A three-dimensional analytical tool for modeling reactive transport

In this note, we present a public domain analytical reactive transport modeling tool (ART3D, version 2.0). The tool is developed in FORTRAN and can be used for solving a system of a set of partial differential equations coupled with a first-order reaction network. ART3D uses a novel analytic solution technique proposed by Clement. The new software includes options for performing Monte Carlo simulations and automated parameter estimation.     

Lamprophyres and carbonatitic lamprophyres related to rifting in the Labrador Sea

Lamprophyre dykes intruded into the Archaean of South West Greenland are believed to coincide with the early stages of rifting in the Labrador Sea area. They yield K/Ar and fission-track ages of 150–115 m.y. which are similar to the apatite fission-track ages from the host rocks but which predate the formation of ocean floor. The strongly undersaturated, often K-rich magmas exhibit the chemical characters of modern rift volcanism with many types present, and the paragenesis and their mineral chemistry reflect the composition and the different physical conditions in the evolution of the lamprophyres. Crystal fractionation and carbonate unmixing are believed to be the main factors in the evolution of the lamprophyre dykes from a primary mantle derived magma. However, the most undersaturated and evolved lamprophyre types cannot be explained in this way, and more complex models must be considered.     

A full-sky prediction of the Sunyaev–Zeldovich effect from diffuse hot gas in the local universe and the upper limit from the WMAP data

We use the Point Source Catalogue Redshift Survey galaxy redshift catalogue combined with constrained simulations based on the IRAS 1.2-Jy galaxy density field to estimate the contribution of hot gas in the local universe to the Sunyaev–Zeldovich (SZ) effect on a large scale. We produce a full-sky healpix map predicting the SZ effect from clusters as well as diffuse hot gas within  80  h ⁻¹ Mpc  . Performing cross-correlation tests between this map and the WMAP data in pixel, harmonic and wavelet space we can put an upper limit on the effect. We conclude that the SZ effect from diffuse gas in the local universe cannot be detected in current cosmic microwave background (CMB) data and is not a large-scale contaminating factor  (ℓ < 60)  in studies of CMB angular anisotropies. We derive an upper limit for the mean temperature decrement of  Δ T < 0.33 μK  at the 2σ confidence level for the 61-GHz frequency channel. However, for future high-sensitivity experiments observing at a wider range of frequencies, the predicted large-scale SZ effect could be of importance.     

Studies of Laser-Driven Radiative Blast Waves

We have performed two sets of experiments looking at laser-driven radiating blast waves. In the first set of experiments the effect of a drive laser’s passage through a background gas on the hydrodynamical evolution of blast waves was examined. The laser’s passage heated a channel in the gas, creating a region where a portion of the blast wave front had an increased velocity, leading to the formation of a bump-like protrusion on the blast wave. The second set of experiments involved the use of regularly spaced wire arrays used to induce perturbations on a blast wave surface. The decay of these perturbations as a function of time was measured for various wave number perturbations and found to be in good agreement with theoretical predictions.     

The Electrostatic Lunar Dust Analyzer (ELDA) for the detection and trajectory measurement of slow-moving dust particles from the lunar surface

Micron and submicron-sized dust particles can be lifted from the lunar surface due to continual micrometeoroid bombardment and electrostatic charging. The characteristics of these dust populations are of scientific interest and engineering importance for the design of future equipment to operate on the lunar surface. The mobilized grains are expected to have a low velocity, which makes their detection difficult by traditional methods that are based on momentum transfer or impact energy. We describe a newly developed instrument concept, the Electrostatic Lunar Dust Analyzer (ELDA), which utilizes the charge on the dust for detection and analysis. ELDA consists of an array of wire electrodes combined with an electrostatic deflection field region, and measures the mass, charge, and velocity vector of individual dust grains. The first basic prototype of the ELDA instrument has been constructed, tested and characterized in the laboratory. The instrument is set up to measure over a velocity range 1–100 m/s and is sensitive to particles from an approximate mass range from 2×10⁻¹⁶ to 10⁻¹¹ kg, depending on the charge state and velocity.     

