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Monash Astro Seminars
3pm, Tuesday 13 October 2009; Maths, Rm. 345
Kurt Liffman
"Meteorites, Bipolar Jet Flows and Relativistic MHD"
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It has been deduced, from a number of lines of evidence, that primitive meteorites are not only samples of asteroids and comets, but are also fossilized samples of the solar nebula - the disk of gas and dust that once surrounded the Sun. Many such meteorites contain small, millimetre-sized, igneous objects called chondrules and CAIs (Calcium Aluminium Inclusions) surrounded by a dark sedimentary-like substance called "matrix". The matrix has never experienced temperatures in excess of 600 K, but the chondrules and CAIs were formed at temperatures in excess of 1800 K. How such material could have formed in the solar nebula has been a subject of scientific speculation for over two centuries.\\ Nearly two decades ago, a theory was published which suggested that chondrules, CAIs and other such objects were formed in or near the interaction region between the inner solar nebula and the early Sun. Moreover it was also suggested that chondrules and their kin were formed in a high-speed jet flow similar to the observed, high speed bipolar flows that are produced from young stellar objects. These small, igneous rocks could then be ejected from the inner solar nebula and subsequently ram into the cooler, outer nebula where they would agglomerate with the cooler, unprocessed nebula material to form the meteorites that we see today. This ``Jet Flow Model" predicted that accretion disks around young stars would be reprocessed by bipolar outflows which would eject heated/reprocessed material from the inner regions to the outer regions of the disk. This prediction is consistent with the observations of crystalline dust in comets, VLTI observational results of a radial distribution of crystalline dust in YSO disks and the high temperature, crystalline materials obtained from Comet Wild 2 by the Stardust mission. \\ As such, primitive meteorites may not only be a fossilized sample of the solar nebula, but also an indirect, high resolution telescope that provides detailed information on the mechanism that produces bipolar jet flows. The Jet Flow Model of disk reprocessing has inspired a new theory of how these flows form, where jet flows are produced by toroidal magnetic fields at the inner edge of the disk surrounding a central object. A possible application of this theory is to the relativistic jet flows observed from Active Galactic Nuclei. It is shown that highly relativistic flows may suffer very little attenuation of the driving magnetic field, while non-relativistic flows have little or no remnant magnetic field in the flow. This may provide an initial model for the formation of radio-loud and radio quiet AGN.
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Please email all enquiries to daniel.price@sci.monash.edu.au or rosemary.mardling@sci.monash.edu.au
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