28 results on '"Wurz P"'
Search Results
2. First experimental data of sulphur ions sputtering water ice
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Galli, A., Vorburger, A., Wurz, P., Cerubini, R., and Tulej, M.
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- 2018
- Full Text
- View/download PDF
3. Europa’s ice-related atmosphere: The sputter contribution
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Vorburger, A. and Wurz, P.
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- 2018
- Full Text
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4. Sputtering of water ice films: A re-assessment with singly and doubly charged oxygen and argon ions, molecular oxygen, and electrons
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Galli, A., Vorburger, A., Wurz, P., and Tulej, M.
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- 2017
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- View/download PDF
5. Monte-Carlo simulation of Callisto’s exosphere
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Vorburger, A., Wurz, P., Lammer, H., Barabash, S., and Mousis, O.
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- 2015
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6. Comet-like tail-formation of exospheres of hot rocky exoplanets: Possible implications for CoRoT-7b
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Mura, A., Wurz, P., Schneider, J., Lammer, H., Grießmeier, J.-M., Khodachenko, M.L., Weingrill, J., Guenther, E., Cabrera, J., Erikson, A., Fridlund, M., Milillo, A., Rauer, H., and von Paris, Ph.
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- 2011
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7. Titan’s atomic hydrogen corona
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Hedelt, P., Ito, Y., Keller, H.U., Reulke, R., Wurz, P., Lammer, H., Rauer, H., and Esposito, L.
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- 2010
- Full Text
- View/download PDF
8. Asteroid exosphere: A simulation for the ROSETTA flyby targets (2867) Steins and (21) Lutetia
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Schläppi, B., Altwegg, K., and Wurz, P.
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- 2008
- Full Text
- View/download PDF
9. The lunar exosphere: The sputtering contribution
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Wurz, P., Rohner, U., Whitby, J.A., Kolb, C., Lammer, H., Dobnikar, P., and Martin-Fernandez, J.A.
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Astronomy ,Earth sciences - Abstract
To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.04.034 Byline: P. Wurz (a), U. Rohner (a), J.A. Whitby (a), C. Kolb (b), H. Lammer (b), P. Dobnikar (c), J.A. Martin-Fernandez (d) Keywords: Moon; Moon; surface; Atmospheres; composition Abstract: We have extended our Monte Carlo model of exospheres [Wurz, P., Lammer, H., 2003. Icarus 164 (1), 1-13] by treating the ion-induced sputtering process from a known surface in a self-consistent way. The comparison of the calculated exospheric densities with experimental data, which are mostly upper limits, shows that all of our calculated densities are within the measurement limits. The total calculated exospheric density at the lunar surface of about 1x10.sup.7m.sup.-3 as result of solar wind sputtering we find is much less than the experimental total exospheric density of about 10.sup.12m.sup.-3. We conclude that sputtering contributes only a small fraction of the total exosphere, at least close to the surface. Because of the considerably larger scale height of atoms released via sputtering into the exosphere, sputtered atoms start to dominate the exosphere at altitudes exceeding a few 1000 km, with the exception of some light and abundant species released thermally, e.g. H.sub.2, He, CH.sub.4, and OH. Furthermore, for more refractory species such as calcium, our model indicates that sputtering may well be the dominant mechanism responsible for the lunar atmospheric inventory, but observational data does not yet allow firm conclusions to be drawn. Author Affiliation: (a) Physikalisches Institut, Universitat Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland (b) Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria (c) Institute for Physics, University of Graz, Universitatsplatz 5/II, A-8010 Graz, Austria (d) Department for Computer Science and Applied Mathematics, University of Girona, Edifici, P-IV, Campus Montilivi, E-17071 Girona, Spain Article History: Received 12 February 2007; Revised 26 April 2007
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- 2007
10. First ENA observations at Mars: solar-wind ENAs on the nightside
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Brinkfeldt, K., Gunell, H., Brandt, P. C:son, Barabash, S., Frahm, R.A., Winningham, J.D., Kallio, E., Holmstrom, M., Futaana, Y., Ekenback, A., Lundin, R., Andersson, H., Yamauchi, M., Grigoriev, A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Koskinen, H., Stiles, T., Riihela, P., Schmidt, W., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Magnetosphere -- Observations ,Solar wind -- Observations ,Astronomy ,Earth sciences - Abstract
We present measurements with an Energetic Neutral Atom (ENA) imager on board Mars Express when the spacecraft moves into Mars eclipse. Solar wind ions charge exchange with the extended Mars exosphere to produce ENAs that can spread into the eclipse of Mars due to the ions' thermal spread. Our measurements show a lingering signal from the Sun direction for several minutes as the spacecraft moves into the eclipse. However, our ENA imager is also sensitive to UV photons and we compare the measurements to ENA simulations and a simplified model of UV scattering in the exosphere. Simulations and further comparisons with an electron spectrometer sensitive to photoelectrons generated when UV photons interact with the spacecraft suggest that what we are seeing in Mars' eclipse are ENAs from upstream of the bow shock produced in charge exchange with solar wind ions with a non-zero temperature. The measurements are a precursor to a new technique called ENA sounding to measure solar wind and planetary exosphere properties in the future. Keywords: Mars; Solar wind; Magnetospheres
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- 2006
11. First ENA observations at Mars: ENA emissions from the martian upper atmosphere
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Futaana, Y., Barabash, S., Grigoriev, A., Holmstrom, M., Kallio, E., Brandt, P. C:son, Gunell, H., Brinkfeldt, K., Lundin, R., Andersson, H., Yamauchi, M., McKenna-Lawler, S., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Sales, T., Riihela, P., Schmidt, W., Koskinen, H., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Galli, A., Krupp, N., Woch, J., Franz, M., and Asamura, K. Dierker, C.
