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Forecast of radio propagation

Forecast of radio propagation (Paul Hermann banner)

To assess the conditions for the radio propagation in the near future, various indices and indicators of current solar and geomagnetic activity are needed, which are available on various banners and pages of amateur radio sites.

Despite all the variety of data sources, one of the most popular are banners, which are provided completely free of charge by Paul Herrman (N0NBH). Below is a summary of each of the banner parameters. The designations of the same parameters may differ on different banners, so in some cases several options are given.

Solar activity

Solar Flux Index (SFI)

SFI – is an indicator of the intensity of radiation at a frequency of 2800 MHz generated by the Sun. This value does not have a direct effect on the radio propagation, but its value is much easier to measure, and it correlates well with the levels of solar ultraviolet and X-ray radiation.

Sunspot Number (SN)

SN is not just the number of spots on the Sun. The value of this value depends on the number and size of the spots, as well as on the nature of their location on the surface of the Sun.

The range of SN values is from 0 to 250. The higher the value of SN, the higher the intensity of ultraviolet and X-ray radiation, which increases the ionization of the Earth's atmosphere and leads to the formation of layers D, E and F. With an increase in the ionospheric ionization level, the maximum applicable frequency (MUF) also increases.

Thus, an increase in the values of SFI and SN indicates an increase in the degree of ionization in the layers E and F, which in turn has a positive effect on the conditions for the radio propagation.

Hard X-Rays (X-Ray)

The value of this indicator depends on the intensity of the X-ray radiation reaching the Earth. The parameter value consists of two parts – a letter reflecting the radiation activity class and a number showing the radiation power in units of W/m2. The degree of ionization of the ionosphere layer D depends on the intensity of X-ray radiation.

Usually in the daytime, layer D absorbs radio signals in the low–frequency HF bands (1.8 – 5 MHz) and significantly weakens signals in the 7 – 10 MHz frequency range.

With an increase in the intensity of X-ray radiation, layer D expands and in extreme situations can absorb radio signals in almost the entire HF band, complicating radio communication and sometimes leading to almost complete radio silence, which can last several hours.

X-ray intensity scale

This value reflects the relative intensity of all solar radiation in the ultraviolet range (wavelength 304Å). Ultraviolet radiation has a significant effect on the ionization level of the ionospheric layer F.

The value of 304A correlates with the value of SFI, so its increase leads to an improvement in the conditions for the radio propagation by reflection from the F layer.

Proton Flux (PtnFlx/PF)

PF is the density of protons inside the Earth's magnetic field.

The usual value does not exceed 10.

Protons that have interacted with the Earth's magnetic field move along its lines in the direction of the poles, changing the density of the ionosphere in these zones. At values of proton density over 10000, the attenuation of radio signals passing through the polar zones of the Earth increases, and at values over 100000, the complete absence of radio communication is possible.

Electron Flux (ElcFlx/EF)

This parameter reflects the intensity of the electron flux inside the Earth's magnetic field. The ionospheric effect of the interaction of electrons with a magnetic field is similar to the flow of protons on auroral routes at EF values exceeding 1000.

Interplanetary Magnetic Field (Bz)

The Bz index reflects the strength and direction of the interplanetary magnetic field.

A positive value of this parameter means that the direction of the interplanetary magnetic field coincides with the direction of the Earth's magnetic field, and a negative value indicates a weakening of the Earth's magnetic field and a decrease in its shielding effects, which in turn increases the impact of charged particles on the Earth's atmosphere.

Solar Wind (SolarWind/SW)

SW is the velocity of charged particles (km/h) that have reached the Earth's surface.

The index value can be in the range from 0 to 2000. A typical value is about 400. The higher the particle velocity, the more pressure the ionosphere experiences. At SW values exceeding 500 km/h, the solar wind can cause a disturbance of the Earth's magnetic field, which will eventually lead to the destruction of the ionospheric layer F, a decrease in the level of ionospheric ionization and deterioration of the conditions of propagation in the HF bands..

Signal Noise Level (SigNoiseLvl)

This value in units of the S-meter scale shows the level of the noise signal that arises as a result of the interaction of the solar wind with the Earth's magnetic field.

Geomagnetic activity

Planetary A Index (K-Ind)

Index A indicates the state of the Earth's magnetic field and is the average index K for a day. It shows the overall trend and a snapshot of the overall state.

The higher the A index, the more interference and the higher the signal absorption. First of all, the high-frequency bands will be affected, and then the low-frequency bands.

The value of geomagnetic activity indices

It can vary from 0 to 400, but it is very rare to see numbers over 75. Usually the values are in the range from 4 to 50. If the index A is less than 7, the general conditions are optimal. However, when it exceeds 7, conditions at high frequencies become unfavorable. Values less than 10 are more favorable for HF communications. High index values mean excessive absorption of radio waves in the ionosphere.

Planetary K Index (K-Ind)

The K index indicates the state of the Earth's magnetic field for the previous 3 hours. They show the current level of activity of the Earth's magnetic field. Please note that the data may not correspond to the geographical area in which you are located, however, they are averaged to a certain extent.

The values of the K index range from 0 to 9. Smaller values mean a quieter state of the ionosphere. It is important to monitor the direction of change of this index. If it increases, then we can expect a deterioration in the passage, especially in the circumpolar areas.

A K index value equal to or greater than three indicates high magnetic activity. This value helps to predict the conditions of propagation in the rest of the period. If the K index jumps up sharply in the current period, you will notice a rapid change in the quality of communication (attenuation, interference, etc.), which will first occur on high-latitude communication channels (due to Aurora, etc.).

Aurora (Aurora/AurAct)

The value of this parameter is a derivative of the power level of solar energy, measured in gigawatts, which reaches the polar regions of the Earth. This level is updated every time the NOAA-12 POES satellite passes over the pole, and a new hemispheric energy index is calculated.

The parameter can take values in the range from 1 to 10. The higher the level of solar energy, the stronger the ionization of the ionosphere layer F. The greater the value of this parameter, the lower the latitude of the boundary of the auroral cap and the higher the probability of occurrence of auroras.

At high values of the parameter, it becomes possible to conduct long-range radio communications on VHF, but at the same time polar routes at HF frequencies can be partially or completely blocked.

Aurora Latitude (AurLat)

The maximum latitude at which an auroral passage is possible.

Maximum Usable Frequency (MUF)

The value of the maximum applicable frequency measured at the specified meteorological observatory (or observatories, depending on the type of banner) at the given time (UTC).

Earth–Moon–Earth Degradation (EME Deg)

This parameter characterizes the amount of attenuation in decibels of the radio signal reflected from the lunar surface on the Earth–Moon–Earth track, and can take the following values: VeryPoor (>5.5 dB), Poor (>4 dB), Fair (>2.5 dB), Good (>1.5 dB), Excellent (≤1.5 dB).

Geomagnetic Field (GeomagField)

This parameter characterizes the current geomagnetic situation based on the K index value. Its scale is conventionally divided into 9 levels from Inactive to ExtremeStorm. At values of Major, Severe and ExtremeStorm, the propagation on the HF bands worsens until they are completely closed, and the probability of an auroral propagation increases.

Source for English translation: https://lik-o-dil-es.blogspot.com/

See also: https://www.hamqsl.com/

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