Geomagnetic storm

The sun sends big clouds toward Earth.

These clouds shake the shield around our world. This shaking is called a magnetic storm.

Sometimes the clouds are very strong. They can push on our world's shield. This makes energy move through the air.

These storms can make the sky glow. You might see pretty lights in the sky. These lights are called auroras.

Big storms can also shake power lines. They can make lights go out in homes.

Some storms are very large. They can even make compasses act silly. It is a big show from space!

The Sun sends big clouds toward Earth. These clouds are made of plasma. Plasma is a type of gas.

These clouds can cause a geomagnetic storm. This is a disturbance in Earth's magnetosphere. The magnetosphere is the magnetic shield around our world.

Storms happen when solar wind hits this shield. Large clouds from the Sun are called coronal mass ejections. We call these CMEs for short.

When a CME hits, it pushes on our shield. This transfers power into the magnetosphere. It can also make the sky glow. These lights are called auroras.

Big storms can cause trouble on Earth. In 1859, the Carrington Event happened. It was a very large storm. It caused telegraph wires to spark and catch fire. In 1989, a storm hit Quebec. It shut down the power for six million people. Scientists use tools like magnetometers to study these storms. These tools measure changes in the magnetic field.

A geomagnetic storm is a temporary disturbance in the Earth's magnetosphere. This magnetosphere is the magnetic shield that surrounds our world. These storms happen when large structures from the Sun interact with that shield. One type of structure is called a coronal mass ejection, or CME. These are large clouds of plasma that come from the Sun. Another type is called a corotating interaction region, or CIR. These form where high-speed and low-speed solar winds meet.

These storms matter because they change how energy moves around our planet.

When these solar structures reach Earth, they change how our shield works. First, the increased pressure from the solar wind pushes against the magnetosphere. This causes the shield to compress inward toward the Earth. Next, the magnetic field of the solar wind interacts with Earth's own magnetic field. This interaction transfers extra energy into the magnetosphere. This causes plasma to move more through the shield. It also increases electric currents in the magnetosphere and the ionosphere.

During the main phase, these currents can even weaken the magnetic field on the side of Earth facing the Sun.

Scientists have studied these events for a long time. In 1930, Sydney Chapman and Vincenzo C. A. Ferraro wrote a paper about them. They suggested that solar flares send plasma clouds toward Earth. They thought the trip took 113 days, but we now know it takes only 1 to 5 days. Earlier, Kristian Birkeland used special tubes to show how rays move toward magnetic poles. He thought this might explain why the sky glows in certain places.

These early ideas helped us understand the link between the Sun and our sky.

History shows us that these storms can be very powerful. The largest one ever recorded is the Carrington Event in September 1859. It was so strong that it caused telegraph wires to spark and catch fire. It even gave electric shocks to the people using them. In March 1989, another big storm hit Quebec. It caused the power grid to fail in just a few seconds. This left six million people without electricity for nine hours.

These events show how much the Sun can affect our technology.

You might have seen the results of these storms in the sky. When storms happen, they often create beautiful auroras. These are glowing lights that usually appear near the North and South Poles. During very large storms, these lights can be seen much further south. For example, the 1859 storm showed auroras as far south as Hawaii and Italy.

Scientists use tools called magnetometers to measure these changes. They track a value called the Dst index to see how strong a storm is. This helps us understand the amazing connection between the Sun and Earth.

A geomagnetic storm is a temporary disturbance in the Earth's magnetosphere. This magnetosphere is the magnetic shield that surrounds our planet. These storms are driven by interactions between the magnetosphere and large-scale structures of plasma and magnetic fields. These structures originate on or near the Sun. Two main types of structures cause these storms. The first is the interplanetary coronal mass ejection, or CME. These are large clouds of plasma that often come from solar active regions. The second is the corotating interaction region, or CIR. CIRs form at the boundary between high-speed and low-speed streams of solar wind.

The process of a storm happens in several distinct steps. First, solar structures reach the Earth. The increased pressure from the solar wind compresses the magnetosphere. Next, the magnetic field of the solar wind interacts with Earth's magnetic field. This interaction transfers increased energy into the magnetosphere. This causes plasma to move more through the magnetosphere due to increased electric fields. It also increases electric currents in the magnetosphere and the ionosphere. During the main phase, enhanced currents like the ring current weaken the Earth's dayside magnetic field. This allows solar wind pressure to push the magnetopause boundary closer to Earth.

Scientists measure the intensity of these storms using the Dst index. This index estimates the global change of the horizontal magnetic field at the equator. It is computed once per hour using magnetometer stations. During quiet times, the Dst stays between +20 and −20 nano-Tesla (nT). A storm has three specific phases: initial, main, and recovery. The initial phase, or storm sudden commencement, sees the Dst increase by 20 to 50 nT. The main phase occurs when the Dst decreases to less than −50 nT. This phase usually lasts between 2 and 8 hours. Finally, the recovery phase returns the Dst to its quiet value. This phase can last from 8 hours up to 7 days.

Storms are classified by their minimum Dst values. A moderate storm has a minimum between −50 nT and −100 nT. An intense storm falls between −100 nT and −250 nT. A super-storm is any event where the minimum Dst is less than −250 nT. The U.S. National Oceanic and Atmospheric Administration also uses the G-scale. This rates storms from G1, the weakest, to G5, the strongest.

Our understanding of these events grew through scientific discovery. In 1930, Sydney Chapman and Vincenzo C. A. Ferraro published a theory of magnetic storms. They argued that solar flares emit plasma clouds, which we now call CMEs. They originally thought these clouds took 113 days to reach Earth. We now know the journey actually takes only 1 to 5 days. Their work built upon the ideas of Kristian Birkeland. Birkeland used cathode-ray tubes to show how rays are deflected toward magnetic poles. He theorized this process was responsible for the auroras seen in polar regions.

History shows that these storms can have massive impacts on technology. The largest recorded storm was the Carrington Event in September 1859. It was caused by a massive CME that reached Earth in only eighteen hours. The horizontal field was reduced by 1600 nT. This event caused telegraph wires to deliver electric shocks and start fires. Aurorae were visible as far south as Hawaii, Mexico, Cuba, and Italy. In March 1989, a storm caused the Hydro-Québec power grid to collapse in seconds. This left six million people without power for nine hours.

Geomagnetic storms connect many different parts of space science. They relate to solar activity, such as the sunspot cycle. Storm frequency increases during solar maxima. They also impact the ionosphere, which can cause radio and radar scintillation. This interference can disrupt navigation by magnetic compasses. In 2003, the Halloween Solar Storms caused extreme radio blackouts and damaged satellites. One such storm even caused U.S. Navy sea mines to detonate in North Vietnam. Scientists continue to monitor these events using magnetometers and particle detectors to protect our modern world.