A massive cluster of sunspots, AR2770, was observed last week, spaceweather.com said using images of the Sun’s surface from NASA’s Solar Dynamics Observatory (SDO). According to the report, this particular group of sunspots has already given off a few minor space flares, causing nothing larger than “minor ionization waves rippling through Earth’s upper atmosphere.”
- Solar flares, when strong enough, can disrupt satellite and radio transmission, and more severe ones can cause “geomagnetic storms” that can damage transformers in power grids.
A sunspot is an area of the sun that appears dark on the surface and is relatively cooler than the surrounding parts. These spots, some up to 50,000 km in diameter, are visible markers of the Sun’s magnetic field, which forms a blanket that protects the solar system from harmful cosmic radiation.
- In the photosphere, the outer surface of the Sun that radiates heat and light; sunspots are the areas where the star’s magnetic field is strongest; about 2,500 times the Earth’s magnetic field.
- Most sunspots appear in groups that have their own magnetic field, the polarity of which is reversed during each solar cycle, which lasts about 11 years.
- In each of these cycles, the number of sunspots increases and decreases.
- The current solar cycle, which began in 2008, is in its “solar minimum” phase, when the number of sunspots and solar flares is at a routine low level.
Why sunspots appear dark
Because sunspots have high magnetic pressures, atmospheric pressure in the surrounding photosphere is lowered, inhibiting the flow of hot gases from the Sun’s interior to the surface.
- For this reason, sunspot temperatures are thousands of degrees cooler than the surrounding photosphere, which has a temperature of 5800 degrees Kelvin.
- Sunspot temperatures are around 3800 degrees Kelvin.
- Because they stop the convective flow of heat and light, sunspots appear dark.
- They usually consist of a dark region called “shadow”, which is surrounded by a lighter region called “penumbra”.
Solar flares and coronal mass ejections
When a sunspot reaches up to 50,000 km in diameter, it can release a large amount of energy that can cause solar flares. Flares are caused by explosions that are triggered due to the twisting, crossing, or rearrangement of magnetic field lines near sunspots.
- Sometimes solar flares are accompanied by coronal mass ejections (CMEs); large bubbles of radiation and particles emitted by the Sun that explode in space at high speed.
- CMEs can trigger an intense light in the Earth’s sky, called the aurora.
- The energy of the solar flare explosion may be equivalent to a trillion “little boy” atomic bombs dropped on Hiroshima and Nagasaki in 1945.
Damage from solar flares
Solar flares can have a major effect on radio communications, Global Positioning System (GPS) connectivity, power grids and satellites. In 1967, a large solar flare almost led to nuclear war during the Cold War, according to a report from space.com.
- In May of the same year, the US Air Force Ballistic Missile Early Warning System radar sites in Alaska, Greenland and the United Kingdom were blocked due to the flare, prompting the American officials wrongly hold the Soviet Union responsible for the radar failures.
- It was only after scientists from the North American Aerospace Defense Command (NORAD) informed U.S. officials about the solar flare that the issue subsided.
- Recently, scientists developed a new model that can successfully predict seven of the largest solar flares since the last solar cycle, out of a set of nine with help from NASA’s Solar Dynamics Observatory.