Explain the concept of Sun-spot cycle with special reference to solar minimum.
Explain the changes that it brings on sun’s surface during solar minimum.
Discuss the effects of solar minimum on earth.
Sun-spot cycle is the solar magnetic activity cycle with the average time period of eleven years. It refers to changes in the Sun’s activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (changes in the number and size of sunspots, flares, and other manifestations).
Sun Spot Cycle:
Sun-spots are regions where the solar magnetic field is very strong.
The number of sunspots observed on the “surface” of the Sun varies from year to year.
This rise and fall in sunspot counts varies in a cyclical way is called “the Sunspot Cycle”.
Solar minimum is the period of least solar activity in the eleven year solar cycle.
During this time, sunspot and solar flare activity diminishes. According to NASA and other agencies, a solar minimum is about to occur in 2019-20.
Changes on sun’s surface due to solar minimum:
• Intense activity such as sunspots and solar flares subside during the solar minimum
• The sun does not become dull, rather the solar activity simply changes form.
• During the solar minimum, coronal holes can last for a longer time. Coronal holes are vast regions in the sun’s atmosphere where the sun’s magnetic field opens up and allows streams of solar particles to escape the sun as the fast solar wind.
Effects of solar minimum on earth:
• It could enhance the effects of space weather events including geomagnetic storms, auroras, potentially disrupting communications and navigation systems.
• During the solar minimum, upper atmosphere cools down, which reduces the frictional drag in the low Earth orbit. Without the normal drag, the space debris has the tendency to hang around longer or to fall back to Earth.
• It could enhance the effect of space weather events including geomagnetic storms, auroras and potentially disturbing power supply, satellites, communications and navigation systems.
• The sun’s magnetic field weakens and provides less shielding from cosmic rays. This can pose an increased threat to astronauts travelling through space.