The Response of African Equatorial/Low‐Latitude Ionosphere to 2015 St. Patrick's Day Geomagnetic Storm

Abstract

Total electron content (TEC) has been used to study the response of the African equatorial/low‐latitude ionosphere to the 17 March 2015 intense storm. Daily variations of symmetric H index, z component of interplanetary magnetic field, polar cap index, and H component of the Earth's magnetic field were analyzed along with TEC obtained from stations classified into western (11.53°E to 5.24°W) and eastern (25.00°E to 40.20°E) sectors. Storm time behavior of TEC was compared with the mean TEC of quiet days. TEC was enhanced over both sectors at the beginning of the storm while it reduced after the main phase as a result of prompt penetration of electric field and disturbance dynamo electric field (DDEF), respectively. The magnetic effect of the disturbed ionospheric electric current showed oscillations and minima in response to prompt penetration of electric field, which further enhanced the equatorial ionization anomaly. The effect of DDEF estimated from the ionospheric disturbance dynamo manifested in the form of decrease in the amplitude of the horizontal component of the Earth magnetic field (H) several hours after the beginning of the disturbance and during the recovery phase. Consequently, ionospheric irregularities were suppressed over all stations in both sectors on 17 and 18 March due to westward DDEF. On the 19 March, however, there was a difference in the pattern of irregularities over both sectors.

Large‐Scale Ionospheric Disturbances During the 17 March 2015 Storm: A Model‐Data Comparative Study

“…Furthermore, despite being an equinoctial event, the storm effects exhibited large hemispheric differences that were attributed to neutral composition changes. The storm's regional effects were also reported extensively, such as TIDs in the European‐African sector (e.g., Amaechi et al, ; Borries et al, ) and over North and South America (Figueiredo et al, ), the effects of PPEF over India (Tulasi Ram et al, ) and in the Asian‐Australian sector (Kuai et al, ), equatorial ionospheric disturbances over southern Asia (Jiang et al, ; Spogli et al, ), the TOI structure (Liu et al, ) and the SED plume (Zhang et al, ) over North America, positive and negative storm phases in the mid‐ and low‐latitude regions (Fagundes et al, ; Nava et al, ), ionospheric irregularities at high latitudes (Cherniak et al, ; Cherniak & Zakharenkova, ; Prikryl et al, ) and in the Latin American sector (Barbosa et al, ), and the formation of equatorial plasma bubbles (Carter et al, ; Kil et al, ; Patra et al, ; Zakharenkova et al, ).…”

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

“…The ROT is computed for every 30‐s time interval and then converted to TECU/min unit. The small‐scale density irregularities can then be characterized using the standard deviation of ROT index (ROTI) which is estimated for every 5‐min time interval (i.e., ) (Amaechi et al, ; Oladipo et al, ; Pi et al, ). Figure shows the ROTI (bottom panel) comparison with an independently measured S 4 index from high‐resolution GNSS receiver (middle panel) and VHF receiver (top panel).…”

Geomagnetic Activity Control of Irregularities Occurrences Over the Crests of the African EIA

“…The St. Patrick's Day storm of 17 March 2015 has received considerable attention. As such, interplanetary and magnetic conditions during this event have been described in several literatures (e.g., Amaechi et al, 2018aAmaechi et al, , 2018bBorries et al, 2016;Nava et al, 2016;Nayak et al, 2016). The SSC started on 17 10.1029/2020EA001183…”

“…Also, when a magnetic quiet day immediately follows a storm and there is no auroral activity and by implication weak convection electric field that is different from that during the storm, DP2 becomes zero and Ddyn can also be approximated to Diono (Amory-Mazaudier et al, 2017). Based on these, a running average filter that takes the mean value of 4 h of Diono data with sliding of 1 h was used for the separation of Ddyn from DP2 (Amaechi et al, 2018b;Azzouzi et al, 2015;Fathy et al, 2014). This method of separation and related assumptions remain valid only for short-duration PPEF (≤3 h) but not during cases of long lasting PPEF.…”