Magnetohydrodynamics of an active region

Multi-region relaxed magnetohydrodynamics with anisotropy and flow

Complex magnetic fields in an active region

High-resolution observations of the full Stokes vector in Fe i spectral lines around 5250 Å obtained at the Swedish Vacuum Solar Telescope on La Palma with the ZIMPOL I Stokes polarimeter in a complex active region reveal the presence of anomalously shaped Stokes profiles indicating the coexistence of at least two magnetic components within the same spatial resolution element. These Stokes prof...

extremal region detection guided by maxima of gradient magnitude

a problem of computer vision applications is to detect regions of interest under dif- ferent imaging conditions. the state-of-the-art maximally stable extremal regions (mser) detects affine covariant regions by applying all possible thresholds on the input image, and through three main steps including: 1) making a component tree of extremal regions’ evolution (enumeration), 2) obtaining region ...

An adaptive finite element method for magnetohydrodynamics

We describe a procedure for the adaptive h-refinement solution of the incompressible MHD equations in stream function form using a stabilized finite element formulation. The mesh is adapted based on a posteriori spatial error estimates of the magnetic field using both recovery and order extrapolation techniques. The step size for time integration is chosen so that temporal discretization errors...

An Improved Virial Estimate of Solar Active Region Energy

The MHD virial theorem may be used to estimate the magnetic energy of active regions based on vector magnetic fields measured at the photosphere or chromosphere. However, the virial estimate depends on the measured vector magnetic field being forcefree. Departure from force-freeness leads to an unknown systematic error in the virial energy estimate, and an origin dependence of the result. We pr...