|
Auroral Activity
| When a solar wind blow reaches the Earth, it
creates additional ionization in the areas around the magnetic poles. The radio propagation paths that cross the
poles may be degraded because of increased absorption of the radio
signal. The auroral activity index ranges
from 1 to 10. |
 
Taken from
http://www.sec.noaa.gov
Real Time K-index
|
The K index showing the geomagnetic
conditions, indicates HF noise primarily below 10 MHz.
|
|
| K - Index |
Geomagnetic
Conditions |
HF Noise |
Aurora |
| 0 |
Very Quiet |
S1-S2 |
None |
| 1 |
Quiet |
S1-S2 |
None |
| 2 |
Quiet |
S1-S2 |
Very Low |
| 3 |
Unseettled |
S2-S3 |
Very Low |
| 4 |
Active |
S3-S3 |
Low |
| 5 |
Minor Storm |
S4-S6 |
High |
| 6 |
Major Storm |
S6-S9 |
Very High |
| 7 |
Severe Storm |
S9+ |
Very High |
| 8 |
Severe Storm |
Blackout |
Extreme |
| 9 |
Extreme |
Blackout |
Extreme |
|
|
Taken from
http://geo.phys.uit.no/knum |
Solar Wind
| The solar wind is a constant outflow of
gasses, electrons and particles from the sun. Disturbances to the solar wind from a solar
flare or coronal hole, can cause serious disruptions to HF
by triggering a geomagnetic storm When BZ component is
negative (southward) coupling with earth magnetic field is
strongest and geomagnetic activity will increase.
Solar wind speed is highly variable ranging from 200 km/s to 1000 km/s,
increasing following a
major solar flare, generating noise on the HF bands.
Dynamic pressure of the solar wind is a function of speed
and intensity |
|
Sunspots
| Sunspots are cooler areas on
the solar surface. These active regions should be carefully
watched for possible flare activity.
A solar flare releases energy
than can affect HF propagation: 1. ionizing radiation that
arrives at earth immediatly; 2. a supersonic shockwave
riding along the solar wind; 3. dense particles behind the
shockwave that arrives two to three days after the flare.
Good DX contacts are possible
immediately following a solar flare until sundown due to
improved reflectivity and the higher MUF opening higher
bands. Night time conditions on 80-40 can be excellent.
About two days after a solar flare, the shockwave arrives on
earth triggering a geomagnetic storm. |
|
X-ray flux levels
| A
solar flare is an explosion on the Sun. There are 3 categories: X-class
flares are big; they are major events that can trigger
planet-wide radio blackouts and long-lasting radiation
storms. M-class flares are medium-sized; they can
cause brief radio blackouts that affect Earth's polar
regions. Minor radiation storms sometimes follow an M-class
flare. C-class flares
are small with few noticeable consequences here on Earth. |
|
Taken
from http://sec.noaa.gov/today.html
Short historical graph of WWV numbers
|
The solar flux, indicating the level of
ionization, affects HF propagation above 10 MHz. The
solar flux does not affect 7 MHz and below, since the MUF
seldom drops below 10 MHz. The higher the inonization the
more reflective our ionosphere is to HF signals, and the
higher the MUF. Sunspots are cooler areas on
the solar surface. These active regions should be carefully
watched for possible flare activity. A index,
is derived by averaging the K-index. It ranges from 0-20 for
quiet conditions, up to 400 for extreme conditions,
representing the overall planetary geomagnetic conditions. |
|
Taken from http://dxlc.com
Comparison of cycles 21, cycle 22
and cycle 23
|
The solar cycle last over a 7-11 year
period. During the low part of the cycle (SF<100; SSN<43)
the sun is quiet, with low ionizing radioation and lower
MUF, 10MHz during the night and 20MHz during the day. During
the high part of the cycle (SF>100; SSN>43) the sun is
active, with higher MUF, 18MHz during the night and 30+ MHz
during the day.
Solar flares expose earth to increased
ionization radiation, possibly temporarily raising the MUF. |
|
Taken from
http://www.dxlc.com
Cycle 23 / Cycle 24 Prediction
Taken fromhttp://www.sec.noaa.gov/SolarCycle/
|
|