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NEW FRAMEWORK CONFRONTS A MONSTER SPACE WEATHER EVENT

Covering the whole physics from the Sun to the Earth, a new simulation tool is being applied to the biggest solar event in recent history, a month-long series of outbursts dubbed the "Halloween 2003 space storms." This Space Weather Modeling Framework (SWMF) is the product of a Computational Technologies (CT) investigation at the University of Michigan.

"With the help of the CT Project, we just delivered our last major milestone, which is a fully operational framework with nine models working together," said SWMF principal investigator Tamas Gombosi, who is chair and professor of the Department of Atmospheric, Oceanic, and Space Sciences at Michigan. "This is the first time that we have exercised this brand new tool for a very challenging major event. It is a fortunate combination of simulation advances and the Sun cooperating in a very exciting way."

SWMF has its origins in Michigan's BATS-R-US code developed under the CT Project (then known as the Earth and Space Sciences Project) beginning in 1996. Many of the SWMF models are considered world-class, Gombosi said, "but coupled together, they are better than the sum of their parts." The current SWMF links 9 models to represent the complex physics of space weather:

• A Solar Coronal model (SC) represents the Sun's corona (atmosphere) using solar observation data.
• An Eruptive Events Generator (EE) inputs a coronal mass ejection (CME) into the initial conditions of the simulation. The CME then propagates outward through the SC and Inner Heliosphere models self-consistently.
• A Solar-energetic Particles model (SP) describes the transport, acceleration, and scattering of these particles from the solar event to the Earth's atmosphere.
• An Inner Heliosphere model (IH) simulates the solar wind from the outer boundary of the corona (SC) to the Earth's magnetosphere and beyond, based on magnetohydrodynamics (MHD).
• A Global Magnetosphere model (GM) describes the connection between the inner heliosphere and the outer portion of the Earth's magnetosphere, based on MHD.
• A Radiation Belt model (RB) tracks trapped particles.
• An Inner Magnetosphere model (IM) calculates the dynamic behavior of particles and the electric fields and currents in the Earth's inner magnetosphere and computes their effects on the inner magnetosphere and upper atmosphere.
• An Upper Atmosphere model (UA) simulates the dynamics of the Earth's thermosphere and ionosphere.
• An Ionospheric Electrodynamics model (IE) calculates the electric potential in the Earth's ionosphere.

The Halloween 2003 storms are the first real application of the complete SWMF. "There were several unique features, which is why it is very important to exercise simulation tools," Gombosi said. Beginning in late October and lasting through early November, three sunspots, including one the size of Jupiter, launched a series of solar eruptions. Among the 60 solar flares was the most massive ever observed, an X-28 flare accompanied by a CME on November 4. The Sun spewed out several billion tons of matter at an astonishing 8 million kilometers per hour. Although this blob of charged gas did not hit Earth, geomagnetic storms resulting from multiple Earth-bound flares and CMEs had widespread effects: Two satellites were knocked out of commission, and 28 more were damaged. Airlines diverted their planes. Sweden suffered a power outage. Astronauts on the International Space Station had to take cover several times. The Northern Lights reached as far south as Florida.

The Michigan team's Halloween 2003 simulation is a monster in its own right. "This is the biggest simulation we have done," Gombosi stressed. "No one has ever attempted such a simulation." To fully represent the Sun-Earth connection, SWMF must traverse 150 million kilometers of space, beginning 100 meters above the Sun's surface (the corona) and ending 100 kilometers above the Earth (the ionosphere).

Following solar gas and particles through space, boxes in the computational mesh divide up to 15 times to cover scales down to 200 kilometers. Without employing this adaptive mesh refinement (AMR) technique, the simulation could not be run on today's supercomputers. Even with AMR, the simulation will ultimately consume 500,000 processor-hours on NASA's new Columbia supercomputer, an SGI Altix system at Ames Research Center in Moffett Field, CA. With a highly scalable code, "we can run faster than real time with 1,000 processors," Gombosi said. His group is running the simulation using 512 processors, so it will take 40 days of computing time to model the 30 days of space weather.

Since the Halloween 2003 space storms were well observed from ground-based telescopes and orbiting spacecraft, there is a useful collection of data for comparison. Validating the simulation will help prepare SWMF as a community tool. Michigan is transferring the software to GSFC's Community Coordinated Modeling Center and NOAA's Space Environment Center in Boulder, CO. Researchers in these organizations will use SWMF codes for operational solar and space weather forecasting as well as scientific analysis.

Gombosi and Michigan colleagues Darren De Zeeuw, Aaron Ridley, and Gabor Toth will be presenting SWMF and Halloween 2003 simulation results at the American Geophysical Union Fall 2004 Meeting, being held December 13-17 in San Francisco, CA.

This article originally appeared in the ESDCD News, a publication of the Earth and Space Data Computing Division at NASA's Goddard Space Flight Center. The ESDCD News is available at:

http://esdcd-news.gsfc.nasa.gov/