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maura hagan

	Maura Hagan, Director of ASP

Connection between persistent global meteorological weather patterns and quiescent space weather conditions

Maura Hagan in collaboration with Astrid Maute, Ray Roble, and Art Richmond (all of ESSL/HAO) collaborated with Thomas Immel and Scott England (both of University of California-Berkeley) in a numerical study that provides strong evidence of a connection between persistent global meteorological weather patterns and quiescent space weather conditions. They conducted a set of numerical experiments with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) in their attempt to replicate the longitudinal variability observed in the low-latitude ionosphere by the far ultraviolet (FUV) instrument on the IMAGE satellite. The accompanying illustration shows a 4-peaks in the TIME-GCM northern hemisphere electron density structure associated with the equatorial ionization anomaly, which captures the salient features of the IMAGE FUV data. Hagan and colleagues showed that this observed variability could not be explained by the offset between the geographic and geomagnetic equators, but could be attributed to nonmigrating tidal effects on the E-region dynamo-driven electric field. They accounted for the these effects by introducing tidal fields obtained from global-scale wave model (GSWM) calculations at the 30-km TIME-GCM lower boundary. They showed that an eastward propagating diurnal nonmigrating tide is primarily responsible for the wave 4 structure seen in the northern hemisphere by IMAGE FUV data. This tide is excited in the GSWM by a parameterization that accounts for latent heat release associated with raindrop formation in the deep tropical tropospheric clouds.

Reference:
Hagan, M. E., A. I. Maute, R. Roble, A. D. Richmond, T. J. Immel, and S. L. England (2007), Connections between deep tropical clouds and the Earth's ionosphere, Geophys. Res. Lett., doi:10.1029/2007GL030142, in press.

Figure Caption: Contours of TIME-GCM electron density (cm-3) as a function of longitude and latitude near 450 km altitude and 20 hours local solar time for March equinox and geomagnetically undisturbed conditions. This asynoptic map exemplifies the perspective of a days worth of measurements made by a slowly precessing or Sun-syncronous satellite. The red bands on either side of the magnetic equator are pre-sunset signatures of the equatorial ionization anomaly (EIA). The EIA enhancements evident at multiple longitudes are attributable to eastward electric field enhancements produced by nonmigrating zonal wind tide perturbations in the E-region dynamo region (ca. 100-150 km). These tides are excited by latent heat release associated with raindrop formation in the tropical troposphere as modeled by the GSWM and introduced into TIME-GCM at the 30-km model lower boundary.