Usually abbreviated as SSN. Higher sunspot numbers indicate increased ionizing radiation from the sun which enhances the ionosphere's ability to refract HF signals, The sunspot number can vary from zero to over 200 during the peak of the 11-year solar
cycle.
Solar Flux
Usually abbreviated as SFI (and often simply as "I"). Measurement of radio signals from the sun. The index is taken once a day at a frequency of 2800 MHz (10.7 cm). Increased radio noise from the sun means more ionizing radiation and correlates with the sunspot
number. Solar flux values range from 60 (no sunspots) to 300.
90-day Solar Flux
Usually abbreviated as SFI90. It is the average Solar Flux in
the past 90 days. It is usually a better indicator of propagation
conditions than SFI, that only represents the Solar Flux at a given day/time.
Values range from 60 to 300.
K Indexes
K indexes reflect the geomagnetic conditions (solar particle effects on the earth's magnetic field)
and their values range from 0 to 9. Lower numbers mean quieter ionosphere.
Trends in the K indexes are important to watch. When K rises you can expect HF
propagation conditions to worsen, particularly towards the polar regions. On
VHF bands a high K index would mean the possibility of an Aurora opening.
K index: Siebert (1971)
defines "K variations are all irregular disturbances of the
geomagnetic field caused by solar particle radiation within the 3-h interval
concerned. All other regular and irregular disturbances are non K
variations. Geomagnetic activity is the occurrence of K variations".K is a local index, describing disturbances in the vicinity of
each observatory.
Ks index: Using
statistical methods, J.
Bartels generated conversion
tables to eliminate these disturbances. By applying the conversion
tables, a standardized indexKs for each of the 13
selected observatories is determined. In contrast to the K
values, the Ks index is expressed in a scale of thirds (28 values:
0o, 0+, 1-, 1o, 1+, 2-, 2o, 2+, ... , 8o, 8+, 9-, 9o). The main purpose of the
standardized index Ks is to provide a basis for the global
geomagnetic index Kp.
Kp index:Kp is
the average of the Ks indexes from a number of "Kp
stations" distributed around the globe and gives a "planetary"
overview of the geomagnetic activity.
A Indexes
A indexes are derived from K indexes but converted to a linear
scale in gammas (nanoTeslas). They can range from 0 to 400 but it is rare to
see it go above 75 o 100. More often you will see A index readings between
about 4 and 50. Values below 10 are very desirable for HF communications.
Higher A numbers can mean excessive absorption of HF radio waves due to
increased storm conditions in the ionosphere.
A index: Indicates the
disturbances for the last 24 hours in the vicinity of an observatory. It's
obtained averaging the eight K indexes and converting the result according to
the table below.
ap index: Is the direct
result of the conversion of the three-hour Kp index according to the
table below.
Ap index: The daily index Ap
is obtained by averaging the eight values of ap for each day.
Conversion of geomagnetic Indexes
Ionospheric conditions
K index
A index
Quiet
0-1
0-7
Unsettled
2
8-15
Active
3
16-29
Minor storm
4
30-49
Major storm
5
50-99
Severe storm
6-9
> 99
Kp index
ap index
0o
0
0+
2
1-
3
1o
4
1+
5
2-
6
2o
7
2+
9
3-
12
3o
15
3+
18
4-
22
4o
27
4+
32
5-
39
5o
48
5+
56
6-
57
6o
80
6+
94
7-
111
7o
132
7+
154
8-
179
8o
207
8+
236
9-
300
9o
400
Space Weather
Usually abbreviated as SWX. It is value summarizing the Space Weather
conditions due to Solar storms.
Space Weather conditions
SWX value
Quiet
0
Minor storm
1
Moderate storm
2
Strong storm
3
Severe storm
4
Extreme storm
> 4
Hemispheric Power Index
The Hemispheric Power Index is an estimated forecast of the total
hemispheric energy flux in GW of precipitating auroral electrons. There are
two Indexes, one for each Hemisphere, although both values are usually
very similar. The value shown at DXMAPS is for the North Hemisphere. It can
help to determine the intensity of a possible aurora that could affect radio
communications.
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