The Sun has come all of one day away from breaking its record for the longest period of inactivity for the last decade - reaching a mid-summer low and falling into yet another state of "hibernation". Yesterday, on the first day of autumn, new sunspots appeared on the surface of the Sun following an absence of almost 50 days. The small group of just two spots was registered by the NOAA as number 1025 when it formed yesterday in the Sun's northern hemisphere close to its eastern limb. Astrophysicists had to wait almost two months for this event: the group of sunspots occupying the last line of the catalogue (number 1024), vanished from the solar disk on 11 July this year.
Although sunspots have been systematically observed and recorded by mankind since 1749, an uninterrupted record only dates back to 1849. It is thought that from this date solar observations have been made and recorded every day, without exception. The lowest dip in activity over those 160 years was recorded almost one hundred years ago in 1913. Then, a year before WWI, mankind observed an "empty" Sun for a duration of 92 days, from 8 April until 8 July. The uniqueness of this period if further underlined by the fact that the second longest period of inactivity is "only" 63 days - seen from 11 March until 18 May, 1901. The third longest period with no sunspots was a little earlier in 1879 and lasted 54 days, from 16 February until 10 April.
The immediate proximity of these three record lows in sunspot sightings is clearly no coincidence. They were all observed over 4 solar cycles at the turn of the XX Century. Today, this is thought to be proof that the Sun has not only a well-known 11 year cycle, but also more global cycles of 100- and even 1000-year periods. It is thought that the coincidence of these cycles at a single point may cause prolonged lows in solar activity lasting many years; the most famous of these being the Mounder Minimum, which lasted from 1645 until 1715 and coincided with a minor ice age.
While the first three global lows in solar activity (over the last 160-year history of observation) were spread out across almost 4 cycles, the periods in 4th and 5th place in the list came at almost exactly the same time. They were both observed during the current solar minimum, over the past two years. The first low lasted 51 days, from 21 July until 11 September last year. Until today this period was considered the lowest point of the current solar cycle, following which activity slowly began to increase. Now, almost a year later, it seems the Sun has hit a new low almost as "deep" as the first. The low in activity that came to an end yesterday was observed from 12 July until 1 September and lasted 49 days - making it the fifth longest period of inactivity for the last 160 years.
The current state of the Sun is of great interest. Now there are just over three years (out of eleven) before the predicted solar minimum in 2012. In this regard, the most interesting question is whether the Sun can reach the expected level of activity in such a short time or whether we are indeed facing a historic moment when several minimums belonging to 100- and 1000-year cycles converge at a single point before our very eyes. Moreover, if, at the beginning of the last century, the phases of the global cycles were separated by almost 40 years then this time, judging by the concentration and frequency of the observed lows in activity, they may coincide within one cycle and completely suppress any solar activity for an indefinite period of time. In terms of the total number of days without sunspots (to date: 706 days on 1 September), the current 23rd solar cycle has already set the record for the entire 160-year period of uninterrupted observation.
