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The Structure and Dynamics of the Outer Atmosphere of ∊ Eri

Published online by Cambridge University Press:  26 May 2016

S. A. Sim  and
C. Jordan
S. A. Sim
Affiliation:
Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2BW, UK
C. Jordan
Affiliation:
Department of Physics (Theoretical Physics), University of Oxford, 1 Keble Road, Oxford, OX1 3NP, UK

Abstract

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We present results from our study of the active dwarf ∊ Eri (K2 V) based on ultraviolet spectra recorded with the Space Telescope Imaging Spectrograph and the Far Ultraviolet Spectroscopic Explorer. A combination of simple theoretical arguments and observational constraints derived from measured line fluxes are used to deduce new information about the structure of the upper transition region/corona. The area filling factor of emitting material is determined in the upper atmosphere as a function of temperature. This provides new constraints on how the magnetic field might spread out in the atmosphere of an active main sequence star. Measured emission line widths are used, together with a new semi-empirical model of the atmosphere, to place limits on the energy fluxes carried by MHD waves. These are compared with estimates of the energy input required to support the combined radiative/conductive losses in the upper atmosphere. It is shown that, in principle, waves which propagate at the Alfvén speed could provide sufficient energy to heat the corona.

Type
Part 5: Stellar Magnetic Activity and Evolution
Information
Symposium - International Astronomical Union , Volume 219: Stars as Suns : Activity, Evolution and Planets , 2004 , pp. 254 - 258
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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