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

Solar energetic particle events

Lario (2005)

Flares or shocks?

Large gradual SEP events nearly always accompanied with both!

–30 min

Solar energetic particle events

Lario (2005)

Present paradigm of SEP acceleration in gradual events

CME-driven shocks are the mainsource of deka-MeV protons duringthe largest SEP events

CME driven shocks

Diffusive shock acceleration

∆u = u2 – u1

SW frame

u1

u2

Turbulent foreshock

Outward-streaming ions scattering off turbulence leadto amplification of fluctuationsBootstrapping!

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

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

1c

2c

3c

4c

Three different initial particle distributionsMathematical model (—) developedfor turbulent region explainssimulations (- - -)

New tool for space weather modelling

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)

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