Average equatorial zonal and vertical ion drifts determined from San Marco D electric field measurements


  • Nelson C. Maynard,

  • Thomas L. Aggson,

  • Federico A. Herrero,

  • M. Carmen Liebrecht,

  • Jack L. Saba


San Marco D electric field measurements have been averaged in terms of their equivalent ion drift to produce an average pattern of equatorial zonal and vertical ion drifts. Variations with season, solar activity, Kp, lunar phase and longitude have been analyzed. Similarities and some differences from previous Jicamarca, DE 2 and AE-E results are seen. Confirmation is given of the dominance of the F region dynamo in the 1900-2100 local time region. The daytime zonal ion drift is larger for high F10.7 values than that for low values. There is little variation between high and low values of Kp. Superrotation is evident in this data set and is larger at equinox compared to solstice. At the June solstice there are significant differences between the average ion drifts in the longitude sector where the geomagnetic equator is north of the geographic equator (Indian sector) and the sector where the geomagnetic equator is south of the geographic equator (Peruvian sector). The daytime upward velocity is larger in the Indian sector than in the Peruvian sector, and it reverses later in the evening in the Indian sector. Daytime westward zonal velocities are larger and the nighttime eastward velocities are smaller in the Indian sector. A presunrise enhancement is seen in the downward velocity in the Indian sector but not in the Peruvian sector. Significant variations are also seen with the phase of the moon. In light of current theory, the lunar variations suggest a complex interaction of E and F region dynamo sources with conductivity, changing in phase and character with latitude.