Press Release

NASA Spacecraft Fleet Tracks Blast Wave Through Solar System

By SpaceRef Editor
July 8, 2004
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NASA Spacecraft Fleet Tracks Blast Wave Through Solar System
07.08.04.sun.jpg

A fleet of spacecraft dispersed throughout the solar
system gave the best picture to date of the effects of blast
waves from solar storms as they propagate through the solar
system.

The “Halloween” solar storms in October-November 2003 were
the most powerful ever measured. The storms’ effects on Earth
were severe enough to cause the rerouting of aircraft, affect
satellite operations, and precipitate a power failure in
Malmoe, Sweden. Long-distance radio communications were
disrupted because of the effects on the ionosphere, and
northern lights (aurora borealis) were seen as far south as
Florida.

No NASA satellites near Earth were severely damaged by the
storms. The International Space Station astronauts curtailed
some of their activities and took shelter in the Russian-
supplied Service Module several times during the storm.
Because this kind of event will have significant implications
for radiation protection requirements for explorers who
venture outside the Earth’s protective magnetosphere
(magnetic field), scientists have been working for years to
develop the capability to predict when these massive storms
will erupt.

“Over many decades, improvements in weather forecasting have
saved lives and property. Space weather forecasting is still
in development, but is needed to better protect our space
infrastructure and future human and robotic explorers,” said
Carl Walz, Astronaut and Program Executive for Advanced
Concepts and Project Prometheus at NASA Headquarters,
Washington.

The storms rocked the inner solar system from Mars to Saturn.
The Mars Radiation Environment Experiment (MARIE) instrument
on the Mars Odyssey spacecraft orbiting Mars was disabled by
radiation. The Ulysses spacecraft near Jupiter and the
Cassini spacecraft near Saturn both detected radio waves from
magnetic storms generated as the blast wave slammed into the
vast magnetic fields around those giant planets.

The material launched by the huge solar storms last fall
blasted by Earth at five million miles per hour (eight
million km/hr) and raced past spacecraft near Earth, Mars,
Jupiter and Saturn on its way to NASA’s twin Voyager
spacecraft at the fringes of the solar system.

The most recent reports come from the Voyagers, which are
near an unexplored region where the solar wind becomes
turbulent as it crashes into the thin gas between stars.
Slowing as it plowed into the outer heliosphere (a large
bubble of space around the sun which is “blown up” by fast-
moving solar wind), the blast wave reached Voyager 2 at seven
billion miles (11 billion kilometers) from the sun on April
28 and continued toward Voyager 1 at almost nine billion
miles (14.5 billion km) from the sun.

There are at least two kinds of solar storm effects: prompt
radiation, and shocks that accelerate electrically charged
(ionized) atomic particles. The prompt radiation travels at
nearly the speed of light, causes the most severe electrical
effects on satellites, and has the greatest impact on long-
distance radio communications. The prompt radiation was
detected in radio waves throughout the solar system after
each storm.

The shocks that accelerate particles to millions of miles per
hour take a little longer to develop, but they pack the
biggest wallop to the aurora, power grids and energetic
particles that become trapped in Earth’s radiation belts.
These storms created a new radiation belt near Earth that
lasted for several weeks. The shocks created by the storms in
the inner solar system not only accelerated electrons and
protons to high energy, they also trapped the particles in
the inner heliosphere. This resulted in elevated radiation
levels everywhere between Venus and Mars that decayed
gradually over a period of weeks.

The widely dispersed spacecraft are helping scientists piece
together a more comprehensive picture of how disturbances
propagate through the solar system. What determines the
evolving shape and variable speed with which the shocks
travel in different directions is not well understood. The
differences in the speeds and arrival times at Mars and Earth
suggest that the process is not simple. The sun’s magnetic
field also affects how well connected different places in the
solar system are. Understanding how particle-accelerating
shocks travel through the solar system will help us
understand and predict how radiation levels will change in
different locations in space.

In the months ahead, the blast wave will crash into the
heliopause, the tangible edge of the heliosphere, where the
material ejected by the sun piles up against the wind from
nearby stars. The collision may generate extremely low-
frequency radio signals that will give us a much more
accurate understanding of the size of the sun’s domain. The
energy carried by the material will push the interstellar gas
outward by as much as 400 million miles (640 million km),
about 4 times the distance from the sun to the Earth.

More information is available on the web at:
http://www.gsfc.nasa.gov/topstory/2004/0708flare.html

SpaceRef staff editor.