Accession Number : ADA259703


Title :   Environmental Conditions Responsible for Solar Activity


Descriptive Note : Annual technical rept. 1 Oct 91-1 Oct 92,


Corporate Author : STANFORD UNIV CA CENTER FOR SPACE SCIENCE AND ASTROPHYSICS


Personal Author(s) : Sturrock, Peter A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a259703.pdf


Report Date : 30 Nov 1992


Pagination or Media Count : 18


Abstract : This report describes progress toward understanding the theoretical basis for solar activity. One of our key accomplishments has been the insight we have gained into the eruption of coronal magnetic structures. Roumeliotis, Sturrock and Antiochos have made numerical and analytic calculations which indicate that coronal magnetic fields being sheared by convective motions acting on their photospheric footpoints evolve smoothly until the shear surpasses a certain critical amount. After that, the coronal field exhibits very sensitive dependence on the photospheric boundary conditions, in the sense that small changes in the footpoint displacements produce huge changes in the height of the coronal field. We propose that this nonlinear behavior of sheared magnetic fields is the explanation for eruptive phenomena such as coronal mass ejections and solar flares. We are also developing several approaches for understanding coronal heating. In particular, Sturrock has proposed a model In which turbulent reconnection deep within the chromosphere produces local heating as well as a burst of magnetohydrodynamic waves that propagate upward to heat the corona. Roumeliotis is working on the theory that twisted flux loops in the corona undergo an internal resistive kink instability that unwinds the internal field and releases magnetic energy to heat the loop.... Solar activity, Coronal heating, Flares, Magnetic fields.


Descriptors :   *MAGNETIC FIELDS , *SOLAR ACTIVITY , MODELS , HEAT , SOLAR FLARES , MAGNETOHYDRODYNAMIC WAVES , CHROMOSPHERE , LOOPS , ENERGY , RELEASE


Subject Categories : Astrophysics
      Electricity and Magnetism
      Thermodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE