Friday, 29 June 2018

27/06/2018 50MHz FT8 Activity from PSKR M0BEW

27/06/2018 50MHz FT8 Activity from PSKR M0BEW.

Overall M0BEW heard.

Overall M0BEW heard.

Overall heard.

Europe heard.

Asia heard.

UK Activity.


Tim M0BEW.

Thursday, 28 June 2018

Mid-Latitude Sporadic-E - A Review

Mid-Latitude Sporadic-E - A Review.
Michael Hawk - Novemeber 12, 2001

Over the years, many observations, theories, and discussions have taken place surrounding the
sporadic-E (E-skip) phenomenon. This article was originally written in response to a brief review
of the basics of sporadic-E that I wrote for the April 1993 VUD. Unfortunately, other obligations
prevented this article from being completed to my satisfaction until now. Although a large amount
of material exists on the subject, I have not found one concise source of theories, correlations,
and facts. And many of the subjects overview papers oversimplify or misrepresent some of these
It is the purpose of this paper to provide a review of sporadic-E knowledge from a DX’ers
perspective, while simultaneously bridging in observations from academia.
It is important to keep in mind that the ideas conveyed herein are theories, hypotheses, and
observations. The fact remains that the catalyst for sporadic E is unknown and the behavior of
mid-latitude sporadic E is unpredictable. When you start to believe that correlations and
observations are fact, sporadic E will surprise you with an inexplicable result.

1.0 Background
1.1 Ionosphere Overview
1.2 Sporadic-E Definition
2.0 Sporadic-E Characteristics
2.1 Ionization
2.2 Distances Propagated and MUF
2.3 Cloud Movement
2.4 Daily Variation
2.5 Monthly Variation
2.6 Annual Comparison
2.7 Sunspot Cycle
2.8 Worldwide Occurrence
3.0 Sporadic-E Mechanisms
3.1 Introduction
3.2 Ionospheric Wind Shear
3.3 Thunderstorms and Associated Phenomena
3.4 Other Weather
3.5 Meteors and Cometary Origin
3.6 Geomagnetic Activity
4.0 Sporadic-E Classifications
4.1 Introduction
4.2 Temperate Es
4.3 Equatorial Es
4.4 Auroral Es
4.5 Type n Es
4.6 Backscatter
5.0 Cloud Formations
5.1 Two-cloud formations
5.2 Tilted Clouds
6.0 Conclusions


1.1 Ionosphere Overview
The ionosphere is the region of the Earth’s atmosphere containing free electrons and atoms, and
associated ions produced by the sun’s ultraviolet radiation (<100 nm wavelength).1 The
ionosphere is known to influence radio wave propagation of frequencies up to around 300 MHz,
and is located in the lower portion of the thermosphere, beginning at about 80 km altitude.2
The ionosphere is known to consist of several distinct regions of ionization. Altitude,
consistency, and ion type differentiate these regions. The first discovered subregion was named
the E layer (E for Electric Layer). At later dates, additional layers were discovered at lower (D
region) and higher (F region) altitudes.3
1 One nm = 10-9 meters
2 One mile = one kilometer X .62
3 The term layer is rarely used when describing the various parts of the ionosphere. “Region” is more
commonly used, since the “regions” don’t have a sudden terminating point that the word “layer” would imply. Instead, the various regions gradually merge together.

The D region is primarily known for its absorption of radiowaves at low frequencies. It quickly
dissipates at night, allowing distant AM radio reception to occur.
The F region is the primary refractor/reflector of HF (shortwave) frequencies. Its “reflectivity”
displays a direct relation to solar activity. During years of peak solar activity, the F region will
have a much higher ionization density, allowing for higher frequencies and sharper angles of
waves to be reflected. TV DX’ers and 6 Meter ham operators look forward to solar cycle peaks,
as those years are when the F region can bring distant DX up to 50 or 60 MHz.
The E region of the ionosphere is located about 90 to 160 km in altitude. The height can vary a
little, and, along with electron [ionization] density, depends on solar zenith angle and solar
activity. During daylight hours, electron density (a measure of the ionization level) can reach 105
electrons/cm3. At night, when the supply of x-rays from the sun is cut off, ionization levels drop to
103 e/cm3. These ionization densities are expected under normal conditions, absent of sporadic-

