15 August 2012, 14:37 Science Text size A A A

The sun hasn't cracked, but it's going down

Solar activity did not increase in 2012: perhaps the Little Ice Age is ahead

"Crack" in the Sun. Observations from Earth.

tesis.lebedev.ru // APO + LEN Observatory Perhaps the Earth is at the beginning of a new ice age: solar activity did not increase in 2012, although its calculated maximum occurred precisely in this year. What is happening to the Sun now is comparable to the so-called Maunder and Dalton minima in the 17th-19th centuries, which coincided with a sharp decrease in global temperatures. However, the connection between the earth's climate and solar activity has not yet been proven.

Since the mid-18th century, the Zurich Observatory began regular studies of solar activity. The cycle with which scientists began their observations was called the first solar cycle. Accordingly, 23 cycles have passed since then, and we are currently in the middle of a new, 24th cycle, which is very mysterious.

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Graph of solar activity since the beginning of continuous observations. All 23 solar cycles are visible // spaceweather.com

The maximum of the 23rd cycle occurred in 2001, and it is easy to see that the next maximum could be expected in 2012. The estimated minimum (that is, the end of the 23rd cycle and the beginning of the 24th) occurred in 2006–2007, after which a smooth rise should have begun. But in reality this did not happen. Instead of a smooth rise, there was a completely incomprehensible gradual decline, and in 2008–2009 there was a deep minimum in solar activity, when it literally went to zero. Usually the minimum passes above the zero mark, but here a very rare minimum was observed. Since the second half of 2009, a new increase in activity began to be recorded on the Sun.

But by August 15, 2012, it stopped growing and fell below last year’s level.

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The current view of the Sun (on the left; the image was taken by the SDO observatory on August 14, 2012) and the view of the Sun near the maximum of the previous solar cycle (on the right; the image was taken by the SOHO observatory on July 15, 2000) // tesis.lebedev.ru

The current level of activity is four times lower than the maximum values recorded in 260 years of continuous observations of the Sun, and only a few percent higher than during the last failure of solar activity - the Dalton minimum in 1790-1830. Such conclusions follow from solar flare activity and analysis of Wolf numbers - the main way to measure and describe solar activity cycles.

The unexpected lull of the Sun in 2008–2009 gave rise to a number of forecasts about the characteristics of the future solar maximum, among which at least two opposite scenarios could be distinguished .

According to the first scenario, the Sun should release approximately the same total amount of energy in each cycle. Accordingly, if the activity of the Sun was suppressed for several years, then in subsequent years the rate of energy release should compensate for this lag, that is, be noticeably higher than average. Based on this, one would expect the growth phase of the new cycle to be unusually fast; at the same time, having “accelerated”, the Sun at its peak could reach exceptionally high activity values.

The second scenario is based on observations according to which, in the entire history of solar exploration, extremely high maxima have never been recorded on it.

At the same time, however, at least two extremely deep declines in activity were recorded. The first of them was measured directly: this is the already mentioned so-called Dalton minimum, in which the Sun was during its fifth and sixth cycles (from 1784 to 1810). The second minimum is known from indirect evidence (from early observations by amateur astronomers and radiocarbon dating methods) and is the best known of all. This is the so-called Maunder Minimum, which lasted from 1645 to 1715, that is, more than half a century, and coincided with the coldest phase of the so-called Little Ice Age (note that a reliable connection between these two events has not yet been established). Since the Maunder and Dalton minimums are very close (they are separated by less than a hundred years), it is often believed that the later Dalton minimum is, as it were, an echo (second wave) of the Maunder minimum. After this, over the next 200 years of observations, the Sun worked like a clock. The second scenario for the development of solar activity in the new cycle precisely suggested that an exceptionally deep dip in solar activity in 2006–2009 could be a harbinger of a new major failure lasting at least several solar cycles, that is, from 25 to 100 years. <2>

Despite apocalyptic reports from various media about the impending end of the world in 2012, which will come after “the Sun burns the Earth in September-December 2012,” analysis of flare activity and the number of sunspots show that the scenario of an extremely high solar cycle on the Sun is not realized.

But the second scenario is becoming increasingly probable - an extremely weak solar cycle, comparable in level to the Dalton minimum.

Thus, the maximum monthly Wolf number (an indicator characterizing the number of sunspots) recorded this year is only W = 69.0 - it was achieved in May 2012. During the record solar cycle No. 19 for the last 260 years at its maximum an almost four times greater value of W=253.8 was achieved. Thus, the Sun is still very far from record activity, while, on the contrary, there is very little left to uniquely low activity values. During cycle number 5 (the beginning of the Dalton minimum), the highest level of activity was W=62.3, and during the next cycle the maximum was recorded at W=96.2. This is only a few percent lower (and for cycle No. 6 even higher) than the current level recorded on the Sun.

Lower solar cycles have not been observed in 260 years.

Thus, although the Sun has not yet entered a state of a new global disruption of activity (such a conclusion cannot be made based on only three years of observations), it is very close to it. In addition, since 2011, solar activity has stopped growing. The peak of Wolf numbers was not reached this year (when the maximum was expected), but in November 2011 (W=96). Thus, solar activity this year is almost 50% lower than in the previous year, despite the fact that since March solar activity has been stabilized for almost half a year at the level of W = 64–69, equal to the level of the Dalton minimum.

According to specialists from the Laboratory of X-ray Solar Astronomy of the Lebedev Physical Institute , the second half of this year will be decisive for understanding where our star is moving. During this time, it will become clear whether the Sun has developed an upward trend or whether our star has frozen at the current level, or even begun to fall to even lower values. “If the current level of activity is not significantly (one and a half to two times) increased in the next 6-12 months, this will mean that the Sun is going through one of the lowest solar cycles in history, which were previously recorded only during long-term outages activity, almost inevitably accompanied by sharp changes in the Earth’s climate,” scientists say.

Speaking of the latest news related to the Sun, we cannot help but note an interesting structure that has been observed over the past few days: it is a thin, dark structure with jagged edges, at first glance very similar to a crack. <5>Actually, this structure became another reason for some media to write another scare story about the end of the world and title it with a scary title in the style of “The Sun Cracked.”

For some reason, none of the authors of sensational publications thought about the fact that the Sun is not a solid body and, being a gaseous object, cannot crack.

The nature of the crack is not a mystery to astrophysics. This is a dark “fibre” consisting of very cold (for a star) gas - with a temperature of less than 10 thousand degrees. Such structures do not lie on the surface of the Sun, but are elevated above it by several thousand kilometers; at the same time, they are supported by magnetic field lines, forming a kind of pedestal. In fact, such fibers are giant solar clouds. Due to the low temperature (and it is more than 100 times lower than the temperature of the surrounding corona), the fibers do not create their own radiation, and due to their high density they do not transmit light from the surface of the Sun. As a result, a dark structure appears on the disk, sometimes in a rather bizarre configuration, very similar to a crack at low resolution.