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Physics 777 Plasma Physics and Magnetohydrodynamics (MHD)

Physics 777 Plasma Physics and Magnetohydrodynamics (MHD). Instructor: Gregory Fleishman Lecture 12 . Particle Acceleration. 18 November 200 8. Plan of the Lecture. Elementary Concepts: DC Electric Fields and Adiabatic Motion Fermi Acceleration Stochastic Acceleration by Weak Turbulence

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Physics 777 Plasma Physics and Magnetohydrodynamics (MHD)

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  1. Physics 777Plasma Physics and Magnetohydrodynamics (MHD) Instructor: Gregory Fleishman Lecture 12. Particle Acceleration 18 November 2008

  2. Plan of the Lecture • Elementary Concepts: DC Electric Fields and Adiabatic Motion • Fermi Acceleration • Stochastic Acceleration by Weak Turbulence • Acceleration by a Shock Wave • Acceleration by Strong Turbulence and Shock Ensemble • Other Examples of Particle Acceleration

  3. Section 1. Elementary concepts of particle acceleration • How charged particles are being energized (accelerated)? • Role of magnetic and electric fields. • Adiabatic motion in a trap with moving walls. Regular acceleration/deceleration. • Stochastic acceleration due to random wall motion.

  4. Section 2. Fermi Acceleration. Challenge: acceleration mechanism must ensure a power-law spectrum; frequently – over many orders of magnitude. Credit: Cronin et al (1997); Livio Scarsi(2008)

  5. BUT: how magnetic clouds can accelerate particles?

  6. Section 3. Stochastic Acceleration by Weak Turbulence.

  7. Section 4. Acceleration by a Shock Wave.

  8. RECALL

  9. Shock front in SNR 1006

  10. Section 5.Acceleration by Strong Turbulence and Shock Ensemble Superbubbles in SMC

  11. Turbulent acceleration in solar flares Sample trajectory magnetic field lines • B0 = 20G, dBx ~ dBy ~ 20G, dBz ~ 100G • Outer scales • lx=ly=1km, lz=20km Credit: L. Vlahos

  12. Section 6. Other Examples of Particle Acceleration

  13. Section 7. Homework • Complete written project report is due; no excuse.

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