Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017

Ram Kumar Vankadara,Daniel Okoh,Gopi Krishna Seemala,Tarun Kumar Pant,Sampad Kumar Panda,Venkata Ratnam Devanaboyina,Rolland Fleury,Punyawi Jamjareegulgarn,Christine Amory-Mazaudier,Mohd Anul Haq

doi:10.3390/rs14030652

Abstract

Scintillation due to ionospheric plasma irregularities remains a challenging task for the space science community as it can severely threaten the dynamic systems relying on space-based navigation services. In the present paper, we probe the ionospheric current and plasma irregularity characteristics from a latitudinal arrangement of magnetometers and Global Navigation Satellite System (GNSS) stations from the equator to the far low latitude location over the Indian longitudes, during the severe space weather events of 6–10 September 2017 that are associated with the strongest and consecutive solar flares in the 24th solar cycle. The night-time influence of partial ring current signatures in ASYH and the daytime influence of the disturbances in the ionospheric E region electric currents (Diono) are highlighted during the event. The total electron content (TEC) from the latitudinal GNSS observables indicate a perturbed equatorial ionization anomaly (EIA) condition on 7 September, due to a sequence of M-class solar flares and associated prompt penetration electric fields (PPEFs), whereas the suppressed EIA on 8 September with an inverted equatorial electrojet (EEJ) suggests the driving disturbance dynamo electric current (Ddyn) corresponding to disturbance dynamo electric fields (DDEFs) penetration in the E region and additional contributions from the plausible storm-time compositional changes (O/N2) in the F-region. The concurrent analysis of the Diono and EEJ strengths help in identifying the pre-reversal effect (PRE) condition to seed the development of equatorial plasma bubbles (EPBs) during the local evening sector on the storm day. The severity of ionospheric irregularities at different latitudes is revealed from the occurrence rate of the rate of change of TEC index (ROTI) variations. Further, the investigations of the hourly maximum absolute error (MAE) and root mean square error (RMSE) of ROTI from the reference quiet days’ levels and the timestamps of ROTI peak magnitudes substantiate the severity, latitudinal time lag in the peak of irregularity, and poleward expansion of EPBs and associated scintillations. The key findings from this study strengthen the understanding of evolution and the drifting characteristics of plasma irregularities over the Indian low latitudes.

Highlights

The study of spatiotemporal propagation of ionospheric irregularities during space weather events remains an interesting topic among the ionospheric community
The highlighting feature of the space weather event of 6–10 September 2017 is that it was associated with multiple X- and M-class solar flare eruptions, including the strongest solar flare (X9.3) of solar cycle-24
SSC-1 is not followed by a geomagnetic storm; rather, the episode started after SSC-2 with a two-stage main phase, manifesting two prominent minima in symmetric H index (SYMH)

Summary

Introduction

The study of spatiotemporal propagation of ionospheric irregularities during space weather events remains an interesting topic among the ionospheric community. The scintillations are known to be the random fluctuations of the signal amplitude and phase caused by the rapid small-to-medium scale plasma irregularities in the ionosphere, whose occurrence characteristics may change during the disturbed space weather condition. Most of the aspects of the large-scale delay errors corresponding to the total electron content (TEC) along the signal ray path through the ionosphere have been resolved in the past, the scintillation effects remain a challenging task for the ionospheric modeling community as they can cause a serious threat to dynamic systems, depending on the space-based navigation services. The day-to-day dependence of the lives, technology infrastructure, navigation, and positioning are concerning the space-based navigation services, which in turn depends on accurate modeling and the mitigation of effects due to plasma irregularities

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