First Observations of Equatorial Ionospheric Electric Fields Driven by Storm‐Time Rapidly Recurrent Magnetospheric Substorms

Abstract

Geomagnetic storm ionospheric electrodynamics at the magnetic equator are examined in detail using upgraded, higher time resolution, Jicamarca incoherent scatter radar drift observations, SuperMAG geomagnetic field, and solar wind data to study equatorial ionospheric electric fields during the 8 September 2017 storm main and early recovery phases. We show that during a period of mostly large and southward Interplanetary Magnetic Field (IMF) Bz there were numerous daytime prompt penetration vertical and zonal plasma drifts. These prompt penetration events were closely associated with rapidly recurring (quasi‐periods ∼30 − 60 min) magnetospheric substorms with expansion phases corresponding to upward and westward drift (eastward and downward electric field) perturbations, and recovery phases to opposite polarity changes. The magnitudes of the zonal prompt penetration drifts were about twice larger than those of the vertical drifts. Our study suggests that magnetospheric substorms are the main drivers of prompt penetration electric fields during extended periods (over ∼2 hr) of nearly steady southward IMF Bz. We also find that in general substorms are major driving factors for disturbance electric fields during geomagnetic active times. Our data highlight the powerful capabilities of the Jicamarca incoherent scatter radar as a tool for detailed studies of short‐lived solar wind‐magnetosphere‐ionosphere coupling processes.

Simultaneous Global Ionospheric Disturbances Associated With Penetration Electric Fields During Intense and Minor Solar and Geomagnetic Disturbances

“…It is worth noting that at least during the 6 September event, these oscillations occurred when Bz was steadily southward and AU/AL fluctuated, indicating a possible connection to substorm PEF. During the substorm PEF events reported by Fejer and Navarro (2022) for the 8 September period, SGDs were similarly present in our GNSS data (figures not shown). Dinsmore et al (2021) reported a semi-coherent ionospheric pulsing structures (SCIPS) feature in dTEC and the Millstone Hill incoherent scatter radar electron density data.…”

“…Here we broadly define PEF as ionospheric electric fields observed at mid‐ and low latitudes that could not be explained by either regular wind‐driven dynamo electric fields or storm‐time disturbance wind dynamo, but appear to be primarily of solar wind‐magnetospheric and geomagnetic disturbance origin. Important PEF sources include the IEF change, solar wind dynamical pressure change‐related shock front arrival (e.g., Huang, 2020a; Kikuchi et al., 2016), substorm (Fejer & Navarro, 2022), and SubAuroral Polarization Stream (Huang, 2020b) which may appear extended equatorward (Foster & Burke, 2002) and be impacted by auroral streamers (Gallardo‐Lacourt et al., 2017). Significant progress has been made in our understanding of the PEF since the 1970s, although some fundamental questions remain highly debatable, for example, what is the physics for the solar wind energy and momentum to be transmitted to the low latitude and equatorial ionosphere (Tu & Song, 2019)?…”

Responses of Ionospheric Radial Currents to Subauroral Polarization Streams During Quiet Periods

“…The zonal drift data provided by Jicamarca radar have excellent potential to address the question about low latitude ionospheric electrodynamic coupling. For example, Fejer and Navarro (2022) investigated the response of the ionospheric electric field during substorms using plasma drift data observed by Jicamarca radar. Previous studies (e.g., Fejer et al., 1985; Kudeki et al., 1981) had found that the Jicamarca F region zonal drifts were westward at daytime and eastward at nighttime, indicating the outward and inward electric field, respectively.…”

“…Jicamarca incoherent scattering radar locates near the magnetic equator (11.9°S, 76.8°W), and measures the vertical and zonal ion velocity in E‐ and F‐region over the magnetic equator since 1962 (Fejer, 2011; Fejer & Navarro, 2022; Fejer et al., 2005). The detailed measuring of F‐region plasma drift can refer to Woodman (1972).…”

Association of Equatorward Extended Auroral Streamers With Overshielding Conditions at Equatorial Latitudes: First Observations

“…The streamer events during case#4 (15 March 2015) occurred during nearly steady southward conditions, and we found that overshielding conditions over equatorial latitudes coincided with the bright equatorward extending streamers. Fejer and Navarro (2022) identified substorms based on the sharp decrease in the SML index and suggested that magnetospheric substorms are the main drivers of prompt penetration electric fields during extended periods (over ∼2 hr) of nearly steady southward IMF Bz. However, our study shows that overshielding conditions can be associated with equatorward extended auroral streamers even under southward IMF‐Bz conditions, and the sharp decrease in the SML index can be associated with such streamers (Yadav et al., 2022).…”