Midlatitudinal Special Airglow Structures Generated by the Interaction Between Propagating Medium‐Scale Traveling Ionospheric Disturbance and Nighttime Plasma Density Enhancement at Magnetically Quiet Time.

This paper reports a special midlatitudinal medium‐scale traveling ionospheric disturbance (MSTID) event, accompanied by a poleward surge of airglow depletion/enhancement and a bifurcation of depletion during the magnetically quiet period. These special structures were generated during a decreasing height of ionosphere with nighttime plasma density enhancement and increment of airglow emission intensity possibly caused by a passing‐by midnight brightness wave. We suggest that the interaction of the passing‐by MSTID and nighttime plasma density enhancement resulted in the poleward surge and bifurcation of airglow depletion. The nighttime plasma density enhancement could feed the high plasma density to interact with the airglow depletions of MSTID, causing the poleward surge and bifurcation of airglow depletion by the secondary gradient drift instability. The poleward surged airglow enhancement within two adjacent depletions of MSTID is also firstly reported in this study. Plain Language Summary: It was generally believed that the midlatitudinal ionosphere is fairly quiescent until the first report of airglow structure of the medium‐scale traveling ionospheric disturbance by Garcia, Kelley, Makela, and Huang (2000, https://doi.org/10.1029/1999JA000305). Kelley et al. (2000, https://doi.org/10.1029/2000GL000022) and Garcia, Kelley, Makela, Sultan, et al. (2000, https://doi.org/10.1029/1999JA000306) further reported magnetically storm‐time "intense mid‐latitude spread F" events accompanied by poleward surged bifurcations of airglow depletions, which caused the severe perturbations of GPS signal. Those two events were most likely the interactive result of airglow depletion and enhanced plasma density region from the equatorial ionization anomaly crest region driven by magnetic storms. In this paper, we report a very similar airglow event accompanied by a poleward surged airglow depletion/enhancement and a bifurcation of depletion but occurred at magnetically quiet time in Xinglong, China. We suggest that the interaction of the passing‐by medium‐scale traveling ionospheric disturbance and the nighttime plasma density enhancement/nighttime increment of airglow emission intensity from a possible source of midnight brightness wave resulted in the poleward surged bifurcation of aiglrow depletion, most likely driven by the secondary gradient drift instability. This event can broaden our knowledge on the dynamical process of midlatitudinal ionosphere and provide a new guidance for further investigation of the midlatitudinal special airglow events. Key Points: MSTID with a poleward surged airglow depletion/enhancement and a bifurcation of depletion occurred during the magnetically quiet timeSecondary gradient drift instability could have developed the poleward surged bifurcation of depletionThis event is suggested to be caused by the interaction between MSTID and NPDE [ABSTRACT FROM AUTHOR]