June 7, 2000 -- Yesterday the orbiting Solar and Heliospheric Observatory (SOHO) recorded a powerful series of solar eruptions including a full-halo coronal mass ejection (CME).

"The halo CME was magnificent," says Gary Heckman, a space weather forecaster at the NOAA Space Environment Center. "Based on [the characteristics of the eruption], this looks like a sure bet to produce a geomagnetic storm."

The velocity of the ejected material was at least 908 km/s, says Dr. Simon Plunkett, an operations scientist with the SOHO coronagraph team at the Naval Research Laboratory and the Goddard Space Flight Center. "The CME should reach Earth in a little less than 48 hours. This would put its arrival around midday on Thursday, June 8."

Above: This frame from a

 

shows a coronal mass ejection billowing away from the Sun on June 6, 2000. The solid-colored blue disk in the middle is an occulting disk that blocks out the Sun's intense light to reveal the faint corona, along with background stars and planets. The white circle shows the true size of Sun. These images were captured by the wide field coronagraph on board the orbiting ESA/NASA Solar and Heliospheric Observatory.

 

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Coronal mass ejections can carry up to 10 billion tons of electrified gas traveling at speeds as high as 2000 km/s. "Halo events" are CMEs aimed toward the Earth. As they loom larger and larger they appear to envelop the Sun, forming a halo around our star.

They may sound menacing, but CMEs pose little danger to people on Earth. Our planet's magnetic field serves as an effective shield against solar wind storms. The same familiar force that causes compass needles on Earth to point north also extends far into space. When a CME hits the magnetosphere -- the region around Earth controlled by its magnetic field -- most of the incoming material is deflected away from our planet.
  If a gust of solar wind is very strong -- as this one might be -- it can compress the magnetosphere and unleash a geomagnetic storm. In extreme cases, such storms can induce electric currents in the Earth that interfere with electric power transmission equipment. Satellite failures are possible, too. Geomagnetic storms can also trigger beautiful aurorae. These "Northern Lights" are usually seen at high latitudes, but they have been spotted farther south than Florida during intense disturbances. The last time this happened was April 6, 2000.
  Left: This rare red-colored aurora over North Carolina was photographed by Chuck Adams on April 6, 2000. The bright object near the horizon is the Moon. Also visible in the background are the Pleiades, Taurus, and Orion. The photographer used a Nikon FM2 camera equipped with a 28mm f/2 lens. The exposure time was one minute on Kodak Elite 100 slide film. (Copyright 2000, Chuck Adams, all rights reserved.)

A Double Whammy

The June 6, 2000, coronal mass ejection was accompanied by two of the most intense solar flares since a brilliant eruption in February 2000.

"CMEs can occur without a flare," says Dr. David Hathaway, a solar physicist at the Marshall Space Flight Center, "but today is the more typical case where a flare is also part of the eruption.

"Solar flares and CMEs occur whenever there's a rapid, large-scale change in the Sun's magnetic field. The solar active region that produced the eruptions [on June 6] had a complicated magnetic configuration - oppositely directed magnetic fields were seen right next to each other."
 

Whenever space weather forecasters see a complex magnetic field like the one exhibited by sunspot group 9026 (where yesterday's eruptions occurred) they know that solar flares are likely. In fact, the NOAA Space Environment Center predicted a possible major flare from 9026 several days ago. The region has been producing mid-sized flares since it rotated into view over the eastern limb of the Sun on June 1.
 

 

Above: This short animation shows the first of two X-class solar flares erupting from sunspot group 9026 at 13:36 UT on June 6, 2000. Click on the image for . The images were recorded by SOHO's Extreme Ultraviolet Telescope at 304 Angstroms. The full halo CME now heading for Earth appears to be associated with a second, more powerful flare that occurred one and a half hours later. Animations of that flare are available from the SOHO Extreme Ultraviolet Telescope or (Holloman AFB). Right: This SOHO MDI white light image of the Sun shows the location of sunspot group 9026 on June 7, 2000.

Does this spate of solar activity means that Solar Maximum has finally arrived?

"This is an indication that solar maximum is upon us," says Hathaway. There is a common misconception that "Solar Max" is a single episode of high activity. Not so, Hathaway cautions. The solar maximum will last over an extended period of time, perhaps as long as two years interspersed with many powerful solar flares and CMEs.

Waiting and Watching

When the CME arrives, scientists aren't sure how big the geomagnetic storm will be.

