Superfountain Effect Linked With 17 March 2015 Geomagnetic Storm Manifesting Distinct F₃ Layer

Abstract

The existence of an additional stratification in the daytime equatorial ionospheric F region (the F3 layer) was known since the 1940s. However, its characteristics and the underlying physical mechanism have been uncovered only recently. In this paper, we present and discuss the F3 layer characteristics observed by six ionosondes distributed over equatorial and low latitudes (−20° to +25° dip latitudes) in the Brazilian longitude sector during the strongest geomagnetic storm (DstMin = −223 nT) of solar cycle 24, the St. Patrick's Day storm of 17 March 2015. Two eastward prompt penetration electric field (PPEF) events, as seen in equatorial electrojet, occurred during the main phase of the storm on 17 March 2015, a strong one (~100 nT) at around ~1200 UT and a weak one (~50 nT) at around ~1725 UT. Local time variations in the F3 layer occurrence and ionospheric base height (h′F), peak height (hmF), and peak electron density (Nmax) are investigated. Notably, the F3 layer occurred at all six locations, more distinctly during the stronger PPEF event. The large latitudinal extend in the occurrence of the F3 layer in opposite hemispheres (−20° to +25° dip latitudes) covering the equatorial ionization anomaly crests observed for the first time is interpreted in terms of the combined effect of the super plasma fountain generated by the eastward PPEF and storm time equatorward neutral wind.

Ionospheric Scale Index Map Based on TEC Data During the Saint Patrick Magnetic Storm and EPBs

“…However, in the same time interval, the ionograms (Figure 10) showed a transition from occurrences of Spread‐F at 08 UT (05 LT at 45°W, before sunrise) to a condition favorable enough to develop an F3 layer at 10 UT (07 LT at 45°W, after sunrise). Such a layer is especially clearly identified CGK21 (indicated with an arrow), in the upper border of the southern crest of the EIA, and has been reported in previous studies related to the Saint Patrick magnetic storm (Venkatesh et al, 2019). Over FZA0M, where DIX showed higher values, the ionograms reveled high altitude Spread‐F between 07:30 and 08:30 UT (05 LT at 45°W), when it is supposed to have no Spread‐F.…”

“…The recovery phase has taken place at 22 UT on 17 March 2015, after the Dst reached −223 nT. On this complicated scenario, we may have several external drivers acting in the ionospheres, such as prompt penetration electric field (PPEF, C. M. M. Denardini et al, 2011; Forbes et al, 1995; Venkatesh et al, 2019) and disturbance dynamo electric field (DDEF, Blanc & Richmond, 1980; Nava et al, 2016; Nogueira et al, 2011). Indeed, Mansilla (2019) reported negative disturbances in foF2 after this storm commencement at low and mid‐low latitudes over Brazil, followed by positive disturbances in foF2.…”

The Impact of the Disturbed Electric Field in the Sporadic E (Es) Layer Development Over Brazilian Region

“…An abrupt increase in the AE parameter together with incursion of the IMF Bz to negative values was observed on March 17 at around 0600 UT, followed by a decrease in the base height of the layer over the regions, featuring a PPEF (see the line labeled "PPEF" in Figure 1). The PPEF events during this magnetic storm were described by Batista et al (2017) and Venkatesh et al (2019). They showed that an eastward PPEF in the afternoon acted as the main driver for the F3 layer formation in the equatorial and low latitudes.…”

“…Here, we chose this event as an example of the effects in Es layer dynamics over the Brazilian region during the disturbed periods. Our motivation to study this magnetic storm is that the response of the lower ionospheric parameters is concentrated in the D region (Maurya et al, 2018); TEC distribution (Astafyeva et al, 2015;Spogli et al, 2016;Venkatesh et al, 2017;Wu et al, 2016), F region (Batista et al, 2017;De Michelis et al, 2020;Venkatesh et al, 2017Venkatesh et al, , 2019, and in the space weather indices (Denardini et al, 2020). The St. Patrick's Day storm and its consequences on Es layers were not deeply studied yet as far as we know.…”

Inhibition of F3 Layer at Low Latitude Station Sanya During Recovery Phase of Geomagnetic Storms

“…Since then, investigations related to the F3 layer have become an activate topic in the ionospheric study. Many researches have investigated the formation of ionospheric F3 layer over the equatorial and low‐latitude region with regard to its diurnal, seasonal, solar activity, and geomagnetic activity variations at different locations (e.g., Balan et al., 2000, 1998, 2008, 2011, 2018; Batista et al., 2002, 2017; Chaitanya et al., 2013; Hsiao et al., 2001; Jenkins et al., 1997; Klimenko, Klimenko, et al., 2012, Klimenko, Zhao, et al., 2012; Lin, Richmond, Bailey, et al., 2009; Lin, Richmond, Liu et al., 2009; Lynn et al., 2000; Paznukhov et al., 2007; Rama Rao et al., 2005; Sreeja et al., 2009, 2010; Tardelli & Fagundes, 2015; Tardelli et al., 2016; Thampi et al., 2007; Uemoto et al., 2011, 2006, 2007; Venkatesh et al., 2019, 2020, 2017; Zain et al., 2008; Zhao et al., 2005; Zhao, Wan, Reinisch, et al., 2011; Zhao, Wan, Yue, et al., 2011; Zhao et al., 2014; Zhu et al., 2013). From those studies, the general characteristics about the F3 layer are summarized as follows: (a) F3 layer generally occurs during the daytime (08:00–17:00 LT) within about ±10° geomagnetic latitudes, and become much evident in 10:00–14:00 LT. (b) F3 layer is frequently occurred on the summer side of the geomagnetic equator, especially under the solar minimum condition.…”