1.2 Sporadic-E Definition
Within the E region, very thin regions of extremely dense ionization can form. These regions can
apparently be caused by several mechanisms, and have a wide variety of characteristics.
Because of this, one single definition cannot be completely accurate. According to the Space
Environmental Services Center, “sporadic E (Es) is transient, localized patches of relatively high
electron density in the E region of the ionosphere which significantly affect radio wave
propagation. Sporadic E can occur during daytime or nighttime, and it varies markedly with
latitude. Es can be associated with thunderstorms, meteor showers, solar activity, and
geomagnetic activity.”
There are several problems with this definition, but it seems to be the best “official” definition
available. This definition provides no insight into the diurnal characteristics of Es. The definition
lends too much credence towards the thunderstorm and meteor shower correlations. The
relationship with thunderstorms has been highly controversial in amateur circles, but most
academia studies have ruled out such possibilities. The relation to meteor showers is still highly
studies, as some indirect correlations have been observed. Both of these possible Es
mechanisms are discussed in more depth later in this paper.
A much more precise definition of Es was found in a book titled “Worldwide Occurrence of
Sporadic E”, written by Ernest K. Smith, PhD, 1957.4 Sporadic E was defined as “a
comparatively strong and protracted transmission (several minutes to several hours) “returned”
from the E region of the ionosphere by some mechanism other than the normal reflection process
from the daytime E layer.”
Through the use of careful and generic wording, this definition fits almost any type of Es currently
The careful wording of Dr. Smith’s definition is important, because there are a wide variety of
sporadic-E types. In the temperate latitudes alone, through the use of ionosondes (data
displayed in ionogram format), four have been identified.5 See figure 1. An ionogram shows the
altitude at which different frequency waves are reflected back to the originating point.
Figure 1 Sample Ionogram.


2.1 Ionization
4 National Bureau of Standards Publication. A few copies are available through rare bookstores for $20-$80. May 2001 check of revealed 2 copies available through independent dealers.
5 An ionogram is a plot of the group path height of reflection of ionospherically returned (echoed) radio waves as a function of frequency. Figure 1 is an example. Vertically incident measure the date for this graph.

An ion is an atom or group of atoms having an electric charge. This results when a neutral atom
of group of atoms loses or gains one or more electrons. For this reason, either ion density, or
more commonly electron density, can be used for ionospheric “strength” calculations. The most
common E region ions are O2+, O+, and NO+, as well as some metallic ions.
The reason an atom or group of atoms may lose an electron is primarily through the welldocumented
impact of solar radiation. Throughout the day, the level of production of ions
exceeds the level at which the ions recombine with electrons. At night, the production of ions
ceases with the setting of the sun, and the slow process of recombination gradually lowers the
electron density. Additionally, recombination rates are inverse to altitude. This can be
demonstrated by the fact that the D region diminishes quickly at sunset, minimizing absorption of
low frequencies (< 8 MHz). If it weren’t for this fact, long range propagation on the AM broadcast
band wouldn’t occur until well after sunset. At the “higher” regions, enough electrons continue to
persist throughout the night, allowing refraction in the E and F regions to continue all night.
As previously mentioned, normal ionization levels in the E region during the day are around 105
e/cm3. Note that Es can have ionization levels twice the normal amount. This high density
accounts for the high maximum useable (refractable) frequencies (MUF) that occur with Es.
There are several formulas which, through the use of electron density, approximate the critical
frequencies6 (foEs), MUF’s, and other parameters. Many are highly inaccurate extrapolations
from other propagation types.

Although ionization levels are quite high when Es occurs, the highest levels are generally
confined to very small patches, commonly referred to as clouds. The shape of the clouds is likely
ragged, and not true circles or ellipses. Additionally, clouds have been shown to have concave
undersides in many instances, with tilts up to 10°. For simplified calculations, however, they are
often thought of as pure circles or ellipses, with axis parallel to the horizontal plane. In cases
such as these, the diameter of the cloud could be to several hundred km. The vertical thickness
of these clouds is usually quite small – no more than a few km thick. The thickness of clouds has
been measured by rocket flights through ionized areas.
During large/intense Es outbreaks, elevated ionization can be very widespread. In these
conditions, the concepts of Es “clouds” is tough to identify at lower frequencies. Embedded in
this “sheet” of elevated ionization density are small patches of very high ionization. At higher
frequencies, these very dense areas can be identified, and the “cloud” concept holds.

