MODEL STUDY OF GROUND MAGNETIC SIGNATURES OF TRAVELING CONVECTION VORTICES

We conducted a model study of ground magnetic signatures of traveling convection vortices (TCVs) that included both the ionospheric conducti vity enhancement associated with the TCVs and the ground induction eff ect. We found that the localized conductivity enhancement can cause a significant distortion of the TCV current system and lead to a distort ion of the ground magnetic disturbance patterns. The patterns of all t hree magnetic components are asymmetric, mainly in the E-W direction, and the patterns of the Z component show the strongest asymmetry (20-3 0%). We also found that the effect of induction currents on ground mag netic signatures of the TCVs is insignificant (less than 5%). The resu lts show that because of the presence of localized conductivity enhanc ements the polarity and speed of the TCVs can significantly influence the distortion features of ground magnetic patterns. The upward and do wnward current filaments of a TCV with a clockwise leading convection cell can wrap with each other, resulting in a rotation of the whole gr ound magnetic disturbance pattern. This rotation feature is most signi ficant when the speed of the TCVs is high.