A systematic structuring of magnetic fields over scales much smaller than the mean free path of photospheric photons may be responsible for the observed asymmetrical Stokes profiles. We explore this possibility by deriving the radiative transfer equation for microstructured magnetic atmospheres (the MISMA approximation). This equation is

We show that the alteration between intervals of cyclic activity and grand minima like the Maunder minimum in the 17th century, which is characteristic for the long-term variation of the solar activity, can be described as on-off intermittency arising in a dymano driven by the instability of magnetic flux tubes in the overshoot layer below the

LMC-SMP83 is a planetary nebula in the Large Magellanic Cloud whose central star is recently reported by Pena et al. to show decreases in temperature and luminosity of at least 50% over a time span of seven years. Serendipitously, this object is observed with the Planetary and Faint Object Cameras onboard the Hubble Space Telescope between 1991

EL TRABAJO RECOGIDO EN LA PRESENTE MEMORIA SE BASA EN OBSERVACIONES REALIZADAS CON EL FOTOMETRO LOI-T INSTALADO EN EL OBSERVATORIO DEL TEIDE. SE ESTABLECE UN PROCEDIMIENTO PARA EL ANALISIS DE LOS DATOS, CALCULO DE LOS FILTROS OPTIMOS PARA LA IDENTIFICACION DE LOS MODOS, MEDIDA DE FRECUENCIAS, ANCHURAS, AMPLITUDES Y DESDOBLAMIENTO ROTACIONAL. EN SU

EL TRABAJO DESARROLLADO EN LA PRESENTE TESIS DOCTORAL CONSISTE EN EL DISEÑO Y FABRICACION DE UN ESTABILIZADOR DE IMAGENES BIDIMENSIONALES OPTIMIZADO PARA IMAGENES SOLARES DE VARIADA MORFOLOGIA, INCLUYENDO LAS DE BAJO CONTRASTE. EL SISTEMA PERMITE IGUALMENTE REALIZAR OTRO TIPO DE TAREAS TALES COMO EL SEGUIMIENTO DE ESTRUCTURAS DURANTE LARGOS

We present early-time infrared (IR) and optical spectroscopy, and optical photometry, of the Type Ia supernova 1994D. These observations provide the most complete optical-IR spectral coverage ever achieved for a Type Ia at this phase. Optical and IR spectra were obtained as early as 9d before maximum light. The combined optical and IR spectra of SN