Related papers: Penumbral thermal structure below the visible surf…
Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction) magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra antipodal to the main region of flux…
Sunspot penumbrae show a fine structure in continuum intensity that displays considerable dynamics. The magnetic field, in contrast, although also highly structured, has appeared to be relatively static. Here we report the discovery of…
A sunspot emanates from a growing pore or protospot. In order to trigger the formation of a penumbra, large inclinations at the outskirts of the protospot are necessary. The penumbra develops and establishes by colonising both umbral areas…
The fine structure of solar prominences and filaments appears as thin and long threads in high-resolution images. In H-alpha observations of filaments, some threads can be observed for only 5 - 20 minutes before they seem to fade and…
ALMA observations of the Sun at mm-$\lambda$ offer a unique opportunity to investigate the temperature structure of the solar chromosphere. In this article we expand our previous work on modeling the chromospheric temperature of the quiet…
We study 7530 sunspot umbrae and pores measured by the Hinode Spectropolarimeter (SP) between November 2006 and November 2012. We primarily seek confirmation of the long term secular decrease in the mean magnetic field strength of sunspot…
The generation of magnetic flux in the solar interior and its transport from the convection zone into the photosphere, the chromosphere, and the corona will be in the focus of solar physics research for the next decades. With 4m class…
The high spatial, temporal and spectral resolution achieved by Hinode instruments give much better understanding of the behavior of some elusive solar features, such as pores and naked sunspots. Their fast evolution and, in some cases,…
It is well-known that the global acoustic oscillations of the Sun's atmosphere can excite resonance modes within large-scale magnetic concentrations. These structures are conduits of energy between the different layers of the solar…
We have employed a penumbral model, that includes the Evershed flow and convective motions inside penumbral filaments, to reproduce the azimuthal variation of the net circular polarization (NCP) in sunspot penumbrae at different…
Observations with the 1-m Swedish Solar Telescope of the flows seen in penumbral filaments are presented. Time sequences of bright filaments show overturning motions strikingly similar to those seen along the walls of small isolated…
From the inversion of a time series of high resolution slit spectrograms obtained from the quiet sun, the spatial and temporal distribution of the thermodynamical quantities and the vertical flow velocity is derived as a function of…
Using high-resolution transition region (TR) observations taken by the Interface Region Imaging Spectrograph (IRIS) mission, Tian et al. (2014b) revealed numerous short-lived subarcsecond bright dots (BDs) above sunspots (mostly located in…
Wave propagation through sunspots involves conversion between waves of acoustic and magnetic character. In addition, the thermal structure of sunspots is very different than that of the quiet Sun. As a consequence, the interpretation of…
Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops giving rise to turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned…
Context: Evershed clouds (ECs) represent the most conspicuous variation of the Evershed flow in sunspot penumbrae. Aims: We determine the physical properties of ECs from high spatial and temporal resolution spectropolarimetric measurements.…
High-resolution time series of sunspots have been obtained with the Swedish 1m Solar Telescope between 2003 and 2006 at different locations on the solar disc. Proper motions in seven different active regions have been studied. The analysis…
We present observations of a precursory signature that would be helpful for understanding the formation process of sunspot penumbrae. The Hinode Solar Optical Telescope successfully captured the entire evolution of a sunspot from the pore…
Context. It has been reported that the boundary between the umbra and the penumbra of sunspots occurs at a canonical value of the strength of the vertical magnetic field, independently of the size of the spot. This critical field strength…
Bright points (BPs) in the solar photosphere are radiative signatures of magnetic elements described by slender flux tubes located in the darker intergranular lanes. They contribute to the ultraviolet (UV) flux variations over the solar…