Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Current-Sheet Formation
- 3 Magnetic Annihilation
- 4 Steady Reconnection: The Classical Solutions
- 5 Steady Reconnection: New Generation of Fast Regimes
- 6 Unsteady Reconnection: The Tearing Mode
- 7 Unsteady Reconnection: Other Approaches
- 8 Reconnection in Three Dimensions
- 9 Laboratory Applications
- 10 Magnetospheric Applications
- 11 Solar Applications
- 12 Astrophysical Applications
- 13 Particle Acceleration
- References
- Appendix 1 Notation
- Appendix 2 Units
- Appendix 3 Useful Expressions
- Index
11 - Solar Applications
Published online by Cambridge University Press: 14 October 2009
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Current-Sheet Formation
- 3 Magnetic Annihilation
- 4 Steady Reconnection: The Classical Solutions
- 5 Steady Reconnection: New Generation of Fast Regimes
- 6 Unsteady Reconnection: The Tearing Mode
- 7 Unsteady Reconnection: Other Approaches
- 8 Reconnection in Three Dimensions
- 9 Laboratory Applications
- 10 Magnetospheric Applications
- 11 Solar Applications
- 12 Astrophysical Applications
- 13 Particle Acceleration
- References
- Appendix 1 Notation
- Appendix 2 Units
- Appendix 3 Useful Expressions
- Index
Summary
Much of the impetus for the development of reconnection theory began with R. G. Giovanelli's efforts to develop an electromagnetic theory of solar flares. His first paper on this subject had the title “A Theory of Chromospheric Flares” (Giovanelli, 1946), which is somewhat outdated because flares are now thought of as primarily a coronal phenomenon rather than a chromospheric one. The prodigious advances in X-ray and radio astronomy since Giovanelli's time have made it increasingly clear that what is seen in the chromosphere by ground-based optical telescopes is a response to coronal activity. During a flare, the heated plasma in the corona becomes so hot (T > 107K) that the emitted radiation lies outside the visible portion of the spectrum. Thus, the coronal flare is imperceptible to telescopes observing in the visible spectrum.
Despite the title of his paper, Giovanelli proposed what is essentially a coronal theory of flares. He argued that the chromospheric emissions seen during a flare are produced by a bombardment of energetic electrons accelerated along field lines by electric fields in the vicinity of coronal magnetic null points. This concept still prevails today. However, Giovanelli thought that the electric fields could be produced by induction as the magnetic fields in the photosphere shifted their position slowly over time. Nowadays, such a process is considered to be far too slow to produce a sufficiently strong and impulsive electric field.
After Dungey's (1953) pioneering work on reconnection, Sweet (1958a) and Parker (1957) reconsidered Giovanelli's neutral-point model as a reconnection process which taps the energy stored in the magnetic field associated with coronal currents.
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- Magnetic ReconnectionMHD Theory and Applications, pp. 359 - 424Publisher: Cambridge University PressPrint publication year: 2000
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