HR: 0800h
AN: SA11A-1105    [Abstracts]
TI: The Maunder Minimum Ionosphere
AU: * Smithtro, C G
EM: sojka@gaim.cass.usu.edu
AF: Air Force Institute of Technology, Bldg. 641 2950 Hobson Way, Wright-Patterson AFB, OH 45433-7765 United States
AU: Sojka, J J
EM: sojka@gaim.cass.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University 4405 Old Main Hill, Logan, UT 84322-4405 United States
AB: The Maunder Minimum epoch, from 1645 to 1715 A.D. was characterized by a near absence of sunspots. Studies of cosmogenic isotopes and Sun-like stars suggest that solar chromospheric and coronal emissions during this period were significantly lower than contemporary solar minima. To study the effect of such a reduction on the Earth's upper atmosphere, we employ a 1-D global average ionosphere and thermosphere model that accounts for the photon flux between 3 and 360 nm. Within the ionosphere, an unexpected transition occurs as the irradiance falls below normal solar minimum levels. The concentration of O$^{+}$ ions decreases rapidly relative to the other ions, such that NO$^{+}$ becomes the dominant F-region ion. The state of the underlying thermosphere, particularly the neutral gas temperature, is largely responsible for this behavior.
DE: 7536 Solar activity cycle (2162)
DE: 2419 Ion chemistry and composition (0335)
DE: 2447 Modeling and forecasting
DE: 2479 Solar radiation and cosmic ray effects
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting