6/13/02 10:38:27 AM Pacific Daylight Time
Interesting to say the least. Sounds like harmonics of the universe too
Solar loops spring into view
13-Jun-2002 Huge loops of very hot gas rising above the Sun's surface
vibrate with enormous energy at times of solar storms. This is the latest
surprise from ESA's flotilla of spacecraft - SOHO, Ulysses and the four
Cluster satellites - with which scientists are trying to make sense of how
disturbances on the Sun affect the Earth.
Santorini symposium 11 - 15 June 2002
As reported today at a scientific meeting on Santorini, Greece, ESA/NASA's
SOHO spacecraft has observed many hot loops of gassy features, invisible to
other instruments. These loops sway from side to side. Scientists
investigating them are now sure that the vibrating loops play a key role in
the Sun's most violent activity.
"It's like twanging a guitar string, although one that's tuned to a very low
bass note," says Werner Curdt, from Germany's Max-Planck-Institut fÃ¼r
Aeronomie and one of SOHO's principal investigators. "Nobody knew about
these vibrations before. They occur only in extremely hot gas, which can be
seen nice and clearly by SUMER [one of the instruments onboard SOHO] as if
it were designed for this purpose. But to be honest, when SUMER was built,
we didn't expect anything as amazing as this."
SUMER (Solar Ultraviolet Measurements of Emitted Radiation) measures the
velocity of gassy features moving in the Sun's atmosphere. It observes the
hot loops most plainly when they stand like enormous arches at the rim of
the Sun, seen sideways on by SOHO. Locking onto extreme ultraviolet
emissions from iron atoms, which are highly ionised at temperatures of 9 to
20 million Â°C, the instrument detects the swaying motion by changes in the
In a typical case, a hot loop, 350 000 kilometres long, rocks forwards and
backwards every 20 minutes. The hot gas moves along the line of sight at
speeds of up to 100 kilometres per second, or 360 000 kilometres per hour.
The gas quickly cools and the motion dies down, after two or three
The tension in the solar guitar string comes from an intense magnetic field
that runs along the loop of gas. The finger that twangs it is probably a
burst of very energetic particles coming from low in the Sun's atmosphere.
When the gas in the loop is hit, the atoms lose almost all their electrons.
That starts intense emission from hot iron ions and an oscillation of the
What does the discovery mean for all of us?
This latest finding by SOHO will fascinate the experts. Dr Curdt's institute
has organized the meeting jointly with the National Observatory of Athens.
Its purpose is to draw together the results of observations of the Sun from
the ground and from spacecraft and to see what is understood in the
behaviour of the solar atmosphere.
Storms on the Sun can endanger astronauts, and damage spacecraft, electric
power systems and computers. They may even affect the Earth's own weather.
For this reason, ESA and other space agencies explore the causes and effects
The ESA-NASA Ulysses spacecraft explores the heliosphere, the vast region
around the Sun filled by the solar wind, where shocks can shake and squeeze
the Earth's protective bubble, the magnetosphere. ESA's Cluster satellites
investigate these solar effects near the Earth. SOHO itself uses many
instruments to monitor the solar storms, including the huge explosions
called flares, which are outbursts of light associated with energetic
particles, and the great puffs of gas called mass ejections.
By revealing intense, local and short-lived activity of a kind that had
escaped the scientists' notice, the vibrating loops are like a new piece of
the jigsaw. When the vibrations die down, they release energy into the Sun's
outer atmosphere. The link to particle outbursts low in the atmosphere may
help scientists to understand why the outbursts are sometimes so strong that
they disrupt the loops and unleash a solar flare. Only by tracing the
connections between the different kinds of eruptions on the Sun can
scientists expect to be able to issue reliable early warnings of solar
outbursts affecting the Earth and its neighbourhood.
The Santorini meeting is looking ahead to future spacecraft, including ESA's
Solar Orbiter due in about ten years' time. The scientists planning their
space instruments will now want to make sure they are able to understand the
energetic solar loops discovered by SOHO.
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