Particle acceleration in collisionless shock with large scale magnetic field variation

Fan Guo, J. R. Jokipii and Jozsef Kota

Lunar & Planetary Laboratory, Department of Planetary Sciences

University of Arizona

Presentation at SHINE meeting, July 27th 2010Presentation at SHINE meeting, July 27th 2010

Large scale shocks associated with magnetic field variation

Termination Shock

advection diffusion drift energy change

Diffusive shock acceleration (DSA; Krymsky 1977, Axford et al. 1977, Bell 1978, Blandford & Ostriker 1978), is the most popular theory for charged-particle acceleration. The basic conclusions of DSA can be drawn from the Parker transport equation (Parker 1965) by considering the shock to be a compressive discontinuity in an infinite one-dimensional and time steady system. DSA is thought to be the mechanism that accelerates anomalous cosmic rays (ACRs) in the Heliospheric termination shock and also SEPs with energy up to GeV in CME shocks.

•Cummings (2008)

Some consideration

• Florinski

• Jokipii

• Kota

• Schwadron

Schwadron & McComas (2006)

Florinski & Zank (2006)

Kota & Jokipii (2008)

Some possibility (spatial source variation)

Jokipii & Kota (2008)

A simple illustrative model

Kota 2008, 2010 submitted

• Consider a sinusoidal

magnetic field variation

Bx = Bx0sin(kx), Bz = Bz0

• Solve transport equation using

stochastic integration

• Spatial units are in 10 AU, time units are in about 1

month. Upstream velocity is 500 km/s, with a strong compression ratio (r=4.) at the shock. ┴/|| = 0.05.

Basic consideration

P = 3.0 P0 P = 10.0 P0

Slide from Alan Cummings, ISSI Workshop

For oblique shocks and smaller fluctuation amplitude

Conclusions• After the consideration of large scale magnetic field

variation, the 1-D diffusive shock acceleration will be significantly altered.

• The charged particles will be trapped and accelerated in the regions where the foot points converging each other, creating ‘hot spot’ of accelerated particles.

• The particles would transport towards ‘hot spot’ region and get accelerated, as a consequence of particle transport.

Thanks for your attention!