In order to understand the McIntosh Classification system better, two terms have to be defined: It takes only slightly longer than the old system to classify all the groups on the sun for a given day using the McIntosh System, but the information returned and usefulness of the new system makes it worth the slightly added effort. The third letter represents an assessment of the Spot Distribution within the group. This is not necessarily the leading spot, but rather the LARGEST. The Second letter represents an assessment of the Largest Spot of the group. A Modified Zurich Class was used rather than a totally new system to be an making it easier for observers that might be reluctant to switch to the new system. It basically retains the old Zurich Class but G and J were removed as being redundant. The new classifications consist of three letters. In 1966, Patrick McIntosh of the Space Enviroment Services Center of the National Oceanic and Atmospheric Administration, introduced a sunspot classification system that improved the older Zurich system. It would have been highly advantageous, on the basis of a few parameters, to weed out many less productive groups. An observer would have to spend much time at the telescope observing every well developed group in hopes of seeing these elusive events. In order for flares to be studied, a reliable system for identifying flare producing sunspot groups was needed.
Even with the most active class, F, a forecaster had a marginal chance of predicting flare probability in any given 24 hour period. This was a problem for flare forecasters on whose work various broadcast and space industries depended. But not all such groups produce big flares. Groups of classes D, E, and F are the big flare producers. So a large group will rise rapidly from class A to E and decay more slowly as it goes from E to J. In general, the greater the area of a group the more asymmetrical will be its growth curve.
Most groups go only part way through the sequence and then either rapidly go backwards through the classes or decay to the final class. It consists of nine steps or classes (A through J, omitting I) that delineate characteristic evolutionary stages of sunspot groups, though not all groups go through all classes. Waldmeier devised the Zurich Sunspot Classification of these groups. These White Light Flares or WLFs were once thought to be relatively rare. In some cases flares can be so energetic that they will even be seen in the light of the continuum of the spectrum (between the dark absorption lines) as viewed in the amateur’s telescope. Since flares are in emission in these lines, whereas the rest of the disk of the Sun is generally in absorption, they appear quite bright against the disk. Flares are best seen in monochromatic light such as H-alpha or the H and K lines of calcium where only light of one absorption line is allowed to enter the telescope. In visible spectrum observations done by amateurs the relationship is not quite as good. More energetic flares tend to be of longer duration, especially when observed in shorter wavelengths. Typically, flares last a few minutes to as much as four hours though most are from ten to twenty minutes in duration. These releases take different times to traverse the space between Earth and Sun but eventually impact the Earth’s atmosphere causing changes in propagation of radio waves and the beautiful aurorae seen at temperate and polar latitudes. Subatomic particles are shot out at various speeds as well. Larger flares can emit as much as a thousandth the energy of the sun during the duration of that flare. Flares release prodigious amounts of energy across most of the electromagnetic spectrum and are thus observable by a number of techniques. Flares are sudden discharges of energy and subatomic particles that take place in and around large sunspot groups as magnetic fields change above the groups. Flare production and strength are two such parameters. There are many other manifestations of solar activity also quantified that indicate well the level of activity. Solar activity is not just gauged by the number of sunspots observed.
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