Observation of sporadic E layer altitude partially modulated by the Traveling Ionospheric Disturbances at high latitudes over Zhongshan station

Abstract

At Zhongshan (69° S, 76° E) Antarctica we investigate the sporadic $E$ ($Es$)-layer virtual height modulation, observed by an ionosonde, during the passage of the Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), observed by a SuperDARN radar. Two events were identified, on 04 October 2011 at 07:00 - 12:00 UT and 29 February 2012 at 00:00 - 04:00 UT with periods of $\sim$15.0 and $\sim$12.0 min, respectively. The magnitude of average height modulation of the $Es$-layer was $\sim$3.7 to $\sim$17.1 and $\sim$0.5 to $\sim$7.3 km, respectively, with the same periods as the MSTIDs. Ray tracing during the events shows that the likely MSTID propagation was up to $\sim$300 km in the ionospheric $F$-region. The computed ion vertical drift velocity using SuperDARN radar and magnetometer data, and $Es$-layer altitude modulation observed by the ionosonde have moderate to strong positive correlation of 0.71 ± 0.22 and 0.51 ± 0.16, respectively. We show that the MSTIDs polarization electric field, which is mapped down from the $F$-region along the near-vertical magnetic field, moderately contributes to the modulation of the $Es$ layer altitude via the $E\times B$ drift mechanism.