Space weather
Space weather refers to the atmospheric conditions influenced by solar activity, particularly from the sun's emissions of charged particles and radiation. This phenomenon can significantly impact Earth's upper atmosphere and technology, giving rise to events like auroras and geomagnetic storms. Solar activity is cyclical, with an approximately eleven-year cycle of increased activity known as solar maximum, during which sunspots, solar flares, and coronal mass ejections (CMEs) are more prevalent. While minor solar events may create beautiful displays of auroras, more severe events, such as geomagnetic storms, can lead to disruptions in communications, satellite operations, and power grids. Historical incidents, such as the 1859 Carrington Event and the 1989 Quebec blackout, illustrate the potential hazards posed by significant space weather. Governments and scientific bodies are increasingly aware of these risks, initiating guidelines and monitoring systems to prepare for possible future events. The interplay between solar phenomena and Earth’s magnetic field is crucial in understanding the broader implications of space weather on human infrastructure and safety.
Space weather
Space weather refers to conditions on the sun that can affect Earth's upper atmosphere and impact human technology and infrastructure. Examples of space weather range from the constant stream of charged electrical particles emitted from the sun to massive solar eruptions and flares that send clouds of radiation and gas into space. These solar conditions can result in brilliant displays of aurora lights at Earth's poles or geomagnetic storms that can fry electronics and disrupt communications. The effects of severe space weather have impacted Earth in the past, disabling the early telegraph system in 1859 and knocking out the power grid in Canada in 1989. A near miss with a potentially devastating solar storm in 2012 prompted some governments to prepare for the possibility of catastrophic space weather in the future.
Background
The sun is a giant nuclear reactor that has been fusing together its fuel of hydrogen gas at the center of the solar system for billions of years. The fusion process creates enormous amounts of energy and intense heat that radiates outward from the sun's core to the solar atmosphere called the corona. Charged particles and gas from the corona are constantly being emitted into space from the sun. These charged particles, such as electrons, protons, and atomic nuclei, are called the solar wind.
While the solar wind is continually streaming away from the sun, its speed and density fluctuate according to conditions in the solar atmosphere. The level of solar activity varies over time. Periods of high solar activity run in cycles, with the sun reaching a peak of activity every eleven years. During this peak, known as the solar maximum, the sun produces a greater amount of solar weather phenomena such as sunspots, solar flares, and coronal mass ejections (CMEs). These events can expel massive amounts of radiation, charged particles, and gas into space and can potentially impact Earth if they are aimed in its direction.
Sunspots are areas on the sun's surface that contain strong magnetic fields and appear darker because their temperatures are thousands of degrees cooler than the surrounding regions. Sunspots are generally located near the sun's equator and act as caps, containing more intense energy below. Sunspot activity often occurs in conjunction with solar flares.
Solar flares are large explosions caused by the release of magnetic energy from the surface of the sun. When a flare erupts, it can last from minutes to hours and can launch accelerated amounts of radiation and highly charged particles into the solar system. Solar flares can impact Earth, but to do so the eruption must be on the side of the sun facing the planet and be pointed directly at it.
CMEs are the most common cause of space weather on Earth. A CME occurs when the sun's magnetic field warps and violently expels huge clouds of solar material. These bubbles of gas, charged particles, and magnetic fields move much faster than the solar wind and fly into space at speeds of several million miles per hour. A CME can contain as much as a billion tons of matter—far more than a solar flare—and is steered by the solar wind as it sweeps out into space.
Impact
Most weather on Earth's surface occurs in the troposphere, the lowest level of the atmosphere. Space weather is caused by the effects of solar activity on the magnetosphere, ionosphere, and thermosphere in the upper atmosphere. Radiation, such as X-rays and gamma rays, emitted from such activity travels the ninety-three million miles from the sun at the speed of light and reaches Earth in eight minutes. The gas and charged particles thrown off by the sun take a bit longer but still travel at tremendous speed. They could arrive at the planet within minutes or hours.
When electrically charged particles from the sun reach Earth's upper atmosphere, they encounter the planet's magnetic field and are funneled toward the north or south poles. As these particles interact with molecules in the thermosphere, they release energy in the form of light. This energy is the source of the cascading aurora displays known as the northern or southern lights. The solar wind causes most auroras, which are normally confined to higher latitudes near the poles. During times of heightened solar activity, auroras occur more frequently and can be seen farther from the poles.
Intense solar outbursts caused by solar flares or CMEs can cause a space weather phenomenon called a geomagnetic storm. These storms occur when large amounts of accelerated gas and charged particles slam into Earth's magnetosphere. The magnetosphere protects the planet from a direct hit, but the high-energy particles can travel along the lines of the magnetic field and affect the planet's surface. Low-level geomagnetic storms usually result in intense aurora displays and disruptions in radio communications, which travel through the ionosphere. More severe storms can cause orbiting satellites to fail and result in wide-scale disruptions to global positioning systems, electronic equipment, and power grids.
In 1859, the largest geomagnetic storm in recorded history hit Earth and crippled the telegraph industry across Europe and North America. Telegraph operators reported that sparks flew from their machines, and some of the internal components were melted. In 1989, a large solar flare touched off a geomagnetic storm that damaged power plants across North America and caused a blackout in Quebec, Canada, that left millions of people without power for nine hours.
In 2012, a pair of CMEs crossed over Earth's orbit, missing the planet by a week. Scientists say that if the solar event had impacted Earth, it could have caused catastrophic damage to power grids, communications, and infrastructure. Estimates of possible damage ranged in the trillions of dollars, and recovery time could have taken years. In February 2022, another solar flare caused a geomagnetic storm that knocked thirty-eight newly launched satellites out of low-Earth orbit. The storm affected Earth’s atmosphere and caused the satellites to experience an unusual amount of atmospheric drag, which impacted their ability to achieve orbit. In 2016, US President Barack Obama delivered an executive order issuing guidelines for dealing with the possibility of such severe space weather. The guidelines assigned responsibilities to government agencies in the case of a catastrophic geomagnetic event and set up a system to monitor and forecast space weather.
In 2024, changes in space weather caused the Northern Lights to become visible at unusual latitudes across the world. A severe geomagnetic storm reached Earth in October, traveling down magnetic field lines into the Earth's atmosphere. This caused the gases in the atmosphere to illuminate, creating auroras where none would typically be visible.
Bibliography
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