2.2 Distances Propagated and MUF
Through the use of simple geometry, it can be figured that the theoretical maximum distance for a
transmitted signal to be propagated after only one encounter with the Es region (“single hop”
propagation) is 2100 km. This appears to be very accurate for the HF bands (< 30 MHz), but
many transmissions exceeding 2350 km have been observed in the VHF bands. This is likely
due to much improved “groundwave” and tropospheric characteristics, which add distance to the
theoretical maximum on both sides of the typical model.7 Figure 2 shows average distances
received on FM broadcast and TV broadcast frequencies. The average FM distance is likely
longer because of the simple relationship between electron density and critical angle of
propagation. In other words, it is “easier” for the atmosphere to produce shorter distance
propagation in the lower frequency low-band VHF range.

Figure 2 Distance propagated at FM and low band VHF TV frequencies, collected from VUD

6 Critical Frequency (fo) is the highest frequency that reflects/echoes a vertically transmitted radio wave back to the transmission point. A relatively low critical frequency can result in a “high” MUF, given that the waves related to the MUF are encountering the ionization at a high angle (no perpendicular as is required for critical frequency measurements).

7 Many believe a gradual bending of the wave occurs, as the density of the media changes, rather than mirror-like reflection. Although this is not pure refraction either, refraction is the generally accepted term.

Remember that simple geometry will not take into account the gradual “bending” of a wave (the
property similar to refraction discussed previously). For the ease of calculations, you can assume
“reflection” occurs instead by taking into account the “virtual height” of the refraction. Many
formulas revolve around the virtual height, which is an altitude higher than where the actual
refraction is taking place. See figure 3.

It has been observed frequently that if one patch of ionization forms, others of varying strength
likely exist or will form shortly. If this is the case, and two patches exist within the horizon of a
midpoint, the theoretical distance propagated by Es can nearly be doubled, so long as the clouds
are in line with both the transmitter and receiver. This “double hop” propagation is fairly common
during widespread occurrences of Es, especially below 70 MHz. Similarly, three or more clouds
could potentially line up, providing even further distances propagated. Of course, the likelihood
that each of the cloud are adequate strength and geometrically lined up is pretty slim, especially if
you’re interest is in higher frequencies.

One other factor as to the maximum distance propagated by Es is the height of the Es cloud.
According to ionosonde (devices used to measure reflectivity of the ionosphere) data, Es usually
occurs around 90-100 km altitude. This data also reveals that multiple layers of “clouds” have
formed on occasion, usually spaced by about 6 km. Varying heights might allow for longer or
shorter distances propagated, but remember that we are constrained to an altitude close to 100
km, so the variances will be small. On a side note, as mentioned earlier, the E region exists
between 90 and 160 km. Since Es consistently occurs around 100 km, many scientists refer to a
distinct “Es Layer”.

As electron density of the cloud increases, its critical angle also increases. In other words, at a
given frequency, a cloud may have a critical angle of 40°. In an hour, the electron density may
have increased enough to raise the critical angle to 45°. This would result in a shorter minimum
path length. Refer to figure 4.

Figure 4 critcal angle (f) and frequency relation

Figure 4 is meant to demonstrate that a region of ionization will “refract” signals of varying
frequencies differently. A higher frequency may be unaffected, while lower frequencies are more
and more impacted. In the example, the 60 MHz frequency is the highest frequency (MUF) that is
getting refracted back to the Earth. The critical angle for a 60 MHz signal is represented by f. A
lower frequency, say, 30 MHz, would be refracted at an even smaller angle, resulting in a smaller
critical angle than the 60 MHz signal.
At even lower frequencies, the critical angle might be 90°, meaning a signal sent straight up is
reflected back down. The highest frequency at which a vertically incident wave is reflected back
to the transmission point is known as the critical frequency (fo). Formally defined, critical
frequency is the frequency capable of penetration just to the layer of maximum ionization with a
vertically incident wave. Radio waves of lower frequencies are refracted back to the ground, and
those at higher frequencies pass through.

Since both critical frequency and critical angle are functions of ionization density, relations can be
modeled mathematically. If you know what the MUF is, you can calculate what the critical angle
or critical frequency is. Similarly, if you know either the critical angle or critical frequency, you can
calculate the MUF.

