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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.04.012 Byline: F. Duru (a), D.A. Gurnett (a), J.D. Winningham (b), R. Frahm (b), R. Modolo (a) Keywords: Ionospheres; Mars; Solar wind Abstract: The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express (MEX) spacecraft is capable of measuring ionospheric electron density by the use of two main methods: remote radar sounding and from the excitation of local plasma oscillations. The frequency of the locally excited electron plasma oscillations is used to measure the local electron density. However, plasma oscillations are not observed when the plasma flow velocity is higher than about 160km/s, which occurs mainly in the solar wind and magnetosheath. As a consequence, in many passes, there is a sudden disappearance of the plasma oscillations as the spacecraft enters into the magnetosheath. This fact allows us to identify a flow velocity boundary on the dayside, between the ionosphere of Mars and the shocked solar wind. This paper summarizes the results of the measurement of 552 orbits mostly over a period from August 4, 2005 to August 17, 2007. The boundary points found using MARSIS have been verified by measurements from the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) Electron Spectrometer (ELS) instrument on Mars Express. The average position of the flow velocity boundary is compared to flow velocity simulations computed using hybrid model and other boundaries. The boundary altitude is slightly lower than the magnetic pile-up boundary determined using Phobos 2 and Mars Global Surveyor (MGS) crossings, but it is in good agreement with the induced magnetospheric boundary determined by ASPERA-3. Investigation of the effect of the crustal magnetic field revealed that the flow velocity boundary is raised at the locations with strong crustal magnetic fields. Author Affiliation: (a) Dept. of Physics and Astronomy, University of Iowa, Iowa City, IA 52240, USA (b) Southwest Research Inst., PO Drawer 28510, San Antonio, TX 28510, USA Article History: Received 5 September 2008; Revised 3 April 2009; Accepted 4 April 2009

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

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

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

Abstract: Thin copper-oxide layers formed on Cu-metal due to the exposure to ambient air at short and long timescales were investigated by means of reflection mode grazing incidence X-ray absorption spectroscopy under specular and non-specular conditions. The quantitative evaluation of near edge X-ray absorption, as well as specular and non-specular EXAFS data measured for various different grazing angles show that the oxide film is best described by a model structure consisting of a duplex type oxide layer with an outer layer of CuO in contact with the gas atmosphere and an inner Cu2O layer at the interface to the underlying Cu-metal. [Copyright &y& Elsevier]

Abstract: We report the measurements of the response of a delta-doped Charge Coupled Device (CCD) in imaging mode to beams of charged and neutral particles. That is, the detector imaged the incident beam over its 1024×1024 pixels, integrating the number of particles counted in each pixel during the exposure period. In order to count individual particles the exposure time would have had to be reduced considerably compared to the typical ⩾5s used in these studies. Our CCD thus operated in a different manner than do conventional particle detectors such as the CEM and MCP that normally are used in a particle counting mode. The measurements were carried out over an energy range from 0.8 to 30keV. The species investigated include H, H+, He+, N+, N2 +, and Ar+. The energy and ion mass covered wider ranges than previous measurements for the CCD. The results of these measurements show, as in the case of the previous measurement, for a given ion the CCD response increases with energy and for a given particle energy the response decreases with increasing mass of the particle. These results are in agreement with predictions of the theory of the range of ions in solids. The results also show the possibility for the application of the delta doped CCD as a detector for low energy particle measurements for space plasma physics applications. [Copyright &y& Elsevier]

Abstract: Recently aurora-type UV emissions were discovered on the nightside of Mars [Bertaux, J.-L., Leblanc, F., Witasse, O., et al., 2005. Discovery of an aurora on Mars. Nature 439, doi:10.1038/nature03603]. It was suggested that these emissions are produced by suprathermal electrons with energies of tens of eV, rather than by the electrons with spectra peaked above 100eV [Leblanc, F., Witasse, O., Winningham J., et al., 2006. Origin of the martian aurora observed by spectroscopy for investigation of characteristics of the atmosphere of Mars (SPICAM) onboard Mars Express. J. Geophys. Res. 111, A09313, doi:10.1029/2006JA011763]. In this paper we present observations of fluxes of suprathermal electrons (–100eV) on the Martian nightside by the ASPERA-3 experiment onboard the Mars Express spacecraft. Narrow spikes of suprathermal electrons are often observed in energy-time spectrograms of electron fluxes at altitudes between 250 and 600km. These spikes are spatially organized and form narrow strips in regions with strong upward or downward crustal magnetic field. The values of electron fluxes in such events generally could explain the observed auroral UV emissions although a question of their origin (transport from the dayside or local precipitation) remains open. [Copyright &y& Elsevier]

The near surface structure of Li-intercalated rutile and anatase TiO2 electrodes was investigated with grazing incidence reflection mode XANES spectroscopy. Though real in situ experiments are not feasible due to the extremely strong parasitic absorption of the electrolyte, a new cell was constructed. It enables the electrochemical processing of samples which are sensitive to oxidation as well as it permits reflection mode X-ray experiments after the controlled emersion of the electrodes from the electrolyte. Our results show that even Li containing electrolytes and Li intercalated electrodes can be processed inside the cell. During the electrochemical Li intercalation in rutile, only a thin surface layer of some few nm thickness was changed by the lithiation. The structure of this layer seems to have a similar structure compared to the Li titanate Li0.6TiO2 (space group imma). The anatase layer could be fully intercalated showing the characteristic Li-titanate structure. In the surface region the Li intercalation results in an edge shift that corresponds to Ti3+ states in contrast to the Ti3.4+ states in the bulk. [Copyright &y& Elsevier]

The near surface structure of Li-intercalated rutile TiO2-electrodes was investigated with grazing incidence reflection mode XAFS (EXAFS and XANES) spectroscopy. Though real in situ experiments are not feasible due to the extremely strong parasitic absorption of the electrolyte, a new cell was constructed which enables the electrochemical processing of samples which are sensitive towards oxidation as well as it permits reflection mode X-ray experiments after the controlled emersion of the electrodes from the electrolyte. Our results show that even Li containing electrolytes and Li intercalated electrodes can be processed inside the cell. During the electrochemical Li intercalation in rutile, only a thin surface layer of some few nm thickness was changed by the lithiation, the thickness of which is increasing with decreasing intercalation potential. A detailed XANES and EXAFS data analysis gives strong evidence that the structure of this layer is identical compared to that of polycrystalline Li-titanate Li0.6TiO2 (anatase type space group imma). [Copyright &y& Elsevier]