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 main source of deka-MeV protons during the largest SEP events

CME driven shocks

Diffusive shock acceleration ∆u = u 2 – u 1 SW frame u1u1 u2u2

Turbulent foreshock Outward-streaming ions scattering off turbulence lead to amplification of fluctuations Bootstrapping!

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  θ Bn = 2.8° V s = 1920 km/s R = 14–22 R  θ Bn = 5.4° V s = 1820 km/s R = 25–36 R  θ Bn = 8.7° V s = 1620 km/s R = 40–60 R  θ Bn = 14° V s = 1430 km/s     1a 2a 3a 4a 1b 2b 3b 4b 1c 2c 3c 4c Three different initial particle distributions Mathematical model (—) developed for turbulent region explains simulations (- - -) 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/ ) under grant agreement no , and is supported in part by the University of Helsinki