It is important to note that the models for calculating MUF and critical frequency are more reliable
for other types of propagation than Es. Generally, the “secant law” is used to make these
calculations, but under some conditions can underestimate or overestimate MUF for Es.
For a moment, if we assume that the model holds true, we can plot the relation between critical
frequency and MUF. This is demonstrated in Figure 5.

Figure 5 Critical Frequency and MUF

Figure 5 shows a linear relation between MUF and fo. This is derived from two common formulas:

N represents the electron density in e/m3. Observations have shown that Es does NOT have a
totally linear relation as the above formulas would indicate. Despite this, this discussion is
important to understand the principles involved.

Why is any of this useful, anyway? Critical frequency measurements are recorded by ionosondes
– devices that transmit a spectrum of waves straight up, and determine the height and strength of
the reflection, and determine the critical frequency. Many observatories and research centers
continuously monitor the ionosphere, and some even post the results near real-time on the

2.3 Cloud Movement
Within the ionosphere at the E region and below, strong currents exist. After the formation of an
ionized cloud, these currents move the cloud, usually to the west or northwest. Just as weather
patterns generally move in one direction (west to east) localized events can and do cause
weather to occasionally stagnate or even move in the opposite direction. Similarly, sporadic-E
clouds can move in any direction on occasion – especially north and south (and less likely to the

The velocity of these clouds has been measured in a variety of ways. These include the use of
Doppler shifts and VHF oblique propagation. The result varies between 20-130 m/s (110+ mph).
Higher velocities are also thought to exist.
Calculation of the velocity of clouds through the use of VHF oblique propagation is slightly less
scientific, but a process that anyone observing an Es opening can use. The process revolves
around plotting the location of the cloud by identifying the transmitting and receiving locations. A
line is drawn between the two points, and the midpoint identified. The midpoint is the
approximate location of the ionized area. Several data points are necessary, and a long period of
time required to make this approximation. Possible caveats to this method include irregular
shaped clouds and the existence of multiple clouds of ionization confusing the location.
Measuring Doppler shifts requires the use of highly technical (and expensive) equipment. In spite
of this, errors in this method exist as well. The part of the cloud reflecting the wave may have a

different velocity than the cloud as a whole. A strong analogy is that of a balloon. A balloon may
be moving in one direction, but the molecules inside are moving in random directions.

2.4 Daily Variation
It has long been known that Es doesn’t simply occur “during the day”. It is known that ionization
levels throughout the ionosphere tend to have two peaks, centered on either side of noon. Es
occurrence seems to follow a similar trend.

Figure 6 is a graph of the occurrence of Es during summer months. As can be seen, the summer
peak is in the morning (0700-1200) and a secondary peak occurs 2000-2200. This graph comes
from White Sands, NM over a 7 year period. It is important to note that the White Sands data
seemed more “skewed” towards the morning peak than similar measurements taken in other midlatitude locations. However, all indicated a slightly stronger likelihood of Es in the morning than in the afternoon/evening.

Figure 6 Percentage of time Es exceeds FoEs of 5 MHz, from White Sands, NM 1948-1954

Figure 6 was obtained from A survey of the present knowledge of sporadic-E ionization, JA
Thomas and EK Smith, Journal of Atmospheric and Terrestrial Physics Vol 13.
Remember that despite the apparent greater likelihood of Es in the morning hours, this data was
collected over a period of years. This diurnal characteristic is much less noticeable in the day to
day casual observation of DX’ers. And don’t turn the radio off after dark! Many still remember an
opening that occurred after midnight on June 19, 1992, resulting in MUF’s of 144 MHz+.
Additionally, during the winter peak (discussed in the next section), Es is most common just after

2.5 Monthly Variation
In observing Es on a larger time scale, it is well documented that Es occurs most often in the
summer, with a secondary peak in the winter. These peaks are centered very close to the
solstices. The summer peak can be characterized by probability of occurrence being 5 to 8 times
that of winter. The use of the descriptors “summer” and “winter” is intentional, as the peak in the
Southern Hemisphere is in it’s summer months, which is the Northern Hemisphere’s winter.
Similar to the diurnal characteristics discussed in the previous sections, year to year observations
will not always demonstrate the “normal” behavior. Some years have occurrences common in
“off peak” months, such as October and February. Other years peak early or late.
2.6 Annual Comparison

Patrick Dyer, WA5IYX and Emil Pocock, W3EP, have shown that there seems to be a pattern to
the quantity of Es observed each year.8 These observations come from use of his records over
the 11 year period in which Dyer consistently monitored the FM band. He noted a potential 4 to 6
years cycle.

