Creation of magnetic energy in the solar atmosphere

We show that a magnetic flux tube can grow in strength and size provided the temperature increases outward at the edge of the tube where the axial magnetic field declines to its external value. The radius of the tube increases at a rate determined by our theory. It is the coincidence of temperature and magnetic field gradients of opposite sign that generates the new field, and if this is lost the tube ceases to grow. The phenomenon is illustrated by adopting plausible distributions for the temperature and magnetic field strength, which yield an expression for the rate of growth of the magnetic field magnitude B. The mechanism provides a possible explanation of the fibrous nature of solar magnetic fields.