The Phase Of Totality

As totality begins, the first thing to note is the chromosphere, as discussed in Chapter 5. The chromosphere is seen as a pinkish region (hence its name) along the limb near where the diamond ring just blinked out. It comprises a layer about 2,500 miles thick above the photosphere, but so much less intense that it cannot be seen except during an eclipse.

The corona, a pearly white crown extending several solar diameters above the surface, may have been apparent in the minute before second contact. Typically the corona is a million times fainter than the solar surface, which is why it cannot be seen except when the photosphere is mostly extinguished. The form of the corona varies with the solar cycle, which had a peak in 2000/ 2001. When the Sun is very active, a complete white aureole may occur, rather than the patchy corona with significant concentrations—the plumes and streamers—seen during periods of lower activity (as was portrayed in Figure 1-3).

Prominences may or may not be present. Figure 1-5 shows rather vividly that such structures are transient, often lasting only hours or days. Like the weather on any date, they cannot be predicted until, at best, the day before an eclipse. If there are any present, then the nineteenth-century term for these loops and arcs—the red flames—provides a pretty good summary of their appearance. Prominences may snake above the surface by a third or more of the solar radius.

Some solar eclipses produce totality for as much as seven minutes (such as those indicated in Figure 2-2), but typically the period is between two and three minutes. Some people experience that as lasting an age; for others it is come and gone in no time at all. Charles Lambert, a member of the French eclipse expedition to Sudan in 1860, had this to say: "But at the moment of totality, all became silent and dumb. Neither a cry nor a rustling, nor even a whisper was heard, but everywhere there was anxiety and consternation. To everyone the two minutes of the eclipse were like two hours." On the other hand British astronomer Edward Dunkin, who went to northern Scandinavia to observe an eclipse in 1851, was frustrated by the brevity of totality. "So absorbed was I during this short interval that when the limb of the Sun reappeared I could scarcely realize the fact that two and a half minutes had elapsed since the commencement of totality. These were truly exciting moments, and although I had hastily witnessed most of the phenomena, I felt somewhat disappointed that more had not been accomplished. Few can imagine how much I longed for another minute, for what I had witnessed seemed very much like a dream." Things are hectic during the hundred seconds or so of total eclipse with which one may be blessed. Keen amateur as tronomers tend to record dictation tapes ahead of time, with countdowns for what they need to do to get all their planned photographs. Activity is frenetic and it's easy to get caught up with just staring, missing some of the things one might like to note while there is the fleeting opportunity.

Totality ends with third contact, when the diamond ring appears again. For the few minutes of totality, the eclipse should be viewed without filtration, but those goggles need to be on again for when the solar surface flashes back into view. Apart from perhaps damaging your eyes, the unattenuated brightness striking your retina will limit your ability to see Baily's beads clearly. You might also miss the subsequent phenomena, such as the lunar shadow rushing eastwards as the Moon withdraws from the Sun. Then there is another hour or so of partial eclipse until fourth contact, when the Moon ceases all overlap with the solar disk, but that of course is all rather anticlimactic.

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