The Simultaneous Observations of Nighttime Ionospheric <i>E</i> Region Irregularities and <i>F</i> Region Medium‐Scale Traveling Ionospheric Disturbances in Midlatitude China

<jats:title>Abstract</jats:title><jats:p>Coupling of ionospheric <jats:italic>E</jats:italic> and <jats:italic>F</jats:italic> regions in the midlatitude region has been studied for a couple of years. In this study, we investigate the nighttime disturbances in <jats:italic>E</jats:italic> and <jats:italic>F</jats:italic> regions in midlatitude China region by using Wuhan ionosonde, Wuhan very high frequency coherent scatter radar, and Mengcheng airglow imager. We present two case studies of simultaneous observations of diffuse sporadic <jats:italic>E</jats:italic> (<jats:italic>E</jats:italic>s) layers, quasiperiodic echoes of <jats:italic>E</jats:italic> region irregularities, spread <jats:italic>F</jats:italic>, and medium‐scale traveling ionospheric disturbances. Results of case studies indicate that diffuse <jats:italic>E</jats:italic>s layers and <jats:italic>E</jats:italic> region irregularities can be associated with the <jats:italic>F</jats:italic> region medium‐scale traveling ionospheric disturbances or spread <jats:italic>F</jats:italic> through polarization electric field mapping along the field lines. We then analyze the data set of Wuhan ionosonde and Wuhan very high frequency radar during 2015–2016 and find that the coincidence of diffuse <jats:italic>E</jats:italic>s layers, quasiperiodic echoes of <jats:italic>E</jats:italic> region irregularities, and spread <jats:italic>F</jats:italic> is high at local nighttime. Our results provide the first observational evidence in midlatitude China region to support the concept that polarization electric field generated in the <jats:italic>E</jats:italic> region irregularities could map along the magnetic field lines and excite electrodynamic disturbances in <jats:italic>F</jats:italic> region, such as Perkins instability.</jats:p>