Guide to the ANZA DX Net Propagation Page

The ANZA DX Net makes use of trans-equatorial and grayline propagation in the 15 and 20 meter bands. The highlighted terms, used in links on the Propagation page, characterize 1) solar activity, the source of ions and ionizing radiation; 2) solar wind, the delivery mechanism, 3) ionosphere, the ionized region of Earth's atmosphere, through which radio frequency emissions are propagated, reflected and refracted as influenced by 4) the Earth's magnetic field; the ionized bubble. The bubble is mapped by density, height and depth; highlighting usable frequencies, path lengths and magnetic distortions.

The the Sun is the source of ionizing radiation, delivered by the solar wind. That is the atmosphere is ionized by solar radiation. The total amount of ionizing radiation is described by solar flux. Sunspots emit increased radiation and produce occasional flares (coronal mass ejection, CME) which enhance solar flux and disturb the ionosphere a few days later, when directed toward Earth. Sunspots are seen on the SDO solar images, where various features of the Sun are highlighted in various wavelengths of electro-magnetic radiation. Latest LASCO C₂ and C₃ are 4 day time-lapse animations, in which the Sun is masked so flares in the chromosphere are visible. Earth directed coronal mass ejections promptly splatter the sensors with high energy radiation. Comets, planets and UFO's are also seen in the C₂ image. The relative strength of total sunspot radiation is measured by the daily Sunspot Number (SN), to be confused with the 13-month running average Smoothed Sunspot Number (SSN). Sun spots are most effective when located near the center of the sun as seen from earth. That is, when earth-directed. Solar flux varies with the ~11 year solar flare cycle, ranging from 60 ~ 150 through the cycle. Note that early-cycle flares tend to occur at higher latitude on the Sun, so have less influence on solar flux at Earth. Late-cycle flares tend to occur at mid latitudes, increasing directivity toward Earth, as shown in the Butterfly Diagram. Sunspots have a stronger influence on propagation after the peak of the cycle. Note that the Sun rotates every 25 days, so a spot appears on the left, traverses the face of the Sun for a week, then disappears for 3 weeks and, if it persists, comes around again. The average distance from Sun to the Earth is 150 million kilometres (93 million miles). The actual distance varies as Earth's elliptical orbit of the Sun, from a minimum (perihelion) to a maximum (aphelion) and back again once each year. The minimum occurs ~January 3rd, Earth is ~147 million km from the Sun. The maximum occurs ~July 4th, Earth is ~152 million km from the Sun, difference ~5 million km, ~3%. Solar electro-magnetic radiation travels at the speed of light, about 8 minute transit time. Particles (electrons, protons, ions) travel at the speed of the solar wind, ~2 days transit time.

The solar wind is characterized by speed and plasma (X-ray, electron and proton) density, temperature and magnetic polarity. Interaction of the magnetic fields results in distortion (disturbance) of the Earth's magnetic field and the ionized bubble. The degree of immediate, local magnetic distortion is described by the K index. The K index is particular to a specific location, but is generalized to planetary by averaging Kp observations from multiple observatories, updated at 3 hour interval. The Ap index is the daily, 24 hour average Kp from a number of observatories. Larger values mean greater magnetic distortion, some paths are degraded, others may be enhanced, atmospheric noise may increase and geomagnet currents may be induced on pipelines, powerlines, data cables, etc. The K index changes abruptly when a coronal mass ejection arrives at Earth, a few days after eruption. When the magnetic polarity of the solar wind is strongly different from that of the earth (negative Bz, near opposite polarity, solar wind plasma is pumped into polar regions), aurora occurs at the Earth's magnetic poles. This polar concentration causes reflections, commonly known as auroral multi-path (echo, flutter) or polar propagation. The Dst and pc3 are also indices of geomagnetic field disturbance.

DX radio-wave propagation is all about reflections off of ion rich layers of the ionosphere, ionized by solar radiation and shaped by magnetic fields. Solar flares emit highly energetic protons, electrons, ions and X-rays which penetrate the upper ionospheric F-region, generate QRN and ionize the lower, D-region.

When the D-region is ionized, radio waves are absorbed, prevented from reaching the F-region for DX propagation. D-Region Absorption Prediction (D-RAP) maps the affected area and frequencies. Also known as Daylight Fadeout, only those circuits in daylight are be effected. The proton, X-ray flux and fade alerts also indicate fade potential.

The height and density of the ionospheric layers influences the length of the path and usable frequencies. The total electron count (TEC) map generally describes the ionized bubble. The height of the ionized bubble (hmF2) controls the path length, higher reflector allows a longer path. The density of ionized gas (foF2) controls the Maximum Usable Frequency (MUF), that is, which bands are open. The T-index is based on real time foF2 measurements and accounts for ionospheric storms. Following geomagnetic activity, the typical ionospheric response at mid latitudes is to become depressed, resulting in lower value of the T index. The Australian Bureau of Meteorology, Space Weather Services (BOM/SWS) maps are centered on the mid-Pacific, 180 degrees longitude. The BOM/SWS foF2 map is available for both perspectives.

The best path occurs when both stations are under the ionized bubble and the path passes through a region of strong, high F-layer ionization and low D-layer ionization. Good DX on the ANZA DX Net, 0400-0600 UTC, utilizes trans-equatorial paths, through the highly-ionized, central portion of the bubble, where direct solar radiation is occuring. The location of the bubble changes continuously (due to Earth's rotation) and seasonally (due to inclination of the Earth's axis). The ionized bubble traverses to the south after the June 20 solstice, through the September 23 equinox, to the December 20 solstice, then traverses north, through the March 21 equinox to the June 20 solstice. Peak propagation between Oceania and North America occurs about the June solstice. In the belly of the flare cycle, the path is open from April through August. Near the peak of the cycle, the path is open all year. Enhanced propagation also occurs along the day/night grayline.

The indicators on this page serve to forecast and explain actual, simplified propagation conditions. A variety of fine-scale structures of planetary ionospheres, depicted in the following graphic, also influence propagation and QRN.

The Earth's magnetic field, which originates in the core, changes continuously and irregularly.

Some fluctuations of propagation and QRN are not explained by the simple model that is based on surface and satellite observations. QRN with geomagnetic storms (elevated A and K) is also caused by geomagnetic perturbation of electric fields in conductive Earth materials that induce geomagnetic currents. The geoelectric field at the surface of the earth induces currents in artificial conductors, such as power lines, communication cables, pipelines, and railway lines. Geomagnetic QRN may be ionospheric and/or local. The Aus GIC (Geomagnetically Induced Currents) map depicts geoelectric field potential in Australia.