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Mars probes -- Observations ,Mars (Planet) -- Atmosphere ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
The neutral particle detector (NPD) on board Mars Express has observed energetic neutral atoms (ENAs) from a broad region on the dayside of the martian upper atmosphere. We show one such example for which the observation was conducted at an altitude of 570 km, just above the induced magnetosphere boundary (IMB). The time of flight spectra of these ENAs show that they had energies of 0.2-2 keV/amu, with an average energy of ~1.1 keV/amu. Both the spatial distribution and the energy of these ENAs are consistent with the backscattered ENAs, produced by an ENA albedo process. This is the first observation of backscattered ENAs from the martian upper atmosphere. The origin of these ENAs is considered to be the solar wind ENAs that are scattered back by collision processes in the martian upper atmosphere. The particle flux and energy flux of the backscattered ENAs are 0.9-1.3 x [10.sup.7] [cm.sup.-2] [s.sup.-1] and ~9.5 x [10.sup.9] eV [cm.sup.-2] [s.sup.-l], respectively. Keywords: Mars, atmosphere; Solar wind; Atmospheres, dynamics; Atmospheres, structure; Ionospheres
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- 2006
12. Energetic neutral atoms (ENA) at Mars: properties of the hydrogen atoms produced upstream of the martian bow shock and implications for ENA sounding technique around non-magnetized planets
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Kallio, E., Barabash, S., Brinkfeldt, K., Gunell, H., Holmstrom, M., Futaana, Y., Schmidt, W., Sales, T., Koskinen, H., Riihela, P., Lundin, R., Andersson, H., Yamauchi, M., Grigoriev, A., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Kozyra, J., Luhmann, J.G., Roelof, E., Williams, D., Livi, S., Brandt, P. C:son, Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Monte Carlo method -- Usage ,Hydrogen bonding -- Properties ,Mars (Planet) -- Atmosphere ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
We have studied the interaction of fast solar wind hydrogen atoms with the martian atmosphere by a three-dimensional Monte Carlo simulation. These energetic neutral hydrogen atoms, H-ENAs, are formed upstream of the martian bow shock. Both H-ENAs scattered and non-scattered from the martian atmosphere/exosphere were studied. The colliding H-ENAs were found to scatter both to the dayside and nightside. On the dayside they contribute to the so-called H-ENA albedo. On the nightside the heated and scattered hydrogen atoms were found also in the martian wake. The density, the energy distribution function and the direction of the velocity of H-ENAs on the nightside are presented. The present study describes a novel 'ENA sounding' technique in which energetic neutral atoms are used to derive information of the properties of planetary exosphere and atmosphere in a similar manner as the solar wind photons are used to derive atmospheric densities by measuring the scattered UV light. A detailed study of the direction and energy of the scattered and non-scattered H-ENAs suggest that the ENA sounding is a method to study the interaction between the planetary atmosphere and the solar wind and to monitor the density, and likely also the magnetization, of the planetary upper atmosphere. Already present-day ENA instrument should be capable to detect the analyzed particle fluxes. Keywords: Mars, atmosphere
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- 2006
13. First ENA observations at Mars: charge exchange ENAs produced in the magnetosheath
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Gunell, H., Brinkfeldt, K., Holmstrom, M., Brandt, P. C:son, Barabash, S., Kallio, E., Ekenback, A., Futaana, Y., Lundin, R., Andersson, H., Yamauchi, M., Grigoriev, A., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Sales, T., Riihela, P., Schmidt, W., Koskinen, H., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Environmental aspects ,Mars (Planet) -- Observations ,Magnetosphere -- Observations ,Astronomy ,Earth sciences - Abstract
Measurements of energetic neutral atoms (ENA) generated in the magnetosheath at Mars are reported. These ENAs are the result of charge exchange collisions between solar wind protons and neutral oxygen and hydrogen in the exosphere of Mars. The peak of the observed ENA flux is 1.3 x [10.sup.11] [m.sup.-2] [sr.sup.-1] [s.sup.-1]. For the case studied here, i.e., the passage of Mars Express through the martian magnetosheath around 20:15 UT on 3 May 2004, the measurements agree with an analytical model of the ENA production at the planet. It is possible to find parameter values in the model such that the observed peak in the ENA count rate during the spacecraft passage through the magnetosheath is reproduced. Keywords: Mars; Solar wind; Magnetospheres
