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Sunspots contain multiple small-scale structures in the umbra and in the penumbra. Despite extensive research on this subject in pre-Hinode era multiple questions concerning fine-scale structures of sunspots, their formation, evolution and decay remained open. Several of those questions were proposed to be pursued by Hinode (SOT). Here we review some of the achievements on understanding sunspot structure by Hinode in its first 10 years of successful operation. After giving a brief summary and updates on the most recent understanding of sunspot structures, and describing contributions of Hinode to that, we also discuss future directions. This is a section (#7.1) of a long review article on the achievements of Hinode in the first 10 years.
Recent spectro-polarimetric observations of a sunspot showed the formation of bipolar magnetic patches in the mid penumbra and their propagation toward the outer penumbral boundary. The observations were interpreted as being caused by sea-serpent mag
The sunspot penumbra comprises numerous thin, radially elongated filaments that are central for heat transport within the penumbra, but whose structure is still not clear. To investigate the fine-scale structure of these filaments, we perform a depth
The fine-structure of magnetic field of a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere. High spatial resolution spectropolarimetric observations were recorded with the 1.5-meter GREGOR telescope
Coronal mass ejections (CMEs) originate from closed magnetic field regions on the Sun, which are active regions and quiescent filament regions. The energetic populations such as halo CMEs, CMEs associated with magnetic clouds, geoeffective CMEs, CMEs
We use 5 test data series to quantify putative discontinuities around 1946 in 5 annual-mean sunspot number or group number sequences. The series tested are: the original and n