Spring 2006 Issue
The saying “we are not alone” has often been
used in the past to describe the UFO phenomenon. In a way, this phrase is
also appropriate to describe the various ionospheric phenomena that result
in the different radio propagation modes that we experience on the planet
Earth, in particular those which occur in the E-region of the ionosphere.
Sporadic-E propagation is one such propagation mode, and it occurs in
force during the respective summer months of the Northern and Southern
Hemispheres on the 6-meter band, where signals are efficiently reflected
off ion layers in the E-region. Another E-region phenomenon is the
mysterious aurora mode, where radio signals are reflected off the active
aurora in a backscatter mode and have tremendous distortion. Radio
amateurs get to experience these really interesting modes by operating on
the VHF bands at the right time.
Such an area of exploration would be extremely helpful in increasing our knowledge base of terrestrial modes of VHF propagation on Earth, such as aurora and sporadic-E. While other planets have noticeable differences in the reasons why these phenomena occur, the understanding of these differences and why they exist will ultimately lead to a clearer understanding of the behavior of aurora and sporadic-E propagation modes on Earth.
In this article we will concentrate on the
above two E-region propagation modes on Earth and explore the form in
which they exist on other planets in our solar system. The formal,
structured ionosphere that exists on Earth—where there is a clear
distinction between layers (known as the D, E, and F region)—may or may
not exist in a similar manner on other planets. Although the presence of a
metallic-ion layer (which is what sporadic-E is on Earth) and an
aurora-type phenomenon has been noted in the ionosphere of other planets,
at this time no determination of different layers has been made.
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