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- 2006
14. Plasma intrusion above Mars crustal fields--Mars Express ASPERA-3 observations
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Franz, M., Winningham, J.D., Dubinin, E., Roussos, E., Woch, J., Barabash, S., Lundin, R., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Soobiah, Y., Linder, D.R., Kataria, D.O., Kallio, E., Sales, T., Riihela, P., Schmidt, W., Koskinen, H.E.J., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Mars probes -- Observations ,Magnetosphere -- Observations ,Astronomy ,Earth sciences - Abstract
Using data of the ASPERA-3 instrument on board the European Mars Express spacecraft we investigate the effect of the martian crustal fields on electrons intruding from the magnetosheath. For the crustal field strength we use published data obtained by the Mars Global Surveyor MAG/ER instrument for a fixed altitude of 400 km. We use statistics on 13 months of 80-100 eV electron observations to show that the electron intrusion altitude determined by a probability measure is approximately linearly dependent on the total field strength at 400 km altitude. We show that on the dayside the mean electron intrusion altitude describes the location of the Magnetic Pile-Up Boundary (MPB) such that we can quantify the effect of the crustal fields on the MPB. On the nightside we quantify the shielding of precipitating electrons by the crustal fields. PACS: 96.30.Gc; 94.05.-a; 96.12.Jt Keywords: Mars; Magnetospheres
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- 2006
15. Numerical interpretation of high-altitude photoelectron observations
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Liemohn, Michael W., Frahm, R.A., Winningham, J.D., Ma, Y., Barabash, S., Lundin, R., Kozyra, J.U., Nagy, A.F., Bougher, S.M., Bell, J., Brain, D., Mitchell, D., Luhmann, J., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., McKenna-Lawler, S., Sharber, J.R., Scherrer, J.R., Jeffers, S.J., Coates, A.J., Linder, D.R., Kataria, D.O., Kallio, E., Koskinen, H., Sales, T., Riihela, P., Schmidt, W., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Photoelectron spectroscopy -- Observations ,Ionosphere -- Spectra ,Astronomy ,Earth sciences - Abstract
The Electron Spectrometer (ELS) instrument of the ASPERA-3 package on the Mars Express satellite has recorded photoelectron energy spectra up to apoapsis (~10,000 km altitude). The characteristic photoelectron shape of the spectrum is sometimes seen well above the ionosphere in the evening sector across a wide range of near-equatorial latitudes. Two numerical models are used to analyze the characteristics of these high-altitude photoelectrons. The first is a global, multi-species MHD code that produces a 3-D representation of the magnetic field and bulk plasma parameters around Mars. It is used here to examine the possibility of magnetic connectivity between the high-altitude flanks of the martian ionosheath and the subsolar ionosphere. It is shown that some field lines in this region are draped interplanetary magnetic lines while others are open field lines (connected to both the IMF and the crustal magnetic field sources). The second model is a kinetic electron transport model that calculates the electron velocity space distribution along a selected, non-uniform, magnetic field line. It is used here to simulate the high-altitude ELS measurements. It is shown that the photoelectrons are essentially confined to the source cone, as governed by magnetic field inhomogeneity along the field line. Reasonable agreement is shown between the data and the model results, and a method is demonstrated for inferring properties of the local and photoelectron source region magnetic field from the ELS measurements. Specifically, the number of sectors in which photoelectrons are measured is a function of the magnetic field intensity ratio and the field's angle with respect to the detector plane. In addition, the sector of the photoelectron flux peak is a function of the magnetic field azimuthal angle in the detector plane. Keywords: Mars; Magnetospheres; Ionospheres; Magnetic fields
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- 2006
16. Observations of magnetic anomaly signatures in Mars Express ASPERA-3 ELS data
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Soobiah, Y., Coates, A.J., Linder, D.R., Kataria, D.O., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Barabash, S., Lundin, R., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Kallio, E., Koskinen, H., Sales, T., Riihela, P., Schmidt, W., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Solar wind -- Observations ,Magnetic fields -- Observations ,Mars (Planet) -- Atmosphere ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
