相关论文: Sunspot Group Development in High Resolution
Context. The relation between solar surface rotation and sunspot activity still remains open. Sunspot activity has dramatically reduced in solar cycle 24 and several solar activity indices and flux measurements experienced unprecedentedly…
We report the simultaneous presence of chromospheric umbral flashes and associated umbral waves, and propagating coronal disturbances, in a sunspot and related active region. We have analyzed time-distance maps obtained using the…
Kodaikanal Solar Observatory (KoSO) possesses one of world's longest and homogeneous records of sunspot observations that span more than a century (1904-2017). Interestingly, these observations (originally recorded in photographic…
High-resolution imaging observations from the Hinode spacecraft in the CaII 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…
The $F_{10.7cm}$ radio flux and the Sunspot Number are the most widely used long-term indices of solar activity. They are strongly correlated, which led to the publication of many proxy relations allowing to convert one index onto the…
Sunspot drawings are provided on a regular basis at the Kanzelhoehe Solar Observatory, Austria, and the derived relative sunspot numbers are reported to the Sunspot Index Data Center in Brussels. From the daily sunspot drawings, we derived…
Context : Penumbrae are an important characteristic of sunspots, whose formation is intricately related to the nature of sub-photospheric magnetic fields. Aims : We study the formation of a penumbra in a decaying sunspot and compare its…
Sunspot groups are the main source of solar flares, with the energy to power them being supplied by magnetic-field evolution (e.g. flux emergence or twisting/shearing). To date, few studies have investigated the statistical relation between…
We employ high resolution filtergrams and polarimetric measurements from Hinode to follow the evolution of a sunspot for eight days starting on June 28, 2007. The imaging data were corrected for intensity gradients, projection effects, and…
Correlations have been studied between longitudinal and latitudinal shifts of sunspot groups in the period 1986-1998. This study is based on the Debrecen Photoheliographic Data (DPD). The latitudinal distribution of the correlation values…
We analyzed the daily sunspot-group data reported by the Greenwich Photoheliographic Results (GPR) during the period 1874-1976 and Debrecen Photoheliographic Data (DPD) during the period 1977-2017 and studied North-South asymmetry in the…
Sunspot numbers are important tracers of historical solar activity. They are important in the prediction of oncoming solar maximum, in the design of lifetimes of space assets, and in assessing the extent of solar-radiation impact on the…
We study the latitudinal distribution and evolution of sunspot areas from Solar Cycle 12 to Solar Cycle 23 (SC12-SC23) and sunspot-groups of from Solar Cycle 8 to Solar Cycle 23 (SC8-SC23) for even and odd cycles. The Rician distribution is…
The frequencies of the solar acoustic oscillations vary over the activity cycle. The variations in other activity proxies are found to be well correlated with the variations in the acoustic frequencies. However, each proxy has a slightly…
The ratio of penumbral to umbral area of sunspots is an important topic for solar and geophysical studies. Hathaway (Solar Physics, 286, 347, 2013) found a curious behaviour in this parameter for small sunspot groups (areas smaller than 100…
We analyse the chromospheric Doppler velocity oscillations in a sunspot using the high resolution spectral observations obtained from the Fast Imaging Solar Spectrograph(FISS) of the New Solar Telescope at the Big Bear Solar Observatory.…
We present a series of numerical sunspot models addressing the subsurface field and flow structure in up to 16 Mm deep domains covering up to 2 days of temporal evolution. Changes in the photospheric appearance of the sunspots are driven by…
Aims. Our aim is to examine the solar cycle variability of magnetically simple and complex active region. Methods. We studied simple ($\alpha$ and $\beta$) and complex ($\beta\gamma$ and $\beta\gamma\delta$) active regions based on the…
Sunspot regions often form complexes of activity that may live for several solar rotations, and represent a major component of the Sun's magnetic activity. It had been suggested that the close appearance of active regions in space and time…
We analyze a solar active region observed by the Hinode CaII H line using the time-distance helioseismology technique, and infer wave-speed perturbation structures and flow fields beneath the active region with a high spatial resolution.…