High-speed video observations of two sprites with halo features were analyzed with concurrent measurements of broadband magnetic sferics. Both events were produced by positive cloudto-ground (CG) strokes. Moreover, the halo features appeared less than 0.5 ms after the return stroke, and the first sprite elements followed within 1 and 3 ms, respectively, for the two cases. The persistent charge transfer in the causative stroke from long continuing current can maintain the continuous glowing of existing sprite elements, and also may aid the vertical development and enhanced luminescence of later sprite elements. The observations with electric field (E-field) simulations by the transmission line model provide evidence that the induction component of the lightning-induced E-field contributes significantly to halo formation. Our results suggest additional measurements and analysis are needed to identify the specific role of induction E-field in addition to the well-known quasi-electrostatic (QE) field in the lightning-induced impact on the mesosphere.

red sprite;high-speed video observation