Mars Express (MEX) Analyser of Space Plasmas and Energetic Atoms (ASPERA-3) data is providing insights into atmospheric loss on Mars via the solar wind interaction. This process is influenced by both the interplanetary magnetic field (IMF) in the solar wind and by the magnetic 'anomaly' regions of the martian crust. We analyse observations from the ASPERA-3 Electron Spectrometer near to such crustal anomalies. We find that the electrons near remanent magnetic fields either increase in flux to form intensified signatures or significantly reduce in flux to form plasma voids. We suggest that cusps intervening neighbouring magnetic anomalies may provide a location for enhanced escape of planetary plasma. Initial statistical analysis shows that intensified signatures are mainly a dayside phenomenon whereas voids are a feature of the night hemisphere. Keywords: Magnetic fields; Solar wind; Mars
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- 2006
17. Carbon dioxide photoelectron energy peaks at Mars
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Frahm, R.A., Winningham, J.D., Sharber, J.R., Scherrer, J.R., Jeffers, S.J., Coates, A.J., Linder, D.R., Kataria, D.O., Lundin, R., Barabash, S., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Kallio, E., Sales, T., Riihela, P., Schmidt, W., Koskinen, H., Kozyra, J.U., Luhmann, J.G., Roelof, E.C., Williams, D.J., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaudk, J.-A., Fedorov, A., Thocaven, J.J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Carbon dioxide -- Environmental aspects ,Electron spectroscopy -- Observations ,Mars (Planet) -- Atmosphere ,Mars (Planet) -- Composition ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
The ELectron Spectrometer (ELS) from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) flown on the Mars Express spacecraft has an 8% energy resolution, combined with the capability to oversample the martian electron distribution. This makes possible the resolution and identification of electrons generated as a result of the He 304 [Angstrom] ionization of C[O.sub.2] at the martian exobase on the dayside of the planet. Ionospheric photoelectrons were observed during almost every pass into the ionosphere and C[O.sub.2] photoelectron peaks were identified near the terminator. Atmospherically generated C[O.sub.2] photoelectrons are also observed at 10,000 km altitude in the martian tail near the inner magnetospheric boundary. Observations over a wide range of spacecraft orbits showed a consistent presence of photoelectrons at locations along the inner magnetospheric boundary and in the ionosphere, from an altitude of 250 to 10,000 km. Keywords: Mars; Ionospheres; Atmospheres; Magnetospheres
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- 2006
18. First ENA observations at Mars: subsolar ENA jet
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Futaana, Y., Barabash, S., Grigoriev, A., Holmstrom, M., Kallio, E., Brandt, P. C:son, Gunell, H., Brinkfeldt, K., Lundin, R., Andersson, H., Yamauchi, M., McKenna-Lawler, S., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Sales, T., Riihela, P., Schmidt, W., Koskinen, H., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Magnetosphere -- Observations ,Solar wind -- Observations ,Astronomy ,Earth sciences - Abstract
The Neutral Particle Detector (NPD), an Energetic Neutral Atom (ENA) sensor of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) on board Mars Express, detected intense fluxes of ENAs emitted from the subsolar region of Mars. The typical ENA fluxes are (4-7) x [10.sup.5] [cm.sup.-2] [sr.sup.-1] [s.sup.-1] in the energy range 0.3-3 keV. These ENAs are likely to be generated in the subsolar region of the martian exosphere. As the satellite moved away from Mars, the ENA flux decreased while the field of view of the NPD pointed toward the subsolar region. These decreases occurred very quickly with a time scale of a few tens of seconds in two thirds of the orbits. Such a behavior can be explained by the spacecraft crossing a spatially constrained ENA jet, i.e., a highly directional ENA emission from a compact region of the subsolar exosphere. This ENA jet is highly possible to be emitted conically from the subsolar region. Such directional ENAs can result from the anisotropic solar wind flow around the subsolar region, but this can not be explained in the frame of MHD models. Keywords: Mars, atmosphere; Solar wind; Magnetospheres
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- 2006
19. Electron oscillations in the induced martian magnetosphere
