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Major Magentic Storms 1868-2007
According to the AA* criteria
Because of the difference in units of presentation, the values of AA* and Ap* are not the same so that different major magnetic storm onset and end threshold values are used for the two series. However their comparison for the years of overlapping coverage show that relative frequency of occurrence of major storms per year are similar. Another reason for differences is that an index derived from magnetic perturbation values at only two observatories easily experiences larger extreme values if either input site is well situated to the overhead ionospheric and.or field aligned current systems producing the magnetic storm effects. Although not documented here, it is interesting to note that the overall level of magnetic disturbance from year to year has increased substantially from a low around 1900 Also, the level of mean yearly aa is now much higher so that a year of minimum magnetic disturbances now is typically more disturbed than years at maximum disturbance levels before 1900.
The Effect of Sunspot Size and Latitude On Magnetic Field Strength in Sunspots
Mullins, Sarah E. and Stanley, Sheena
Dr. Steve Rapp A. Linwood Holton Governor’s School
Abstract-We conducted research to determine the magnetic field strength via Zeeman line splitting in infrared (IR) spectra for targeted sunspots of different sizes and latitudes. The unique infrared capability and large aperture of the McMath-Pierce telescope made it perfect for this type of study. We collected several data sets over a two-day period. Using computer programs KP and Image J, we reduced the data and determined the magnetic field strength of active regions on the Sun at that time. A total of three active sunspot regions were observed and reduced for further research. After reducing and analyzing the data we collected, we can say that size and latitude are factors in the magnetic field strength of sunspots. The greater the area of a sunspot, the greater the magnetic field strength is. The closer the sunspot is to the poles of the Sun, the greater the magnetic field strength is.