Magnetized Mars: Transformation of Earth-like magnetosphere to Venus-like induced magnetosphere

Using a global numerical model, we have studied how the present Martian magnetosphere may have looked in the past when the planet had a global intrinsic magnetic field. A Mars version (HYB-Mars) of the self-consistent quasi-neutral hybrid model was used which treats the ions as particles and the electrons as a massless charge-neutralizing fluid. We compare four cases where an intrinsic dipole magnetic field was 0 nT (the present situation), 10, 30, and 60 nT at the surface of Mars along the magnetic equator. We find that the 10 nT dipolar magnetic field already results in a magnetosphere which in many respects is more Earth-like than, a non-magnetized, “induced” magnetosphere. However, the 10 nT dipole magnetosphere is still relatively strongly connected to the interplanetary magnetic field, while the 30 nT dipole case, and especially the 60 nT dipole case, results in a magnetosphere whose morphology is determined predominantly by the Martian intrinsic magnetic field. A change of the magnetosphere due to a decreasing dipole magnetic field strength from 60 to 0 nT could have happened during the history of Mars when a globally magnetized Mars turned into the present, globally non-magnetized, planet.     

Comparison of Recoveries by Lead Fire Assay and Nickel Sulfide Fire Assay in the Determination of Gold/ Platinum/ Palladium and Rhenium in Sulfide Ore Samples

We compared the recovery of gold, palladium and platinum by two fire assaying procedures, using nickel sulfide and lead as collectors. The presence of appreciable amounts of sulfide minerals in the sample caused interferences in both procedures. An in-house reference sample, a reference sample of high-grade sulfide ore and samples of high sulfide content from the Recsk porphyry copper ore in Hungary were analysed by both methods. The elements were determined by inductively coupled plasma-atomic emission (ICP-AES) and/or inductively coupled plasma-mass spectrometry (ICP-MS). It was found that for the sulfide ore samples, the recoveries of Au and Pd are sometimes lower by nickel sulfide fire assay than by lead fire assay. Recovery of Re by nickel sulfide fire assay was found to be low: the average recovery of five repeated analyses of the reference sample NIST SRM 330 was 9% with a relative standard deviation of 48%. Increasing the amount of S in the fusion flux gave better recovery.     

Location of the bow shock and ion composition boundaries at Venus—initial determinations from Venus Express ASPERA-4

For the first time since 1992 when the Pioneer Venus Orbiter (PVO) ceased to operate, there is again a plasma instrument in orbit around Venus, namely the ASPERA-4 flown on Venus Express (inserted into an elliptical polar orbit about the planet on April 11, 2006). In this paper we report on measurements made by the ion and electron sensors of ASPERA-4 during their first five months of operation and, thereby, determine the locations of both the Venus bow shock (BS) and the ion composition boundary (ICB) under solar minimum conditions. In contrast to previous studies based on PVO data, we employ a 3-parameter fit to achieve a realistic shape for the BS. We use a different technique to fit the ICB because this latter boundary cannot be represented by a conic section. Additionally we investigate the dependence of the location of the BS on solar wind ram pressure (based on ASPERA-4 solar wind data) and solar EUV flux (using a proxy from Earth).     

A comparison of global models for the solar wind interaction with Mars

We present initial results from the first community-wide effort to compare global plasma interaction model results for Mars. Seven modeling groups participated in this activity, using MHD, multi-fluid, and hybrid assumptions in their simulations. Moderate solar wind and solar EUV conditions were chosen, and the conditions were implemented in the models and run to steady state. Model output was compared in three ways to determine how pressure was partitioned and conserved in each model, the location and asymmetry of plasma boundaries and pathways for planetary ion escape, and the total escape flux of planetary oxygen ions. The two participating MHD models provided similar results, while the five sets of multi-fluid and hybrid results were different in many ways. All hybrid results, however, showed two main channels for oxygen ion escape (a pickup ion ‘plume’ in the hemisphere toward which the solar wind convection electric field is directed, and a channel in the opposite hemisphere of the central magnetotail), while the MHD models showed one (a roughly symmetric channel in the central magnetotail). Most models showed a transition from an upstream region dominated by plasma dynamic pressure to a magnetosheath region dominated by thermal pressure to a low altitude region dominated by magnetic pressure. However, calculated escape rates for a single ion species varied by roughly an order of magnitude for similar input conditions, suggesting that the uncertainties in both the current and integrated escape over martian history as determined by models are large. These uncertainties are in addition to those associated with the evolution of the Sun, the martian dynamo, and the early atmosphere, highlighting the challenges we face in constructing Mars’ past using models.     

Demonstration of a virtual active hyperspectral LiDAR in automated point cloud classification

In this paper, a measurement system for the acquisition of a virtual hyperspectral LiDAR dataset is presented. As commercial hyperspectral LiDARs are not yet available, the system provides a novel type of data for the testing and developing of future hyperspectral LiDAR algorithms. The measurement system consists of two parts: first, backscattered reflectance spectra are collected using a spectrometer and a cutting-edge technology, white-light supercontinuum laser source; second, a commercial monochromatic LiDAR system is used for ranging. A virtual hyperspectral LiDAR dataset is produced by data fusion. Such a dataset was collected on a Norway spruce (Picea abies) sample. The performance of classification was tested using an experimental hyperspectral algorithm based on a novel combination of the Spectral Correlation Mapper and a region growing algorithm. The classifier was able to automatically distinguish between needles, branches and background, in other words, perform a difficult task using only traditional TLS data.     

National and international cooperation at Kevo Subarctic Research Station,Finnish Lapland

GeoJournal - Because the facilities for research work in many scientific fields are good in the circumpolar north, every effort to widen cooperation between research institutes should be supported....     

Morphology of the magnetic field near Mars and the role of the magnetic crustal anomalies: Dayside region

We have studied the morphology of magnetic flux tubes near Mars and have found that the magnetic field lines near Mars forms a wing-like flux tube structure downstream of the bow shock. These magnetic flux tubes are concentrated close to the plane, which contains the center of Mars, the interplanetary magnetic field, and the Mars-Sun line. Regions near Mars on dayside were found to be magnetically connected to the region downstream of the bow shock in the sunlight. The study suggests that the photoelectrons that were observed on the nightside far from Mars are associated with magnetic field lines which are, or which were, magnetically connected to the Martian dayside region.