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Winningham, J.D., Frahm, R.A., Sharber, J.R., Coates, A.J., Linder, D.R., Soobiah, Y., Kallio, E., Espley, J.R., Lundin, R., Barabash, S., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Scherrer, J.R., Jeffers, S.J., Kataria, D.O., Kozyra, J.U., Luhmann, J.G., Roelof, E.C., Williams, D.J., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Koskinen, H., Sales, T., Riihela, P., Schmidt, W., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Magnetosphere -- Observations ,Solar oscillations -- Observations ,Mars (Planet) -- Environmental aspects ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment flown on the Mars Express (MEX) spacecraft includes the Electron Spectrometer (ELS) as part of its complement. The ELS instrument measures the differential electron flux spectrum in a 128-level logarithmic energy sweep within a time period of 4 s. The orbital path of MEX traverses the martian sheath, cusps, and tail where ELS recorded periodic electron intensity oscillations. These oscillations comprised periodic variations of up to an order of magnitude (peak to valley) in energy flux, with the largest amplitudes in the tens to hundreds of eV range. The observed oscillations displayed periods ranging from minutes down to the instrument sweep resolution of 4 s. In the cases analyzed here, the frequency of the integrated electron energy flux typically peaked between 0.01 and 0.02 Hz. This frequency range is nearly the same as the typical [O.sup.+] gyrofrequency in the magnetosheath, calculated using magnetometer data from Mars Global Surveyor. Due to the motion of the spacecraft, it is unclear if the wave structures observed were permanent standing waves or rather constituted waves propagating past the spacecraft. Keywords: Mars; Magnetosphere
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- 2006
20. Solar wind plasma protrusion into the martian magnetosphere: ASPERA-3 observations
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Dubinin, E., Winningham, D., Franz, M., Woch, J., Lundin, R., Barabash, S., Fedorov, A., Frahm, R., Sharber, J.R., Coates, A.J., Krupp, N., Sauvaud, J.-A., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Thocaven, J.-J., Asamura, K., Curtis, C., Hsieh, K.S., Sandel, B., Koskinen, H., Kallio, E., Riihela, P., Schmidt, W., Sales, T., Kozyra, J., Luhmann, J., McKenna-Lawler, S., Cerulli-Irelli, R., Orsini, S., Maggi, M., Roelof, E., Williams, D., Livi, S., Wurz, P., Bochsler, P., Dierker, C., Grande, M., and Carter, M.
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Solar wind -- Observations ,Magnetosphere -- Observations ,Mars (Planet) -- Environmental aspects ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
The ASPERA-3 experiment onboard the Mars Express spacecraft revealed, near the wake boundary of Mars, a spatially narrow, strip-like plasma structure composed of magnetosheath-like electrons and planetary ions. The peak electron energy often exceeds the peak energy at the bow shock that indicates a significant heating (acceleration) during the structure formation. It is shown that this structure is formed during efficient plasma penetration into the martian magnetosphere in the region near the terminator. The penetration of sheath electrons and their gradual heating (acceleration) is accompanied by a change of the ion composition from a solar wind plasma to a planetary plasma dominated by oxygen ions. A possible mechanism of plasma inflow to the magnetosphere is discussed. Keywords: Mars; Magnetospheres
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- 2006
21. Structure of the martian wake
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Fedorov, A., Budnik, E., Sauvaud, J.-A., Mazelle, C., Barabash, S., Lundin, R., Acuna, M., Holmstrom, M., Grigoriev, A., Yamauchi, M., Andersson, H., Thocaven, J.-J, Winningham, D., Frahm, R., Sharber, J.R., Scherrer, J., Coastes, A.J., Linder, D.R., Kataria, D.O., Kallio, E., Koskines, H., Sales, T., Riihela, P., Schmidt, W., Kozyra, J., Luhmann, J., Roeloff, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Heavy ions -- Observations ,Magnetosphere -- Observations ,Mars (Planet) -- Atmosphere ,Mars (Planet) -- Observations ,Astronomy ,Earth sciences - Abstract
We present the first results from the ion mass analyzer IMA of the ASPERA-3 instrument on-board of Mars Express. More than 200 orbits for May 2004-September 2004 time interval have been selected for the statistical study of the distribution of the atmospheric origin ions in the planetary wake. This study shows that the martian magnetotail consists of two different ion regimes. Planetary origin ions of the first regime form the layer adjacent to the magnetic pile-up boundary. These ions are accelerated to energy greater than 2000 eV and exhibit a gradual decreasing of energy down to the planetary tail. The second plasma regime is observed in the planetary shadow. The heavy ions (considered as planetary ones) are accelerated to the energy of the solar wind protons. Obviously the acceleration mechanism is different for the different plasma regimes. Study of two plasma regimes in the frame referred to the interplanetary magnetic field (IMF) direction (we used MGS magnetometer data to obtain the IMF clock angle) clearly shows their spatial anisotropy. The monoenergetic plasma in the planetary shadow is observed only in the narrow angular sector around the positive direction of the interplanetary electric field. Keywords: Mars; Magnetospheres
