Sunspots are Solar features located in active regions of the Sun, whose number is an indicator of the Sun’s magnetic activity. The Objective of this work is to study two automatic Sunspot detection algorithms such as Watershed transformation and K-means Clustering. In this paper, Sunspot is obtained by above stated methods from the full-disk solar images. This work presents a performance compar...

Daily records of sunspot group areas compiled by the Royal Observatory, Greenwich, from May of 1874 through 1976 indicate a curious history for the penumbral areas of the smaller sunspot groups. On average, the ratio of penumbral area to umbral area in a sunspot group increases from 5 to 6 as the total sunspot group area increases from 100 to 2000 μHem (a μHem is 10−6 the area of a solar hemisp...

Long-lived (>20 days) sunspot groups extracted from the Greenwich Photoheliographic Results (GPR) are examined for evidence of decadal change. The problem of identifying sunspot groups which are observed on consecutive solar rotations (recurrent sunspot groups) is tackled by first constructing manually an example dataset of recurrent sunspot groups and then using machine learning to generalise ...

This paper establishes in a general way the existence of a connection between the stationary equilibria of an infinite horizon economy and the equilibria of a naturally related finite economy. More specifically, the connection is established first between the cycles of a stationary overlapping generations economy and the equilibria of a related finite economy with a cyclical structure. Then the...

Analysis of data for Washington and Watheroo indicates differences in the relationship between føF2 and sunspot number for the current and preceding sunspot cycles. The sunspot number is therefore not entirely satisfactory as an index for ionospheric variations. Consequently, ionospheric data for the current cycle only should be used in preparing ionospheric radio propagation predictions whenev...

We review the evidence for the argument that Rudolf Wolf’s calibration of the Sunspot Number is likely to be correct and that Max Waldmeier introduced an upwards jump in the sunspot number in 1945. The combined effect of these adjustments suggests that there has been no secular change in the sunspot number since coming out of the Maunder Minimum ∼1715. 1 The Sunspot Record(s!) The Sunspot Recor...

The historical record of sunspot areas is a valuable and widely used proxy of solar activity and variability. The Royal Greenwich Observatory (RGO) regularly measured this and other parameters between 1874 and 1976. After that time records from a number of different observatories are available. These, however, show systematic differences and often have significants gaps. Our goal is to obtain a...

We study the behaviour of sunspot activity in 16101750, i.e. just prior to, during and slightly after the Maunder minimum, using the new series of group sunspot numbers (Hoyt & Schatten 1998). We apply the delayed component technique and show that, while the transition from the normal cyclic evolution to the minimum was very abrupt, the recovery from the minimum was gradual, proceeding through ...

The propagation of solar waves through the sunspot of AR 9787 is observed using temporal cross-correlations of SOHO/MDI Dopplergrams. We then use three-dimensional MHD numerical simulations to compute the propagation of wave packets through self-similar magneto-hydrostatic sunspot models. The simulations are set up in such a way as to allow a comparison with observed cross-covariances (except i...

Vector magnetic fields of moving magnetic features (MMFs) are well observed with the Solar Optical Telescope (SOT) aboard the Hinode satellite. We focus on the evolution of three MMFs with the SOT in this study. We found that an MMF having relatively vertical fields with polarity same as the sunspot is detached from the penumbra around the granules appeared in the outer penumbra. This suggests ...