Can the Solar Wind Trigger Thunderstorms?
The sun is obscured by thick cloud during a thunderstorm in California in 2009.
Extreme Space Weather
Oct. 3, 2011 --
With hurricanes, floods, massive thunderstorms, heat waves and wildfires, we might be inclined to believe that the weather on Earth is sometimes less than hospitable to the life that inhabits it. But compared to other planets, stars and other bodies in the cosmos, the weather on Earth is downright mild. In this slide show, explore what conditions are like elsewhere in the universe. By the time you're done reading this slide show, you'll know exactly what to say the next time you hear someone whining about the weather: "Quit complaining. At least we don't live on HD 209458b."
Credit: Paul A. Kempton
The Sauna Planet "It's not the heat; it's the humidity" is a common expression on especially muggy days in the heat of the summer. But on exoplanet GJ 1214b, we guarantee you won't notice the difference. Located about 40 light-years from our planet, this super-Earth waterworld is believed to possess an atmosphere of dense steam. The exoplanet is between two and 10 times larger than Earth and located approximately 70 times closer to its parent star. Essentially, this planet is one giant sauna, turned up to temperatures in excess of 1,000 degrees Fahrenheit (537 degrees Celsius).
Mars Storms Hurricanes are the largest storms on Earth. With powerful wind gusts and heavy rains, the storms can take a devastating toll on millions at a time. But in terms of size, they can't compare to the dust storms that can roll across Mars and affect the entire planet. In fact, some storms are so large that amateur astronomers can occasionally view them using ground based telescopes. During dust storms, wind gusts can reach up to 300 miles per hour, far stronger than any storm ever recorded on Earth.
Supersonic Planet If you're a windsurfing enthusiast, HD189733b may be just the right place for you. That is, at least it would be if it weren't 60 light-years away and orbiting its parent star so closely. Classified as a hot Jupiter, this gas giant hosts wind speeds that exceed the speed of sound. And since, as Adam Showman of the University of Arizona Lunar and Planetary Laboratory explains, the speed of sound of HD189733b is 10 times faster than it is on Earth, that's a pretty significant accomplishment. To put a number on it, the winds can reach speeds of around 6,700 miles (10,870 kilometers) per hour. That should help to cool down any potential visitors, since the temperature on the surface of the planet facing the sun can reach 1,700 degrees Fahrenheit (926 degrees Celsius).
Tidally Locked World Located some 150 light-years from Earth, HD 209458b is a hot Jupiter with one major convenience: You never have to bother to set your watch. The planet is in a tidally locked orbit with its parent star, meaning one side is always facing the sun and the other side is stuck in perpetual night. Because of this disparity, the planet also has strong winds similar to those of HD189733b. However, wind speeds on this planet only reach 4,500 miles per hour, making it a better option for a thrill-seeking windsurfer who might still be holding out hope of keeping a hair or two in place.
Credit: Jon Lomberg/Univ. of Toronto
Forget Jupiter The swirling storm at the center of Jupiter's Great Red Spot might get all the attention in our solar system. But that storm is a tiny tyke compared to the one on this brown drawf. Affectionately called "2MASS J21392676+0220226," this brown dwarf is located approximately 47 light-years away.
Solar Storms Unlike the weather mentioned in every other entry on this slide show, storms on the sun can have a significant impact on life on Earth. As storm activity increases in frequency as the sun approaches its solar maximum in its 11-year cycle, solar flares and coronal mass ejections can threaten the functionality of satellite systems, affecting computer, navigation and telecommunications networks on Earth, as well as potentially disrupt power grids. Unfortunately, an umbrella won't do us much good in the event of a massive solar storm as the sun blasts plasma particles at Earth at speeds of hundreds of miles per hour. But that doesn't mean there's reason to panic, either. (Not yet, anyway.)
