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ionized tail. dust tail. SLIDE SHOW 6. SOLAR WIND. Observations of comets suggested solar outflow (Biermann). Parker (1958) proposed supersonic expansion. Confirmed in 1960s by spacecraft measurements (Mariner 2, 1962). Slow wind (300 km/s) + Fast solar wind (700 km/s).
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ionized tail dust tail SLIDE SHOW 6. SOLAR WIND • Observations of comets suggested solar outflow (Biermann). • Parker (1958) proposed supersonic expansion. • Confirmed in 1960s by spacecraft measurements (Mariner 2, 1962) • Slow wind (300 km/s) + Fast solar wind (700 km/s) Where from ?
Corona, as seen from eclipse (1970) • “Helmet streamers” • low down confined by Sun’s B • - far out -- radial structures • Dark open regions reaching surface -- source of fast solar wind.
Corona varies in shape in solar cycle Sunspot minimum Sunspot maximum
From X-ray telescope – Skylab (1970s) Open regions show up as dark Coronal holes -- at poles in sunspot minimum -- source of fast solar wind
ULYSSES: The first space mission to orbit the Sun out of the ecliptic plane Ulysses trajectory
FAST Solar Wind (700 km/s) in coronal holes SLOW Solar Wind (300 km/s) in equatorial streamers ULYSSES: solar wind velocity (polar plot) Background = composite image of the Sun from SOHO Sunspot minimum Red= inward field Blue= outward field
ULYSSES: cf first and second orbit 1994-95 (s. min)2000-01 (s. max) Negative polarity B Positive polarity B
From above: velocity is radial • Carries Sun’s B with it --> spiral {Interplanetary Magnetic Field (IMF)}
Characteristics of the interplanetary medium at the orbit of the Earth