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

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

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

Planetary X-ray fluorescence analogue laboratory experiments and an elemental abundance algorithm for C1XS

We have conducted laboratory experiments as an analogue to planetary XRF (X-ray fluorescence) missions in order to investigate the role of changing incidence (and phase) angle geometry and sample grain-size on the intensity of XRF from regolith-like samples. Our data provide evidence of a grain-size effect, where XRF line intensity decreases with increasing sample grain-size, as well as an almost ubiquitous increase in XRF line intensity above incidence angles of ~60°. Data from a lunar regolith simulant are also used to test the accuracy of an XRF abundance algorithm developed at the Rutherford Appleton Laboratory (RAL), which is used to estimate the major element abundance of the lunar surface from C1XS (Chandrayaan-1 X-ray Spectrometer) XRF data. In ideal situations (i.e., when the input spectrum is well defined and the XRF spectrum has a sufficient signal to noise ratio) the algorithm can recover a known rock composition to within 1.0 elemental wt. % (1 σ)

Microwave generation from an electron horseshoe distribution: theory and experiment

When a beam of electrons encounters an increasing magnetic field along its vector of motion, conservation of the magnetic moment results in the formation of a crescent or horseshoe-shaped velocity distribution. A scenario analogous to this occurs in the terrestrial auroral zone where particles are accelerated into the polar regions of the earth's magnetic dipole and expand adiabatically in velocity space. The resultant horseshoe-shaped velocity distribution has been shown to be unstable to a cyclotron-maser type instability [1-3]. This instability has been postulated as the mechanism responsible for auroral kilometric radiation and also nonthermal radiation from other astrophysical bodies [4]. In this paper we describe both theory, simulations and a laboratory experiment to investigate the generation of microwave radiation when an electron beam is magnetically compressed by a factor of 35

Laboratory investigation of cyclotron emission processes for auroral radiation

When a beam of electrons encounters an increasing magnetic field along its vector of motion, conservation of the magnetic moment results in the formation of a crescent or horseshoe shaped velocity distribution. A scenario analogous to this occurs in the terrestrial auroral zone where particles are accelerated into the polar regions of the Earth's magnetic dipole and expand adiabatically in velocity space. The resultant horseshoe shaped velocity distribution has been shown to be unstable with respect to a cyclotron-maser type instability. This instability has been postulated as the mechanism responsible for auroral kilometric radiation and thermal radiation from other astrophysical bodies. In this paper we present the results of recent numerical simulations and laboratory investigations of radiation emissions from electron beam which have been subject to magnetic compression. Electron beam diagnostics demonstrated the formation of the desired velocity distribution. Radiation was generated at both 11.7GHz and 4.45GHz by an electron beam of current 5-25A and energy 75kV subject to magnetic compression ration of up to 30. Conversion efficiencies between beam and radiation power were achieved of up to 2.5% and strong agreement was achieved between the numerical investigations and the experimental measurements