Solar Flares and Sun Spots

from NASA

A sun spot so huge it was seen without a telescope reminds us that the Sun controls our fate. On October 18th, 2014 the largest sun spot (or region of activity) observed in 24 years appeared on the surface of the sun. The sun spot, identified as AR 12192, fired off 10 sizable solar flares in the 11 days that it traversed across the face of the sun. The sun spot was so large it was seen by those looking at the sun with eclipse glasses during the partial eclipse of the sun on October 23, 2014 giving the sky watches a good show, though the region did not flare during the eclipse.

The largest solar flare was on October 24th. "Despite all the flares, this region did not produce any significant coronal mass ejections," said Alex Young a solar scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Though I did not know it,apparently you can have massive solar flares without coronal mass ejections, However, most big flares do have coronal mass ejections.

So we're learning that a large active regions don't always equal the biggest solar events.Solar activity can be divided into four main components: solar flares, coronal mass ejections, high-speed solar wind, and solar energetic particles that appear to be associated with solar flares and coronal mass ejections. These phenomena are all related to sun spots and can only impact earth when they occur on the side of the sun facing Earth. 

The Sun is not always active, it through periods of high and low activity that repeat approximately every 11 years. Although cycles as short as 9 years and as long as 14 years have been observed. The solar or sunspot cycle is how scientists mark the changes in the Sun's activity. We are currently in what scientists have labeled Cycle #24 which was about a full year overdue. Solar minimum is period of several Earth years when the number of sunspots is lowest; solar maximum occurs in the years when sunspots are most numerous. During solar maximum, activity on the Sun and the effects of space weather on our terrestrial environment are high. At solar minimum, the sun may go many days with no sunspots visible. At maximum, there may be several hundred sunspots on any day. Scientists tell us we should have seen a solar maximum late in 2013 for this cycle, but there may be a larger cycle (100 years or more) that impacts the shorter cycles.

Though the first sun spot was observed by Galileo in 1610, continuous daily observations of the sun were begun at the Zurich Observatory in 1849. Areas on the Sun near sunspots often flare up, heating solar material to millions of degrees in just seconds and blasting billions of tons of that material into space, these blasts are called solar flares and are from tremendous explosions on the surface of the Sun. A solar flare is an intense burst of radiation. Flares release energy in many forms - electro-magnetic (Gamma rays and X-rays), energetic particles (protons and electrons), and mass flows and can heat up the Earth's upper atmosphere. Coronal Mass Ejections disrupt the flow of the solar wind and produce disturbances that can strike the Earth itself. Solar material streams out through space, impacting any planet or spacecraft in its path.  Although the Sun's corona has been observed during total eclipses of the Sun for thousands of years, we did not know about the existence of coronal mass ejections until the 1970’s. 

The solar wind streams off of the Sun in all directions at speeds of about a million miles per hour. The source of the solar wind is the Sun's hot corona, the Sun's outer atmosphere. The corona is significantly hotter than the surface of the Sun, though we do not understand why. The corona is 1,800,000°F while the surface of the Sun has a temperature of only about 10,000°F. The processes that heat the corona, maintains it at these high temperatures, and accelerate the solar wind is not understood. The solar wind is not uniform. Although it is always directed away from the Sun it changes speed and carries magnetic clouds. The solar wind speed variations shake the Earth's magnetic field and can produce storms in the Earth's magnetosphere and can cause current surges in power lines that destroy equipment and knock out power over large areas.