Observation of a solar flare induced interplanetary shock and helium-enriched driver gas

Abstract

On February 13, 1967, a class 3B solar flare occurred at 20°N, 10°W. The resultant disturbance in the solar wind was observed by the Los Alamos plasma probe on Vela 3A and the Ames Research Center magnetometer on Explorer 33. The initial discontinuity in the solar wind was identified as a shock. The normal to the shock made an angle of 60° with the plane of the ecliptic. This extreme angle of tipping indicates that the shock from this flare did not propagate spherically from the sun as described by simple theory. Nine hours after the shock passed, plasma containing 22% helium was observed. Since the solar wind normally contains 4% helium, this observation adds to the increasing body of evidence that flares occur in regions relatively rich in helium. The velocity of the solar wind continued to increase after the helium plasma passed, i.e., at 1 AU the helium‐enriched material was still being propelled from behind. This observation is evidence that the plasma continued to be accelerated at the sun for an extended period of time after the flash phase of the flare.

Coronal mass ejections and their sheath regions in interplanetary space

“…Figure 2g shows the helium to proton ratio in the solar wind. Enhanced abundances of helium relative to protons following shock waves were among the earliest identified ICME signatures, although at the time, they were identified with a solar flare source (Hirshberg et al 1970(Hirshberg et al , 1972Borrini et al 1982). While some individual ICMEs indeed show clear enhancements of the alpha to proton ratio (larger than 0.08-0.1), statistical studies have shown that on average, this ratio in ICMEs is not that distinct from values found in the slow solar wind (e.g., Lynch et al 2003;Richardson and Cane 2004;Rodriguez et al 2016).…”

“…These speculations stemmed from the attempts to explain geomagnetic disturbances (e.g., Lindeman 1911;Chapman and Ferraro 1929;Bartels 1932) and so-called Forbush decreases in cosmic ray intensities (Forbush 1937;Morrison 1956;Cocconi et al 1958;Piddington 1958). The first ICME observations emerged in the 1970s suggesting loop-or bubble-like structures behind interplanetary shocks (e.g., Hirshberg et al 1970;Gosling et al 1973;Palmer et al 1978). For a more detailed historical review on ICMEs, and their role in understanding solar-terrestrial relationships, we guide the reader to Gopalswamy (2016).…”

The association of coronal mass ejections with their effects near the Earth

“…Their very different origin is discernible from their different elemental composition (Hirshberg et al, 1970), ionization state (Bame et al, 1979;Schwenn et al, 1980;Gosling et al, 1980;Zwickl et al, 1982;Henke et al, 1998;Lepri et al, 2001), temperature depressions (Gosling et al, 1973;Montgomery et al, 1974;Richardson and Cane, 1995), cosmic ray intensity decreases ("Forbush decreases", see, e.g. Cane et al, 1994), the appearance of bi-directional distributions of energetic protons and cosmic rays (Palmer et al, 1978;Richardson et al, 2000) and supra-thermal electrons (Gosling et al, 1987;Shodhan et al, 2000).…”

Heliocentric distance dependence of the interplanetary magnetic field

“…For general reviews see Burlaga (1971b), Hundhausen (1972) and Dryer (1975). It is generally believed that most interplanetary shocks observed at I AU originate at or near the sun, in particular from a solar active regio (Gold, 1955;Hirshberg, 1968;Hirshberg et al, 1970;Hundhausen, 1970;Hundhausen et al, 1970). The majority of the shocks observed at I AU have been associated with solar flare events (e.g.…”