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NOAA Space Weather Scales

The NOAA Space Weather Scales were introduced as a way to communicate to the general public the current and future space weather conditions and their possible effects on people and systems. Many of the SEC products describe the space environment, but few have described the effects that can be experienced as the result of environmental disturbances. These scales will be useful to users of our products and those who are interested in space weather effects. The scales describe the environmental disturbances for three event types: geomagnetic storms, solar radiation storms, and radio blackouts. The scales have numbered levels, analogous to hurricanes, tornadoes, and earthquakes that convey severity. They list possible effects at each level. They also show how often such events happen, and give a measure of the intensity of the physical causes.

The three Space Weather Scales are listed below.

Geomagnetic Storms

Solar Radiation Storms

Radio Blackouts


NOAA Space Weather Scale for Geomagnetic Storms

 

Category

Effect

Physical measure

Average Frequency
(1 cycle = 11 years)

Scale

Descriptor

Some or all of these effects are possible

   

Geomagnetic Storms

Kp values*
determined every 3 hours

Number of storm events when Kp level was met;
(number of storm days)

G 5

Extreme

Power systems: grid systems can collapse and transformers experience damage.

Spacecraft operations: extensive surface charging, problems with orientation, uplink/downlink, and tracking satellites.

Other systems: pipeline currents reach hundreds of amps, HF (high frequency) radio propagation impossible in many areas for one to two days, satellite navigation degraded for days, low-frequency radio navigation out for hours, and the aurora seen as low as the equator.

Kp = 9

4 per cycle
(4 days per cycle)

G 4

Severe

Power systems: possible voltage stability problems, portions of grids collapse and protective devices trip.

Spacecraft operations: experience surface charging and tracking problems, orientation problems need corrections.

Other systems: induced pipeline currents affect preventive measures, HF radio propagation sporadic, satellite navigation degraded for hours, low-frequency radio navigation disrupted, and the aurora seen as low as in the tropics.

Kp = 8, including a 9-

100 per cycle
(60 days per cycle)

G 3

Strong

Power systems: voltage corrections required, false alarms triggered on protection devices, and high "‘gas-in-oil"’ transformer readings likely.

Spacecraft operations: surface charging on satellite components, increased drag on satellite, and orientation problems need corrections.

Other systems: intermittent satellite navigation and low-frequency radio navigation problems, HF radio intermittent, and the aurora seen as low as mid-latitudes.

Kp = 7

200 per cycle
(130 days per cycle)

G 2

Moderate

Power systems: high-latitude power systems affected.

Spacecraft operations: corrective actions are required by ground control; changes in drag affect orbit predictions.

Other systems: HF radio propagation fades at higher latitudes, and the aurora seen as low as 50 degrees.

Kp = 6

600 per cycle
(360 days per cycle)

G 1

Minor

Power systems: weak power grid fluctuations.

Spacecraft operations: minor impact on satellite operations

Other systems: the aurora seen at high latitudes (60 degrees); migratory animals begin to be affected.

Kp = 5

1700 per cycle
(900 days per cycle)

* may change to use other measures, such as DST, as basis.


NOAA Space Weather Scale for Solar Radiation Storms

Category

Effect

Physical measure

Average Frequency
(1 cycle = 11 years)

Scale

Descriptor

Some or all of these effects are possible

   

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 levels to passengers and crew in commercial jets at high latitudes (approximately 100 chest x-rays).

Satellite operations: loss of some satellites, memory impacts cause loss of control, serious noise in image data, star-trackers unable to locate sources; permanent damage to solar panels.

Other systems: No HF (high frequency) communications possible in 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).

Satellite operations: memory device problems, noise on imaging systems, star-trackers cause orientation problems, and solar panels degraded .

Other systems: blackout of HF radio communications through the polar cap and increased navigation errors over several days.

104

3 per cycle

 

S 3

Strong

Biological: radiation hazard avoidance recommended astronauts on EVA; passengers and crew in commercial jets at high latitudes receive low-level radiation (approximately 1 chest x-ray).

Satellite operations: likely single-event upsets, noise in imaging systems, permanent damage to exposed components/detectors, and decrease of solar panel currents.

Other systems: degraded HF radio propagation through the polar cap and navigation position errors.

103

10 per cycle

 

S 2

Moderate

Biological: none.

Satellite operations: infrequent single-event upsets.

Other systems: small effects on HF propagation through the polar cap and navigation at the polar cap impacted.

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
** These events can last more than one day.


NOAA Space Weather Scale for Radio Blackouts

Category

Effect

Physical measure

Average Frequency
(1 cycle = 11 years)

Scale

Descriptor

Some or all of these effects are possible

   

Radio Blackouts

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. No HF radio contact with mariners or en route aviators.

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.

X20
(2 x 10-3)

Less than 1 per cycle

 

R 4

Severe

HF Radio: HF radio communication blackout for one to two hours on most of the sunlit side of Earth. HF radio contact lost during this time for mariners and en route aviators.

Navigation: Outages of low-frequency navigation signals cause increased error in positioning for mariners and general aviators for one to two hours. Minor disruptions of satellite navigation possible on the sunlit side of Earth.

X10
(10-3)

8 per cycle
(8 days per cycle)

 

R 3

Strong

HF Radio: Wide area blackout of HF radio communication signals, loss of radio contact for mariners and en route aviators for about an hour on sunlit side of Earth.

Navigation: Low-frequency navigation signals degraded for about an hour, affecting maritime and general aviation positioning.

X1
(10-4)

175 per cycle
(140 days per cycle)

R 2

Moderate

HF Radio: Limited blackout of HF radio communication signals on sunlit side, loss of radio contact for tens of minutes for mariners and en route aviators.

Navigation: Degradation of low-frequency navigation signals for tens of minutes affecting maritime and general aviation positioning.

M5
(5 x 10-5)

350 per cycle
(300 days per cycle)

R 1

Minor

HF Radio: Weak or minor degradation of HF radio communication signals on sunlit side, occasional loss of radio contact for mariners and en route aviators.

Navigation: Low-frequency navigation signals degraded for brief intervals affecting maritime and general aviation positioning.

M1
(10-5)

2000 per cycle
(950 days per cycle)

* Flux, measured in the 0.1-0.8 nm range, in W·m-2.


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