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Weather, Space

Weather, Space

Space weather describes the conditions in space that affect Earth and its technological systems. Space weather is a consequence of the behavior of

GEOMAGNETIC STORMS
Category Effect Physical measure Average Frequency (1 cycle = 11 years)
Scale Descriptor Duration of event will influence severity of effects Kp values* determined every 3 hours Number of storm events when Kp level was met; (number of storm days)
G 5 Extreme Power systems: widespread voltage control problems and protective system problems can occur, some grid systems may experience complete collapse or blackouts. Transformers may experience damage. Kp=9 4 per cycle (4 days per cycle)
Spacecraft operations: may experience extensive surface charging, problems with orientation, uplink/downlink and tracking satellites.
Other systems: pipeline currents can reach hundreds of amps, HF (high frequency) radio propagation may be impossible in many areas for one to two days, satellite navigation may be degraded for days, low-frequency radio navigation can be out for hours, and aurora has been seen as low as Florida and southern Texas (typically 40° geomagnetic lat.)**
G 4 Severe Power systems: possible widespread voltage control problems and some protective systems will mistakenly trip out key assets from the grid. Kp=8, including a 9- 100 per cycle (60 days per cycle)
Spacecraft operations: may experience surface charging and tracking problems, corrections may be needed for orientation problems.
Other systems: induced pipeline currents affect preventive measures, HF radio propagation sporadic, satellite navigation degraded for hours, low-frequency radio navigation disrupted, and aurora has been seen as low as Alabama and northern California (typically 45° geomagnetic lat.)**
G 3 Strong Power systems: voltage corrections may be required, false alarms triggered on some protection devices. Kp=7 200 per cycle (130 days per cycle)
Spacecraft operations: surface charging may occur on satellite components, drag may increase on low-Earth-orbit satellites, and corrections may be needed for orientation problems.
Other systems: intermittent satellite navigation and low-frequency radio navigation problems may occur, HF radio may be intermittent, and aurora has been seen as low as Illinois and Oregon (typically 50° geomagnetic lat.)**
G 2 Moderate Power systems: high-latitude power systems may experience voltage alarms, long-duration storms may cause transformer damage. Kp=6 600 per cycle (360 days per cycle)
Spacecraft operations: corrective actions to orientation may be required by ground control; possible changes in drag affect orbit predictions.
Other systems: HF radio propagation can fade at higher latitudes, and aurora has been seen as low as New York and Idaho (typically 55° geomagnetic lat.)**
G 1 Minor Power systems: weak power grid fluctuations can occur. Kp=5 1700 per cycle (900 days per cycle)
Spacecraft operations: minor impact on satellite operations possible.
Other systems: migratory animals are affected at this and higher levels; aurora is commonly visible at high latitudes (northern Michigan and Maine)**
* Based on this measure, but other physical measures are also considered.
** For specific locations around the globe, use geomagnetic latitude to determine likely sightings (see www.sec.noaa.gov/Aurora)
SOLAR RADIATION STORMS
Category Effect Physical measure Average Frequency (1 cycle = 11 years)
Scale Descriptor Duration of event will influence severity of effects Flux level of 10 MeV (ions)* Number of events when flux level was met**
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. 105 Fewer than 1 per cycle
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.
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. 104 3 per cycle
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.
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). 103 10 per cycle
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.
S 2 Moderate Biological: none. 102 25 per cycle
Satellite operations: infrequent single-event upsets possible.
Other systems: small effects on HF propagation through the polar regions and navigation at polar cap locations possibly affected.
S 1 Minor Biological: none. 10 50 per cycle
Satellite operations: none.
Other systems: minor impacts on HF radio in the polar regions.
* Flux levels are 5 minute averages. Flux in particles·s1·ster1·cm2 based on this measure, but other physical measures are also considered.
** These events can last more than one day.
RADIO BLACKOUTS
Category Effect Physical measure Average Frequency (1 cycle = 11 years)
Scale Descriptor Duration of event will influence severity of effects GOES X-ray peak brightness by class and by flux* Number of events when flux level was met; (number of storm days)
R 5 Extreme HF Radio : Complete HF (high frequency**) radio blackout on the entire sunlit side of the Earth lasting for a number of hours. This results in no HF radio contact with mariners and en route aviators in this sector. X20 (2×103) Fewer than 1 per cycle
Navigation : Low-frequency navigation signals used by maritime and general aviation systems experience outages on the sunlit side of the Earth for many hours, causing loss in positioning. Increased satellite navigation errors in positioning for several hours on the sunlit side of Earth, which may spread into the night side.
R 4 Severe HF Radio : HF radio communication blackout on most of the sunlit side of Earth for one to two hours. HF radio contact lost during this time. X10 (103) 8 per cycle (8 days per cycle)
Navigation : Outages of low-frequency navigation signals cause increased error in positioning for one to two hours. Minor disruptions of satellite navigation possible on the sunlit side of Earth.
R 3 Strong HF Radio : Wide area blackout of HF radio communication, loss of radio contact for about an hour on sunlit side of Earth. X1 (104) 175 per cycle (140 days per cycle)
Navigation : Low-frequency navigation signals degraded for about an hour.
R 2 Moderate HF Radio : Limited blackout of HF radio communication on sunlit side, loss of radio contact for tens of minutes. M5 (5×105) 350 per cycle (300 days per cycle)
Navigation : Degradation of low-frequency navigation signals for tens of minutes.
R 1 Minor HF Radio : Weak or minor degradation of HF radio communication on sunlit side, occasional loss of radio contact. M1 (105) 2000 per cycle (950 days per cycle)
Navigation : Low-frequency navigation signals degraded for brief intervals.
* Flux, measured in the 0.1-0.8 nm range, in W·m-2. Based on this measure, but other physical measures are also considered.
** Other frequencies may also be affected by these conditions.

the Sun, the nature of Earth's magnetic field and atmosphere, and our location in the solar system.

While most people know that the Sun is overwhelmingly important to life on Earth, few of us know about the effects caused by this star and its variations. Scientists can observe variations such as sunspots , coronal holes , prominences , flares , and coronal mass ejections . These dramatic changes to the Sun send material and energy hurtling towards Earth.

Space is sometimes considered a perfect vacuum , but between the Sun and the planets is a turbulent area dominated by the fast-moving solar wind . The solar wind flows around Earth and distorts the geomagnetic field lines. During solar storms, the solar wind can gust wildly, causing geomagnetic storms.

Systems affected by space weather include satellites, navigation, radio transmissions, and power grids. Space weather also produces harmful radiation to humans in space. The NOAA Space Weather Scales list the likely effects of various storms. The list of consequences has grown in proportion to humankind's dependence on technological systems, and will continue to do so.

see also Solar Wind (volume 2); Space Environment, Nature of (volume 2); Sun (volume 2).

Barbara Poppe

Internet Resources

NOAA Space Weather Scales. <http://www.sec.noaa.gov/NOAAscales/>.

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space weather

space weath·er • n. natural processes in space that can affect the near-earth environment, satellites, and space travel, such as magnetospheric disturbances solar coronal events.

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