat)abstract
- Spacecraft potential measurements by the EFW electric field experiment on the Cluster satellites can be used to obtain plasma density estimates in regions barely accessible to other type of plasma experiments. Direct calibrations of the plasma density as a function of the measured potential difference between the spacecraft and the probes can be carried out in the solar wind, the magnetosheath, and the plasmashere by the use of CIS ion density and WHISPER electron density measurements. The spacecraft photoelectron characteristic ( photoelectrons escaping to the plasma in current balance with collected ambient electrons) can be calculated from knowledge of the electron current to the spacecraft based on plasma density and electron temperature data from the above mentioned experiments and can be extended to more positive spacecraft potentials by CIS ion and the PEACE electron experiments in the plasma sheet. This characteristic enables determination of the electron density as a function of spacecraft potential over the polar caps and in the lobes of the magnetosphere, regions where other experiments on Cluster have intrinsic limitations. Data from 2001 to 2006 reveal that the photoelectron characteristics of the Cluster spacecraft as well as the electric field probes vary with the solar cycle and solar activity. The consequences for plasma density measurements are addressed. Typical examples are presented to demonstrate the use of this technique in a polar cap/lobe plasma.
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- Thorleifsson, Gudmar, et al.
(författare)
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Common sequence variants in the LOXL1 gene confer susceptibility to exfoliation glaucoma
- 2007
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 317:5843, s. 1397-1400
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is a leading cause of irreversible blindness. A genome-wide search yielded multiple single-nucleotide polymorphisms (SNPs) in the 15q24.1 region associated with glaucoma. Further investigation revealed that the association is confined to exfoliation glaucoma (XFG). Two nonsynonymous SNPs in exon 1 of the gene LOXL1 explain the association, and the data suggest that they confer risk of XFG mainly through exfoliation syndrome (XFS). About 25% of the general population is homozygous for the highest-risk haplotype, and their risk of suffering from XFG is more than 100 times that of individuals carrying only low-risk haplotypes. The population-attributable risk is more than 99%. The product of LOXL1 catalyzes the formation of elastin fibers found to be a major component of the lesions in XFG.
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