MHD Wave Coupling From Photosphere To Corona
Magneto-acoustic gravity waves in a vertical field
Freddie Mather
Robertus Erdelyi(University of Sheffield)
University of Sheffield
The theory of wave propagation within the Sun has been well studied. Acoustic waves are prevalent within the Sun, oscillating the body as a whole, and have been observed as 5 minute oscillations on numerous occasions. Vertical magnetic fields are common within the Sun and in the atmosphere in structures such as Sunspots and coronal holes to name but a few. It is therefore important to develop a theory based on a vertical magnetic field.

Within the Sun the magnetic fields contribution to some of the waves propagating here is small but as we climb higher into the atmosphere the magnetic field starts to have a serious effect on wave propagation. We therefore must use magneto-hydrodynamic theory to study wave propagation here. Yet we must also incorporate gravity into our theory due to the strong field causing the plasma to be stratified. We therefore call these waves, magneto-acoustic gravity (MAG) waves.

In this talk we will show how, by defining a new variable (the pressure perturbation over the background density), we can provide a simple hypergeometric solution in an isothermal atmosphere for MAG waves in a vertical field, which can be shown to reduce to Zhugzhda's original hypergeometric solution for the horizontal velocity component. The same formalism can then be used to derive a simple hypergeometric solution for the vertical velocity component. Thereby providing analytic inroads that simplify previous results. We will also show, using these new solutions, how the energy of standing-waves could be distributed in the solar atmosphere.


16:30 - 18:00
EX - C3 (150)