Context. The space missions MOST, COROT and Kepler are going to provide us with highprecision optical photometry of solar-like stars with time series extending from tens of days to several years. They can be modelled to obtain information on stellar magnetic activity by fitting the rotational modulation of the stellar flux produced by the brightness inhomogeneities associated with photospheric ...

The magnetic, thermal and velocity structure of a regular sunspot, observed close to solar disk center is presented. Spectropolarimetric data obtained with the Tenerife Infrared Polarimeter (TIP) in two infrared Fe I lines at 15 648.5 Å and 15 652.8 Å are inverted employing a technique based on response functions to retrieve the atmospheric stratification at every point in the sunspot. In order...

The usual conclusion in the literature is that sunspots reduce welfare because of the agents’ risk aversion. However, if sunspots can lead to escape from an inferior steady state (poverty trap), this conclusion does not necessarily hold. Escaping trajectories can have much higher welfare than those remaining in the poverty trap. The ex—post welfare effect can be positive for initial conditions ...

Small-scale fluctuations of magnetic field and velocity may be responsible for the Stokes asymmetries observed in all photospheric magnetic structures (the MISMA hypothesis). We support the hypothesis showing that atmospheres with optically-thin micro-structure reproduce the polarization of Fe I λ6301.5 Å and Fe I λ6302.5 Å observed in a sunspot. Ten thousand spectra were fitted by model MISMAs...

This study is the first which gives the climatology of the ionosphere at the northern tropical crest of ionization in the Asian sector. We use the data from Phu Thuy station, in Vietnam, through three solar cycles (20, 21 and 22), showing the complete morphology of ionosphere parameters by analyzing long term variation, solar cycle variation and geomagnetic activity effects, seasonal evolution ...

A Hale cycle, one complete magnetic cycle of the Sun, spans two complete Schwabe cycles (also referred to as sunspot and, more generally, solar cycles). The approximately 22-year Hale cycle is seen in magnetic polarities of both sunspots and polar fields, as well as in the intensity of galactic cosmic rays reaching Earth, with oddand even-numbered solar cycles displaying qualitatively different...

[1] The cosmic ray record for the interval 1428–2005 has been inverted using the method of Caballero-Lopez et al. (2004) to estimate the annual averages of the heliomagnetic field (HMF) near Earth. There is good agreement with the results obtained by others using two independent methodologies based upon the sunspot and geomagnetic records. This provides confidence in the overall validity of all...

The validity of a technique developed by the authors to identify historical occurrences of intense geomagnetic storms, which is based on finding approximately coincident observations of sunspots and aurorae recorded in East Asian histories, is corroborated using more modern sunspot and auroral observations. Scientific observations of aurorae in Japan during the interval 1957–2004 are used to id...

The motion of an individual magnetic flux tube inside the penumbra of a sunspot is studied numerically. Here, we present preliminary results. The thin flux tube approximation together with a simplified radiative heat exchange with the surroundings is used to study the evolution of a flux tube embedded into a background given by a global magneto-static sunspot model. The investigation is underta...