Coronal mass ejection (left) and solar flare. Picture courtesy Nasa

Every 11 years the Sun becomes active. Quite a number of solar features display pronounced activities during this period and the phenomenon can affect the earth in a big way. This period of enhanced activity is called the Solar Maxima and the 11-year period is often referred to as the 11-year solar cycle.

A visible feature during a solar maxima is the increase in the number of sunspots — dark spots on the surface of the sun — caused by the interaction of the solar plasma with the random magnetic fields on the surface. The sunspots reach their maximum count during solar maxima and then decrease, only to increase again over another 11-year-period.

A major feature of the 11-year solar cycle is that during the solar maximum years, the sun’s magnetic field goes through a complete reversal — the Sun’s north and south magnetic poles flip.

Sun’s increased magnetic activity causes huge volumes of charged particles being ejected from its atmosphere, which, with speeds ranging from 700-1,500 km/second flow past the solar system, at times causing widespread disruption in the space weather of solar system bodies, including the earth.

Decades of careful observation of these events have indicated that when these high-speed charged particles — comprising electrons, protons and heavy ions — reach the earth and interact with its geomagnetic field, the result can be serious.

In general the interactions of these charged particles with particles in our atmosphere cause the aurorea in the polar regions — aurora borealis near the earth’s north magnetic pole and aurora australis near the south magnetic pole.

The flow of these charged particles also causes other events that can disrupt our life. It has been observed that solar storms caused by huge amount of material emitting from the solar surface (solar flares) or enormous volumes of charged particles emerging from the sun’s atmosphere (coronal mass ejection) can disrupt the earth’s geomagnetic field, that can result in malfunctioning of the satellites circling the earth.

The telecommunication system, now totally dependant on satellites, can take a hit. The charged particles, once they hit the earth’s atmosphere, can disrupt and destroy electrical and electronic installations and instruments of earth.

The global positioning satellites, if affected, can disrupt vehicular communication systems. Solar flares or coronal mass ejections can also affect large parts of high-tension power grids.

Air travellers at 33,000 feet above the sea level can be exposed to X-ray radiation 30 times or more that what is needed for a chest X-ray.

There is no way we can avoid the influx of the solar wind but fortunately scientists think that the solar maxima in 2013 is the weakest in the past 100 years. So one can expect that nothing spectacularly wrong will happen to the earth but it cannot be predicted. One has to remember that scientists have till today failed to understand completely the cause of the magnetic polarity reversal and they have limited capacity to predict a solar storm and its magnitude.

The author is director, research & academic, MP Birla Planetarium