Ken Neubeck, WB2AMU, proposed that this potential sub-cycle of Es is related to the latitudinal
location of sunspots on the sun.9 During the approximately 11 year solar cycle, not only do the
quantity of sunspots change, but the location of sunspot groupings also changes. Beginning at
the solar minimum, sunspots are primarily located at about 30° latitude on both sides of the solar
equator. As the cycle progresses, the locations of the spots slowly converge to the solar equator.
At the end of the cycle, a transitional period occurs where spot groupings may exist at both 5°
and 30°.

8 See P.J. Dyer and E. Pocock, “Eleven Years of Sporadic E”, QST, March 1992, pp 23-28

9 See K. Neubeck, “Sporadic-E and Auroral Propagation”, World Radio, March 1993 pp 19-28

Neubeck believes that during these transition periods, Es peaks will be diminished, and there will
be more occurrences of Es during abnormal months. The end result being less Es than normal
for the year.
I would hesitate to start to draw conclusions based on an 11 year study – which would only
constitute 2 Es cycles, if in fact they exist. Neubeck’s theory has been largely discarded as a
“casual observation” rather than something to pursue in the scientific community, due to lack of
long-term data, a concrete scientific explanation of how sunspot location would impact Es, and
lack of scientific data or loose correlation of sunspot latitude to any cycles of ionization on Earth.

2.7 Sunspot Cycle
By overlaying a graph of the 2800 MHz solar flux (a measure of solar radiation intensity), Dyer’s
graph showed no correlation to the solar flux. This is opposite of normal F region propagation,
where the quantity and intensity of propagation at higher frequencies is directly related to the
amount of sunspots.

Sunspots appear as dark spots on the sun’s surface, and are relatively cool in temperature. They
can range from 750 km in diameter to tens of thousands. The important aspect of a sunspot with
regards to propagation is the area that surrounds the spot. These areas have much increased
radiation. If many spots exist on the sun, the total radiation emitted increases substantially,
leading to higher ionization levels on earth, which improves F region and normal E region
propagation. However, it does not appear that this impacts Es directly.

2.8 Worldwide Occurrence
As already mentioned, the Es season is reversed in the southern hemisphere. Also, the amount
of time Es occurs is not constant through common latitudes. Generally, Es is more common in
the temperate latitudes closer to the tropics. Many amateurs in the USA have made the common
observation that Florida and Mexico seem to be the most common “pests” in Es DX’ing.
However, even “southern latitude” generalization is not 100% accurate. Long-term studies have
indicated a large increase in occurrence near Japan.10


3.1 Introduction
For decades, professionals and amateurs alike have been baffled by the cause of Es. Even the
intense study during the IGY11, the advent of rocket exploration of the ionosphere, ionosonde
deployment, and other technological advances have only brought up more questions than they
have answered. Because of the extreme difficulty encountered by scientists in isolating the
mechanism which causes Es, it is fairly apparent that it must be a complicated series of events,
requiring the right “ingredients” for the final product of Es to result.
Some of the following possible mechanisms have been touched on already. Of course, ionization
by the sun’s ionization is likely a base “ingredient” as well.

3.2 Ionospheric Wind Shear
The wind shear theory of sporadic-E formation is generally credited to J.D. Whitehead of the
University of Queensland, Australia. The basic theory is based on the east-west winds in the E
region. These winds are caused by gravity waves, and can result in vertical movement. Vertical
shears can compress ions into a thin layer, resulting in high density ionization. This effect seems
to particularly apply to the metallic ions of Fe+ (Iron) and Mg+ (Magnesium). This is because the
recombination rate of these ions is greater than other molecular ions, allowing them to remain
charged (ionized) long enough to be pooled together into highly dense thin sheets.
The theory identifies a relation between the horizontal component of the Earth’s magnetic field as
impacting the probability as to whether Es will form under shearing conditions.
The shearing effects in the E region are well documents. Additionally, many experiments on
horizontal winds and electron density have given support to this theory with respect to midlatitude

The theory does not explain other types of Es as well as it does mid-latitude Es. However, this is
not of much concern to DX’ers, as we primarily observe the “true” Es type that occurs in the midlatitudes.

