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What Is Space Weather?

Rain, wind, and storms are everyday features of our weather on Earth. But beyond our atmosphere, scientists are monitoring phenomena in space that are a close cousin to terrestrial weather. Space weather, the name scientists adopted in the late twentieth century to describe changes in space, has become a keen area of study for many heliophysicists, meteorologists, and skywatchers.

Understanding space weather means looking beyond our experiences on the Earth’s surface. Rather than wind, rain, thunder, and seasonal changes, space weather develops differently and produces outcomes unlike terrestrial weather.

So, can space weather cause a tornado, hurricane, thunderstorm, or temperature swings? Generally speaking, the impacts of space weather tend to affect us more in other ways. Space weather falls into a different category.

Causes of Space Weather

It starts with the sun—our dynamic star that’s under constant change. As the sun changes, so does the space around it. Solar flares and eruptions release enormous amounts of energy—much more energy than has been produced on Earth in all of human history—over the course of just a few minutes! These events are so powerful and enormous they can be felt across the solar system, from the sun's surface to tens of millions of miles away on Earth and beyond.

As the sun evolves, changes in its magnetic field store vast amounts of energy. Often this energy dissipates gradually, heating the sun's atmosphere or being swept away by solar wind. Sometimes a fraction of it is released impulsively, triggering powerful events that can lead to severe space weather near Earth. Satellites, sensors, and imaging technology record those activities in real time for researchers at NOAA’s Space Weather Prediction Center who analyze the data each day to monitor and predict changes in space weather. Solar flares, coronal mass ejections, coronal holes, and geomagnetic storms cause scientists to take note.

Solar Eruptions: Flares and Coronal Mass Ejections

Solar eruptions are massive explosions on the sun that send huge amounts of energy and mass streaming into space. Eruptions manifest in many ways: solar flares are short, impulsive bursts of electromagnetic radiation that blast X-rays and energetic particles into interplanetary space. Weak flares are common occurrences on the sun, while massive flares, which can last for days, are the most energetic events in the solar system.

Another manifestation of solar eruptions, called coronal mass ejections, or CMEs, are powerful outbursts of magnetic field and plasma from the Sun's corona. CMEs can contain as much mass as 10,000 modern aircraft carriers and fling solar matter into space at speeds high enough to reach the outer edges of the solar system. Billions of tons of electrified plasma and subatomic particles from the sun’s corona fire off like a blast into space by a CME at speeds typical of 600 to 900 km/s, with speeds varying widely. The most powerful CMEs can reach speeds of several thousand km/s.

Image of a coronal mass ejection (CME) on March 15, 2013
CMEs, coronal mass ejections, act like shockwaves in space.
Credit: NASA

Coronal Holes

Coronal holes, dark regions in the sun’s atmosphere detected by ultraviolet and X-ray imaging, are the source of high-speed solar wind streams. The winds generated by the coronal hole pass virtually unhampered into space. Sometimes present for many months, the holes rotate as the sun rotates every month. These high-speed streams collide with the slow solar wind that is generated outside the holes. The visual effect resembles the spiral of a rotating sprinkler, which scientists call the Parker Spiral. This collision can lead to the formation of shockwaves in the solar wind and can produce disturbances to Earth’s magnetosphere, the protective magnetic field that surrounds the planet for thousands of miles above the surface.

Geomagnetic Storms

Flares, CMEs, and high speed streams cause space weather-induced storms near Earth referred to as geomagnetic storms. These near-Earth responses to events from the sun demonstrate the far-reaching impact of the star’s tremendous power. The sun’s eruptions, precursors to storms, become problematic once they interact with the Earth’s magnetosphere and ionosphere. Storms can disrupt systems on Earth, from radar to airline navigational tools.

GPS signals are susceptible to geomagnetic storms, which can change a receiver’s ability to calculate an accurate position from a satellite signal. With more than 2,000 satellites in space and GPS features common in cell phones, the implications can be broad if signals are hampered. At home, our telecommunications systems, radio waves, cellular service, and power grids can all be affected by space weather.

In March 1989, millions of people lost power when a geomagnetic storm caused a power grid failure in Quebec and even melted some power transformers in New Jersey. During another incident around Halloween 2003, a geomagnetic storm forced airline rerouting, halted spacecraft instrumentation, and caused a power failure in Sweden.

The Northern Lights come about from particles reacting to the everyday atmospheric matter in Earth’s protective buffer.

The Human Experience

Though space weather can reach Earth’s immediate vicinity within a few days or less, observations from key satellites, GOES and DSCOVR, help detect potential harm. Nonetheless, the random nature of flares, solar winds, and CMEs—the underlying causes of storms—make predictions more difficult. In October 2016, a U.S. presidential executive order required the development of a nationwide strategy to cope with security and disaster issues related to space weather.

However, not all outcomes of space weather are negative. Aurorae claim the distinction of being a natural, beautiful consequence of space weather. Aurorae could be considered space weather’s equivalent to the rainbow, except that the shimmering curtains of light have nothing to do with rain. They develop from the collision of charged particles from solar eruptions with our upper atmosphere. The same space weather event of Halloween 2003 that caused so many problems also created a remarkable aurora. That aurora borealis, also known as the Northern Lights, was so spectacular, regions around the globe reported sightings.

Photo of aurora
The Northern Lights come about from particles reacting to the everyday atmospheric matter in Earth’s protective buffer.

Space Weather Data

NCEI stores a broad assortment of space weather data for public use. Solar and space environmental data archives include extensive collections from solar observatories, ground ionospheric sounders, and satellites. The datasets include solar radio flux, sunspot numbers, solar imagery, and geomagnetic indices. They are used to produce forecasts, such as the monthly sunspot number forecast. Most notably, sunspot numbers represent one of the longest continuous climate records available. The data give scientists the means to make many forecasts and issue space weather advisories and alerts.