Cassini UVIS observations of Jupiter's auroral variability

The Cassini spacecraft Ultraviolet Imaging Spectrograph (UVIS) obtained observations of Jupiter's auroral emissions in H₂ band systems and H Lyman-α from day 275 of 2000 (October 1), to day 81 of 2001 (March 22). Much of the globally integrated auroral variability measured with UVIS can be explained simply in terms of the rotation of Jupiter's main auroral arcs with the planet. These arcs were also imaged by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope (HST). However, several brightening events were seen by UVIS in which the global auroral output increased by a factor of 2-4. These events persisted over a number of hours and in one case can clearly be tied to a large solar coronal mass ejection event. The auroral UV emissions from these bursts also correspond to hectometric radio emission (0.5-16 MHz) increases reported by the Galileo Plasma Wave Spectrometer (PWS) and Cassini Radio and Plasma Wave Spectrometer (RPWS) experiments. In general, the hectometric radio data vary differently with longitude than the UV data because of radio wave beaming effects. The 2 largest events in the UVIS data were on 2000 day 280 (October 6) and on 2000 days 325-326 (November 20-21). The global brightening events on November 20-21 are compared with corresponding data on the interplanetary magnetic field, solar wind conditions, and energetic particle environment. ACE (Advanced Composition Explorer) solar wind data was numerically propagated from the Earth to Jupiter with an MHD code and compared to the observed event. A second class of brief auroral brightening events seen in HST (and probably UVIS) data that last for ∼2 min is associated with auroral flares inside the main auroral ovals. On January 8, 2001, from 18:45-19:35 UT UVIS H₂ band emissions from the north polar region varied quasiperiodically. The varying emissions, probably due to auroral flares inside the main auroral oval, are correlated with low-frequency quasiperiodic radio bursts in the 0.6-5 kHz Galileo PWS data.     

The Planetary Fourier Spectrometer (PFS) onboard the European Mars Express mission

The Planetary Fourier Spectrometer (PFS) for the Mars Express mission is an infrared spectrometer optimised for atmospheric studies. This instrument has a short wave (SW) channel that covers the spectral range from 1700 to (1.2-) and a long-wave (LW) channel that covers 250- (5.5-). Both channels have a uniform spectral resolution of . The instrument field of view FOV is about 1.6^° (FWHM) for the Short Wavelength channel (SW) and 2.8^° (FWHM) for the Long Wavelength channel (LW) which corresponds to a spatial resolution of 7 and 12 km when Mars is observed from an height of 250  km. PFS can provide unique data necessary to improve our knowledge not only of the atmosphere properties but also about mineralogical composition of the surface and the surface-atmosphere interaction.The SW channel uses a PbSe detector cooled to 200-220 K while the LW channel is based on a pyroelectric (L_iT_aO₃) detector working at room temperature. The intensity of the interferogram is measured every 150 nm of physical mirrors displacement, corresponding to 600 nm optical path difference, by using a laser diode monochromatic light interferogram (a sine wave), whose zero crossings control the double pendulum motion. PFS works primarily around the pericentre of the orbit, only occasionally observing Mars from large distances. Each measurements take 4 s, with a repetition time of 8.5 s. By working roughly 0.6 h around pericentre, a total of 330 measurements per orbit will be acquired 270 looking at Mars and 60 for calibrations. PFS is able to take measurements at all local times, facilitating the retrieval of surface temperatures and atmospheric vertical temperature profiles on both the day and the night side.     

