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Saturday, April 1, 2017
A 7-Year 10-Meter Es Propagation Study Using PropNET - Part 2 of 5
The Spring/Summer Es Season From
the Beginning to the End:
The chart represents the actual number of 10-Meter PropNET PSK31 captures at my location (North Central Texas) for each day from April 20 till August 15, 2005–2011. At first it was difficult to see any clear trends using daily numbers, but within 5 years it finally called attention to several factors related to Es propagation. I was startled to see specific days being so active and other days close to those peaks were fairly quiet. Each annual season measured in this study was 131 days (concentrated data on 113), in which nearly 20 days were extremely active. The other days measured show a steady increase once the season began, then a peak around the solstice, and slow decline into mid August.
To more clearly demonstrate trends and determine peaks, I used a daily averaging approach. It was begun in the first year of analysis (2005) in order to smooth out the daily trends and focus activity to specific dates of the season. The following chart shows the average number of daily captures 6 days prior to and including the day charted. Rather than using actual dates, the chart indicates the number of days prior to and after the Summer Solstice (6/21). The chart better displays concentrations of Es propagation. The chart shows that from 22 to 12 days prior to solstice (5/31 to 6/09, 6/06 peak) was the most active period for Es. In the latter years of the study, a peak developed just prior to the Summer Solstice. During the season there are 7 apparent concentrations of Es activity.
The events of a typical season show:
1. A quick rise in activity seven weeks prior to the summer solstice.
2. The absolute peak about 2 weeks prior to solstice.
3. A distinguishing lull approaching the solstice.
4. A second peak near the solstice.
5. A steady high rate of activity 2 weeks after solstice.
5. A gradual decline throughout the remainder of the season along with occasional bursts.
Rather than a perfect bell shaped curve, activity appears to be skewed to the right and is right-tailed. The median (midpoint) of the total captures in this study occurs on 6/22, the day after the Summer Solstice. The “median” capture point also proves that Es propagation is a seasonal phenomenon.
Trends appeared to be prevalent although captures varied greatly for day to day. A polynomial regression analysis was applied to the 7 year daily average captures. Although not perfect, a good trend line was established at 2 degrees (x²). Raising the degree did little improvement to the coefficient of determination at .6432 (measured from 0 to1). This coefficient has improved year to year and each trend tightens.
The beginning of the season was on April 26. The peak of approximately 167 captures occurs on June 22. The season trends towards an August 21 end. Trend line activity is at least 50% of peak from May 14 till August 2. Activity is 90% of peak from June 4 to July 11. Again, the trend line indicates rapidly early rise and late decline, with a skewing towards the latter half.
Another method to view Es activity was to chart the total PropNET captures it into one week segments. The following chart shows total captures in one week periods from 8 weeks prior to and 8 weeks past the Summer Solstice It is one of the only charts that show some inconsistencies in the season and leads to looking at outside influences to Es. In the first years, the 6th week of the season was the best. There was right skewing of the data during that time. In the later years of the study, the 8th through the 11th weeks rapidly caught up in total. The Summer Solstice occurs the 2nd day of Week 9. A lull of total captures in weeks 7 and 9 was noticeable in the early years. It was not until 2008 (solar cycle bottom) that the 8th week became the most active of the season. One notable trend each year was an increase in activity beginning with Week 14 and Week 16. For this reason, I should have extended the study at least two more weeks, 18 in total. It will be accounted for in the probability analysis.
The Time of the Day That Es Occur:
My belief from practical experience and with other researchers was that Es seemed to be best in the late afternoon/early evening hours. I discovered in this analysis that it is the morning hours towards midday that are the best time for Es. More operating activity from Hams generally occurs during the later hours of day, and that was the probable cause for the assumption. The afternoon hours are still very active, but not to the level experienced in the morning hours. The afternoon hours still have unique characteristics.
All time charts are displayed in Daybreak (Sunrise) to Daybreak (Sunrise) order and expressed in Daylight Savings Time (Central). At this location, the sun rose in the 6 AM (6) CDT hour and sets during the 8 PM (22) CDT hour. 10-Meter Es were decisively diurnal (daytime-patterned). Therefore, it was best to display all results in daytime hours first, followed by evening and twilight hours.
The following chart is the number of Spring/Summer Es captures by hour for each year of the study. After seeing different Diurnal patterns between 2005 and 2006, this encouraged me to do a third year of participation to determine a true pattern. The 2006, 2007 and 2008 data would look similar in many regards. The final 3 years (2009, 2010 & 2011) would display a more equal “dual-diurnal” pattern. What I got out of these charts was that each year does have similar trends, but each one has its own distinctive personality.
Once again to better display hourly trends, the next chart is displayed as a 3-hour average. For example, the plot for 6 AM is the average of 5, 6 and 7 AM. Averaging does not change the overall totals, but smooths out the transitions between each hour. This method works best in demonstrating what Es actually do.
After accumulating the 7 years together, it was very clear to see that Spring/Summer Es are diurnal and are generally better during in the late morning hours. Once the sun rises, Es rapidly increase. Once the sun sets, Es decline sharply. Most dominant in 2007 through 2011, the overall chart shows a “dual-peak” diurnal pattern.
Activity Week to Week:
The following chart displays 3-hour average captures for the 16-Week Spring/Summer Es season (8 weeks each side of the Summer Solstice). The 6th week of the season is the most active and clearly appears similar in trends to the overall seasonal data chart. The 8th week grew rapidly the last half of the analysis and had a distinctive dual diurnal peak. The 1st, 2nd, and 13th weeks are least active, but clearly show a diurnal pattern as well. Only the early and latter weeks of the season fail to show a dual-peaked diurnal pattern.
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