Umbral dots (UDs) are transient, bright features observed in the umbral region of a sunspot. We study the physical properties of UDs observed in sunspots of...
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PublicationInvestigating the Relation between Sunspots and Umbral Dots
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PublicationLimitations of the Ca II 8542 Å Line for the Determination of Magnetic Field Oscillations
Chromospheric umbral oscillations produce periodic brightenings in the core of some spectral lines, known as umbral flashes. They are also accompanied by...
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PublicationLine Asymmetries and the Microstructure of Photospheric Magnetic Fields
A systematic structuring of magnetic fields over scales much smaller than the mean free path of photospheric photons may be responsible for the observed...
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PublicationLong-term evolution of three light bridges developed on the same sunspot
One important feature of sunspots is the presence of light bridges. These structures are elongated and bright (as compared to the umbra) features that seem to...
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PublicationLong-term Variation of Solar Activity by a Dynamo Based on Magnetic Flux Tubes
We show that cyclic activity and Maunder-type grand minima can be explained by a dynamo driven by the instability of magnetic flux tubes in the overshoot layer...
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PublicationMagnetic aspects of the evolution of sunspots
The spectroscopic determinations of the solar magnetic fields are based on the Zeeman effect observed in relation to a number of absorption lines of the solar...
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PublicationMagnetic field fluctuations in the shocked umbral chromosphere
Context. Umbral chromospheric observations show the presence of magnetoacoustic shocks. Several recent studies have reported magnetic field fluctuations...
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PublicationMagnetic field oscillations in sunspots and active regions
In order to investigate the oscillatory behaviour of the magnetic field in sunspots and pores, full Stokes measurements of 1.56 μm iron lines have been...
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PublicationMagnetic fields of opposite polarity in sunspot penumbrae
Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of...