Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- 13 The contents of the Universe – the grand design
- 14 Aspects of stellar evolution relevant to high energy astrophysics
- 15 Dead stars
- 16 Accretion power in astrophysics
- 17 Interstellar gas and magnetic field
- 18 Synchrotron radiation and the radio emission of the Galaxy
- 19 The origin of the electron energy spectrum in our Galaxy
- 20 The origin of high energy protons and nuclei
- 21 The acceleration of high energy particles
- Appendices – astronomical nomenclature
- Further reading and references
- Index
21 - The acceleration of high energy particles
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgements
- 13 The contents of the Universe – the grand design
- 14 Aspects of stellar evolution relevant to high energy astrophysics
- 15 Dead stars
- 16 Accretion power in astrophysics
- 17 Interstellar gas and magnetic field
- 18 Synchrotron radiation and the radio emission of the Galaxy
- 19 The origin of the electron energy spectrum in our Galaxy
- 20 The origin of high energy protons and nuclei
- 21 The acceleration of high energy particles
- Appendices – astronomical nomenclature
- Further reading and references
- Index
Summary
The problem
We have left to the last chapter of this volume one of the most intriguing problems in high energy astrophysics – the mechanisms by which high energy particles are accelerated to ultrarelativistic energies. In these first two volumes, sites where particles are accelerated include solar flares, the boundary of the Earth's magnetosphere, pulsar magnetospheres, supernovae and supernova remnants. In volume 3, we will find evidence for particle acceleration in active galactic nuclei and in extended radio sources. It is appropriate to consider the problem of the acceleration of charged particles at this point because a number of important features of the cosmic rays are common to the energy spectra of particles in other astrophysical environments.
The specific features of particle acceleration which we have to account for are as follows.
1 A power-law energy spectrum for particles of all types. The energy spectrum of cosmic rays and the electron energy spectrum of many non-thermal sources have the form
where the exponent x lies in the range roughly 2.2–3. For the cosmic rays, x = 2.5–2.7 at energies ∼ 1–103 GeV (Section 9.1), with slightly flatter spectra for primary nuclei such as iron. The typical spectra of radio sources correspond to electron spectra with x ≈ 2.6 with a scatter of about 0.4 about this mean value. The continuum spectra of quasars in the optical and X-ray wavebands correspond to x ∼ 3.
2 The acceleration of cosmic rays to energies E ∼ 1020 eV.
3 […]
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- High Energy Astrophysics , pp. 344 - 364Publisher: Cambridge University PressPrint publication year: 1994