Technological infrastructure affected by space weather events. Credit: NASA
Illustration of the various dynamic
and constant solar effects on Earth. The two solar constants, sunlight and solar
wind, takes 8 minutes and 4 days, respectively, to reach Earth. Arrival times of
dynamic solar events such as Flares, solar energetic particles and CMEs, are
approximated and range from immediate effect to several days. Credit:
NASA/Berkley
Biological
Intense solar flares release very-high-energy particles that can be as injurious
to humans as the low-energy radiation from nuclear blasts. Earth's atmosphere
and magnetosphere allow adequate protection for us on the ground, but astronauts
in space are subject to potentially lethal dosages of radiation. The penetration
of high-energy particles into living cells, measured as radiation dose, leads to
chromosome damage and, potentially, cancer. Large doses can be fatal
immediately. Solar protons with energies greater than 30 MeV are particularly
hazardous. In October 1989, the Sun produced enough energetic particles that an
astronaut on the Moon, wearing only a space suit and caught out in the brunt of
the storm, would probably have died.
Communications
Earth's Magnetosphere
Credit: NASA
Many communication systems utilize the ionosphere to reflect radio signals over
long distances. Ionospheric storms can affect radio communication at all
latitudes. Some radio frequencies are absorbed and others are reflected, leading
to rapidly fluctuating signals and unexpected propagation paths. TV and
commercial radio stations are little affected by solar activity, but
ground-to-air, ship-to-shore, Voice of America, Radio Free Europe, and amateur
radio are frequently disrupted. Radio operators using high frequencies rely upon
solar and geomagnetic alerts
to keep their communication circuits up and running.
Some military detection or early-warning systems are also affected by solar
activity. The Over-the-Horizon Radar bounces signals off the ionosphere in order
to monitor the launch of aircraft and missiles from long distances. During
geomagnetic storms, this system can be severely hampered by radio clutter. Some
submarine detection systems use the magnetic signatures of submarines as one
input to their locating schemes. Geomagnetic storms can mask and distort these
signals.
Satellites
Solar flares can also doom satellites. Reaching the earth in just eight minutes,
their powerful UV and X rays help heat up and expand the atmosphere, thereby
increasing molecular drag on low-orbiting satellites and shortening their
orbital life. Another problem for satellites differential charging. During
geomagnetic storms, the number and energy of electrons and ions increase. When a
satellite travels through this energized environment, the charged particles
striking the spacecraft cause different portions of the spacecraft to be
differentially charged. Eventually, electrical discharges can arc across
spacecraft components, harming and possibly disabling them.
Bulk charging
(also called deep charging) occurs when energetic particles, primarily
electrons, penetrate the outer covering of a satellite and deposit their charge
in its internal parts. If sufficient charge accumulates in any one component, it
may attempt to neutralize by discharging to other components. This discharge is
potentially hazardous to the satellite's electronic systems.
Electric Power
When magnetic fields move about in the vicinity of a conductor such as a wire,
an electric current is induced into the conductor. This happens on a grand scale
during geomagnetic storms. Power companies transmit alternating current to their
customers via long transmission lines. The nearly direct currents induced in
these lines from geomagnetic storms are harmful to electrical transmission
equipment.
Oil & Gas Pipelines
Alaska Pipeline
Rapidly fluctuating geomagnetic fields can induce currents into pipelines.
During these times, several problems can arise for pipeline engineers. Flow
meters in the pipeline can transmit erroneous flow information, and the
corrosion rate of the pipeline is dramatically in creased. If engineers
unwittingly attempt to balance the current during a geomagnetic storm, corrosion
rates may increase even more. Pipeline managers routinely receive alerts and
warnings to help them provide an efficient and long-lived system.
Auroras
aurora borealis
Auroras most often glow green, the color emitted by oxygen atoms high in the
upper atmosphere after they are struck by bombarding electrons from Earth's
magnetosphere. Red displays are rarer, sometimes involving energized nitrogen
molecules lower down in the atmosphere -- an indication of a more potent
geomagnetic storm. Auroras that extend away from the poles and closer to the
equator also reflect strong storm conditions.
The Northern Lights/Southern Lights, or Aurora Borealis, is natures own
gigantic light-show. An Aurora Borealis occurs when the particles from the sun
are being thrown against the earth by the solar wind. When the particles collide
with the earths atmosphere, the energy of the particles are turned into light.
NASA: The Mystery of the Aurora
NOAA Space Weather Scale for Solar
Radiation Storms
Category
Effect
Physical measure
Average Frequency
(1 cycle = 11 years)
Scale
Descriptor
Duration of event will influence
severity of effects
Solar Radiation Storms
Flux level of >= 10 MeV particles
(ions)*
Number of events when flux level was met (number
of storm days**)
S 5
Extreme
Biological: unavoidable high radiation
hazard to astronauts on EVA (extra-vehicular activity); high radiation
exposure to passengers and crew in commercial jets at high latitudes
(approximately 100 chest x-rays) is possible.
Satellite operations: satellites may be
rendered useless, memory impacts can cause loss of control, may cause
serious noise in image data, star-trackers may be unable to locate
sources; permanent damage to solar panels possible.
Other systems: complete blackout of HF
(high frequency) communications possible through the polar regions, and
position errors make navigation operations extremely difficult.
105
Fewer than 1 per cycle
S 4
Severe
Biological: unavoidable radiation hazard to
astronauts on EVA; elevated radiation exposure to passengers and crew in
commercial jets at high latitudes (approximately 10 chest x-rays) is
possible.
Satellite operations: may experience memory
device problems and noise on imaging systems; star-tracker problems may
cause orientation problems, and solar panel efficiency can be degraded.
Other systems: blackout of HF radio
communications through the polar regions and increased navigation errors
over several days are likely.
104
3 per cycle
S 3
Strong
Biological: radiation hazard avoidance
recommended for astronauts on EVA; passengers and crew in commercial
jets at high latitudes may receive low-level radiation exposure
(approximately 1 chest x-ray).
Satellite operations: single-event upsets,
noise in imaging systems, and slight reduction of efficiency in solar
panel are likely.
Other systems: degraded HF radio
propagation through the polar regions and navigation position errors
likely.
Other systems: small effects on HF
propagation through the polar regions and navigation at polar cap
locations possibly affected.
102
25 per cycle
S 1
Minor
Biological: none.
Satellite operations: none.
Other systems: minor impacts on HF radio in
the polar regions.
10
50 per cycle
* Flux levels
are 5 minute averages. Flux in particles·s-1·ster-1·cm-2.
Based on this measure, but other physical measures are also considered.
** These events can last more than one day.
