What's the Weather Like in Space?

In addition to the unique weather occurring on each of our neighboring planets, there's also space weather—disturbances driven by various eruptions on the Sun, that occur within the vastness of interplanetary space (the heliosphere) and in the near-Earth space environment.

Like the weather on Earth, space weather occurs around the clock, changes continuously and at will, and can be damaging to human technologies and life. However, since space is a nearly perfect vacuum (it contains no air and is a mostly empty expanse), its weather types are alien to those of Earth. Whereas Earth weather is made up of water molecules and moving air, space weather is composed of “star stuff”—plasma, charged particles, magnetic fields, and electromagnetic (EM) radiation, each emanating from the Sun.

Types of Space Weather

The Sun not only drives Earth’s weather but the weather in space, as well. Its various behaviors and eruptions each generate a unique type of space weather event.

Solar Wind

Because there’s no air in space, wind as we know it can’t exist there. However, there is a phenomenon known as the solar wind—streams of charged particles called plasma, and magnetic fields that constantly radiate from the Sun out into interplanetary space. Ordinarily, the solar wind travels at “slow” speeds of nearly one million miles per hour, and takes about three days to journey to Earth. But if coronal holes (regions where magnetic field lines stick straight out into space rather than looping back onto the Sun’s surface) develop, the solar wind can gust freely out into space, traveling at up to 1.7 million mph—that’s six times faster than a lightning bolt (stepped leader) travels through the air.

Sunspots

Most space weather features are generated by the Sun's magnetic fields, which ordinarily are aligned but can tangle over time due to the Sun's equator rotating faster than its poles. For example, sunspots—dark, planet-sized regions on the Sun’s surface—occur where bundled field lines upwell from the Sun's interior to its photosphere, leaving cooler (and thus, darker) areas at the heart of these messy magnetic fields. As a result, sunspots emit powerful magnetic fields. More importantly, though, sunspots act as a "barometer" for how active the Sun is: The greater the number of sunspots, the more stormy the Sun generally is—and thereby, the more solar storms, including solar flares and coronal mass ejections, scientists expect.

Similar to episodic climate patterns on earth like El Niño and La Niña, sunspot activity varies over a multi-year cycle lasting about 11 years. The current solar cycle, cycle 25, began at the close of 2019. Between now and 2025, when scientists predict sunspot activity will peak or reach "solar maximum," the Sun’s activity will ramp up. Eventually, the Sun's magnetic field lines will reset, untwist, and realign, at which point sunspot activity will decline to a "solar minimum," which scientists predict will occur by 2030. After this, the next solar cycle will begin.

Solar Flares

Appearing as blob-shaped flashes of light, solar flares are intense bursts of energy (EM radiation) from the Sun’s surface. According to the National Aeronautics and Space Administration (NASA), they occur when the churning motion within the Sun’s interior contorts the Sun’s own magnetic field lines. And just like a rubber band that snaps back into shape after being tightly twisted, these field lines explosively reconnect into their trademark loop shape, hurling vast amounts of energy out into space during the process. 

Although they only last minutes to hours, solar flares release about ten million times more energy than a volcanic eruption, according to NASA’s Goddard Space Flight Center. Because flares travel at light speed, it only takes them eight minutes to make the 94-million-mile-long trek from the Sun to Earth, which is the third-closest planet to it.

Coronal Mass Ejections

Occasionally, the magnetic field lines that twist up to form solar flares become so strained that they break apart before reconnecting. When they snap, a giant cloud of plasma and magnetic fields from the Sun’s corona (uppermost atmosphere) explosively escapes. Known as coronal mass ejections (CMEs), these solar storm blasts typically carry a billion tons of coronal material into interplanetary space. 

CMEs tend to travel at speeds of hundreds of miles per second, and take one to several days to reach Earth. Yet, in 2012, one of NASA’s Solar Terrestrial Relations Observatory spacecraft clocked a CME at up to 2,200 miles per second as it left the Sun. It’s considered the fastest CME on record.

How Space Weather Impacts Earth

Space weather emits vast amounts of energy into interplanetary space, but only solar storms that are Earth-directed, or that erupt from the side of the Sun that's presently aimed at Earth, have the potential to impact us. (Because the Sun rotates about once every 27 days, the side that faces us changes from day to day.)

When Earth-directed solar storms do occur, they can spell trouble for human technologies as well as human health. And unlike terrestrial weather, which at most impacts multiple cities, states, or countries, the effects of space weather are felt on a global scale. 

Geomagnetic Storms

Whenever solar material from the solar wind, CMEs, or solar flares arrives at Earth, it crashes into our planet's magnetosphere—the shield-like magnetic field generated by electrically charged molten iron flowing in Earth's core. Initially, the solar particles are deflected away; but as the particles pushing against the magnetosphere pile up, the buildup of energy eventually accelerates some of the charged particles past the magnetosphere. Once inside, these particles travel along Earth's magnetic field lines, penetrating the atmosphere near the north and south poles and creating geomagnetic storms—fluctuations in Earth's magnetic field.

Upon entering Earth's upper atmosphere, these charged particles wreak havoc in the ionosphere—the layer of the atmosphere extending from about 37 to 190 miles above earth's surface. They absorb high frequency (HF) radio waves, which can make radio communications as well as satellite communications and GPS systems (which use ultra-high frequency signals) to go on the fritz. They can also overload electrical power grids, and can even penetrate deep into the biological DNA of humans traveling in high-flying aircraft, exposing them to radiation poisoning.

Auroras

Not all space weather journeys to Earth to make mischief. As high-energy cosmic particles from solar storms push past the magnetosphere, their electrons begin reacting with gases in Earth's upper atmosphere and spark auroras across our planet’s skies. (The aurora borealis, or northern lights, dance at the north pole, while the aurora australis, or southern lights, sparkle at the south pole.) When these electrons mingle with Earth's oxygen, green auroral lights are ignited, whereas nitrogen produces red and pink auroral colors.

Ordinarily, auroras are visible in Earth's polar regions only, but if a solar storm is particularly intense, their luminous glow can be seen at lower latitudes. During a CME-triggered geomagnetic storm known as the the 1859 Carrington Event, for example, the aurora could be seen in Cuba.

Global Warming and Cooling

The Sun's brightness (irradiance) also impacts Earth's climate. During solar maximums, when the Sun is its most active with sunspots and solar storms, Earth naturally warms; but only slightly. According to the National Oceanic and Atmospheric Administration (NOAA), only about one-tenth of 1% more solar energy reaches the Earth. Likewise, during solar minimums, Earth's climate cools slightly.

Forecasting Space Weather

Thankfully, scientists at NOAA's Space Weather Prediction Center (SWPC) monitor how such solar events may affect Earth. This includes providing current space weather conditions, such as the solar wind speed, and issuing three-day space weather forecasts. Outlooks predicting conditions as far as 27 days ahead are also available. NOAA has also developed space weather scales that, similarly to hurricane categories and EF tornado ratings, quickly convey to the public whether any impacts from geomagnetic storms, solar radiation storms, and radio blackouts will be minor, moderate, strong, severe, or extreme.

NASA's Heliophysics Division supports the SWPC by conducting solar research. Its fleet of more than two dozen automated spacecraft, some of which are positioned at the Sun, observe the solar wind, the solar cycle, solar explosions, and changes in the Sun's radiation output around the clock, and relay these data and images back to Earth.