Like the Earth, the Sun, which is made of electrified gases called plasma, also generates its own magnetic field via a process called a dynamo , which is driven by internal fluid motion. However, the Sun's magnetic field is colossally more powerful and complex than Earth's.
It is so large in fact, that it reaches far past the edge of our solar system, and works similarly in that it helps to protect the planets within it from harmful cosmic particles from farther out in space. All solar activity is driven by the Sun's magnetic fields, so the more complex they are, the more solar activity there is. Plus, since the Sun's gases are constantly moving, they stretch and twist the magnetic fields.
We can see manifestations of the Sun's magnetic field in the form of sunspots, which are cooler, dark areas on the sun's surface which mark regions where magnetism is the strongest. Sunspots are associated with various types of solar activity and the number and location of sunspots are a key indicator of the Sun's overall activity.
The solar cycle is a nearly periodic change in the Sun's activity between the time where we can observe the most and least number of sunspots, and generally lasts around 11 years. Sometimes the surface of the Sun is very active with lots of sunspots, while other times it is quieter with only a few or even none. Also, at the peak of each solar cycle, the Sun's magnetic field changes polarity as its inner magnetic dynamo reorganizes itself.
This can stir up stormy space weather around our planet. The cosmic particles from deep space that the field protects us from may also be affected, since when a magnetic field reversal occurs, it becomes more wavy, and can act as a better shield against them. Solar activity associated with space weather that can affect the Earth includes phenomena such as:.
Solar flares and CMEs are types of large solar eruptions that spew forth from the violent surface of the Sun.
However, their sizes are massively different, they look and travel differently, and their effects on surrounding planets vary. Solar flares are localized intense bursts of radiation, and some of the energy they release can reach the Earth relatively quickly in less than 10 minutes if our planet is in its path.
Additionally, high-energy solar energetic particles are believed to be released just ahead of solar flares and CMEs. CMEs are much larger eruptions that hurl massive clouds of magnetized plasma far into space, plowing right through the continuous flow of charged particles that normally stream from the Sun, called solar wind, and can reach Earth in up to three days.
Evolution of the Sun in extreme ultraviolet light from through , as seen from the telescope aboard Europe's PROBA2 spacecraft. Sunspots are areas of particularly strong magnetic forces on the Sun's surface.
They appear darker than their surroundings because they are cooler. Even so, scientists have discovered that when there are lots of sunspots, the Sun is actually putting out MORE energy than when there are fewer sunspots. During solar maximum, there are the most sunspots, and during solar minimum, the fewest. Through special filters, sunspots may look like the picture on the left. The sunspot groups are as big as the giant planet Jupiter!
On the right is a closeup of some other sunspots. The larger sunspot on the right is bigger than Earth! Solar flares happen because of the constantly moving magnetic fields in the Sun's atmosphere. As the Sun approaches solar maximum the most active part of its year cycle , its magnetic fields become more and more complex.
The magnetic fields loop around, and cross over each other, cutting each other off, and reconnecting. You have probably seen what happens when you sprinkle iron filings on a bar magnet. The iron filings line up along the magnetic lines of force. The year sunspot cycle is actually half of a longer, year cycle of solar activity. Each time the sunspot count rises and falls, the magnetic field of the Sun associated with sunspots reverses polarity; the orientation of magnetic fields in the Sun's northern and southern hemispheres switch.
Thus, in terms of magnetic fields, the solar cycle is only complete with the fields back the way they were at the start of the cycle after two year sunspot cycles. This solar cycle is, on average, about 22 years long - twice the duration of the sunspot cycle. Some scientists believe there is evidence for other, longer-period variations in the sunspot and solar cycles. Other scientists are skeptical about such claims.
Most scientists think we need more data, spanning longer periods of time, to definitively resolve this issue. Besides these regular cycles, the Sun has exhibited periods of very unusual sunspot counts.
Most notably, from about to there were very few sunspots - in some years none at all were observed! This period, now called the Maunder Minimum after E. Extreme eruptions can even affect electricity grids on Earth. Some cycles have maximums with lots of sunspots and activity. Other cycles can have very few sunspots and little activity. Scientists work hard to improve our ability to predict the strength and duration of solar cycles. These predictions can help them forecast these solar conditions, called space weather.
Forecasting of the solar cycle can help scientists protect our radio communications on Earth, and help keep NASA satellites and astronauts safe, too.
Credit: NASA. Solar activity can affect satellite electronics and limit their lifetime.
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