10 EK Smith, “Temperate Zone Sporadic E Maps (foEs > 7 MHz),” Radio Science, Vol 13 (1978), pp 571-575

11 The IGY was the International Geophysical Year. Solar Cycle 19, peaking in the late 1950’s, was the largest cycle on record. Scientists, in anticipation of a high intensity peak, declared the peak year the IGY.
This was done to raise awareness within the scientific community, and led to intense study of solarterrestrial relations. No other time period has brought such significant advances in the study of radio wave propagation.

The windshear theory, when combined with tidal winds, is widely regarded as an accurate and
plausible explanation of Es. A 1998 review of the theory by JD Mathews (Journal of Atmospheric
and Terrestrial Physics, Vol 60, pp 413-435) has once again reaffirmed the theory.

3.3 Thunderstorms and Associated Phenomena
The possible correlation of Es to thunderstorms is a theory that refuses to die. This theory can be
traced as far back as the 1920’s. In 1933, Naismith and Appleton had some success in finding a
correlation. These scientists are well known for their ground breaking ionospheric study and
documentation, so the possible correlation was not taken lightly. However, in 1938 they
concluded that the results from 1933 might have been inaccurate. The theory was rejuvenated in
the 1950’s when a study in India showed a possible correlation to squall-line thunderstorms (but
not super-cells).

No studies intending to link thunderstorms to sporadic-E have resulted in conclusive data. For
years, the scientific community doubted any possible relation, given the simple fact that
thunderstorms occur in the troposphere (0-14 km altitude), and Es occurs at 100 km. In between
the troposphere and the ionosphere’s E region exist invisible barriers where the medium of the
atmosphere radically changes. These transition zones, named the tropopause and stratopause,
prevent certain interactions between layers from occurring due to the change atomic content,
wind, temperature, and other attributes.

Additionally, thunderstorms are generally localized events. On the other hand, Es “outbreaks”
frequently occur, in which Es clouds are reported over large portions of the planet. As much
as1/6 of the Earth may be within line of site of an Es cloud capable of foEs > 6 MHz during these
outbreaks. Similarly, long term observations of data collected from ionosondes also don’t
indicate a correlation between thunderstorm frequency and Es frequency.

The thunderstorm correlation theory primarily hangs on in amateur circles. Ionospheric
researchers quickly point to the fact that the diurnal, monthly, and yearly characteristics of
thunderstorms do not match sporadic-E closely at all. Similarly, the worldwide distribution of Es
does not match that of thunderstorms.

But, as with most areas of sporadic-E, the analysis is not that simple. In recent years, it has been
discovered that a higher level of interaction does occur between lower and upper layers of the
earth’s atmosphere. In fact, one aspect has been reported and well documented in mainstream
media – sprites and blue jets (sometimes referred to as upward lightning).

Red sprites are optical phenomenon that occurs directly above a thunderstorm, associated with
it’s lightning. They can extend to about 90-95 km altitude – right to the E region, but not into the
E region. The duration of a sprite is only 3-10 milliseconds, as measured by high-speed
photometers. Sprites are rarely visible to the human eye. It is estimated that sprites occur in
conjunction with less than 1% of lightning strokes in a thunderstorm. The true mechanism of a
sprite is not known.

Blue Jets are similarly related to thunderstorms, and are only visible with special television
systems. Blue Jets only reach altitudes of 45-50 km, and emanate from the tops of
“thunderheads” in a cone shape.

