Abstract
Abstract. In this work, the results of the analysis on total electron content (TEC) data before, during and after the geomagnetic storm of 8 September 2017 are reported. One of the responses to geomagnetic storms due to the southern vertical interplanetary magnetic field (Bz) is the enhancement of the electron density in the ionosphere. Vertical TEC (VTEC) from the Center for Orbit determination in Europe (CODE) along with a statistical method were used to identify positive and/or negative ionospheric storms in response to the geomagnetic storm of 8 September 2017. When analyzing the response to the storm of 8 September 2017 it was indeed possible to observe an enhancement of the equatorial ionization anomaly (EIA); however, what was unexpected was the identification of a local TEC enhancement (LTE) to the south of the EIA (∼40∘ S, right over New Zealand and extending towards the southeastern coast of Australia and also eastward towards the Pacific). This was a very transitory LTE that lasted approximately 4 h, starting at ∼ 02:00 UT on 8 September where its maximum VTEC increase was of 241.2 %. Using the same statistical method, comparable LTEs in a similar category geomagnetic storm, the 2015 St. Patrick's Day storm, were looked for. However, for the aforementioned storm no LTEs were identified. As also indicated in a past recent study for a LTE detected during the 15 August 2015 geomagnetic storm, an association between the LTE and the excursion of Bz seen during the 8 September 2017 storm was observed as well. Furthermore, it is very likely that a direct impact of the super-fountain effect along with traveling ionospheric disturbances may be playing an important role in the production of this LTE. Finally, it is indicated that the 8 September 2017 LTE is the second one to be detected since the year 2016.
Highlights
Anomalies in the ionosphere can be the product of different natural phenomena (Afraimovich et al, 2013)
According to the National Oceanic and Atmospheric Administration (NOAA) space weather service, this geomagnetic storm can be classified as a G4 severe storm (Kp = 8)
The origin of this geomagnetic storm lies in the coronal mass ejection (CME) that occurred on 6 September 2017 at ∼ 12:40 UT
Summary
Anomalies in the ionosphere can be the product of different natural phenomena (Afraimovich et al, 2013). According to several studies (e.g., Huang et al, 2005; Mannucci et al, 2005; Astafyeva, 2009), one common response to a geomagnetic storm due to the excursion of the southward interplanetary magnetic field is the significant increment in the equatorial and midlatitude total electron content (TEC), which manifests as an enhancement of the equatorial ionization anomaly (EIA; Appleton, 1946; McDonald et al, 2011). Such increase in TEC in the EIA is possible to visualize in global ionospheric maps (GIMs).
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