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

TLDR: In this article, the effects of a space weather event on several longitudinal sectors (Asia, Africa, America, and the Pacific) have been analyzed using various parameters such as total electron content (TEC), geomagnetic field, and column [O/N2] ratio.

Abstract: We present a study concerning a space weather event on 25–29 August 2018, accounting for its ionospheric and magnetic signatures at low latitudes and midlatitudes. The effects of a storm in several longitudinal sectors (Asia, Africa, America, and the Pacific) have been analyzed using various parameters such as total electron content (TEC), geomagnetic field, and column [O/N2] ratio. Positive ionospheric storms are found in all the longitudinal sectors having its maximum effects in the Asian sector, whereas the negative ionospheric storms have been observed in the summer hemisphere (Northern Hemisphere). A large decrease in [O/N2] ratio in the Northern Hemisphere is a possible cause of the observed negative storm effects. Ionospheric F2 region maximum electron density (NmF2) and TEC have shown a positive correlation during this storm. The study suggests that storm time‐generated wind does not have a uniform planetary extension and mainly affects dayside (America and Pacific) and duskside (Africa) sectors. During the space weather event, we observe an asymmetric variation of the magnetic field as a function of the longitude. On the other hand, the magnetic variations at midlatitudes are found to be symmetric in both hemispheres. A signature of the disturbance dynamo (anti‐Sq circulation) has been observed, mainly at low latitudes. We emphasize that the partial ring current (PRC), estimated by the ASYM‐H magnetic index, must also be taken into account along with the SYM‐H index for a better approximation of ionospheric currents. The study further suggests existence of several electric current cells in the ionosphere, which is consistent with the Blanc‐Richmond model.

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Table 3: The geographic coordinates of the considered magnetometers.

Table 4: Percentage increase/Decrease in vTEC from average daily values at GPS stations.

Figure 8: a) Low-latitudes magnetometer H variations in specific longitudinal sectors, from 23 August to 01 September, 2018. From top to bottom, the panels correspond to GUA (Asian sector), TAM (African sector), KOU (American sector), ASYM/H index and SYM/H index. On each panel, the observed H-component (black) is superimposed by the regular Sq variations (blue) and the disturbed ionospheric electric currents Diono (red), b) Same as Figure 8a for three mid-latitudes magnetic stations in the northern hemisphere: BMT, CLF and SBL, c) Same as Figure 8a for three mid-latitudes magnetic stations in the southern hemisphere, namely GNG, HER and PIL.

Figure 7: a) NmF2 variations in Asian sectors, from 23 August to 02 September 2018. From top to bottom, the panels correspond to JJ433 (north), GUS13 (equat) and BR52P (south) stations b) Same as Figure 7a for three ionosondes in the African sector: AT138, ASOOQ and LV12P, c) Same as Figure 7a for three ionosondes, namely, PRJ18, SAAOK and PSJ5J in the American sector,.

Figure 9: a) from top to bottom: Bz component of IMF and Magnetic disturbance due to PPEF (DP2), in the Asian, African and American sectors from 25 to 29 August 2018 b) Magnetic disturbance Ddyn at low latitudes stations in the different longitude sectors from 23 August to 02 September 2018.

Table 1: The geographic latitudes, longitudes and the magnetic dip of the considered GPS stations.