Discovery Space: Cosmic Weather
The sun is not merely a source of light and heat to its surrounding environment. Solar radiation is a factor that influences many cosmic and terrestrial phenomena, some of which can be harmful.
The planetary system is surrounded by the sun’s magnetic field and by solar radiation. The latter includes mainly visible light, thermal radiation, ultraviolet radiation, radio waves, x-rays, and electrically charged particles in the solar wind. The Earth’s atmosphere is equipped with a relatively effective shield, which protects it from such radiation.
Electrically charged particles are deflected by the magnetic field of the Earth. Similar to terrestrial weather conditions, these predominant conditions in space are called cosmic weather. They fluctuate depending on solar activity and may temporarily become harmful.
The moody sun
Sometimes the sun explosively catapults solar matter into space (coronal mass ejections), and small areas of the solar surface may flare up for short periods of time. The energy released during one of these events is almost equivalent to the amount of total solar energy emitted per second.
At this time, the sun also ejects high-energy electrons and protons. So far, it is only possible to partially predict these phenomena. They tend to occur at regular and observable intervals. The intensity of solar radiation and the frequency of its outbursts correspond in fluctuations with the regularly recurring sunspot cycle.
Effects of the Earth’s magnetic field
Electrically charged particles from the sun and the Earth’s upper atmosphere create circular radiation zones in the Earth’s magnetic field. They include the Van Allen radiation belt above the Equator and the equatorial electrojet.
Electric currents above the polar areas reach down to an altitude of about 330,000 feet (100 km) and result in the phenomenon known as the northern or southern lights, visible at lower latitudes. If large amounts of particles hit the Earth’s magnetic field-for example, after a coronal mass ejection by the sun—then a geomagnetic storm can occur.
Geomagnetic storms
Intensified particle radiation amplifies the electric currents of the Earth’s magnetic field, which may overlap with the terrestrial field and cause it to fluctuate, potentially causing geomagnetically induced currents in transmission lines and transformers. For safety reasons, regional power supplies and telecommunication services may be manually shut down.
Increased amounts of charge carriers in the atmosphere, as well as the intense radiation of flares, can also disrupt terrestrial radio communication, satellite communication, and navigation. Geomagnetic storms may also damage satellite electronics. Moreover, the upper atmosphere is heated and expands, which slows down satellites that are close to Earth, potentially altering their orbit.
Radiation exposure risk is slightly elevated for aircraft flying at higher altitudes, and even affects migrating birds and carrier pigeons, which can become disoriented.
THE SOLAR CYCLE
Solar activity is closely linked to the 11 -year sunspot cycle. Sunspots are the result of locally amplified magnetic fields that emit extreme levels of radiation and can cause intense flares. An increase in sunspots, therefore, can be interpreted as a sign of potentially greater solar
activity and consequently can act as an indicator tor turbulent cosmic weather.
Cosmic weather predictions are important in the case of astronauts, who may be seriously endangered at times of sudden elevations in solar activity. In the event of increased solar activity, astronauts must seek shelter in protected areas of the space station. Efforts in finding
ways of predicting solar activity similar to a terrestrial weather forecast are still ongoing.