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Published byJerome Terence Wade Modified over 9 years ago
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Katya Georgieva Boian Kirov Simeon Asenovski
Solar wind Katya Georgieva Boian Kirov Simeon Asenovski
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Solar wind – expansion of the solar corona
The solar corona is not in hydrostatic equilibruim The corona ( the solar atmosphere) is expanding until it encounters the interstellar matter Eugene Parker (1956) The solar wind carries plasma with embedded magnetic fields to the Earth The interaction of the solar wind with the Earth’s magnetic field leads to geomagnetic disturbances
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3 types of solar wind Slow solar wind: max in sunspot min
background geomagnetic activity galactic cosmic rays modulation solar wind electric field High speed solar wind: max during sunspot declining phase recurrent geomagnetic storms energetic particles precipitation Coronal mass ejections: max during sunspot max Sporadic geomagnetic storms energetic particles precipitation, solar proton events
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3 components of geomagnetic activity corresponding to the 3 types of solar wind
Floor – background geomagnetic activity due to the slow solar wind Sunspot-related geomagnetic activity due to CMEs proportional in number and intensity to the sunspot number Additional geomagnetic activity due to high-speed solar wind
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Different relative importance of the 3 components of geomagnetic activity in different periods
low “floor” of geomagnetic high “floor” of geomagnetic activity activity well expressed dependence of small to vanishing dependence geomagnetic activity on geomagnetic activity on sunspot-related solar activity sunspot –related solar activity small impact of non sunspot high impact of non sunspot- related solar activity related solar activity
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The time the Earth spends in slow solar wind from the equatorial streamer belt depends on the solar cycle phase
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Distribution of slow and fast solar wind
In sunspot min: slow solar wind confined to the ecliptic, fast wind at higher latitudes In sunspot max slow and fast streams at all latitudes Cycle to cycle variations
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Variations of the thickness of the heliospheric current sheet
The thicker the sheet (bigger gamma) – the higher the geomagnetic activity “floor”
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Are solar wind parameters also changing from cycle to cycle?
We look at sunspot min periods Divide the days into 4 groups: - slow background solar wind (V<450 km/s) - faster background solar wind (V>450 km/s) - coronal mass ejections - high speed solar wind
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% of time during sunspot min
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Variations from min to min – slow wind
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Variations from min to min – fast wind
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What is fast solar wind
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By variations
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Solar polarity changes from cycle to cycle
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Solar rotation axis tilted by 7o
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Seasonal variations of IMF direction
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By variations in positive and negative polarity cycles
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NAM and SAM indices
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NAM index in positive and negative polarity cycles
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SAM index in positive and negative polarity cycles
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