• HASAN NAWAZ

      Articles written in Journal of Astrophysics and Astronomy

    • A study of the passage of high-speed solar wind streams, their plasma/field properties and space weather effects of geomagnetic disturbances

      SALMAN TARIQ HASAN NAWAZ FAZZAL QAYYUM ZIA UL-HAQ

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      This study investigated the geomagnetic disturbances and high-speed solar-wind streams (HSSs) during the period of solar storms emitted from coronal holes. The contemplated long-term HSS observations were taken from 1963 to 2016. On the basis of the intensity of geomagnetic activity, solar storms weredivided into four groups: weak ($-$50 nT < $D_{\rm st}$ < $-$30 nT), moderate ($-$100 nT < $D_{\rm st}$ < $-$50 nT), intense($-$200 nT < $D_{\rm st}$ < $-$100 nT) and superstorms ($D_{\rm st}$ < $-$200 nT). The relationship between solar plasma/field parameters and geomagnetic disturbances was also studied in the course of HSSs. For this purpose, statistical distributions and correlation analyses have been performed during the passage of HSSs causing geomagnetic disturbances on the individual stages. It was found that variations in the magnitude of the magnetic field$B$ (nT) and $V$ (km/s) relative to disturbance storm time ($D_{\rm st}$) index occur oppositely. During intense and super solar storms, the Earth’s magnetic field becomes very weak due to a decrease in the $D_{\rm st}$ index. The annualtime-series analysis suggests that the $D_{\rm st}$ and $K_p * 10$ index are of decreasing trends, whereas $Bz$ (nT) and $Ey$ (mV/m) have increasing trends during the study period. $D_{\rm st}$ best correlates with the $K_p * 10$ index with the highest value of correlation coefficient ($R$) to be observed as 0.54. The value of R is found to be 0.51 between $D_{\rm st}$ and $B$ (nT) during the passage of HSSs.

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