The discovery of sprites and blue jets in the early 1990’s shows that there may be many more
undiscovered interactions between activities in the troposphere and stratosphere (and the

Supporting these possibilities was the discovery of Elves and TIPPs – Trans-Ionospheric Pulse
Pairs. Elves (Emission of Light and Very Low Frequency perturbations due to EMP Sources)
appear like a halo in the lower ionosphere, and propagate downwards. They seem to precede

It appears that TIPP’s source is a positive bipolar breakdown – an event associated with
thunderstorms. The impact of TIPPs on the ionosphere’s ionization density and ability to
propagate radio waves is not clear.
All of these newly discovered interactions have renewed focus on the effects of weather in the
ionosphere. To date, no direct or indirect correlation between these events and Es has been

3.4 Other Weather
J.D. Whitehead’s research concluded that according to the wind shear theory, gravity waves
associated with tropospheric weather might have some influence on Es. The late Mel Wilson,
W2BOC, believed that weather could play an important role in the development of Es.12 He
stated that “birthplaces” of Es clouds were often associated with fronts or low pressure systems,
and could produce a series of clouds. His study primarily focuses on the theory that whatever the
catalyst at the birthplace is, it creates a series of clouds that generally move to the northwest.
Not much evidence of weather being the catalyst is provided in his study.

12 Midlatitude Intense Sporadic-E Propagation, QST, December 1970

3.5 Meteor and Cometary Origin
Theory suggests that meteors should play some role in the formation of Es, though likely very
indirect. Many of the ions found by rocket investigation of the E region, and Es formations, have
meteoric origin. As mentioned before, metallic ions appear to be a necessary component, due to
their slower recombination rates. Meteors are a major source of these metallic ions.
Studies have investigated the occurrence of random meteors and total meteors for correlations to
Es. Random meteors, which occur in great numbers every day of the year, have a marked
increase in the June-August period. Investigation of this in closer details reveals the peak is
several weeks after the Es peak in the Northern hemisphere. Additionally, there is no secondary
peak of meteors in the northern hemisphere winter months, as there is with Es. This simple
analysis quickly discounts a meteor-related Es catalyst or mechanism.

In relatively recent studies, a proposal of a cometary origin of Es has come to light.13 Dr. G. Neil
Spokes, amateur radio operator and amateur astronomer, built this theory around data collected
in other studies. The 11-year study of Es at 88 MHz by Pat Dyer and Emil Pocock (referenced
earlier in this article) showed that some dates seemed more favorable for Es. The logical
conclusion that Dr. Spokes suggested for a phenomenon that strictly follows the calendar was an
astronomical one.

Dr. Spokes proposes that gases or tiny particles associated with comet paths were the cause.
This was not such a large leap in thought, as it is already known that comets leave debris in their
paths around the sun. When the earth encounters this debris, meteor showers result.
Unfortunately, the data from the Dyer/Pocock study does not easily identify periods of time when
auroral activity14 may have prevented Es observation, or provide for an offset for our periodic
calendar adjustments. This could account for small changes in the data, lessening (or increasing)
the appearance of year-to-year daily correlations.

As it stands, mathematical studies using random number generators skewed towards a late June
peak provide similar results as the data collected. This isn’t to say that there is absolutely no
chance that there is an astronomical relation – it just shows that “only” 11 years of data is tough
to use as a basis for building an astronomically-based theory.

3.6 Geomagnetic Activity
Correlation between auroral activity and auroral zone Es has been proven to exist, but no
correlation has been shown for temperate zone (mid-latitude) Es. Many of these studies make
use of the planetary A and K indices (24 and 3 hour measures of auroral activity). As previously
mentioned, the A index is difficult to accurately use, since it is a measure of activity over the last
24 hours, and thus, significant activity that occurred several hours ago and “inflate” the result of
the A index. The A index is often not reflective of current conditions.
And unfortunately, the studies which utilized the K index as comparative data over-simplified the
data by either concluding that an index of “2” or greater constituted disturbed conditions (4 would
have been more accurate), or by using only 2 or 3 K index data points from a given 24 hour

The area of geomagnetic activity and its effect on mid-latitude Es (whether as a catalyst or
inhibitor) is an area in need of a long term conclusive study.
Again, a correlation has been shown to exist for high-latitude Es and auroral activity. During very
intense geomagnetic storms, not only can auroral propagation/scatter occur, but Es-like
propagation can occur within the auroral zone. This type of Es is discussed in more detail in the
Section 4.

4.1 Introduction
As was touched on earlier, there have been slight variations in Es characteristics that have lead
to multiple classifications of Es. These characteristics primarily include the latitude they occur at,
height of ionization, and other observed relations.
During the IGY, a standard was developed to further describe these types of Es. Each type of Es
has a lower-case letter designator. These designators are rarely seen in today’s studies, as the
bulk of them deal with just the mid-latitude/temperate zone Es. For this reason, the primary intent
of this section is to demonstrate that not even all Es is the same, further complicating the study of

13 Technical Correspondence, QST, April 1993
14 The Dyer/Pocock study reveals no correlation between Es and the A index, a 24 hour measure of auroral activity. This does not mean that auroral activity does not inhibit mid-latitude Es, as the A index is, by its nature, a lagging indicator and often not reflective of real-time conditions.

