Abstract

Abstract. We study the impact of the geomagnetic storm of 7–9 September 2017 on the low- to mid-latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of two SYM-H minima with values of −146 and −115 nT on 8 September at 01:08 and 13:56 UT, respectively. The study is based on the analysis of data from the Global Positioning System (GPS) stations and magnetic observatories located at different longitudinal sectors corresponding to the Pacific, Asia, Africa and the Americas during the period 4–14 September 2017. The GPS data are used to derive the global, regional and vertical total electron content (vTEC) in the four selected regions. It is observed that the storm-time response of the vTEC over the Asian and Pacific sectors is earlier than over the African and American sectors. Magnetic observatory data are used to illustrate the variation in the magnetic field particularly, in its horizontal component. The global thermospheric neutral density ratio; i.e., O∕N2 maps obtained from the Global UltraViolet Spectrographic Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to characterize the storm-time response of the thermosphere. These maps exhibit a significant storm-time depletion of the O∕N2 density ratio in the northern middle and lower latitudes over the western Pacific and American sectors as compared to the eastern Pacific, Asian and African sectors. However, the positive storm effects in the O∕N2 ratio can be observed in the low latitudes and equatorial regions. It can be deduced that the storm-time thermospheric and ionospheric responses are correlated. Overall, the positive ionospheric storm effects appear over the dayside sectors which are associated with the ionospheric electric fields and the traveling atmospheric disturbances. It is inferred that a variety of space weather phenomena such as the coronal mass ejection, the high-speed solar wind stream and the solar radio flux are the cause of multiple day enhancements of the vTEC in the low- to mid-latitude ionosphere during the period 4–14 September 2017.

Highlights

  • It is well known fact that the geomagnetic storm is a temporary variation of the Earth’s magnetic field induced by the coronal mass ejection (CME) or the high-speed solar wind stream (HSSWS)

  • We present the variations in the variety of parameters such as the global electron content (GEC), the regional electron content (REC), the vertical total electron content (vTEC), the H component of the magnetic field and the thermosphere neutral composition as a result of the G4 category geomagnetic storm of 7–9 September 2017

  • The storm effects are characterized by using the diverse parameters including the global, regional and vertical total electron content derived from the Global Positioning System (GPS) data, the geomagnetic field measured at the ground magnetic observatories and the thermospheric neutral composition obtained from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/Global UltraViolet Spectrographic Imager (GUVI) instrument

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Summary

Introduction

It is well known fact that the geomagnetic storm is a temporary variation of the Earth’s magnetic field induced by the coronal mass ejection (CME) or the high-speed solar wind stream (HSSWS). Patrick’s day storm (the largest geomagnetic storm of the solar cycle 24) by using the TEC data analysis techniques derived from the Global Positioning System (GPS) to understand the positive and negative ionospheric-storm effects due to the energy transfer between the solar wind and the magnetosphere (Fagundes et al, 2016; Nayak et al, 2016) In this context, Nava et al (2016) investigated the low and mid-latitude ionospheric response to the St. Patrick day storm of 2015. Another finding is that the summer storm results in the formation of the plasma bubbles which propagate up to the midlatitudes and cause strong scintillation in the Global Navigation Satellite System (GNSS) signals Based upon this comprehensive analysis, the authors suggested that a number of factors such as the local time at the commencement of the storm and the season play an important role in the modeling of the ionosphere response to the solar activity. The summary and conclusion of this study is presented

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