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- 2006
22. Mass composition of the escaping plasma at Mars
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Carlsson, E., Fedorov, A., Barabash, S., Budnik, E., Grigoriev, A., Gunell, H., Nilsson, H., Sauvaud, J.-A., Lundin, R., Futaana, Y., Holmstrom, M., Andersson, H., Yamauchi, M., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J., Coates, A.J., Linder, D.R., Kataria, D.O., Kallio, E., Koskinen, H., Sales, T., Riihela, P., Schmidt, W., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Thocaven, J.J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Ionospheric research ,Astronomy ,Earth sciences - Abstract
Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: C[O.sup.+.sub.2]/[O.sup.+] and [O.sup.+.sub.2]/[O.sup.+]. The following ratios averaged over all events and energies were identified: C[O.sup.+.sub.2]/[O.sup.+] = 0.2 and [O.sup.+.sub.2]/[O.sup.+] = 0.9. The values measured are significantly higher, by a factor of 10 for [O.sup.+.sub.2]]/[O.sup.+], than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be [O.sup.+], followed by [O.sup.+.sub.2] and C[O.sup.+.sub.2]. We estimate the loss of C[O.sup.+.sub.2] to be 4.0 x [10.sup.24] s-1 (0.29 kg[s.sup.-1]) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found. Keywords: Ionospheres; Mars, atmosphere
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- 2006
23. Electric fields within the martian magnetosphere and ion extraction: ASPERA-3 observations
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Dubinin, E., Lundin, R., Franz, M., Woch, J., Barabash, S., Fedorov, A., Winningham, D., Krupp, N., Sauvaud, J.-A., Holmstrom, M., Andersson, H., Yamauchi, M., Grigoriev, A., Thocaven, J.-J., Frahm, R., Sharber, J., Asamura, K., Coates, A., Curtis, C., Hsieh, K.S., Sandel, B., Koskinen, H., Kallio, E., Riihela, P., Schmidt, W., Sales, T., Kozyra, J., Luhmann, J., McKennan-Lawler, S., Cerulli-Irelli, R., Orsini, S., Maggi, M., Roelof, E., Williams, D., Livi, S., Wurz, P., Bochsler, P., Dierker, C., Grande, M., and Carter, M.
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Mars (Planet) -- Environmental aspects ,Mars (Planet) -- Observations ,Magnetosphere -- Observations ,Ionosphere -- Observations ,Astronomy ,Earth sciences - Abstract
Observations made by the ASPERA-3 experiment onboard the Mars Express spacecraft found within the martian magnetosphere beams of planetary ions. In the energy (E/q)-time spectrograms these beams are often displayed as dispersive-like, ascending or descending (whether the spacecraft moves away or approach the planet) structures. A linear dependence between energy gained by the beam ions and the altitude from the planet suggests their acceleration in the electric field. The values of the electric field evaluated from ion energization occur close to the typical values of the interplanetary motional electric field. This suggests an effective penetration of the solar wind electric field deep into the martian magnetosphere or generation of large fields within the magnetosphere. Two different classes of events are found. At the nominal solar wind conditions, a 'penetration' occurs near the terminator. At the extreme solar wind conditions, the boundary of the induced magnetosphere moves to a more dense upper atmosphere that leads to a strong scavenging of planetary ions from the dayside regions. Keywords: Mars; Solar wind; Magnetospheres; Ionospheres; Magnetic fields
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- 2006
24. Ionospheric plasma acceleration at Mars: ASPERA-3 results
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Lundin, R., Winningham, D., Barabash, S., Frahm, R.A., Andersson, H., Holmstrom, M., Grigoriev, A., Yamauchi, M., Borg, H., Sharber, J.R., Sauvaud, J.-A., Fedorov, A., Budnik, E., Thocaven, J.-J., Asamura, K., Hayakawa, H., Coates, A.J., Linder, D.R., Kataria, D.O., Curtis, C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Reading, D.H., Koskinen, H., Kallio, E., Riihela, P., Schmidt, W., Sales, T., Kozyra, J., Krupp, N., Woch, J., Franz, M., Luhmann, J., McKennan-Lawler, S., Cerulli-Irelli, R., Orsini, S., Maggi, M., Roelof, E., Williams, D., Livi, S., Brandt, P.C:son, Wurz, P., and Bochsler, P.
