Multivariable Comprehensive Analysis of Two Great Geomagnetic Storms of 2015

Abstract

During the year 2015 two great geomagnetic storms (Dst < À200 nT) occurred on 17 March and 22 June. These two geomagnetic storms have similarities. They occurred during the same decreasing phase of the sunspot cycle 24. The interplanetary and magnetospheric environments were calm before the beginning of the storms. Both events were due to Coronal Mass Ejections and High-Speed Solar Wind. Variations of the solar wind velocity and the Bz component of the interplanetary magnetic field were also similar. Two key features that are different for these storms are UT time of the beginning (04:45 UT for 17 March and 18:33 UT for 22 June) and season (equinox and solstice). The comparison of the impact of the storms on the Earth ionosphere and magnetosphere has been performed using diverse parameters including global ionospheric maps of vertical total electron content, data from individual Global Navigation Satellite System receivers, ionosondes, magnetometers, and instruments from different space missions. Visualizing global ionospheric map data as the difference of vertical total electron content between consecutive days allowed understanding better the effect of the storms as a function of time of the beginning of the storm and of the season. It is shown that the presence or absence of scintillations in Global Navigation Satellite System signals during these two storms in African longitude sector is clearly related to the local time at a given station at the beginning of the storm.In addition to many data sets scientists also have access to modeling results that allow them interpreting their observations. Theoretical work carried out by Fuller-Rowell et al. (1994) defined the response of the thermosphere during a magnetic storm due to thermal expansion of the atmosphere with transport of KASHCHEYEV ET AL. 5000

Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs

“…Fathy et al (2014) studied the D dyn variations by various filter techniques. More recently, Nava et al (2016), Migoya‐Orue et al (2016), Rodríguez‐Zuluaga et al (2016), Zaourar et al (2017), and Kashcheyev et al (2018) explored various geomagnetic storms using different data sets, for example, vertical total electron content (VTEC), column [O/N 2 ] ratio, F2 layer maximum electron density (NmF2), F2 region maximum electron density height (hmF2), and magnetic data. By employing signal analysis, they reported existence of short‐period oscillations (DP2) as well as diurnal and semidiurnal fluctuations ( D dyn ) in the geomagnetic field.…”

Response of the low- to mid-latitude ionosphere to the geomagnetic storm of September 2017

“…The authors have shown that the slow CME plays a main role in the commencement of the geomagnetic storms of the solar cycle 24. Kashcheyev et al (2018) have made a comprehensive analysis on the basis of the two great geomagnetic storms (Dst ≤ −200 nT) which occurred on 17 March and 22 June 2015. It is found that the absence or presence of a scintillation in the African sector is associated with the local time at the beginning of the storm.…”

“…The storm effects are analyzed by using the data from the individual GNSS receivers and ground magnetic observatories located in different longitudinal sectors. The approach used in the present study is similar to that used by Nava et al (2016) and Kashcheyev et al (2018). In addition, the storm-time response of the neutral atmosphere in the thermosphere is analyzed by using the global O/N 2 density ratio maps derived from the Global UltraViolet Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite.…”

“…Table 2 shows the geographic and geomagnetic locations of these observatories. In order to calculate the magnetic field variations, we have adopted the approach of Nava et al (2016) and Kashcheyev et al (2018). A brief description of this approach is given here.…”

“…During the second southward excursion of the magnetic field, D iono decreases significantly for MBO and KOU, which are now in the dayside. The D iono contains signatures of the PPEF and DDEF therefore, the observed trend of the D iono can also be explained by these two electric fields (Kashcheyev et al, 2018). Another effect that can be seen during the storm is the variation in the thermospheric neutral composition, i.e., the O/N 2 density ratio.…”