As
I told you last week, NOAA has a scale of geomagnetic activity that
ranges from G0 to G5, where G0 is quiescent, and G5 is the worst
geomagnetic storm around. Now, we've already talked a little bit
about what geomagnetic storms do...
No,
we didn't, you say?
Ah,
but we did. Back when I told you about all the effects that Coronal
Mass Ejections can have. (Solar,
Space, and Geomagnetic Weather, Part 4.) Because
those sorts of things are what cause the geomagnetic storms.
But
probably the best way I can tell you about the effects is simply to
quote from NOAA's scale itself (which can be found here:
http://www.swpc.noaa.gov/NOAAscales/#GeomagneticStorms).
As
I mentioned last week, a G0 is the normal, quiescent geomagnetic
field. This holds until the Kp index reaches 5, and then we begin
minor geomagnetic storming, with the scale hitting G1. According to
NOAA, “Power systems:
weak
power grid fluctuations
can occur. 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).” These are fairly
frequent, with on average close to 2000 per 11-year solar cycle.
At
Kp=6, G2 is considered a moderate storm. “Power
systems: high-latitude
power systems
may experience voltage alarms, long-duration storms may cause
transformer
damage.
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.).” These are a little less
frequent than G1, but still occur at a rate of about 600 every solar
cycle.
When
Kp=7, G3 is a strong geomagnetic storm. “Power
systems: voltage
corrections may be required,
false alarms triggered on some protection devices. Spacecraft
operations: surface
charging [static
electricity buildup; this can lead to arcing]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.).” These are less frequent still, with on average
200 per solar cycle. Also, as the geomagnetic storms increase in
strength, their likelihood of occurrence tends to concentrate around
solar maximum, though this is not a hard and fast rule.
At
Kp=8, G4 is a severe geomagnetic storm. “Power
systems: possible
widespread voltage
control problems and
some protective systems will mistakenly trip
out key assets from the grid.
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.). These are
rarer still, with only about 100 seen per solar cycle.
And
then there's the big boys. Kp=9 means a G5 extreme geomagnetic storm.
“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.
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.).” These are the rarest of all,
but still occur on average 4 per solar cycle.
-Stephanie
Osborn
