Kink instability of solar coronal loops as the cause of solar flares
- 152 Downloads
- 176 Citations
Abstract
Solar coronal loops are observed to be remarkably stable structures. A magnetohydrodynamic stability analysis of a model loop by the energy method suggests that the main reason for stability is the fact that the ends of the loop are anchored in the dense photosphere. In addition to such line-tying, the effect of a radial pressure gradient is incorporated in the analysis.
Two-ribbon flares follow the eruption of an active region filament, which may lie along a magnetic flux tube. It is suggested that the eruption is caused by the kink instability, which sets in when the amount of magnetic twist in the flux tube exceeds a critical value. This value depends on the aspect ratio of the loop, the ratio of the plasma to magnetic pressure and the detailed transverse magnetic structure. For a force-free field of uniform twist the critical twist is 3.3π, and for other fields it is typically between 2π and 6π. Occasionally active region loops may become unstable and give rise to small loop flares, which may also be a result of the kink instability.
Keywords
Flare Solar Flare Flux Tube Magnetic Pressure Radial PressurePreview
Unable to display preview. Download preview PDF.
References
- Anzer, U.: 1968, Solar Phys. 3, 298.Google Scholar
- Bernstein, I. B., Frieman, E. A., Kruskal, M. D., and Kulsrud, R. M.: 1958, Proc. Roy. Soc. London A244, 17.Google Scholar
- Foukal, P.: 1975, Solar Phys. 43, 327.Google Scholar
- Giachetti, R., Van Hoven, G., and Chiuderi, C.: 1977, Solar Phys. 55, 371.Google Scholar
- Gibson, E. G.: 1977, Solar Phys. 53, 123.Google Scholar
- Gold, T. and Hoyle, F.: 1960, Monthly Notices Roy. Astron. Soc. 120, 89.Google Scholar
- Gradshteyn, I. S. and Ryzhik, I. M.: 1965, Tables of Integrals, Series and Products, Academic Press.Google Scholar
- Heyvaerts, J., Priest, E. R., and Rust, D. M.: 1977, Astrophys. J. 216, 123.Google Scholar
- Hood, A. W.: 1979, Ph.D. Thesis, St. Andrews University.Google Scholar
- Hood, A. W. and Priest, E. R.: 1979a, Astron. Astrophys., in press.Google Scholar
- Hood, A. W. and Priest, E. R.: 1979b, submitted.Google Scholar
- Jeffrey, A. and Taniuti, T.: 1966, Magnetohydrodynamic Stability and Thermonuclear Containment, Academic Press.Google Scholar
- Jordan, C.: 1975, in S. R. Kane (ed.), ‘Solar Gamma-, X-, and EUV Radiations’, IAU Symp. 68, 109.Google Scholar
- Kruskal, M. D., Johnson, J. L., Gottlieb, M. B., and Goldman, L. M.: 1958, Phys. Fluids 1, 421.Google Scholar
- Newcomb, W. A.: 1960, Ann. Phys. 10, 232.Google Scholar
- Priest, E. R.: 1976a, in D. J. Williams (ed.), ‘Physics of Solar Planetary Environment’, Am. Geophys. Union 1, 144.Google Scholar
- Priest, E. R.: 1976b, Solar Phys. 47, 41.Google Scholar
- Priest, E. R.: 1978, Solar Phys. 58, 57.Google Scholar
- Raadu, M. A.: 1972, Solar Phys. 22, 425.Google Scholar
- Sakurai, T.: 1976, Publ. Astron. Soc. Japan 28, 177.Google Scholar
- Shafranov, V. D.: 1957, J. Nucl. Energy II 5, 86.Google Scholar
- Suydam, B. R.: 1958, International Conference on the Peaceful Uses of Atomic Energy, 2nd Geneva, p. 187.Google Scholar
- Tasso, H.: 1975, Phys. Fluids 17, 1131.Google Scholar
- Tur, T. J. and Priest, E. R.: 1976, Solar Phys. 48, 89.Google Scholar
- Tur, T. J. and Priest, E. R.: 1978, Solar Phys. 58, 181.Google Scholar
- Wesson, J. A.: 1978, Nuclear Fusion 18, 87.Google Scholar