Albedo models for the residual south polar cap on Mars: Implications for the stability of the cap under near-perihelion global dust storm conditions

It is uncertain whether the residual (perennial) south polar cap on Mars is a transitory or a permanent feature in the current Martian climate. While there is no firm evidence for complete disappearance of the cap in the past, clearly observable changes have been documented. Observations suggest that the perennial cap lost more CO₂ material in the spring/summer season prior to the Mariner 9 mission than in those same seasons monitored by Viking and Mars Global Surveyor. In this paper we examine one process that may contribute to these changes—the radiative effects of a planet encircling dust storm that starts during late Martian southern spring on the stability of the perennial south polar cap. To approach this, we model the radiative transfer through a dusty planetary atmosphere bounded by a sublimating CO₂ surface.A critical parameter for this modeling is the surface albedo spectrum from the near-UV to the thermal-IR, which was determined from both space-craft and Earth-based observations covering multiple wavelength regimes. Such a multi-wavelength approach is highly desirable since one spectral band by itself cannot tightly constrain the three-parameter space for polar surface albedo models, namely photon “scattering length” in the CO₂ ice and the amounts of intermixed water and dust.Our results suggest that a planet-encircling dust storm with onset near solstice can affect the perennial cap's stability, leading to advanced sublimation in a “dusty” year. Since the total amount of solid CO₂ removed by a single storm may be less than the total CO₂ thickness, a series of dust storms would be required to remove the entire residual CO₂ ice layer from the south perennial cap.     

Cassini UVIS observations of Europa's oxygen atmosphere and torus

Observations of the Europa environment using the Cassini UltraViolet Imaging Spectrograph (UVIS) show the presence of an extended atomic oxygen atmosphere in addition to the bound molecular oxygen atmosphere first detected by Hubble Space Telescope in 1994 [D.T. Hall, D.F. Strobel, P.D. Feldman, M.A. McGrath, H.A. Weaver, 1995, Detection of an oxygen atmosphere on Jupiter's moon Europa, Nature 373, 677-679]. The atomic oxygen measurement provides a direct constraint on the sputtering and loss of Europa's water ice surface and the interaction of Europa's atmosphere with Jupiter's magnetosphere. We derive a loss rate for O₂ based on the emission rate of the OI 1356 Å multiplet. UVIS detected substantial variability in the oxygen emission from Europa's oxygen atmosphere that we attribute to the viewing geometry. B.H. Mauk, D.G. Mitchell, S.M. Krimigis, E.C. Roelof, C.P. Paranicas [2003, Energetic neutral atoms from a trans-Europa gas torus at Jupiter, Nature 421, 920-922] inferred the presence of a torus of neutral gas at Europa's orbit based on Cassini's energetic neutral atom (ENA) image of the Jupiter system acquired with the Magnetospheric Imaging Instrument (MIMI), with the most likely torus constituents being hydrogen and oxygen species sputtered from Europa. Cassini UVIS data rule out O and O₂ as the possible torus species reported by Mauk et al. however, unless the torus density is so low that it is undetectable by UVIS (less than 8 atoms / cm³). The UVIS observations indicate the presence of atomic hydrogen and possibly other species, but a full analysis is deferred to a following paper. The hydrogen in the present observations shows a local-time asymmetry and complex spatial distribution.     

Laboratory Simulations of Supernova Shockwave Propagation

Supernovae launch spherical shocks into the circumstellar medium (CSM). These shocks have high Mach numbers and may be radiative. We have created similar shocks in the laboratory by focusing laser pulses onto the tip of a solid pin surrounded by ambient gas; ablated material from the pin rapidly expands and launches a shock through the surrounding gas. Laser pulses were typically 5 ns in duration with ablative energies ranging from 1–150 J. Shocks in ambient gas pressures of ~1 kPa were observed at spatial scales of up to 5 cm using optical cameras with schlieren. Emission spectroscopy data were obtained to infer electron temperatures (< 10 eV). In this experiment we have observed a new phenomena; at the edge of the radiatively heated gas ahead of the shock, a second shock forms. The two expanding shocks are simultaneously visible for a time, until the original shock stalls from running into the heated gas. The second shock remains visible and continues to expand. A minimum condition for the formation of the second shock is that the original shock is super-critical, i.e., the temperature distribution ahead of the original shock has an inflexion point. In a non-radiative control experiment the second shock does not form. We hypothesize that a second shock could form in the astrophysical case, possibly in radiative supernova remnants such as SN1993J, or in shock-CSM interaction.