Acceleration of Solar Energetic Particles
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Acceleration of Solar Energetic Particles
Rami Vainio
University of Helsinki, Department of Physics, Finland
University of Turku, Department of Physics and Astronomy, Finland
SPACECAST Stakeholder Meeting, BAS, 7 February 2014
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Solar energetic particle events
Lario (2005)
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Flares or shocks?
Large gradual SEP events nearly always accompanied with both!
–30 min
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Solar energetic particle events
Lario (2005)
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Present paradigm of SEP acceleration in gradual events
CME-driven shocks are the mainsource of deka-MeV protons duringthe largest SEP events
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CME driven shocks
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Diffusive shock acceleration
∆u = u2 – u1
SW frame
u1
u2
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Turbulent foreshock
Outward-streaming ions scattering off turbulence leadto amplification of fluctuationsBootstrapping!
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Modeling in SPACECAST
Proton intensity [cm–2 sr –1 s
–1 MeV
–1]
Alfvén wave intensity [G
2]
Distance of the shock from the Sun = 14 – 22 R
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R = 5.8–11 R
θBn = 2.8°Vs = 1920 km/s
R = 14–22 R
θBn = 5.4°Vs = 1820 km/s
R = 25–36 R
θBn = 8.7°Vs = 1620 km/s
R = 40–60 R
θBn = 14°Vs = 1430 km/s
1a
2a
3a
4a
1b
2b
3b
4b
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Three different initial particle distributionsMathematical model (—) developedfor turbulent region explainssimulations (- - -)
New tool for space weather modelling
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Summary
• Solar energetic particles are accelerated in flares and CME-driven shocks– CME-driven shocks responsible for large gradual events
• SPACECAST project has developed models for particle acceleration in CME-driven shocks– First steps taken towards operational direction by analyzing
simulations and developing a semi-analytical description of ion foreshocks in CMEs
• Next steps: integration of SPACECAST results to a state-of-the-art transport code (see Angels Aran’s presentation)
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Acknowledgements
• The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 262468, and is supported in part by the University of Helsinki