"To get an intense geomagnetic storm from a CME we believe that two things must happen," says Dr. James Spann of the Marshall Space Flight Center, a co-investigator on an ultraviolet imaging camera in orbit aboard NASA's aurora-monitoring Polar satellite. "First, the disturbance must encounter the Earth's magnetic field directly, as opposed to a glancing blow. Second, the magnetosphere must already have stored energy, ready to be released in the form of aurora. If either of these two conditions fail, we're not likely to have an intense auroral display."
 

Left: Click on the image to see what happens when a coronal mass ejection strikes our planet's magnetosphere.

While no one is certain what will happen on the night of June 8, this is a rare opportunity to anticipate an auroral storm with two full days of advance warning. There's plenty of time to set up your camera and prepare late-night observing snacks. You may need a cup of coffee, because the best time to spot aurora borealis is usually during the hours around local midnight (in this case, around the 12 o'clock boundary between June 8 and 9). The Moon will be in a waxing quarter phase, sinking below the horizon at approximately 1:30 a.m. local time on June 9. That will afford dark skies between moonset and dawn for rural observers at mid-latitudes. Unfortunately for sky watchers at higher latitudes (where aurora sightings are usually best), the extended hours of twilight just two weeks before the summer solstice may obscure all but the most intense Northern Lights.

The Science@NASA April 6th, 2000, aurora gallery features a selection of photos with camera settings suitable for recording aurora borealis. More observing tips are available at Jan Curtis's web site "Home of the Northern Lights."

The View from Space

 

A fleet of NASA and NOAA satellites will be monitoring events in space when the CME disturbance arrives tomorrow. These include Polar, GEOTAIL, ACE, POES and others.

Researchers say that the timing of this event couldn't be better for NASA's newest space mission -- the Imager for Magnetopause to Aurora Global Exploration (IMAGE) -- a unique satellite dedicated to the study of space storms. IMAGE's 'first light' pictures of electrified gas in Earth's magnetosphere were released just this week.
 

"We've been waiting for just such an event," says NASA/Marshall's Dr. Dennis Gallagher, a co-investigator on the IMAGE mission. "Hopefully, IMAGE will be in the right place in its orbit at the right time to see the start of any resulting storm in the Earth's magnetosphere."

Right: This sequence of pictures captured by the Ultraviolet Imager on NASA's Earth-orbiting Polar satellite shows an auroral storm over northern Asia on February 24, 2000. Because it records ultraviolet light, Polar's UV camera can see aurora from space on both the day and night sides of Earth. Polar is one of several missions operating as part of the International Solar Terrestrial Physics (ISTP) program. ISTP and IMAGE complement and support one another.

"Before IMAGE, if we wanted to understand what happened during a storm like the one that's coming, we had to combine thousands of point-by-point measurements taken by different satellites during many distinct storms," continued Gallagher. "No single satellite had a continuous, global view of all the action.

"It would be like trying to understand the rules of major league baseball if you were only allowed to watch a few random moments of different games while wearing blinders that only let you see a little bit of the field at once -- like the first base line or right field -- but nothing else. If you watched several different baseball fields in this way over many years, you might eventually start to put together what baseball is all about, but it would be very difficult. Now imagine what you can learn about the game if you were suddenly given sight and could see the whole field at once throughout every game.

"That's how it is with IMAGE and the magnetosphere. We can see the whole thing at once for the first time. I hate to take advantage of this comparison, but with IMAGE it's a whole new ball game!"

Stay tuned to Science@NASA for news and updates about the coming geomagnetic disturbance.

Below: Solar Flares are classified by their x-ray flux in the 1.0 - 8.0 Angstrom band as measured by the NOAA GOES-8 satellite. On June 6, 2000, two solar flares from active region 9026 registered as powerful X-class eruptions.

SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

Southwest Research Institute manages the IMAGE project and leads the IMAGE science investigation. The IMAGE Principal Investigator is James L. Burch.

Web Links

 

NOAA Space Environment Center -official forecaster of space weather events

SpaceWeather.com -daily updates and news about solar flares, coronal mass ejections and geomagnetic activity

More about the "magnetotail" and what causes aurora - from the NASA/Goddard Space Flight center

All about aurora - from the University of Alaska Geophysical Institute

Aurora FAQ - from the University of Alaska Geophysical Institute

Thursday's Classroom -- lesson plans and educational activities about space weather. - from NASA/GSFC

IMAGE home page - from the Southwest Research Institute

IMAGE home page - from NASA/GSFC

Science@NASA stories about IMAGE:

Innovative Space Weather Mission Nears Launch -- Feb. 24, 2000

The RADAR Cop in Space -- March 24, 2000

Space Weather Satellite Blasts Off -- March 27, 2000