Surviving Halloween Solar Scare
Halloween brought more than a few goblins and gremlins for satellite watchers. The rash of solar flares, some the largest ever recorded, have had consequences for many orbiting Earth satellites, and some even in orbit around Mars. The belt of high-energy electrons that normally cradles Earth from afar was greatly enhanced and pushed unusually close to our atmosphere during the violent solar activity that occurred in late October, University of Colorado at Boulder researchers say.
|Sunspots as darkened knots of magnetic energy and rising hot plasma.|
The results were obtained from observations by NASA’s Solar, Anomalous, and Magnetospheric Particle Explorer, or SAMPEX satellite, said CU-Boulder’s Laboratory for Atmospheric and Space Physics Director Daniel Baker. An investigator on SAMPEX, Baker presented results from the data and the Halloween solar storm at the fall American Geophysical Union meeting in San Francisco Dec. 8 to Dec. 12.
The radiation belts, also known as the Van Allen Belts, are named after their discoverer, James Van Allen. "The outer Van Allen Belt is often rather tame and is made up of modest intensities of energetic electrons," said Baker.
These negatively charged elementary particles are confined like beads on a string by the magnetic field lines that emanate from Earth’s iron core and extend far out into space like the flux tubes from a giant bar magnet," he said. During the recent high-energy solar activity of late October and early November — known by scientists as the "Halloween storm" of 2003 — the outer Van Allen belt was pushed and prodded to a nearly unprecedented degree.
|Solar flares issue strong electromagnetic bursts.|
"We have been observing the Van Allen Belts for over 11 years with the SAMPEX spacecraft," said Baker. "We have never seen such a powerful enhancement and distortion of the radiation belts during the lifetime of SAMPEX. Baker noted that the center of the outer Van Allen belt is usually about 12,000 miles to 16,000 miles away from Earth’s surface, as measured above the equatorial region of the Earth.
During the Halloween storm, the Van Allen radiation was greatly increased and pushed inward toward Earth’s surface to an unusually close degree. "From Nov. 1 to Nov.10, the outer belt had its center only about 6,000 miles from Earth’s equatorial surface," he said. "This is a place where ordinarily there are almost no energetic electrons at all."
How the Earth’s radiation belts get so energized and distorted is still largely an unsolved mystery, despite the fact that Van Allen and co-workers discovered the radiation belts more than 45 years ago at the dawn of the space age, he said.
|Spectacular science from the solar observatory, or SOHO, gives the most spectacular view of solar events. SOHO is located 1.5 million kilometers (one million miles) from Earth. It orbits around the First Lagrangian point, where the combined gravity of the Earth and the sun keep SOHO in an orbit locked to the sun-Earth line. |
"Researchers have learned a great deal about electron acceleration in the belts in recent years," said Xinlin Li, a professor and researcher at LASP who works closely with Baker. "We are able to understand and forecast more normal changes in the radiation belts using our present theoretical knowledge, but extreme events such as the Halloween storm are very hard to predict."
Other spacecraft such as NASA’s POLAR satellite also observed the powerful radiation belt changes. Shri Kanekal, a researcher at Catholic University in Washington, D.C., who also is affiliated with LASP, has studied the POLAR measurements and compared them with the SAMPEX data. He found the POLAR data confirmed the surprising enhancement and distortion of the Van Allen Belts.
"The changing, raging character of the radiation belts is more than a scientific curiosity," said Baker. "The charged particles within the belts can have profound and deleterious effects on commercial and operational satellites in near-Earth orbit."
As reported in a recent paper submitted to the scientific journal, Eos, by Ramon Lopez of the University of Texas, J. H. Allen of the National Oceanic and Atmospheric Administration in Boulder and CU-Boulder’s Baker, many serious spacecraft failures and "operational anomalies" occurred during and following the Halloween storm. Many of the problems can be directly related to the hostile radiation environment in near-Earth space.
"We are excited to have the chance to study the most extreme events that nature can throw at us," Baker said. "We hope that in the future, we can predict how even a storm as powerful as the Halloween storm will affect Earth’s environment."
In 1989, before such solar data was modelled in such detail, a solar storm tripped a protective switches in Canadian Hydro-Québec power company. For nine hours, the entire province of Québec was without power. The problem nearly spread to the United States through an interconnected grid, officials said at the time. In a 1997 solar storm, an AT&T Telestar 401 satellite used to broadcast television shows from networks to local affiliates was blacked out. A more serious breakdown of communications occurred in May 1998 when a space storm disabled PanAmSat’s Galaxy IV. Among the Galaxy IV casualties: automated teller machines; gas station credit card handling services; 80 percent of all pagers in the United States; news wire service feeds; CNN’s airport network; and some airline weather tracking services.
|An artist’s rendition of 2001 Mars Odyssey as it entered orbit.|
Of current interest is the effects of the unprecedented solar flares on the Mars Odyssey, a spacecraft designed to orbit the red planet and report back–among other findings–the local radiation environment in anticipation of understanding how its thin atmosphere and space travel might affect future missions. During what are considered the most intense outbreaks, called X-class solar flares, the counts of bombarding charged particles reaching the Martian surface may suddenly rise a thousand-fold. The martian radiation environment experiment on NASA’s 2001 Mars Odyssey orbiter has collected data continuously from the start of the Odyssey mapping mission in March 2002 until late last month. Validation of radiation models is a crucial step in predicting radiation-related health risks for crews of future missions.
But on Oct. 28, 2003, during a period of intense solar activity, the instrument stopped working properly. Controllers’ efforts to restore the instrument to normal operations have not been successful. These efforts will continue for the next several weeks or months.
"Even if the instrument provides no additional data in the future, it has been a great success at characterizing the radiation environment that a crewed mission to Mars would need to anticipate," said Dr. Jeffrey Plaut, project scientist for Mars Odyssey at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Other unaffected parts of the Mars orbiter are unaffected by solar storm, and will provide critical support for the forthcoming January relay of images and data from the Martian rovers on the surface. The European lander, called Beagle 2, will use NASA’s Mars Odyssey orbiter to relay communications to Earth on the lander’s arrival day and in subsequent weeks. Together with another orbiter called the Mars Global Surveyor’s Mars Relay (MR) system, its Mars Orbital Camera will provide near-realtime coverage of engineering telemetry during the critical entry, descent, and landing (EDL) of both rovers, MER-A ("Spirit") and MER-B ("Opportunity").
2001 Mars Odyssey launched on April 7, 2001, and arrived at Mars on October 24, 2001. The mission is mapping the amount and distribution of chemical elements and minerals that make up the Martian surface. The spacecraft especially looks for hydrogen, most likely in the form of water ice, in the shallow subsurface of Mars. One of its three primary instruments is called THEMIS (Thermal Emission Imaging System), for determining the distribution of minerals, particularly those that can only form in the presence of water. It also provides the communications relay for U.S. and international landers, including missions in NASA’s Mars Program, the Mars Exploration Rovers. The name "2001 Mars Odyssey" was selected as a tribute to the vision and spirit of space exploration as embodied in the works of renowned science fiction author Arthur C. Clarke.