Disappearance of equatorial plasma bubble after interaction with mid-latitude medium-scale traveling ionospheric disturbance

Abstract

We report simultaneous observations of an equatorial plasma bubble and a Medium-Scale Traveling Ionospheric Disturbance (MSTID) in 630-nm airglow images taken with an all-sky airglow imager at Shigaraki (34.9°N, 136.1°E; dip angle of the geomagnetic field ̃49°), Japan. Clear depletion of the 630-nm airglow intensity was observed as the equatorial plasma bubble propagated eastward, whereas the MSTID, which had a wavefront aligned from northwest to southeast, propagated southwestward. This result indicates that MSTIDs do not propagate at the same velocity as the ambient plasma, which is clearly shown by the eastward motion of the plasma bubbles. We found that the airglow depletion caused by the plasma bubble disappeared when the plasma bubble encountered the MSTID. The plasma depletion could be filled with ambient rich plasma that moved into the plasma-depleted region by E - B drift associated with the MSTID, indicating that MSTIDs are accompanied by electric field perturbations. © 2012. American Geophysical Union.