EUV emission of coronal loops above an active region (AR) observed by the TRACE satellite (Strong et al. 1994). The footpoints of short, intermediate, and longer loops of varying curvature and intensity are indicated by blue arrows. Typically, the short and most emissive loop is located in the core of an AR, while the longer loops may reach higher into the corona and may also connect to the periphery of the region. The spatial extent of our 3D MHD model is 235 × 235 × 156 Mm³ and is roughly indicated by the red box. Image credit: NASA/LMSAL.