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Mars (Planet) -- Observations ,Ionospheric research -- Observations ,Mars probes -- Observations ,Astronomy ,Earth sciences - Abstract
The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on-board the Mars Express spacecraft (MEX) measured penetrating solar wind plasma and escaping/accelerated ionospheric plasma at very low altitudes (250 km) in the dayside subsolar region. This implies a direct exposure of the martian topside atmosphere to solar wind plasma forcing leading to energization of ionospheric plasma. The ion and electron energization and the ion outflow from Mars is surprisingly similar to that over the magnetized Earth. Narrow 'monoenergetic' cold ion beams, ion beams with broad energy distributions, sharply peaked electron energy spectra, and bidirectional streaming electrons are particle features also observed near Mars. Energized martian ionospheric ions ([O.sup.+], [O.sup.+.sub.2], C[O.sup.+.sub.2], etc.) flow in essentially the same direction as the external sheath flow. This suggests that the planetary ion energization couples directly to processes in the magnetosheath/solar wind. On the other hand, the beam-like distribution of the energized plasma implies more indirect energization processes like those near the Earth, i.e., energization in a magnetized environment by waves and/or parallel (to B) electric fields. The general conditions for martian plasma energization are, however, different from those in the Earth's magnetosphere. Mars has a weak intrinsic magnetic field and solar wind plasma may therefore penetrate deep into the dense ionospheric plasma. Local crustal magnetization, discovered by Acuna et al. [Acuna, M.J., Connerey, J., Ness, N., Lin, R., Mitchell, D., Carlsson, C., McFadden, J., Anderson, K., Reme, H., Mazelle, C., Vignes, D., Wasilewski, P., Cloutier, P., 1999. Science 284, 790-793], provide some dayside shielding against the solar wind. On the other hand, multiple magnetic anomalies may also lead to 'hot spots' facilitating ionospheric plasma energization. We discuss the ASPERA-3 findings of martian ionospheric ion energization and present evidences for two types of plasma energization processes responsible for the low- and mid-altitude plasma energization near Mars: magnetic field-aligned acceleration by parallel electric fields and plasma energization by low frequency waves. Keywords: Mars, atmosphere; Ionospheres; Magnetospheres
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- 2006
25. Ion escape at Mars: comparison of a 3-D hybrid simulation with Mars Express IMA/ASPERA-3 measurements
- Author
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Kallio, E., Fedorov, A., Budnik, E., Sales, T., Janhunen, P., Schmidt, W., Koskinen, H., Riihela, P., Barabash, S., Lundin, R., Holmstrom, M., Gunell, H., Brinkfeldt, K., Futaana, Y., Andersson, H., Yamauchi, M., Grigoriev, A., Sauvaud, J.-A., Thocaven, J.-J., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Coates, A.J., Linder, D.R., Kataria, D.O., Kozyra, J., Luhmann, J.G., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., McKenna-Lawler, S., Orsini, S, Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Franz, M., Asamura, K., and Dierker, C.
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Mars (Planet) -- Observations ,Ionospheric electron density -- Measurement ,Solar wind -- Research ,Astronomy ,Earth sciences - Abstract
We have analysed ion escape at Mars by comparing ASPERA-3/Mars Express ion measurements and a 3-D quasi-neutral hybrid model. As Mars Express does not have a magnetometer onboard, the analysed IMA data are from an orbit when the IMF clock angle was possible to determine from the magnetic field measurements of Mars Global Surveyor. We found that fast escaping planetary ions were observed at the place which, according to the 3-D model, is anticipated to contain accelerated heavy ions originating from the martian ionosphere. The direction of the interplanetary magnetic field was found to affect noticeably which regions can be magnetically connected to Mars Express and to the overall 3-D Mars-solar wind interaction. Keywords: Mars, atmosphere; Ionospheres
- Published
- 2006
26. Mapping of the cusp plasma precipitation on the surface of Mercury
- Author
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Massetti, S., Orsini, S., Milillo, A., Mura, A., De Angelis, E., Lammer, H., and Wurz, P.
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Mercury (Planet) -- Research ,Solar wind -- Research ,Astronomy ,Earth sciences - Abstract
The presence of a magnetosphere around Mercury plays a fundamental role on the way the solar wind plasma interacts with the planet. Since the observations suggest that Mercury should occupy a large fraction of its magnetosphere and because of lack of an atmosphere, significant differences in solar wind-magnetosphere coupling are expected to exist with respect to the Earth case. On the basis of a modified Tsyganenko T96 model we describe the geometry of the magnetic field that could characterize Mercury, and its response to the variations of the impinging solar wind and of the interplanetary magnetic field. The investigation is focused on the shape and dimension of the open magnetic field regions (cusps) that allow the direct penetration of magnetosheath plasma through the exosphere of Mercury, down to its surface. The precipitating particle flux and energy are evaluated as a function of the open field line position, according to different solar wind conditions. A target of this study is the evaluation of the sputtered particles from the crust of the planet, and their contribution to the exospheric neutral particle populations. Such estimates are valuable in the frame of a neutral particle analyser to be proposed on board of the ESA/BepiColombo mission. Keywords: Mercury; Magnetosphere; Solar wind; Magnetic field
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- 2003
27. The variability of Mercury's exosphere by particle and radiation induced surface release processes
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Lammer, H., Wurz, P., Patel, M.R., Killen, R., Kolb, C., Massetti, S., Orsini, S., and Milillo, A.
