Main Objective: To analyse the vertical component of the vector magnetic field in active regions. To study the evolution of the magnetic properties on the boundary of pores and umbrae, if any.
Scientific Justification: Jurcak criterion is an empirical law that states that the boundary between umbra and penumbra is defined by a constant vertical magnetic field in stable sunspots (Jurcak et al. 2018). This means that it exists a critical vertical magnetic field (Bcrit), independent of other conditions such as sunspot size, solar location or solar activity, that completely changes the convective motion on the solar surface. Vertical magnetic fields (Bver) stronger than Bcrit only allow umbral convection. However, umbrae and pores with Bver weaker than Bcrit are unstable and prone to be disintegrated by convective motions (Schmassmann et al. 2018).
Jurcak criterion was defined after statistically analising 88 sunspot scans from Hinode/SOT-SP. This criterion motivates wider analyses of the influence of the vector magnetic field on solar convection. In ourground-based observations (GREGOR, Tenerife, Spain) we aim to characterise solar granulation in terms of the vector magnetic field. The coordination with Hinode/SOT-SP will let us compare space-based to ground-based spectropolarimetric observations and to Jurcak's statistics. |
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