Emerging flux and sunspots
Valentin Martinez Pillet
While spectroscopy and polarimetry are extremely helpful in providing crucial information about the evolution of the solar magnetic fields at the photosphere and above, they provide no information about the magnetic structuring of the subsurface layers. Only through the recently developed techniques of local helioseiosmology can we expect to learn something about crucial aspects of solar magnetism, such as the flux emergence process or the conectivity of the emerged field to deeper layers. This becomes even more crucial as current flux emergence simulations show how difficult is for a magnetic flux tube to surface above the photosphere and enter the stably stratified portion of the solar atmosphere. On the contrary, flux emergence, as observed in almost any wavelength range, is known to be spectacular, showing very little indications of a deceleration in the emergence process into the corona. Similarly, the existence of failed emergence events in the form of horizontal flux tubes that are unable to reach the outer layers of the sun, can only be detected by the techniques of local helioseismology. A brief review of the main objectives that must be covered by SDO/HMI in the context of the physics of flux emergence will be provided.