Credit: ESA/V. Beckmann (NASA-GSFC)
Honorable Mention: Black Holes If you're chasing massive storms in space, nothing quite rivals the strength and intensity of the tidal forces created by a hungry black hole. When black holes tear into stars, they pull in gasses from that star at such high speeds as to create bright gamma-ray bursts that are detectable from Earth. Anything that comes near a black hole is stretched out, then ripped apart and smashed together again with other matter at velocities approaching the speed of light. If there's one storm you absolutely don't want to get caught in this year, it's one created by drifting too close to a black hole.
More stories by Talal Al-Khatib.
It’s no secret that the sun has wide ranging impacts on our planet — it is, after all, the primary energy source for our biosphere. But when it comes to how the sun impacts climate variations and weather phenomena, scientists can have a hard job teasing out the sun-Earth connections.
One connection, however, is no secret. When the solar wind impacts the Earth’s magnetosphere — the global magnetic field that deflects the sun’s ionizing particles to the poles — high latitudes can be treated to a beautiful light display called the aurora. But can the solar wind have other, more “everyday” impacts on our atmosphere? Yes, says a new study published today (May 14) in the journal Environmental Research Letters.
University of Reading scientists have seen, for the first time, that the ionizing particles in the solar wind streams may influence thunderstorm activity levels. This offers compelling evidence that there is a fascinating link between space weather and the triggering of lightning.
“Our main result is that we have found evidence that high-speed solar wind streams can increase lightning rates,” said lead researcher Chris Scott. “This may be an actual increase in lightning or an increase in the magnitude of lightning, lifting it above the detection threshold of measurement instruments.
“Cosmic rays, tiny particles from across the Universe accelerated to close to the speed of light by exploding stars, have been thought to play a part in thundery weather down on Earth, but our work provides new evidence that similar, if lower energy, particles created by our own sun also affect lightning.”
Scott’s team focused on the central England region and studied thunderstorm data from 2000 to 2005 obtained from the UK Met Office’s lighting detection system. Then they took data from NASA’s Advanced Composition Explorer (ACE) spacecraft, which is embedded in the solar wind in a direct line between us and the sun. Any solar wind streams that hit ACE continue “downstream” to Earth.
The sun produces solar wind streams of different velocities, so as the sun rotates, fast solar wind steams “catch up” with the slow wind streams. The region where the streams interact can increase the density of energetic solar wind particles. The Earth will pass through these interaction regions and we will often detect an uptick in space weather.
As the sun rotates every 27 days, high-speed solar wind streams regularly and predictably sweep past the Earth. After accumulating the five years of ACE and Met Office lighting data, the researchers found that, on average, there were 422 lightning strikes over the following 40 days after the Earth passed through one of these dense streams. Over the 40 days prior, there were an average of 321 lightning strikes. The lightning strike peak rate occurred 12-18 days after solar wind stream arrival.
There does seem to be a statistically significant enhancement of lightning activity relative to space weather conditions, but it is worth emphasizing that this study only focused on a small area in central England, so it would be interesting to see if a similar pattern is detected elsewhere around the globe. But if this is a real phenomenon and solar wind particles are triggering lightning bolts, what mechanism could be driving it?
The researchers suggest that as the Earth passes through the high-speed, dense solar wind streams, ionizing solar wind particles have enough energy to penetrate deep into the Earth’s magnetosphere, interacting with our atmosphere.
“We propose that these particles, while not having sufficient energies to reach the ground and be detected there, nevertheless electrify the atmosphere as they collide with it, altering the electrical properties of the air and thus influencing the rate or intensity at which lightning occurs,” said Scott.
This sounds reasonable as it is well known that during solar storms, when energetic solar particles interact with our atmosphere during auroral activity, huge global currents are induced through the Earth’s atmosphere. A similar modification of the electric field in the lower atmosphere may also be occurring, potentially enhancing weather systems and triggering electrical storms.
“In increasing our understanding of weather on Earth we are learning more about its important links with space weather. Bringing the topics of Earth Weather and Space Weather ever closer requires more collaborations between atmospheric and space scientists, in which the University of Reading is already leading the way,” added Giles Harrison, head of Reading’s Department of Meteorology.