Cool Stars 14 - Submitted Abstract # 81
This version created on 05 October 2006

Magnetic Dynamo driven strong XUV Emmissions of Young dG-M Stars and
effects on Hosted Planets and Life


Edward Guinan, Villanova University
Ignasi Ribas, I.E.E.C.
Scott Engle, Villanova University
Laurence DeWarf, Villanova University

The evolution of magnetic activity and the resulting XUV coronal &
chromospheric emissions of dG-M stars with widely different ages are
discussed.  Young solar-type and cooler stars spin rapidly, resulting
in robust magnetic dynamos and intense XUV emissions (as well as
massive plasma outflows = winds).  Over time these stars lose angular
momentum via magnetized winds and their XUV emissions and winds
significantly decrease.  We discuss the XUV emissions of dG-M stars
and the effects these emissions have on hosted planets.  The strong
XUV and plasma emissions of young Sun (inferred from young solar
analogs) appear to have had major effects on the atmospheres and
environments of its nearest planets – playing major roles in the loss
of water on Venus and Mars.  Also discussed are the effects strong XUV
fluxes (and frequent flares) found for young dK & dM stars on possible
hosted planets orbiting within their shrunken habitable zones (0.05 <
HZ < 0.6 AU).  Dwarf M stars are important because they are very
numerous and have long nuclear lifetimes;  they have efficient dynamos
that result in persisting XUV emissions and flares.  Also, a
significant number of dM stars are old (>5 Gyr), presenting
opportunities for the development of highly evolved forms of life on
planets that may host them.  Thus, dM stars will be natural targets
for SETI and Darwin/TPF programs and characterizing their XUV
irradiances, winds and flares over time is important to study their
suitability as habitats for life.

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