Global, low-latitude, vertical ExB drift velocities inferred from daytime magnetometer observations

Navigation and communication, Department of Defense and civilian, customers rely on accurate, low-latitude specification of ionospheric parameters, globally, that are not currently realistic on a day-to-day basis. This paper describes, demonstrates, and speculates about the data sets that are required inputs to the operational ionospheric models that will correct these deficiencies. In order to investigate quiet time, vertical E x B drift velocities at two different longitude sectors, magnetometer observations were obtained for the period between January 2001 and December 2004 from the magnetometers at Jicamarca (0.8 degrees N dip latitude) and Piura (6.8 degrees N dip latitude) in Peru and from Davao (1.4 degrees S dip latitude) and Muntinlupa (6.3 degrees N dip latitude) in the Philippine sector. We choose only geomagnetically "quiet'' days, when the 3-hourly Kp value never exceeds a value of 3 over the entire day, and when the daily Ap value is less than 10. These are "binned'' into three seasons, December solstice, equinox, and June solstice periods. A neural network trained for the Peruvian sector was applied to each of the days in both the Peruvian and Philippine sectors, providing Delta H-inferred vertical E x B drift velocities between 0700 and 1700 local time. For each season, the average E x B drift velocity curves are compared with the Fejer-Scherliess, climatological E x B drift velocity curves in both the Peruvian and Philippine sectors. In the Peruvian sector, the comparisons are excellent, and in the Philippine sector they are very good. We demonstrate that realistic magnetometer-inferred E x B drifts can be obtained in the Peruvian sector on a day-to-day basis and speculate that on the basis of the average, quiet day comparisons, realistic E x B drifts can be obtained on quiet days in the Philippine sector.