Advertisement

Astrophysics and Space Science

, Volume 246, Issue 1, pp 107–118 | Cite as

The role of loop footpoints rotation in single loop flares

  • T. Zaqarashvili
  • B. Chargeishvili
  • J. Sakai
Article

Abstract

We consider that single loop flares can be caused by the rotation of loop footpoints. Choosing a typical geometry for this case we find from MHD equations self-consistent expressions and a set equations governing behaviour of all physical quantities. Numerical simulations have revealed that under the determined conditions for the initial azimuthal velocity and current the pinch instability takes place. The most important parameters of the problem are the plasma β and the ratio of the initial values of longitudinal and poloidal components of the magnetic field-B1. Thus, calculations show that the critical pinch time increases with the increase ofB1 and decreases with the increase of plasma β. So the most effective flares are probable for the most high loops with strong currents. ForB1=10 and β=0.01 the critical pinch time is ≈2.5 s. The critical twist angle for magnetic field depends on the initial one. For low intial twist which corresponds to bigB1 the critical one is more less. For exampleB1=30 gives Φ≈1.8π (when ratio of loop length and radius is 10). Geometrical analysis shows that the present model can explain (for high photospheric rotation) single loop flares taking place on different parts of the loop as on the top of it as closer to one of the footpoints. It depends on the relative rotation momentum of loop footpoints. Subject headings: MHD-Sun:flares.

Keywords

Flare Present Model Physical Quantity Geometrical Analysis Twist Angle 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Ai, G., Li, W., Hirayama, T. and Ichimoto, K.: 1994,X-Ray Solar Physics from Yohkoh, Universal Academy Press, Inc. Tokyo, Japan, 79.Google Scholar
  2. Axford, W.I.: 1969,Rev. Geophys. 7, 421.Google Scholar
  3. Canfield, R.C., Priest, E.R. and Rust, D.M.: 1974, in: Y. Nakagawa and D.M. Rust (eds.),Flare-Related Magnetic Field Dynamics, NCAR, Boulder, Paper 1.Google Scholar
  4. Chargeishvili, B., Zhao, J. and Sakai, J-I.: 1993,Sol. Phys. 145, 297.Google Scholar
  5. Cheng, Chung-Chich: 1977,Astrophys. J. 213, 558.Google Scholar
  6. Colgate, S.A.: 1978,Astrophys. J. 221, 1068.Google Scholar
  7. Coppi, B.: 1975,Astrophys. J. 195, 545.Google Scholar
  8. Dungey, J.W. and Speiser, T.W.: 1969,Planet. Space Sci. 17, 1285.Google Scholar
  9. Hood, A.W. and Priest, E.R.: 1979,Sol. Phys. 64, 303.Google Scholar
  10. Hood, A.W. and Priest, E.R.: 1981,Geophys. Astrophys. Fluid Dynamics 17, 297.Google Scholar
  11. Low, B.C.: 1974,Astrophys. J. 189, 353.Google Scholar
  12. Low, B.C.: 1974b,Astrophys. J. 193, 243.Google Scholar
  13. Machado, M.I.: 1982,Adv. Space Res. 2, 115.Google Scholar
  14. Parker, E.N.: 1966,Astrophys. J. 145, 811.Google Scholar
  15. Parker, E.N.: 1972,Astrophys. J. 174, 499.Google Scholar
  16. Parker, E.N. 1973,Astrophys. J. 180, 247.Google Scholar
  17. Parker, E.N.: 1974a,Astrophys. J. 190, 429.Google Scholar
  18. Petschek, H.E.: 1964, in: W.N. Hess (ed.),Physics in Solar Flares, NASA Sp-50, p. 425.Google Scholar
  19. Priest, E.R.: 1982,Solar Magnetohydrodynamics, Reidel, Dordrecht.Google Scholar
  20. Sakai, J-I. and de Jager, C.: 1989,Sol. Phys. 123, 393.Google Scholar
  21. Sakai, J-I. and de Jager, C.: 1989,Sol. Phys. 123, 329.Google Scholar
  22. Sakai, J-I. and de Jager, C.: 1991,Sol. Phys. 134, 329.Google Scholar
  23. Sakai, J-I. and Koide, S.: 1992,Sol. Phys. 142, 399.Google Scholar
  24. Sakai, J-I.: 1990,Astrophys. J. 365, 354.Google Scholar
  25. Shimizu, T., Tsuneta, S., Acton, L.W., Lemen, J.R. and Uchida, Y.: 1992,Publ. Astron. Soc. Japan 44, L147.Google Scholar
  26. Sonnerup, B.U.O.: 1970,J. Plasma Phys. 4, 161.Google Scholar
  27. Spicer, D.S.: 1977b,Sol. Phys. 53, 305.Google Scholar
  28. Strong, K., Hudson, H. and Dennis, B.: 1994,X-Ray Solars Physics from Yohkoh, Universal Academy Press, Inc. Tokyo, Japan, 65.Google Scholar
  29. Sturrock, P.: 1980,Solar Flares, Colorado Associated University Press.Google Scholar
  30. Svestka, Z.: 1976,Solar Flares, Reidel, Dordrecht.Google Scholar
  31. Takakura, T., Inda, M., Makishima, K., Masuda, S., Kosugi, T., Sakao, T., Sakurai, T. and Ogawara, Y.: 1993,Publ. Astron. Soc. Japan 45, 737.Google Scholar
  32. Van Hoven, G., Chiuderi, C. and Giachetti, R.: 1977,Astrophys. J. 213, 869.Google Scholar
  33. Wilson, P.R.: 1977,Astrophys. J. 214, 611.Google Scholar
  34. Yeh, T. and Axford, W.I.: 1970,J. Plaspa Phys. 4, 207.Google Scholar

Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • T. Zaqarashvili
    • 1
  • B. Chargeishvili
    • 1
  • J. Sakai
    • 2
  1. 1.Department of Theoretical Astrophysics of Abastumani Astrophysical ObservatoryTbilisiRepublic of Georgia
  2. 2.Laboratory for Plasma Astrophysics and Fusion Science, Department of Electronics and Information, Faculty of EngineeringToyama UniversityJapan

Personalised recommendations