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What drives space weather and what has helicity got to do with it? ...or assorted thoughts and questions of a confused PhD student. 19/03/2019. Reko Hynönen 1 1 Aalto-yliopisto Reko.Hynonen@aalto.fi. Purpose of this talk. Solar features. Strong magnetic flux
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What drives space weather and what has helicity got to do with it?...or assorted thoughts and questionsof a confused PhD student 19/03/2019 Reko Hynönen1 1Aalto-yliopisto Reko.Hynonen@aalto.fi
Solar features • Strong magnetic flux • Active regions: simple and complex • Flares • Flux of magnetic helicity?
Solar features • Strong magnetic flux • Active regions: simple and complex • Flares • Flux of magnetic helicity? • Open field lines • High-speed solar wind streams • With high Alfvénicity / cross helicity • CH: Relation to helicity?
Solar features • Strong magnetic flux • Active regions: simple and complex • Flares • Flux of magnetic helicity? • Flares and coronal mass ejections • Transfer of magnetic helicity? • Open field lines • High-speed solar wind streams • With high Alfvénicity / cross helicity • CH: Relation to helicity?
Solar wind structures • Slow, high-density solar wind • High velocity shear • typically low cross helicity • Origin unclear: • One of the source regions:helmet streamers
Solar wind structures • Slow, high-density solar wind • High velocity shear • typically low cross helicity • Origin unclear: • One of the source regions:helmet streamers • Fast, low-density solar wind • Low velocity shear • typically high cross helicity • Origin: Coronal holes
Solar wind structures • Slow, high-density solar wind • High velocity shear • typically low cross helicity • Origin unclear: • One of the source regions:helmet streamers • Fast, low-density solar wind • Low velocity shear • typically high cross helicity • Origin: Coronal holes
Space weather events Energy! Energy Energy!
Space weather events Reconnection! Energy! Energy Energy! Reconnection!
Space weather events Reconnection! Energy! Dungey cycle Energy Energy! Reconnection!
Space weather events Dungey cycle Reconnection! Energy! Dungey cycle Energy Energy! Reconnection!
Space weather events Reconnection! Energy! Dungey cycle Energy Energy! Reconnection!
Space weather events • Geomagnetic storms • Enhancement of ring current • Equatorial, global activity • Measured by storm disturbance indices, like Dst Reconnection! Energy! Dungey cycle Energy Energy! Reconnection!
Space weather events • Geomagnetic storms • Enhancement of ring current • Equatorial, global activity • Measured by storm disturbance indices, like Dst • Substorms • Activity of auroral region (both poles) • Local phenomena • Measured by substorm / electrojet current indices, like AE Reconnection! Energy! Dungey cycle Energy Energy! Reconnection!
Space weather events • Measuring Dst index • Four magnetic stations around equator