Solar Cycle 24 and 25


On January 10, 2008, observers saw a Sunspot with a reversed polarity at solar northern latitude, signifying the start of Solar Cycle 24. Its magnetic polarity was opposite of what the Sunspots of the previous solar cycle had. Each eleven-year solar cycle has a different peak and even different duration. The current cycle (24) is expected to peak in 2011 or 2012, followed by a weak Cycle 25, arguably one of the weakest in centuries. These predictions are based on geomagnetic activity that can foretell a surge some six years ahead.

There is no consensus on the timing of an intense cycle followed by a weak one. One view is based on a recent discovery of a slowdown of what is known as the Sun’s great conveyor belt, which transports hot plasma around. The belt is in fact a massive current of fire within the Sun with two ‘branches’, one in the northern side and the other in the southern side. It is estimated that it would take the belt about 40 years to complete one circuit. And the movement of the belt controls the Sunspot cycle.

Based on computer calculations, astronomers have measured the movement of the belt very precisely, the normal speed of the belt being one metre per second. Recently it has slowed down to 0.75 m a second on the northern side and to 0.35 m a second in the south. Astronomers are surprised to see the slowdown.

The movement of the conveyor belt is inferred indirectly, as it plunges into the solar surface some 2, 00,000 km. The drift of the Sunspots (as magnetic knots that bobble up from the base) would indicate the movement of the conveyor belt. The drift of the Sunspots from mid-solar latitudes towards the Sun’s equator is caused by the motion of the ‘conveyor belt’. According to theory and observation, the spread of the belt foretells the intensity of Sunspot activity for the next 20 years. A slow belt means lower solar activity, while a fast belt indicates stronger activity.

The unexpected solar minimum by 2022 is viewed with mixed feelings. On the one hand, it is considered favorable to astronauts who are by then expected to be on the lunar surface en route to Mars. At the solar minimum, the astronauts would be relatively safe, as there would not be dangerous solar flares. However, cosmic rays are expected to intensify and cause harmful health effects on the astronauts. A weak solar cycle means astronauts on the Moon need not have to worry much about solar flares and radiation storms. On the other hand, space travelers will have to worry more about cosmic rays, which are high-energy particles from deep space that can penetrate metal, plastic, flesh and bone. As solar flares subside, cosmic rays intensify.

Four of the five strongest cycles on record have appeared only in the past 50 years. As the solar cycle changes in its intensity, it would be interesting to watch out for the possible blooming of the Kurinji flower in and around Kodaikanal in line with the predicted peaks or lows.

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