Anomalous Sporadic-E Enhancements and Field-Aligned Irregularities at Low-Latitudes During the Intense Geomagnetic Activities on 17-18 March 2015

During the intense geomagnetic activities on 17-18 March 2015, the anomalous enhancements of critical frequency of sporadic-E (f(o)Es) and field-aligned irregularities (FAIs) were recorded in the mid- and low-latitude E-region. The f(o)Es peaks present good consistency with the occurrence of the FAIs. The AE and PC indices show the similar variation of five continuous peaks of 5-hr period on 17 March, indicating it is the successive substorms responsible for the sequential Joule heating events. The equatorward wind surges due to the Joule heating in polar region transferred the 5-hr period oscillations to the mid-latitude Mesosphere and Low-Thermosphere (MLT) atmosphere and even to the low-latitude sporadic-E (Es) layer. The 5-hr oscillations emerged in the AE and PC indices, mid-latitude MLT region winds, and low-latitude f(o)Es in sequence, indicating the disturbances were traveling equatorward and reached low-latitude E-region. The anomalous FAIs observed by the HCOPAR presented the descending and intermittent echo structures. The substorm-related oscillations are considered to modulate the MLT region tidal winds and induce the anomalous sporadic-E enhancements and FAIs through the wind-shear instability.