Structure and dynamics of the solar chromosphere

Abstract

The thesis "Structure and dynamics of the solar chromosphere" of J.M. Krijger is a study on the behavior of the solar chromosphere, the thin layer just above the solar surface (photosphere) visible in purple red light during a total solar eclipse. The most important result of this thesis is that the chromosphere is filled with acoustic and internal gravity waves that travel upward until they collide with a canopy of expanding magnetic field. The photosphere is the layer of which we see the light with the naked eye. Through this layer poke large and small magnetic tubes. Above the photosphere and the chromosphere sits the hot solar corona of a few million degrees. With observations of among others the space satellite TRACE (Transition Region and Coronal Explorer) J.M. Krijger shows that the photosphere is dominated by flows of the ambient gas that dictate the magnetic field where to go. The possible heating of the chromosphere is an important unsolved problem in solar physics. The chromosphere forms the transition region between the very hot corona, dominated by magnetic fields, and the photosphere where gasflows drag the magnetic field along. In this transition region the magnetic field, which in the photosphere is still trapped in individual tubes, expands to a canopy above which the magnetic field fills the entire space. In this thesis it is shown that the chromosphere is dominated by upward propagating acoustic waves and a magnetic canopy that changes the dynamics of the oscillations. Finally J.M. Krijger shows that the "network" of magnetic field in the chromosphere is formed by magnetic tubes that are swepped together by flows in the photosphere.