Estimating Equatorial F-Region Daytime Vertical E x B Drift Velocities from Ground-Based Magnetometer Measurements in the Philippine Longitude Sector

Ionospheric disturbances can severely impact Department of Defense (DoD) systems, such as radar, satellite and navigation technologies. Forecasting disturbances and describing the Earth's ionosphere, in turn, relies upon innovative computer-based models that gather input parameters from ground and space-borne observations and empirical models for ionospheric drivers. Equatorial E x B drift velocities are significant input parameters that go into many ionospheric models, because they help describe vertical plasma motions near the magnetic equator. Previous work by Anderson, et al [2002] has demonstrated the ability to derive Peruvian longitude sector, daytime vertical E x B drifts from ground-based magnetometer data. The present research extends these results to the Philippines using 56 days of magnetometer data from two stations in 2002. For each day of magnetometer data, corresponding Global Ultraviolet Imager (GUVI) 1356A airglow emission data from the evening equatorial anomaly were used to estimate the average E x B drift velocities [Anderson, private communication, 2003]. These drift values were then compared statistically to the horizontal component of the Philippine magnetometer data for all 56 days. In this process, data were grouped according to F1O.7 values. Overall, the best regression relation resulted from the ascending, April 2002 sample of 13 days of data (correlation coefficient of 0.63). Previous research does not conclusively predict how our April 2002 Philippine slope should compare against the corresponding Peruvian result. Specifically, Richmond [1973] predicts the two slopes should be approximately equal. However, Forbes [1981] suggests the Philippine regression slope should be 30 percent smaller than the corresponding Peruvian slope. Our calculated slope difference between the two regression relations is five percent, leaning more toward Richmond's prediction. However, we must keep in mind that our crest separation versus E x B relation has a correlation of 0.6, leaving 40 percent of unaccounted variance. Unlike Anderson's Peruvian results, no data currently exist to permit validation of our regression relation, yet C/NOFS electric field measurements, when available, may help settle the issue.Air Force Inst of Tech Wright-Patterson AFB OH School of Engineering and Management is the author of 'Estimating Equatorial F-Region Daytime Vertical E x B Drift Velocities from Ground-Based Magnetometer Measurements in the Philippine Longitude Sector', published 2004 under ISBN 9781423519737 and ISBN 1423519736.