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Reko Hynönen 1 1 Aalto-yliopisto Reko.Hynonen@aalto.fi

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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Reko Hynönen 1 1 Aalto-yliopisto Reko.Hynonen@aalto.fi

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  1. 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

  2. Purpose of this talk

  3. Solar features • Strong magnetic flux • Active regions: simple and complex • Flares • Flux of magnetic helicity?

  4. 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?

  5. 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?

  6. Solar wind structures

  7. Solar wind structures • Slow, high-density solar wind • High velocity shear • typically low cross helicity • Origin unclear: • One of the source regions:helmet streamers

  8. 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

  9. 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

  10. Space weather events Energy!  Energy Energy!

  11. Space weather events Reconnection! Energy!  Energy Energy! Reconnection!

  12. Space weather events Reconnection! Energy! Dungey cycle  Energy Energy! Reconnection!

  13. Space weather events Dungey cycle Reconnection! Energy! Dungey cycle  Energy Energy! Reconnection!

  14. Space weather events Reconnection! Energy! Dungey cycle  Energy Energy! Reconnection!

  15. 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!

  16. 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!

  17. Space weather events • Measuring Dst index • Four magnetic stations around equator

  18. Space weather events

  19. Space weather events

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