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.
Next: Distance Analysis
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