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

Abstract

Efiong A.  Ibanga* and Godwin A. Agbo

The response of the ionosphere to heliophysical, interplanetary and geophysical structures during the severe geomagnetic storm (D_st=-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 (N_mF₂) 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 N_mF₂. 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 N_mF₂ 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 N_mF₂ enhancement phenomenon. The study also shows that the F-region virtual height was significantly raised during the main phase of the geomagnetic storm.