Larger and more frequent solar storms will make for potential disruptions and spectacular auroras on Earth
Longer nights during the fall and winter also favour seeing more auroras, but the show is best outside of light-polluted cities.
- Longer nights during the fall and winter also favour seeing more auroras, but the show is best outside of light-polluted cities.
- Impressive auroral events allowed bright auroras to be seen as far south as the United States recently.
- The number of auroras is increasing as the sun’s activity becomes stronger, approaching a solar maximum.
Night visions
- The Earth, in the sun’s outer atmosphere, is surrounded by hot magnetic plasma which rushes past us at speeds of several hundred kilometres per second in a flow called the solar wind.
- Earth has a magnetic field, which protects us from the solar onslaught, but is pushed back by it as well.
- This explains why auroras are seen at night: not only is it dark, but the sun’s energy takes an indirect route by first being stored in the magnetotail.
- If the magnetic fields change rapidly, they can affect large regions of the Earth, building up to cause problems for power networks.
Solar cycles
- About 300 years later, American astronomer George Hale showed that sunspots had intense magnetic fields, several thousand times stronger than Earth’s.
- In the 400 years since Galileo’s observations, we have found that the number of sunspots varies dramatically over an 11-year long cycle.
Energy storage
- Magnetic fields store energy, and sometimes, as in Earth’s magnetotail or near sunspots, this energy can be changed to other forms.
- In the strong fields of sunspots, it can be released as X-rays in rapid, unpredictable flares.
- Sunspots and flares are near the surface or light-emitting layer of the sun, but material can escape from the sun’s strong gravity field.
Space weather forecasts
- However, in this, the following solar cycle, we have already exceeded predicted numbers of sunspots and had large magnetic storms, so predictions may need to be revised upward.
- Although direct measurement of incoming disturbances by satellites in the solar wind gives us only about an hour’s warning of stormy space weather, we can also predict a bit further in advance by watching sunspots rotate into view as the sun turns.
Rare storms
- The strongest flare of Solar Cycle 25 so far occurred on Dec. 14, and was the most powerful eruption the sun has produced since the great storms of September 2017.
- Large solar storms are rare, but we must calmly prepare for possible space weather impacts that should maximize in a few years.
Martin Gerard Connors receives funding from Canada's NSERC.