The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events

We discuss the diagnostic potential of high cadence ultraviolet spectral data when transient ionization is considered. For this we use high cadence UV spectra taken during the impulsive phase of a solar flares (observed with instruments on-board the Solar Maximum Mission) which showed excellent correspondence with hard X-ray pulses. The ionization fraction of the transition region ion O V and in particular the contribution function for the O V 1371A line are computed within the Atomic Data and Analysis Structure, which is a collection of fundamental and derived atomic data and codes which manipulate them. Due to transient ionization, the O V 1371A line is enhanced in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature than in ionization equilibrium. The rise time and enhancement factor depend mostly on the electron density. The fractional increase in the O V 1371A emissivity due to transient ionization can reach a factor of 2--4 and can explain the fast response in the line flux of transition regions ions during the impulsive phase of flares solely as a result of transient ionization. This technique can be used to diagnostic the electron temperature and density of solar flares observed with the forth-coming Interface Region Imaging Spectrograph.Comment: 18 pages, 6 figure

Western oceanus procellarum as seen by c1xs on chandrayaan-1

We present the analysis of an X-ray fluorescence (XRF) observation of the western part of Oceanus Procellarum on the Moon’s nearside made by the Chandrayaan-1 X-ray Spectrometer on 10th February 2009. Through forward modelling of the X-ray spectra, we provide estimates of the MgO/SiO2 and Al2O3/SiO2 ratios for seven regions along the flare’s ground track. These results are combined with FeO and TiO2 contents derived from Clementine multispectral reflectance data in order to investigate the compositional diversity of this region of the Moon. The ground track observed consists mainly of low-Ti basaltic units, and the XRF data are largely consistent with this expectation. However, we obtain higher Al2O3/SiO2 ratios for these units than for most basalts in the Apollo sample collection. The widest compositional variation between the different lava flows is in wt% FeO content. A footprint that occurs in a predominantly highland region, immediately to the north of Oceanus Procellarum, has a composition that is consistent with mixing between low-Ti mare basaltic and more feldspathic regoliths. In contrast to some previous studies, we find no evidence for systematic differences in surface composition, as determined through X-ray and gamma-ray spectroscopy techniques

Numerical simulations of astrophysical cyclotron-maser emission

[Abstract unavailable

Cyclotron maser radiation from astrophysical shocks

One of the most popular coherent radio emission mechanisms is electron cyclotron maser instability. In this article we demonstrate that electron cyclotron maser emission is directly associated with particular types of charged particle acceleration such as turbulence and shocks commonly inferred in astrophysical plasmas

In-situ superconducting YBa2Cu3O7 thin films grown by ion beam co-deposition

The authors present superconducting YBa2C3O7 (YBCO) thin films grown in-situ by three-ion-beam sputtering. Y, Y2O3, Cu, Cu2O, BaF2 and BaCO3 sputter targets have been investigated. The highest quality films were prepared using a BaCo3 target. Auger analysis of films grown using a BaCO3 target show no carbon content. Y2O3 and Cu2O are more suitable than the native metals as sputter targets for YBCO growth as they are much less prone to sputter rate variations with oxygen partial pressure. They also supply oxygen to the growing film. As-deposited YBCO films are metallic (resistivity 240 μΩ cm at 100 K), reflective, and of highly homogeneous composition with Tco transition temperatures of 73 K and transition widths of 15 K. Post-annealing in flowing oxygen improves TCO's to 82 K. Critical currents are in excess of 105 A cm-2 at 77 K. Films are textured with c-axis orientation perpendicular to the (100) SrTiO3 substrate surface. As-deposited superconducting YBCO films have also been prepared on SiO2 and Y2O3 buffer layers on Si wafer

In situ growth of superconducting YBa2Cu3O7-δ thin films on Si with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on Si with conducting indium-tin-oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room-temperature resistivity of about 2 mΩ cm. Superconducting onsets are 92 K with zero resistance at 68

Superconducting YBa2Cu3O7-δ thin films on GaAs with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on GaAs with conducting indium-tin-oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky-like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room-temperatures resistivity of about 1 mΩ c

How to create an artificial magnetosphere for Mars

If humanity is ever to consider substantial, long-term colonization of Mars, the resources needed are going to be extensive. For a long-term human presence on Mars to be established, serious thought would need to be given to terraforming the planet. One major requirement for such terraforming is having the protection of a planetary magnetic field - which Mars currently does not have. The Earth's magnetosphere helps protect the planet from the potential sterilizing effects of cosmic rays and also helps retain the atmosphere, which would otherwise by stripped by large solar storms as they pass over the planet. Mars does have small patches of remnant surface magnetic field, but these are localized in the southern hemisphere and are not of sufficient size or magnitude to protect the planet or a colony. In this article we explore comprehensively for the first time, the practical and engineering challenges that affect the feasibility of creating an artificial magnetic field capable of encompassing Mars. This includes the concerns that define the design, where to locate the magnetic field generator and possible construction strategies. The rationale here is not to justify the need for a planetary magnetosphere but to put figures on the practicalities so as to be able to weigh the pros and cons of the different engineering approaches. The optimum solution proposed is completely novel, although inspired by natural situations and fusion plasma techniques. The solution with the lowest power, assembly and mass is to create an artificial charged particle ring (similar in form to a 'radiation belt'), around the planet possibly formed by ejecting matter from one of the moons of Mars (in a fashion similar to that which forms the Jupiter-Io plasma torus), but using electromagnetic and plasma waves to drive a net current in the ring(s) that results in an overall magnetic field. With a new era of space exploration underway, this is the time to start thinking about these new and bold future concepts and to begin filling strategic knowledge gaps. Furthermore, the principles explored here are also applicable to smaller scale objects like manned spacecraft, space stations or moon bases, which would benefit from the creation of protective mini-magnetospheres

A cyclotron maser instability with application to space and laboratory plasmas

When a beam of electrons moves into a converging magnetic field, the velocity distribution function takes on a horseshoe shape as a result of conservation of magnetic moment. A few years ago it was pointed out that such a distribution is unstable to a cyclotron maser type of instability and it was suggested that this instability might be the source of auroral kilometric radiation (Bingham, R. and Cairns, R. A., Phys. Plasmas 7, 3089 (2000).) and also of emission from certain types of star (Bingham, R., Cairns, R. A. and Kellett, B. J., Astron. Astrophys. 370, 1000 (2001).). Here we present more recent work on this topic. Since the dispersion relation which describes the instability only depends on the factor by which the magnetic field increases and on ratios of the wave plasma and cyclotron frequencies, it is possible to scale the effect to laboratory dimensions. An experiment to do this is being carried out at the University of Strathclyde and is expected to be operational during the summer of 2004. The objective is to investigate whether this mechanism might produce a useful radiation source, as well as to give a laboratory simulation of auroral kilometric radiation. The design of this experiment and its current status are described. On the theoretical side we discuss computer simulations showing the instability and its quasilinear saturation in the geometry of the experiment. We also describe a much more detailed theory of the linear instability than we have presented in previous work. Growth rates have been calculated in cylindrical geometry with various electron beam configurations and different cylindrical mode structures. These, and the simulations, support the conclusion of our earlier work that the instability has a high growth rate