The Sun is a very busy place. Close inspection through telescopes such as the New Solar Telescope at Big Bear Solar Observatory in California reveals a surface roiling with activity.
Types of Activity
Sunspots There are regions where the temperature is somewhat cooler than the surroundings. These show as darker and are known as sunspots. Four Earths would fit in the dark center of this sunspot. They are not cool by any means. The yellow area is 5800 Kelvin (9980˚F). The sunspot is 3800 K (6380˚F).
Sunspots are associated with the magnetic activity of the Sun. The magnetic field of the Sun is not stable or static like that of a permanent magnet. Because of the circulation of huge currents of charged particles within the Sun, the strengths and directions of the magnetic field are continuously changing. Flares Often, there are eruptions of the magnetic field at the surface causing flares to rise and dance. Some of the flares extend out into space as prominences. These are not energetic enough to cause noticeable effects here on Earth.
CME Some rare eruptions can be accompanied by a huge burst of light and radiation whereby a large cloud of solar material is ejected at high speed from the Sun. These are called Coronal Mass Ejections (CME). If they are aimed at Earth, they can have significant effects on power grids, satellites, and auroral activity several days later. Scientists monitor these enormous space weather events for geomagnetic storms, solar radiation storms, and radio blackouts. The difference between flares and CMEs is visually described by this 2 minute NASA video.
CME Effects On Earth
Geomagnetic Storms The most common form of space weather effect on Earth is the geomagnetic storm. Earth is protected by a sheath of magnetic field called the magnetosphere. Our magnetosphere guides energetic particles around Earth. Normally, it is quiet and relatively stable. This video models the protective nature of the magnetosphere of Earth. The Sun is off to the left out of view. At about 20 seconds, there is an increase in activity from the Sun due to a CME. By 30 seconds, the activity begins to subside to normal. The magnetic field lines of Earth point northward as indicated by a compass. The interactions of a CME with the Earth’s magnetosphere can cause damaging effects. Storms are categorized from G1 (minor) to G5 (extreme). In the most extreme cases transformers in power grids may be damaged, spacecraft operation and satellite tracking can be hindered, high frequency radio propagation and satellite navigation systems can be blocked. Aurorae may appear much further south than normal. A CME travels with its own magnetic field. They connect with the field of the Earth on the outside of the magnetosphere for a period of time. If the CME field lines up with Earth’s field, the energy and the charged particles slide around the Earth and cause little change. If the CME field is opposite of Earth’s field, the disturbance can be dramatic and visual. Charged particles can be caught up in the magnetosphere. The shape of the magnetosphere changes. The particles follow the Earth’s field lines into the polar regions as a sort of loop, or ring of aurora. These energetic particles excite the gases in the upper atmosphere and cause them to emit characteristic colors of green, red, and purple hues. This is a common event over the Canadian provinces and similar latitudes around the world both north and south. Sometimes they appear at lower latitudes across the United States as on March 17, 2015. Solar Radiation Storms A solar radiation storm, also called a solar energetic particle (SEP) event, is an intense inflow of radiation of protons and other charged particles from the Sun. The radiation is blocked by the magnetosphere and atmosphere and cannot reach humans on Earth. It could harm humans traveling during spaceflight from Earth to the Moon or Mars. It has little to no effect on airplane passengers or astronauts within Earth’s magnetosphere. Solar radiation storms can also disturb the regions where high frequency radio communications travel. During an SEP, airplanes traveling routes near the poles which rely exclusively on radio communications may be re-routed. Solar radiation storms are rated on a scale from S1 (minor) to S5 (extreme), determined by how many very energetic, fast solar particles move through a given space in the atmosphere. At their most extreme, solar radiation storms can cause complete high frequency radio blackouts, damage to electronics, memory and imaging systems on satellites, and radiation poisoning to astronauts who might be outside of Earth’s magnetosphere. The ISS is not that far away. Radio Blackouts Radio blackouts can occur when the strong, sudden burst of x-rays from a solar flare hits Earth’s atmosphere. These can jam high and low frequency radio signals. The X-rays disturb a layer of Earth’s atmosphere known as the ionosphere, through which radio waves travel. The disruptions to the ionosphere change the paths of the radio waves and degrade the information they carry. The loss of low frequency radio communication causes GPS measurements to be off by up to several miles. They can also affect the applications that govern satellite positioning. Radio blackouts are rated on a scale from R1 (minor) to R5 (extreme). The strongest radio blackouts can result in no radio communication and faulty GPS for hours at a time.
Solar activity increased until about 2013 and then decreased slightly. It has increased since. The trend is predicted to decrease over the next few years to a minimum. The cycle will begin again as is has about every 11 years. Fortunately, we don’t appear to have any direct harmful effects to worry about here on the ground. Indirectly, the solar storms and CME could cause a lot of havoc if they are intense enough to disrupt power grids or communication systems. Alerts are issued when activity warrants. You can check the current space weather conditions at this link.