Solar Fireworks Signal New Space Weather Mystery

May 24, 2005

The most intense burst of solar radiation in five decades accompanied a large solar flare on January 20. It shook space weather theory and highlighted the need for new forecasting techniques, according to several presentations at the American Geophysical Union meeting this week in New Orleans.

The solar flare, which occurred at 2 a.m. EST, tripped radiation monitors all over the planet and scrambled detectors on spacecraft. The shower of energetic protons came minutes after the first sign of the flare. This flare was an extreme example of the type of radiation storm that arrives too quickly to warn interplanetary astronauts.

"This flare produced the largest solar radiation signal on the ground in nearly 50 years," said Dr. Richard Mewaldt of the California Institute of Technology, Pasadena, Calif. He is a co-investigator on NASA's Advanced Composition Explorer (ACE) spacecraft. "But we were really surprised when we saw how fast the particles reached their peak intensity and arrived at Earth."

Normally it takes two or more hours for a dangerous proton shower to reach maximum intensity at Earth after a solar flare. The particles from the January 20 flare peaked about 15 minutes after the first sign.

"That's important because it's too fast to respond with much warning to astronauts or spacecraft that might be outside Earth's protective magnetosphere," Mewaldt said. "In addition to monitoring the sun, we need to develop the ability to predict flares in advance if we are going to send humans to explore our solar system."

The event shakes the theory about the origin of proton storms at Earth. "Since about 1990, we've believed proton storms at Earth are caused by shock waves in the inner solar system as coronal mass ejections plow through interplanetary space," said Professor Robert Lin of the University of California at Berkeley. He is principal investigator for the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). "But the protons from this event may have come from the sun itself, which is very confusing."

The origin of the protons is imprinted in their energy spectrum, as measured by ACE and other spacecraft, which matches the energy spectrum of gamma-rays thrown off by the flare, as measured by RHESSI. "This is surprising because in the past we believed the protons making gamma-rays at the flare were produced locally and the ones at the Earth were produced instead by shock acceleration in interplanetary space," Lin said. "The similarity of the spectra suggests they are the same."

Solar flares and coronal mass ejections (CMEs), associated giant clouds of plasma in space, are the largest explosions in the solar system. They are caused by the buildup and sudden release of magnetic stress in the solar atmosphere above the giant magnetic poles we see as sunspots. The Transitional Region and Coronal Explorer (TRACE) and the Solar and Heliospheric Observatory (SOHO) spacecraft are devoted to observing the sun and identifying the root causes of flares and CMEs, with an eye toward forecasting them.

"We do not know how to predict the flow of energy into and through these large flares", said Dr. Richard Nightingale of the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alta, Calif. "Instruments like TRACE give us new clues with each event we observe."

TRACE has identified a possible source of the magnetic stress that causes solar flares. The sunspots that give off the very largest (X-class) flares appear to rotate in the days around the flare. "This rotation stretches and twists the magnetic field lines over the sunspots", Nightingale said. "We have seen it before virtually every X-flare that TRACE has observed since it was launched and more than half of all flares in that time."

However, rotating sunspots are not the whole story. The unique flare came at the end of a string of five other very large flares from the same sunspot group, and no one knows why this one produced more sudden high energy particles than the first four.

"It means we really don't understand how the sun works," Lin said. "We need to continue to operate and exploit our fleet of solar-observing spacecraft to identify how it works."

Source: NASA

Explore further: NASA balloon recovered a year after flight over Antarctica

Related Stories

NASA balloon recovered a year after flight over Antarctica

February 23, 2017

For 12 days in January 2016, a football-field-sized balloon with a telescope hanging beneath it floated 24 miles above the Antarctic continent, riding the spiraling polar vortex. On Jan. 31, 2016, scientists sent the pre-planned ...

Fermi sees gamma rays from 'hidden' solar flares

January 30, 2017

An international science team says NASA's Fermi Gamma-ray Space Telescope has observed high-energy light from solar eruptions located on the far side of the sun, which should block direct light from these events. This apparent ...

First-ever GPS data release to boost space-weather science

January 30, 2017

Today, more than 16 years of space-weather data is publicly available for the first time in history. The data comes from space-weather sensors developed by Los Alamos National Laboratory on board the nation's Global Positioning ...

Recommended for you

ZTE launches world's first 5G-ready smartphone

February 26, 2017

Chinese telecoms giant ZTE unveiled Sunday what it said is the world's first smartphone compatible with the lightening-fast 5G mobile internet service that networks expect to have up and running by 2020.

Canada conservationist warns of 'cyber poaching'

February 25, 2017

Photographers, poachers and eco-tour operators are in the crosshairs of a Canadian conservationist who warns that tracking tags are being hacked and misused to harass and hunt endangered animals.

Polymer additive could revolutionize plastics recycling

February 24, 2017

When Geoffrey Coates, the Tisch University Professor of Chemistry and Chemical Biology, gives a talk about plastics and recycling, he usually opens with this question: What percentage of the 78 million tons of plastic used ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.