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LOS ANGELES (AP) — The sun unleashed a powerful solar flare early Tuesday, the largest in nearly five years.
Scientists
say the eruption took place on the side of the sun that was not facing
Earth, so there’ll be little impact to satellites and communication
systems.
The
flare had a GOES X-ray magnitude of X6.9, meaning it was more than 3
times larger than the previous largest flare of this solar cycle: the
X2.2 that occurred on Feb 15, 2011. Space scientist Joe Kunches at the
government’s Space Weather Prediction Center in Colorado says there were
reports of brief short-wave radio disruptions in Asia, but little else.
The
sun is transitioning from a quiet period into a busier cycle.
Scientists estimate there will be a spike in the number of such solar
eruptions over the next three to five years.
The last time there was such a strong solar flare was in December 2006.
What signifies an X-class flare?
Solar
flares are giant explosions on the sun that send energy, light and high
speed particles into space. These flares are often associated with
solar magnetic storms known as coronal mass ejections (CMEs). The number
of solar flares increases approximately every 11 years, and the sun is
currently moving towards another solar maximum, likely in 2013. That
means more flares will be coming, some small and some big enough to send
their radiation all the way to Earth.
The
biggest flares are known as “X-class flares” based on a classification
system that divides solar flares according to their strength. The
smallest ones are A-class (near background levels), followed by B, C, M
and X. Similar to the Richter scale for earthquakes, each letter
represents a 10-fold increase in energy output. So an X is ten times an M
and 100 times a C. Within each letter class there is a finer scale from
1 to 9.
C-class
and smaller flares are too weak to noticeably affect Earth. M-class
flares can cause brief radio blackouts at the poles and minor radiation
storms that might endanger astronauts.
And
then come the X-class flares. Although X is the last letter, there are
flares more than 10 times the power of an X1, so X-class flares can go
higher than 9. The most powerful flare measured with modern methods was
in 2003, during the last solar maximum, and it was so powerful that it
overloaded the sensors measuring it. The sensors cut out at X28.
The
biggest X-class flares are by far the largest explosions in the solar
system and are awesome to watch. Loops tens of times the size of Earth
leap up off the sun’s surface when the sun’s magnetic fields cross over
each other and reconnect. In the biggest events, this reconnection
process can produce as much energy as a billion hydrogen bombs.
If
they’re directed at Earth, such flares and associated CMEs can create
long lasting radiation storms that can harm satellites, communications
systems, and even ground-based technologies and power grids. X-class
flares on December 5 and December 6, 2006, for example, triggered a CME
that interfered with GPS signals being sent to ground-based receivers.
NASA
and NOAA?as well as the US Air Force Weather Agency (AFWA) and
others?keep a constant watch on the sun to monitor for X-class flares
and their associated magnetic storms. With advance warning many
satellites and spacecraft can be protected from the worst effects.
