Aims: We investigate the photometric modulation induced by magnetic activity cycles and study the relationship between rotation period and activity cycle(s) in late-type (FGKM) stars. Methods: We analysed light curves, spanning up to nine years, of 125 nearby stars provided by the All Sky Automated Survey (ASAS). The sample is mainly composed of

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Gonçalves et al. (1996) showed the relevance of Alfvén heating in order to establish the stability of quasar broad-line region clouds in the intercloud medium due to thermal instability. Although, photoionization by the continuum radiation from the central source is the most important mechanism to heat and ionize the broad-line region, Alfvenic

Context. We report on the first of a series of studies on coronal bright points which investigate the physical mechanism that generates these phenomena. Aims: The aim of this paper is to understand the magnetic-field structure that hosts the bright points. Methods: We use longitudinal magnetograms taken by the Solar Optical Telescope with the

We study the effects of magnetic field shear (By ≠ 0) and longitudinal propagation of perturbations (ky ≠ 0) on the linear and adiabatic magnetohydrodynamic (MHD) normal modes of oscillation of a potential coronal arcade. In a cold plasma, the inclusion of these two effects produces the linear coupling of discrete fast modes, characterised by a

The MHD normal modes of oscillation of coronal magnetic structures are studied by including two aspects that have not been considered in previous theoretical works of this kind, namely the effects of the magnetic field shear and of the longitudinal propagation in the oscillatory properties of solar coronal structures. We show that, in a cold plasma