Signs
In the Sun, the Moon and The Stars
Solar Climate Change Causing Rougher Space Weather
by Staff Writers
Reading UK (SPX) Mar 30, 2012
Image of a coronal mass ejection (CME) on June 7, 2011, recorded
in ultraviolet light by the Solar Dynamics Observatory (SDO)
satellite. The shock front that forms ahead of these huge
expulsions of material from the solar atmosphere (the event shown
moved at 1,400 km/s) can generate large fluxes of highly energetic
particles at Earth which can be a considerable hazard to
space-based electronic systems and with repeated exposure, a
health risk for crew on board high-altitude aircraft.
Recent research shows that the space age has coincided with a
period of unusually high solar activity, called a grand maximum.
Isotopes in ice sheets and tree rings tell us that this grand
solar maximum is one of 24 during the last 9,300 years and suggest
the high levels of solar magnetic field seen over the space age
will reduce in future.
This decline will cause a reduction in sunspot numbers and
explosive solar events, but those events that do take place could
be more damaging.
Graduate student Luke Barnard of the University of Reading will
present new results on 'solar climate change' in his paper at the
National Astronomy Meeting in Manchester.
The level of radiation in the space environment is of great
interest to scientists and engineers as it poses various threats
to man-made systems including damage to electronics on satellites.
It can also be a health hazard to astronauts and to a lesser
extent the crew of high-altitude aircraft.
The main sources of radiation are galactic cosmic rays (GCRs),
which are a continuous flow of highly energetic particles from
outside our solar system and solar energetic particles (SEPs),
which are accelerated to high energies in short bursts by
explosive events on the Sun.
The amount of radiation in the near-Earth environment from these
two sources is partly controlled in a complicated way by the
strength of the Sun's magnetic field.
There are theoretical predictions supported by observational
evidence that a decline in the average strength of the Sun's
magnetic field would lead to an increase in the amount of GCRs
reaching near-Earth space.
Furthermore there are predictions that, although a decline in
solar activity would mean less frequent bursts of SEPs, the bursts
that do occur would be larger and more harmful.
Currently spacecraft and aircraft are only designed and operated
to offer suitable protection from the levels of radiation that
have been observed over the course of the space age.
A decline in solar activity would result in increased amounts of
radiation in near-Earth space and therefore increased risk of harm
to spacecraft and aircraft and the astronauts and aircraft crews
that operate them.
By comparing this grand maximum with 24 previous examples, Mr.
Barnard predicts that there is an 8% chance that solar activity
will fall to the very low levels seen in the so-called 'Maunder
minimum', a period during the seventeenth century when very few
sunspots were seen.
In this instance, the flux of GCRs would probably increase by a
factor of 2.5 from present day values and the probability of
observing a large SEP event will fall from the presently seen 5
down to 2 events per century.
However, the more probable scenario is that solar activity will
decline to approximately half its current value in the next 40
years, in which case the flux of GCRs will increase by a factor of
1.5 and the probability of large SEP events to increase from the
current value to 8 events per century.
As a result the near-Earth space radiation environment will
probably become more hazardous in the next 40 years.
In presenting his results, Mr. Barnard comments: "Radiation in
space can be a serious issue for both people and the delicate
electronic systems that society depends on. Our research shows
that this problem is likely to get worse over the coming decades -
and that engineers will need to work even harder to mitigate its
impact."