We present time-distance analyses of several active regions and a region of quiet Sun observed with the Global Oscillation Network Group (GONG). Analyzing temporal correlations between the p-mode oscillation signal observed within the sunspots with the signals integrated within surrounding annuli, we connrm the recent nding of Duvall and his colleagues that travel times (+) for outward propagat...

Because of the lack of reliable sunspot observation, the quality of sunspot number series is poor in the late 18th century, leading to the abnormally long solar cycle (1784–1799) before the Dalton minimum. Using the newly recovered solar drawings by the 18–19th century observers Staudacher and Hamilton, we construct the solar butterfly diagram, i.e. the latitudinal distribution of sunspots in t...

Because of the lack of reliable sunspot observation, the quality of sunspot number series is poor in the late 18th century, leading to the abnormally long solar cycle (1784–1799) before the Dalton minimum. Using the newly recovered solar drawings by the 18–19th century observers Staudacher and Hamilton, we construct the solar butterfly diagram, i.e. the latitudinal distribution of sunspots in t...

Magnetic field modifies the properties of waves in a complex way. Significant advances has been made recently in our understanding of the physics of waves in solar active regions with the help of analytical theories, numerical simulations, as well as hi-resolution observations. In this contribution we review the current ideas in the field, with the emphasis on theoretical models of waves in sun...

We present the first results using the Reuven Ramaty High-Energy Solar Spectroscopic Imager, RHESSI, to observe solar X-ray emission not associated with active regions, sunspots or flares (the quiet Sun). Using a newly developed chopping technique (fan-beam modulation) during seven periods of offpointing between June 2005 to October 2006, we obtained upper limits over 3-200 keV for the quietest...

The origin of magnetic field sources in the Sun’s dynamo is central to this paper. The Babcock-Leighton dynamo was originally envisaged as a shallow dynamo. The source of the Sun’s magnetism is now generally thought to reside near the base of the convection zone and that these fields rise by buoyancy to initiate sunspots. We reconsider this aspect of the solar dynamo. We do this by considering ...

Studies and reconstructions of past solar activity require data on sunspots as well faculae/plage network. Such are also important for understanding the magnetic variability Sun Sun-like stars. The longest available direct datasets white-light facular Ca II K observations going back to 1874 1892, respectively. Prior that time, only sunspots. We reassess relationship between plage areas sunspot ...

High-resolution imaging observations from the Hinode spacecraft in the Ca II H line are employed to study the dynamics of the chromosphere above a sunspot. We find that umbral flashes and other brightenings produced by the oscillation are extremely rich in fine structure, even beyond the resolving limit of our observations (0.22”). The umbra is tremendously dynamic, to the point that our time c...

Sunspots have been known in the West since Galileo Galilei and Thomas Harriot first used telescopes to observe the Sun nearly four centuries ago; they have been known to the Chinese for more than two thousand years. They appear as relatively dark patches on the surface of the Sun, and are caused by concentrations of magnetism which impede the flow of heat from deep inside the Sun up to its othe...