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Abstract. Mercury's sodium atmosphere is known to be highly variable both temporally and spatially. During a week-long period from November 13 to 20, 1997, the total sodium content of the Hermean atmosphere increased by a factor of 3, and the distribution varied daily. We demonstrate a mechanism whereby these rapid variations could be due to solar wind-magnetosphere interactions. We assume that photon-stimulated desorption and meteoritic vaporization are the active source processes on the first (quietest) day of our observations. Increased ion sputtering results whenever the magnetosphere opens in response to a southward interplanetary magnetic field (IMF) or unusually large solar wind dynamic pressure. The solar wind dynamic pressure at Mercury as inferred by heliospheric radial tomography increased by a factor of 20 during this week, while the solar EUV flux measured by the Solar EUV Monitor (SEM) instrument on board the Solar and Heliospheric Observatory (SOHO) increased by 20%. While impact vaporization provides roughly 25% of the source, it is uniformly distributed and varies very little during the week. The variations seen in our data are not related to Caloris basin, which remained in the field of view during the entire week of observations. We conclude that increased ion sputtering resulting from ions entering the cusp regions is the probable mechanism leading to large rapid increases in the sodium content of the exosphere. While both the magnitude and distribution of the observed sodium can be reproduced by our model, in situ measurements of the solar wind density and velocity, the magnitude and direction of the interplanetary magnetic field, and Mercury's magnetic moments are required to confirm the results.

[1] We present the first clear observations of an Earthdirected interplanetary disturbance tracked by the Solar Mass Ejection Imager (SMEI). We find that this event can be related to two halo CMEs seen at the Sun about 2 days earlier, and which merged in transit to 1 AU. The disturbance was seen about 16 hours before it reached Earth, and caused a severe geomagnetic storm at the time which would have been predicted had SMEI been operating as a real-time monitor. It is concluded that SMEI is capable of giving many hours advance warning of the possible arrival of interplanetary disturbances.

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We present the results from modeling the coronal mass ejection (CME) properties that have an effect on the Faraday rotation (FR) signatures that may be measured with an imaging radio antenna array such as the Murchison Widefield Array (MWA). These include the magnetic flux rope orientation, handedness, magnetic-field magnitude, velocity, radius, expansion rate, electron density, and the presence of a shock/sheath region. We find that simultaneous multiple radio source observations (FR imaging) can be used to uniquely determine the orientation of the magnetic field in a CME, increase the advance warning time on the geoeffectiveness of a CME by an order of magnitude from the warning time possible from in-situ observations at L 1 , and investigate the extent and structure of the shock/sheath region at the leading edge of fast CMEs. The magnetic field of the heliosphere is largely "invisible" with only a fraction of the interplanetary magnetic-field lines convecting past the Earth; remote sensing the heliospheric magnetic field through FR imaging from the MWA will advance solar physics investigations into CME evolution and dynamics.

The Solar Mass Ejection Imager (SMEI) observes the increased brightness from the density enhancements behind interplanetary shocks that are also observed in situ near the Earth. We use the University of California, San Diego (UCSD) time?dependent three?dimensional (3D) reconstruction technique to map the extents of these density enhancements. Here, we examine shock?density enhancements associated with several well?known interplanetary coronal mass ejections (ICMEs) including those on 30 May 2003 and on 21 January 2005. We compare these densities with reconstructed velocities from the Solar?Terrestrial Environment Laboratory (STELab) interplanetary scintillation (IPS) observations for the 30 May 2003 ICME, and show the shock is present at the front edge of the reconstructed high speed solar wind. The SMEI analyses certify that the brightness enhancements observed behind shocks identified and measured in situ near Earth are a direct response to the plasma density enhancements that follow the shocked plasma

Aims. We develop a novel way of finding total mass density profiles in Sersic ellipticals, to about 3 times the major axis effective radius, using no other information other than what is typically available for distant galaxies, namely the observed surface brightness distribution and the central velocity dispersion σ 0 . Methods. The luminosity density profile of the observed galaxy is extracted by deprojecting the measured brightness distribution and scaling it by a fiduciary, step-function shaped, raw mass-to-light ratio profile (M/L). The resulting raw, discontinuous, total, 3-D mass density profile is then smoothed according to a proposed smoothing prescription. The parameters of this raw M/L are characterised by implementing the observables in a model-based study. Results. The complete characterisation of the formalism is provided as a function of the measurements of the brightness distribution and σ 0 . The formalism, thus specified, is demonstrated to yield the mass density profiles of a suite of test galaxies and is successfully applied to extract the gravitational mass distribution in NGC 3379 and NGC 4499, out to about 3 effective radii.