| 1. |
- Blomberg, Lars, et al.
(författare)
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Electric Field Diagnostics in the Jovian System : Brief Scientific Case and Instrumentation Overview
- 2006
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Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions. ; , s. 335-340
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Jovian plasma environment exhibits a variety of plasma flow interactions with magnetised as well as unmagnetised bodies, making it a good venue for furthering our understanding of solar wind - magnetosphere / ionosphere interactions. On an overall scale the solar wind interacts with the Jovian magnetosphere, much like at Earth but with vastly different temporal and spatial scales. Inside the Jovian magnetosphere the co-rotating plasma interacts with the inner moons. The latter interaction is slower and more stable than the corresponding interaction between the solar wind and the planets, and can thus provide additional information on the principles of the interaction mechanisms. Because of the wealth of expected low-frequency waves, as well as the predicted quasi-static electric fields and plasma drifts in the interaction regions between different parts of the Jovian system, a most valuable component in future payloads would be a double-probe electric field instrument. Recent developments in low-mass instrumentation facilitate electric field measurements on spinning planetary spacecraft, which we here exemplify.
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| 2. |
- Eriksson, Anders, et al.
(författare)
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RPC-LAP : The Rosetta Langmuir probe instrument
- 2007
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 128:04-jan, s. 729-744
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Forskningsöversikt (refereegranskat)abstract
- The Rosetta dual Langmuir probe instrument, LAP, utilizes the multiple powers of a pair of spherical Langmuir probes for measurements of basic plasma parameters with the aim of providing detailed knowledge of the outgassing, ionization, and subsequent plasma processes around the Rosetta target comet. The fundamental plasma properties to be studied are the plasma density, the electron temperature, and the plasma flow velocity. However, study of electric fields up to 8 kHz, plasma density fluctuations, spacecraft potential, integrated UV flux, and dust impacts is also possible. LAP is fully integrated in the Rosetta Plasma Consortium (RPC), the instruments of which together provide a comprehensive characterization of the cometary plasma.
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| 3. |
- Graham, Daniel B., et al.
(författare)
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Enhanced Escape of Spacecraft Photoelectrons Caused by Langmuir and Upper Hybrid Waves
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:9, s. 7534-7553
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Tidskriftsartikel (refereegranskat)abstract
- The spacecraft potential is often used to infer rapid changes in the thermal plasma density. The variations in spacecraft potential associated with large-amplitude Langmuir and upper hybrid waves are investigated with the Magnetospheric Multiscale (MMS) mission. When large-amplitude Langmuir and upper hybrid waves are observed, the spacecraft potential increases. The changes in spacecraft potential are shown to be due to enhanced photoelectron escape from the spacecraft when the wave electric fields reach large amplitude. The fluctuations in spacecraft potential follow the envelope function of the Langmuir and upper hybrid waves. Comparison with the high-resolution electron moments shows that the changes in spacecraft potential associated with the waves are not due to density perturbations. Indeed, using the spacecraft potential as a density probe leads to unphysically large density fluctuations. In addition, the changes in spacecraft potential are shown to increase as density decreases: larger spacecraft potential changes are observed in the magnetosphere, than in the magnetosheath and solar wind. These results show that external electric fields can lead to unphysical results when the spacecraft potential is used as a density probe. The results suggest that fluctuations in the spacecraft potential alone cannot be used to determine whether nonlinear processes associated with Langmuir and upper hybrid waves, such as the ponderomotive force and three-wave decay, are occurring.
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| 4. |
- Karlsson, Tomas, et al.
(författare)
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Rosetta measurements of lower hybrid frequency range electric field oscillations in the plasma environment of comet 67P
- 2017
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 44:4, s. 1641-1651
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Tidskriftsartikel (refereegranskat)abstract
- Electric field measurements from cometary environments are very rare but can provide important information on how plasma waves help fashion the plasma environment. The long dwelling time of the Rosetta spacecraft close to comet 67P/Churyumov-Gerasimenko promises to improve this state. We here present the first electric field measurements from 67P, performed by the Rosetta dual Langmuir probe instrument LAP. Measurements of the electric field from cometocentric distances of 149 and 348 km are presented together with estimates of plasma density changes. Persistent wave activity around the local H2O+ lower hybrid frequency is observed, with the largest amplitudes observed at sharp plasma gradients. We demonstrate that the necessary requirements for the lower hybrid drift instability to be operating are fulfilled. We suggest that lower hybrid waves are responsible for the creation of a warm electron population, the origins of which have been unknown so far, by heating ambient electrons in the magnetic field-parallel direction.
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| 5. |
- Khotyaintsev, Yuri, et al.
(författare)
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The EFW data in the CAA
- 2010
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Konferensbidrag (refereegranskat)abstract
- The Electric Field and Waves (EFW) instrument measures the 2D electric field (in the spacecraft spin plane) and spacecraft potential with sampling rates, on some occasions, up to 36,000 samples/s. We present a summary of the CAA data products produced from the EFW measurements. We briefly describe the production pipeline from the raw data to final data products and discuss the most common caveats.
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| 6. |
- Khotyaintsev, Yuri V., et al.
(författare)
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In-flight calibration of double-probe DC electric field measurements on Cluster
- 2014
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Ingår i: Geoscientific Instrumentation, Methods and Data Systems. - : Copernicus GmbH. - 2193-0856 .- 2193-0864. ; 4:1, s. 85-107
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Tidskriftsartikel (refereegranskat)abstract
- Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of DC and AC electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the EFW instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.
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| 7. |
- Khotyaintsev, Yuri V., et al.
(författare)
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In-flight calibration of double-probe electric field measurements on Cluster
- 2014
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Ingår i: Geoscientific Instrumentation, Methods and Data Systems. - : European Geosciences Union (EGU). - 2193-0856 .- 2193-0864. ; 3:2, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the Electric Field and Wave (EFW) instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.
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| 8. |
- 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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| 9. |
- Wahlund, Jan-Erik, et al.
(författare)
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Cold Plasma Diagnostics in the Jovian System : Brief Scientific Case and Instrumentation Overview
- 2006
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Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions. ; , s. 341-346
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Jovian magnetosphere equatorial region is filled with cold dense plasma that in a broad sense co-rotate with its magnetic field. The volcanic moon Io, which expels sodium, sulphur and oxygen containing species, dominates as a source for this cold plasma. The three icy Galilean moons (Callisto, Ganymede, and Europa) also contribute with water group and oxygen ions. All the Galilean moons have thin atmospheres with residence times of a few days at most. Their ionized ionospheric components interact dynamically with the co-rotating magnetosphere of Jupiter and for example triggers energy transfer processes that give rise to auroral signatures at Jupiter. On these moons the surface interactions with the space environment determine their atmospheric and ionospheric properties. The range of processes associated with the Jovian magnetospheric interaction with the Galilean moons, where the cold dense plasma expelled from these moons play a key role, are not well understood. Conversely, the volatile material expelled from their interiors is important for our understanding of the Jovian magnetosphere dynamics and energy transfer. A Langmuir probe investigation, giving in-situ plasma density, temperatures, UV intensity and plasma speed with high time resolution, would be a most valuable component for future payloads to the Jupiter system. Recent developments in low-mass instrumentation facilitate Langmuir probe in situ measurements on such missions.
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