Signs In The Sun The
Moon and The Stars
18 August 2011 Last updated at 15:11 ET
Sun storms 'to be more disruptive within decades'
By Judith Burns Science reporter, BBC News
A solar storm Solar storms may be more powerful at times of
middling solar activity
Within decades, solar storms are likely to become more disruptive
to planes and spacecraft, say researchers at Reading University.
The work, published in Geophysical Research Letters, predicts that
once the Sun shifts towards an era of lower solar activity, more
hazardous radiation will reach Earth.
The team says the Sun is currently at a grand solar maximum.
This phase began in the 1920s - and has lasted throughout the
space age.
Mike Lockwood, professor of space environment physics at Reading,
said: "All the evidence suggests that the Sun will shortly exit
from a grand solar maximim that has persisted since before the
start of the space age.
"In a grand solar maximum, the peaks of the 11-year sunspot cycle
are larger and the average number of solar flares and associated
events such as coronal mass ejections are greater.
"On the other hand in a grand solar minimum there are almost no
sunpsots for several decades. The last time this happened was
during the Maunder Minimum, between about 1650 and 1700."
The research indicates that most radiation hits the Earth during
periods of middling solar activity. Increased radiation is a
particular problem for aviation and communications - technology
that did not exist the last time the sun cycle ended its grand
maximum.
Ice core data
The research is based on evidence from ice cores and tree trunks
going back 10,000 years. The team measured levels of nitrates and
cosmogenic isotopes which enter our atmosphere and are deposited
in ice and organic material.
Professor Lockwood told BBC News: "You can tell by the
concentration of nitrates in ice sheets that there has been a
solar event. What we showed was that they all cropped up at more
middling activity than we have been used to.
"We used this data to say that an unfortunate combination of solar
conditions is coming our way in the next few decades.
"It's just a question of how much worse the radiation gets and how
long it lasts."
The most disruptive radiation is from solar energetic particles,
which are carried away from the Sun by coronal mass ejections, or
solar storms, which explode from the Sun's surface.
The evidence seems to indicate that although there are fewer solar
storms once the Sun leaves its grand maximum, they are more
powerful, faster and therefore carry more particles.
A decline in solar activity also allows more radiation from other
parts of the galaxy to enter the Solar System.
In a separate study, a team at Stanford University in California,
say they have a developed a technique that could give advance
warning of the formation of sunspots before they become visible on
the Sun's surface. Sunspots are areas of high magnetic activity.
They are significant because these are the areas where solar
storms or coronal mass ejections erupt.
Stathis Ilondis and colleagues, writing in the Journal Science,
say their findings will help give advance warning of solar storms
and the resulting radiation which disrupt communications and
transport on Earth.
solar surface The Stanford researchers used a technique called
helioseismology
The Stanford team used a novel technique called helioseismology,
which is based on analysis of vibrations on the solar surface. The
team discovered that these acoustic signals causing the vibrations
moved faster in regions where sunspots were forming up to 65,000km
(40,000m) deep.
The resulting sunspots appeared on the surface between one and two
days after the differences in vibrations were detected.
Mr Ilondis told BBC News: "It's an early warning for emerging
sunspots. This is our main finding."
"We can also predict the size and strength of the sunspot. And if
it is a large sunspot then it is more probable to produce some big
space weather events like some strong flares."