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Mercury (Planet) -- Research ,Astronomy ,Earth sciences - Abstract
Mercury's close orbit around the Sun, its weak intrinsic magnetic field and the absence of an atmosphere ([P.sub.surface] < 1 x [10.sup.-8] Pa) results in a strong direct exposure of the surface to energetic ions, electrons and UV radiation. Thermal processes and particle-surface-collisions dominate the surface interaction processes leading to surface chemistry and physics, including the formation of an exosphere (N [less than or equal to] [10.sup.14] [cm.sup.-2]) in which gravity is the dominant force affecting the trajectories of exospheric atoms. NASA's Mariner 10 spacecraft observed the existence of H, He, and O in Mercury's exosphere. In addition, the volatile components Na, K, and Ca have been observed by ground based instrumentation in the exosphere. We study the efficiency of several particle surface release processes by calculating stopping cross-sections, sputter yields and exospheric source rates. Our study indicates surface sputter yields for Na between values of about 0.27 and 0.35 in an energy range from 500 eV up to 2 keV if [Na.sup.+] ions are the sputter agents, and about 0.037 and 0.082 at an energy range between 500 eV up to 2 keV when [H.sup.+] are the sputter agents and a surface binding energy of about 2 eV to 2.65 eV. The sputter yields for Ca are about 0.032 to 0.06 and for K atoms between 0.054 to 0.1 in the same energy range. We found a sputter yield for O atoms between 0.025 and 0.04 for a particle energy range between 500 eV up to 2 keV protons. By taking the average solar wind proton surface flux at the open magnetic field line area of about 4 x [10.sup.8] [cm.sup.-2] [s.sup.-1] calculated by Massetti et al. (2003, Icarus, in press) the resulting average sputtering flux for O is about 0.8-1.0 x [10.sup.7] [cm.sup.-2] [s.sup.-1] and for Na approximately 1.3-1.6 x [10.sup.5] [cm.sup.-2] [s.sup.-1] depending on the assumed Na binding energies, regolith content, sputtering agents and solar activity. By using lunar regolith values for K we obtain a sputtering flux of about 1.0-1.4 x [10.sup.4] [cm.sup.-2] [s.sup.-1]. By taking an average open magnetic field line area of about 2.8 x [10.sup.16] [cm.sup.2] modelled by Massetti et al. (2003, Icarus, in press) we derive an average surface sputter rate for Na of about 4.2 x [10.sup.21] [s.sup.-1] and for O of about 2.5 x [10.sup.23] [s.sup.-1]. The particle sputter rate for K atoms is about 3.0 x [10.sup.20] [s.sup.-1] assuming lunar regolith composition for K. The sputter rates depend on the particle content in the regolith and the open magnetic field line area on Mercury's surface. Further, the surface layer could be depleted in alkali. A UV model has been developed to yield the surface UV irradiance at any time and latitude over a Mercury year. Seasonal and diurnal variations are calculated, and Photon Stimulated Desorption (PSD) fluxes along Mercury's orbit are evaluated. A solar UV hotspot is created towards perihelion, with significant average PSD particle release rates and Na fluxes of about 3.0 x [10.sup.6] [cm.sup.-2] [s.sup.-1]. The average source rates for Na particles released by PSD are about 1 x [10.sup.24] [s.sup.-1]. By using the laboratory obtained data of Madey et al. (1998, J. Geophys. Res. 103, 5873-5887) for the calculation of the PSD flux of K atoms we get fluxes in the order of about [10.sup.4] [cm.sup.-2] [s.sup.-1] along Mercury's orbit. However, these values may be to high since they are based on idealized smooth surface conditions in the laboratory and do not include the roughness and porosity of Mercury's regolith. Further, the lack of an ionosphere and Mercury's small, temporally and spatially highly variable magnetosphere can result in a large and rapid increase of exospheric particles, especially Na in Mercury's exosphere. Our study suggests that the average total source rates for the exosphere from solar particle and radiation induced surface processes during quiet solar conditions may be of the same order as particles produced by micrometeoroid vaporization. We also discuss the capability of in situ measurements of Mercury's highly variable particle environment by the proposed NPA-SERENA instrument package on board ESA's BepiColombo Mercury Planetary Orbiter (MPO).
- Published
- 2003
28. Erratum to “Observations of magnetic anomaly signatures in Mars Express ASPERA-3 ELS data” [Icarus 182 (2006) 396–405]
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Soobiah, Y., Coates, A.J., Linder, D.R., Kataria, D.O., Winningham, J.D., Frahm, R.A., Sharber, J.R., Scherrer, J.R., Barabash, S., Lundin, R., Holmström, M., Andersson, H., Yamauchi, M., Grigoriev, A., Kallio, E., Koskinen, H., Säles, T., Riihelä, P., Schmidt, W., Kozyra, J., Luhmann, J., Roelof, E., Williams, D., Livi, S., Curtis, C.C., Hsieh, K.C., Sandel, B.R., Grande, M., Carter, M., Sauvaud, J.-A., Fedorov, A., Thocaven, J.-J., McKenna-Lawler, S., Orsini, S., Cerulli-Irelli, R., Maggi, M., Wurz, P., Bochsler, P., Krupp, N., Woch, J., Fränz, M., Asamura, K., and Dierker, C.
- Published
- 2007
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