Flares observed with XMM-Newton and the VLA

We present lightcurves obtained in X-ray by the XMM-Newton EPIC cameras and simultaneous radio lightcurves obtained with the VLA for five active M-type flare stars. A number of flare events were observed, and by comparing radio with X-ray data, we consider various possible flare mechanisms. In cases where there seems to be a clear correlation between radio and X-ray activity, we use an energy budget argument to show that the heating which leads to the X-ray emission could be due to the same particles emitting in the radio. In cases where there is radio activity without corresponding X-ray activity, we argue that the radio emission is likely to arise from coherent processes involving comparatively few particles. In one case, we are able to show from polarization of the radio emission that this is almost certainly the case. Cases for which X-ray activity is seen without corresponding radio activity are more difficult to explain. We suggest that the heating particles may be accelerated to very high energy, and the resulting synchrotron radio emission may be beamed in directions other than the line of sight.Comment: 12 pages, 10 figure

Propagation through Martian dust at 8.5 and 32 GHz

Independent studies of attenuation of X-band (8.5 GHz) and Ka-band (32 Ghz) radio signals when traversing Martian dust were carried out. These analyses turned out remarkably similar. The computational method is essentially that of T. S. Chu but uses observed optical depth at 0.67 microns rather than visibility as the measure of optical attenuation from which to derive the microwave attenuation. An awkwardness in the approach is that the size distribution of Martian dust particles is not well known, but the mean is probably around 4 microns, whereas in the terrestrial case it is nearer 10 microns. As a consequence, there will be a larger tail of particles still in the Mie regime in the Martian case as compared to the terrestrial one. The computational error will, therefore, be somewhat larger for Martian than Earth-bound dust. Fortunately, the indicated attenuations are small enough for the worst case (1.3 dB at 32 GHz) that the error is academic

Microwave attenuation and brightness temperature due to the gaseous atmosphere: A comparison of JPL and CCIR values

A sophisticated but flexible radiative transfer program designed to assure internal consistency was used to produce brightness temperature (sky noise temperature in a given direction) and gaseous attenuation curves. The curves, derived from atmospheric models, were compared and a new set was derived for a specified frequency range

Consumption and Real Exchange Rates in Dynamic Economies with Non-Traded Goods

We examine the possibility that nontraded goods may account for several striking features of international macroeconomic data: large, persistent deviations from purchasing power parity, small correlations of aggregate consumption fluctuations across countries, and substantial international real interest rate differentials. A dynamic, exchange economy is used to show that nontraded goods in principle can account for each of these phenomena. In the theory there is a close relation between fluctuations in consumption ratios and those in bilateral real exchange rates, but we find little evidence for this relation in time series data for eight OECD countries.consumption correlations, purchasing power parity, real exchange rates

The problem of off duty time in long duration space missions. Volume 3 - An annotated bibliography

Annotated bibliography on studies pertaining to off duty time during long duration manned space flight