Articles | Volume 36, issue 4
Ann. Geophys., 36, 987–998, 2018
Ann. Geophys., 36, 987–998, 2018

Regular paper 12 Jul 2018

Regular paper | 12 Jul 2018

Ionospheric and thermospheric response to the 27–28 February 2014 geomagnetic storm over north Africa

Khalifa Malki1, Aziza Bounhir1, Zouhair Benkhaldoun1, Jonathan J. Makela2, Nicole Vilmer3, Daniel J. Fisher2, Mohamed Kaab1, Khaoula Elbouyahyaoui1, Brian J. Harding2, Amine Laghriyeb1, Ahmed Daassou1, and Mohamed Lazrek1 Khalifa Malki et al.
  • 1Oukaïmeden Observatory, High Energy Physics and Astrophysics Laboratory, FSSM, Cadi Ayyad University, Marrakesh, BP 2390, Morocco
  • 2Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
  • 3LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France

Abstract. The present work explores the ionospheric and thermospheric responses to the 27–28 February 2014 geomagnetic storm. For the first time, a geomagnetic storm is explored in north Africa using interferometer, all-sky imager and GPS data. This storm was due to the arrival at the Earth of the shock of a coronal mass ejection (CME) associated with the solar flare event on 25 February 2014. A Fabry–Perot interferometer located at the Oukaïmeden Observatory (31.206° N, 7.866° W; 22.84° N magnetic) in Morocco provides measurements of the thermospheric neutral winds based on observations of the 630 nm red line emission. A wide-angle imaging system records images of the 630 nm emission. The effects of this geomagnetic storm on the thermosphere are evident from the clear departure of the neutral winds from their seasonal behavior. During the storm, the winds experience an intense and steep equatorward flow from 21:00 to 01:00 LT and a westward flow from 22:00 to 03:00 LT. The equatorial wind speed reaches a maximum of 120 m s−1 for the meridional component at 22:00 LT, after the zonal wind reverses to the westward direction. Shortly after 00:00 LT a maximum westward speed of 80 m s−1 was achieved for the zonal component of the wind. The features of the winds are typical of traveling atmospheric disturbance (TAD)-induced circulation; the first TAD coming from the Northern Hemisphere reaches the site at 21:00 LT and a second one coming from the Southern Hemisphere reaches the site at about 00:00 LT. We estimate the propagation speed of the northern TAD to be 550 m s−1. We compared the winds to the DWM07 (Disturbance Wind Model) prediction model and find that this model gives a good indication of the new circulation pattern caused by storm activity, but deviates largely inside the TADs. The effects on the ionosphere were also evident through the change observed in the background electrodynamics from the reversal in the drift direction in an observed equatorial plasma bubble (EPB). Total electron content (TEC) measurements of a GPS station installed in Morocco, at Rabat (33.998° N, 6.853° W), revealed a positive storm.

Short summary
The novelty of this paper lies in the fact that it addresses the thermosphere–ionosphere coupling in a midlatitude site in north Africa. We have used Fabry–Perot measurements of thermospheric winds and wide-angle camera detection of ionospheric structures at an altitude of about 250 km. We have also used GPS data to extract the TEC over the studied area. We have focused our study on the 27 February geomagnetic storm.