Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Part I Astronomical background
- Part II Physical processes
- Part III High energy astrophysics in our Galaxy
- 12 Interstellar gas and magnetic fields
- 13 Dead stars
- 14 Accretion power in astrophysics
- 15 Cosmic rays
- 16 The origin of cosmic rays in our Galaxy
- 17 The acceleration of high energy particles
- Part IV Extragalactic high energy astrophysics
- Appendix: Astronomical conventions and nomenclature
- Bibliography
- Name index
- Object index
- Index
17 - The acceleration of high energy particles
from Part III - High energy astrophysics in our Galaxy
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Part I Astronomical background
- Part II Physical processes
- Part III High energy astrophysics in our Galaxy
- 12 Interstellar gas and magnetic fields
- 13 Dead stars
- 14 Accretion power in astrophysics
- 15 Cosmic rays
- 16 The origin of cosmic rays in our Galaxy
- 17 The acceleration of high energy particles
- Part IV Extragalactic high energy astrophysics
- Appendix: Astronomical conventions and nomenclature
- Bibliography
- Name index
- Object index
- Index
Summary
Observations of cosmic rays and sources of non-thermal radiation indicate that the process of acceleration of high energy particles must account for the following features:
(i) The formation of a power-law energy spectrum for all types of charged particles. The energy spectrum of cosmic rays and the electron energy spectrum of non-thermal sources have the form dN(E) α E −x dE, where the exponent x typically lies in the range 2–3.
(ii) The acceleration of cosmic rays to energies E ∼ 1020 eV.
(iii) In the process of acceleration, the chemical abundances of the primary cosmic rays should be similar to the cosmic abundances of the elements.
It would be helpful if we could appeal to the physics of laboratory plasmas for some guidance, but the evidence is somewhat ambivalent. On the one hand, if we want to accelerate particles to very high energies, we need to go to a great deal of trouble to ensure that the particles remain within the region of the accelerating field, for example, in machines such as betatrons, synchrotrons, cyclotrons, and so on. Nature does not go to all this trouble to accelerate high energy particles. On the other hand, as soon as we try to build machines to store high temperature plasmas, such as tokamaks, the configurations are usually grossly unstable and, in the instability, particles are accelerated to suprathermal energies.
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- Information
- High Energy Astrophysics , pp. 561 - 582Publisher: Cambridge University PressPrint publication year: 2011