On the Response of the Mid-latitude Ionosphere to the Severe Geomagnetic Storm of March 17-18, 2015

Communication  in Physical Sciences, 2021, 7(4): 542-553 Authors: Efiong A.  Ibanga1* and Godwin A. Agbo2 Received: 25 July 2021/Accepted: 27 December 2021 The response of the ionosphere to heliophysical, interplanetary and geophysical structures during the severe geomagnetic storm (Dst=-223 nT) of March 17-18, 2015 has been investigated. Deviations of ordinary wave critical frequencies from the reference values based on four international geomagnetically quiet days preceding the storm (δfoF2) and F2 layer maximum electron density (NmF2) were calculated using manually scaled foF2 records from a chain of stations in Japan of the mid-latitude Asian sector. Results show that the pre-storm and main phases of the geomagnetic storm were accompanied by a positive ionospheric storm typified by enhancement while the recovery phase was accompanied by a negative storm marked by the depletion of NmF2. Also, foF2 values showed, on average, greater than 20% positive deviation from foF2 during the pre-storm and main phase, and also negative deviations in the recovery phase. Significant enhancement of NmF2 which occurred at least twenty-four hours ahead of the storm onset was observed in all the stations and tends to lend credence to the veracity of the contentious pre-storm NmF2 enhancement phenomenon. The study also shows that the F-region virtual height was significantly raised during the main phase of the geomagnetic storm