Fig. 8

(Left) Schematic diagram of plasma motion during Tonga volcanic eruption based on the hypothesis proposed by Shinagawa et al. (2013). The ionospheric hole region and EIA trough depletion are indicated with blue and yellow shaded regions, respectively. The black lines show the magnetic field lines. The red lines denote the field-aligned plasma transport by neutral wind perturbations induced by the impulsive pressure pulse and the green arrows are those due to prevailing interhemispheric winds. The light-blue shade indicates the O/N2 pattern in the solstice. The plasma motion due to the strong PRE is indicated with yellow lines. (Right) Observation of electron density at 0530 UT (Fig. 5d). The yellow arrows denote the effects of enhanced PRE and the red arrows indicate the plasma motions caused by the impact of the volcano eruption