AAS 204th Meeting, June 2004
Session 36 Stellar-Solar Connection: What the Stars Teach Us about Our Sun
SPD Topical Session, Tuesday, June 1, 2004, 8:30-10:00am, 10:45am-12:30pm, 702/704/706

## [36.06] The Young and Restless Sun: Effects of the Young Sun's Strong Magnetic Activity on Paleo-Planetary Atmospheres

E.F. Guinan, L.E. DeWarf (Villanova University), I. Ribas (Institut d'Estudis Espacials de Catalunya, Spain), H. Lammer (Space Science Institute, Graz, Austria)

Studies of young solar proxies (G0-G5 V stars), as part of the Sun in Time'' program, show that the young Sun was rotating over 10\times faster than today. As a consequence, these young solar type stars (including the young Sun) had vigorous magnetic dynamos and correspondingly strong coronal X-ray and EUV emissions and chromospheric FUV and UV emissions - up to several hundred times stronger than that observed for the present Sun. Also, observations of the youngest solar proxies indicate that the young Sun had frequent and powerful flares and most likely significant winds.

The results of the Sun in Time'' program will be discussed that show the decline of solar coronal and chromospheric activity with slower rotation and increasing age. Also discussed are some of the major effects that the young Sun's strong magnetic activity may have had on the photoionization, photochemistry, and erosion of paleo-planetary atmospheres. Some examples that will be briefly discussed include: the possible erosion of Mercury's mantle, loss of water on Mars and the oxidation of its surface, hydrodynamic mass loss from paleo planetary atmospheres, and the evolution of the Earth's atmosphere and the origin and evolution of life on Earth (and maybe on Mars).

This work was supported by NASA/FUSE grants NAG 5-12125, NAG 5-10387 and NNG04GC76G.

Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.