NOAA Space Weather Scale for Radio Blackouts

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. These scales will be useful to [...] 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.

Category

Effect

Physical measure

Average Frequency
(1 cycle = 11 years)

Scale

Descriptor

Duration of event will influence severity of effects

   

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. This results in no HF radio contact with mariners and en route aviators in this sector.

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 on most of the sunlit side of Earth for one to two hours. HF radio contact lost during this time.

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.

X10
(10-3)

8 per cycle
(8 days per cycle)

 

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.

Navigation: Low-frequency navigation signals degraded for about an hour.

X1
(10-4)

175 per cycle
(140 days per cycle)

R 2

Moderate

HF Radio: Limited blackout of HF radio communication on sunlit side, loss of radio contact for tens of minutes.

Navigation: Degradation of low-frequency navigation signals for tens of minutes.

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 on sunlit side, occasional loss of radio contact.

Navigation: Low-frequency navigation signals degraded for brief intervals.

M1
(10-5)

2000 per cycle
(950 days per cycle)

* 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.


Source: http://sec.noaa.gov/NOAAscales/index.html (November 6, 2000)