Significant Electric Field Perturbations in Low Latitude Ionosphere due to the Passage of Two Consecutive ICMEs During 6–8 September 2017

Abstract

This investigation shows that the significant electric field disturbances in the dip‐equatorial ionosphere during the geomagnetic storm of 6–8 September 2017 are due to the passage of two consecutive interplanetary coronal mass ejections (ICMEs). During the passage of the first ICME sheath, a long duration (∼10 hr) prompt penetration (PP) event is operational in which 60‐min periodic component is found to be present in vertical drift as well as in equatorial electrojet, but the 45‐min periodicity, though present, is not significant in equatorial electrojet. On 8 September, the shock associated with the second ICME enhances the F region vertical plasma drift to ∼150 m/s in the evening hours which is one of the highest vertical drift ever measured over Jicamarca. The same PP electric field causes unusually large enhancement of the equatorial electrojet strength to ∼135 nT in the early morning hours over the Philippine sector. The disturbance dynamo (DD) that follows the storm causes an upward vertical drift of ∼55 m/s during postmidnight hours over Jicamarca which is one of the highest observed. These unusually large electric field perturbations cause significant changes in the F region plasma fountain. It is shown that these electric field perturbations cannot be accounted by PP/DD electric field associated with the geomagnetic storm only and significant contribution from substorm is conspicuous. Therefore, the present investigation highlights the need to evaluate the role of substorm in unusually large electric field perturbations over equatorial ionosphere.

Storm‐Time Coupling of Equatorial Nighttime F Region Neutral Winds and Plasma Drifts

“…The anticorrelated Jicamarca vertical and zonal plasma drifts, during this period of rapidly changing solar wind IMF Bz and By components, strongly indicate that these fluctuations were due to solar wind/magnetosphere driven prompt penetration electric fields (e.g., Fejer, 2011). Simultaneous early morning oscillations with similar periods in the equatorial electrojet over the Philippine sector, presented by Rout et al (2019), are fully consistent with this interpretation. These results suggest that the neutral wind oscillations were likely due to ion drag effect modulated by the prompt penetration vertical plasma drifts.…”

“…These oscillations, which will be discussed later, occurred during a period of enhanced SYMH and relatively small AE and Kp indices. The arrival of the second ICME close to dusk on 7 September caused very strong upward prompt penetration drifts over Jicamarca (e.g., Rout et al, 2019). These drifts lifted the F layer to high altitudes leading to the development of very strong equatorial spread F irregularities, which precluded incoherent scatter drift measurements up to about midnight.…”

“…This complex geomagnetic storm resulted from the passage of two consecutive interplanetary coronal mass ejections (ICMEs), as discussed by Shen et al (2018). The ionospheric and thermospheric effects due to this large geomagnetic storm were discussed in several publications (e.g., Aa et al, 2018;Rout et al, 2019). The storm started with the arrival of the first ICME around 1845 LT (2,345 UT) on 6 September, as indicated by the sudden increase of the SYMH index.…”

Hemispheric Asymmetries in the Mid‐latitude Ionosphere During the September 7–8, 2017 Storm: Multi‐instrument Observations

“…A double‐dip geomagnetic storm occurred on September 7–8, 2017, and has received much attention (Aa et al., 2018, 2019; Habarulema et al., 2020; Imtiaz et al., 2020; Jimoh et al., 2019; Jin et al., 2018; Lei et al., 2018; Mosna et al., 2020; Rout et al., 2019; Shen et al., 2018; Wang et al., 2019; Xiong et al., 2019; Zhang et al., 2019). Figures 1a–1f show the By and Bz components of the IMF in the geocentric solar magnetospheric (GSM) coordinates (IMF By and Bz), solar wind speed, proton number density, dynamic pressure, and the SYM‐H index during September 7–8, 2017.…”

SABER Observation of Storm‐Time Hemispheric Asymmetry in Nitric Oxide Radiative Emission

“…During geomagnetic storm, a large amount of energy/momentum deposited in magnetosphere‐ionosphere‐thermosphere system creates large variations in density, temperature, and composition over the globe via different processes such as convection, particle precipitation, ionization, direct electric field penetration, ion‐drag forcing, and Joule heating (Bag, 2018a, 2018b; Bag et al., 2014, 2017; Bharti et al., 2018; Burns et al., 2004; Fuller‐Rowell et al., 1994, 1996; Huang et al., 2012; Li et al., 2018, 2019; Lu et al., 2010; Prolss, 1993; Richards, 2004; Richmond & Lu, 2000; Richmond & Roble, 1997; Rout et al., 2019; Verkhoglyadova et al., 2016, 2017a, 2017b, and references therein). Two of the most important processes that affect the thermospheric chemistry and dynamics are the auroral electrons and Joule heating.…”