Fall 2006 Issue
Observing the Relationship
Those hams with the benefit of many years of observations on 6 meters have noticed that there is a very interesting relationship between aurora propagation (Au) and sporadic-E (Es). Such a relationship appears to be complex, with many variations observed on 6 meters both during and following a significant aurora event. Indeed, it appears that 6 meters is probably the only amateur radio band for which observations can be made connecting the two phenomena.
The role of metallic ions located in the
ionosphere plays a major part in this complex relationship, and it is
worthwhile to review the movement of these ions during a sporadic-E
Dave Ripton, K2SIX, recently brought to our attention an amazing new search engine for locating scientific papers. It is called scholar.google.com. Upon typing in “sporadic-E,” thousands of hits came up. By refining the search a bit, we found a most interesting paper entitled “Global transport and localized layering of metallic ions in the upper atmosphere,” written in 2000 by Professors Carter and Forbes. Since this is a very in-depth paper, we won’t go into it in detail here. It can be found at the following link: <http:// www.copernicus.org/ EGU/annales/17/ag17/190.pdf>. It is strongly recommended that any ham who has observed the sporadic-E phenomenon on the VHF bands and who is interested in the various nuances of Es go to this link and print a copy of the paper. It provides answers to about 90 percent of the questions surrounding the sporadic-E phenomenon.
The paper explains in detail many of the previous scientific studies of the phenomenon and provides models and schematics of the vertical transport of metallic ions (primarily iron and magnesium ions) in the ionosphere for the different zones of the Earth (equatorial, temperate, and aurora). These metallic ions have been detected during many rocket launches into the E-region over the past 40 years. A detailed schematic diagram of the transport model is provided in this paper.
A pictorial description of the transport model was featured in an article by WB2AMU in the Spring 2004 issue of CQ VHF on page 36 and is in the book VHF Propagation, A Guide for Radio Amateurs, by WB2AMU and Gordon West, WB6NOA (available from CQ Communications). A simplified schematic of this model is provided in figure 1.
Another interesting fact brought out by this
paper is that approximately 100 tons of meteoritic particles enter the
ionosphere daily. This amount is independent of the major meteor showers.
It is noted that there is no significant difference in sporadic-E activity
when there is a major meteor shower. This potential source of sporadic-E
ions appears to come from the daily influx of meteor debris. However, the
meteor debris does not instantly become metallic ions; instead, there is a
subsequent process in which the ablated particles ionize at the 90-km
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