In 1958, Explorer 1 first discovered the Earth’s magneticfield when it detected a region of intense radioactivity as it orbited ellipticallyaround the Earth. The search for solar wind sources dates back to about 1950–with early insights from the end of the previous century and got furthermotivation from Parker’s theoretical work 13.Not everyone acceptedParker’s theory of the solar wind when it was first published in 1958,and itwas debated until observations confirmed it .The solar wind was first observed by the Mariner 2spacecraft in 1962 14.Ulysses spacecrafthas passed above the Sun’s south pole in September 1994 , and above the northpole in 1995 .
It has confirmed the existence of a steady fast flowing solarwind above the poles and has observed many interesting phenomena associatedwith it . The term “geomagnetic storm” was first used by Chapmanand Bartels (1940) to describe the magnetospheric and ionospheric disturbancesintermittently occurring 15. Astudy by Richardson et al.
(2001) concluded that storms associated withhigh-speed solar wind streams originating in coronal holes are most prevalentduring the decay and minimum phase of the solar cycle which are generally smallor medium in size in comparison to solar maximum conditions. Sustained high-speed wind streams thatintersect the Earth’s magnetosphere have been shown to drive geomagneticactivity 16,17.The acceleration of additional energetic electrons in theradiation belts appears to be the primary impact of a fast stream18,19,20,21.
High-speed streams usually also contain stronger Alfv’en waves than the slowwind, and these have been shown (McGregor et al. 2014) to enhancemagnetospheric ultralow frequency (ULF) fluctuations associated with storms andradiation belt dynamics