Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used to identify possible intense historical geomagnetic storms in the interval 210 BC–AD 1918. There are about 270 entries in the sunspot catalogue and about 1150 entries in the auroral catalogue. Special databases have been constructed in which the scientific information in these two catalogues is placed i...

This paper considers a longitude distribution of sunspot groups over 1982–2013, using data from the National Geophysical Data Center (Boulder, USA). The space-time distribution of sunspot groups is analyzed in coordinate sectors calculated from heliographic longitudes of the groups. A longitude extent of a coordinate sector is compared to the average size of one active region (30–40°). Then, in...

We show that only two adjustments are necessary to harmonize the Group Sunspot Number with the Zürich Sunspot Number. The latter being inflated from the 1940s on to the present by 20% due to weighting of sunspot counts according to size of the spots, and corrected by inflating the earlier values as well. The Group Sunspot Number before ∼1885 is too low by ∼50%. With these adjustments a single s...

Bright EUV sunspot plumes have been observed in five out of nine sunspot regions with the Coronal Diagnostic Spectrometer – CDS on SOHO. In the other four regions the brightest line emissions may appear inside the sunspot but are mainly concentrated in small regions outside the sunspot areas. These results are in contrast to those obtained during the Solar Maximum Mission, but are compatible wi...

Sunspot drawings are provided on a regular basis at the Kanzelhöhe 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 the northern, Rn, and southern, Rs, relative sunspot numbers for the time span 1975– 2000. In order to accord with the International Sunspot Numbers Ri, the R...

We analyze the famous Wolf’s sunspot numbers. The time series shows a mean period with duration of 133 months. We observed that the mean period consists of two equal sized phases, descendent and ascendent, that can be well fitted by two ortogonal lines. The sunspot numbers standard deviation period is well fitted by a sine function. We discovered that the distribution of the sunspot number fluc...

The temporal behavior of the sunspot cycles 12–22, as described by quarterly mean values of sunspot areas, can be represented by a single function containing only two parameters: the starting time and the amplitude of a cycle. The parameters are determined for the more recent 11 sunspot cycles and examined for any predictable behavior. As a sunspot cycle progresses, the amplitude parameter can ...

Designing a statistical solar flare forecasting technique can benefit greatly from knowledge of the flare frequency of occurrence with respect to sunspot groups. This study analyzed sunspot groups and Hα and X-ray flares reported for the period 1997 – 2007. Annual catalogs were constructed, listing the days that numbered sunspot groups were observed (designated sunspot group-days, SSG-Ds) and f...

Robert W. Johnson Alphawave Research, Atlanta, GA 30238, USA (Dated: December 26, 2009) Abstract To investigate the relation between observations of the 10.7 cm flux and the international sunspot number so that a physical unit may be ascribed to historical records, both polynomial and power law models are developed giving the sunspot number as a function of flux and vice versa. Maximum likeliho...

In this paper, we measure the rotation of a sunspot in solar active region NOAA 11158 (Solar Target Identifier SOL2011-02-15) that was associated with an M-class flare. The flare occurred when the rotation rate of the sunspot reached its maximum. We further calculate the energy in the corona produced by the sunspot rotation. The energy accumulated in the corona before the flare reached 5.5× 10 ...