15 See Neubeck, World Radio March 1993
These classifications and their characteristics are described in great detail in E.K. Smith’s book,
referenced earlier in this text.
4.2 Temperate (Mid-Latitude)
Temperate zone Es is the type that we in the United States, Europe, and other temperate zone
latitudes are most familiar with. This is the type of Es that this paper primarily deals with.
Four types of Es exist in the temperate zones. They are Type h (high), c (cusp), l (low) and f
(flat). Type h and c are often grouped together into a category called ”sequential” Es. It
originates at higher E region altitudes (140+km) and as it intensifies, works its way downward to
100 km.

Type f is a classification for nighttime Es, as a requirement is that no “regular” E region can be
present. Height of the ionization stay the same with increased ionosonde frequency, producing
an ionogram with a flat-line.

Type l is a daytime-only classification.

4.3 Equatorial Es
The equatorial region is defined as the area of the earth within 10 degrees of the geomagnetic
equator (not the geographic one). Type s (slant) and q (equatorial, or fringe) occur within this

Type q is the most common, as has a high correlation with the equatorial electrojet. The
correlation is so high that it really isn’t even a “sporadic” phenomenon.
Type s can occur at both the auroral and equatorial latitudes.

4.4 Auroral
Type classifications a (auroral), f (flat), r (retardation) and s (slant) occur in this zone.
Type a is commonly called “auroral-E” or “AE” in amateur radio circles. This type of Es has a
direct relation with geomagnetic disturbances, and often occurs in conjunction with auroral
scatter. The birthplace of type a Es is always within the auroral curtain. Since the auroral curtain
can extend well into the mid-latitudes during severe geomagnetic storms, this type of Es can
occur within the mid-latitudes. However, MUF’s rarely exceed 88 MHz from this Es.
Type f in the auroral latitudes varies very little from type a. Type r’s differentiating characteristic is
a thicker ionization area.

4.5 Type n Es
For completeness, we must discuss type n Es. Type n was set aside in the IGY system as a
catch-all for any Es that didn’t fit the above categories.

4.6 Backscatter
Es backscatter is not well understood, and little scientific study of the phenomenon as it applies to
us as DX’ers has been done. Backscatter generally propagates signals from 300-1100 km with a
characteristic multipath flutter. In some cases, an antenna bearing for reception is offset from the
great-circle bearing to the transmitter.

Unfortunately, backscatter sounds similar to tropospheric scatter, and has been reported to last
for 30 seconds to a few minutes, just like tropospheric scatter. Amateurs have reported that
backscatter generally only impacts a very small range of frequencies, where tropospheric scatter
will often affect a larger range, such as the entire FM band (88-108 MHz). I personally have
never heard a backscatter signal that I am aware of, so cannot speak from experience on the


5.1 Two Cloud Formations
Many times, Es openings provide higher MUF’s than what we’d expect through theoretical
calculations. Sometimes, actual MUF’s are as much as twice the value theory would indicate.
This could perhaps be attributed to a two-cloud formation (not to be confused with double hop).
Figure 7 demonstrates a possible scenario.

Figure 7 The Proposed Two-Cloud Es Formation

A two-cloud formation for Es would be somewhat analogous to what can happen with transequatorial
F region propagation. The closer cloud begins the refraction process, and the second cloud finishes the process by refracting the signal back to earth.

It has been proposed that this scenario may exist much more often than thought. As mentioned
earlier, it would not take as dense of ionization to propagated higher frequencies. Thus, many
receptions in the 1000-1400 mile range could be by the process. Additionally, it could be
responsible for those occasional long receptions of 1450 miles or greater.
During intense sporadic-E openings, it is well documented that a widespread elevation of
ionization occurs, and a greater number of strong to intense clouds also exist. This leads some
credence to the thought.

5.2 Cloud Shapes and Tilts
Es ionization may not necessarily form in a thin sheet parallel to the ground. Some studies have
indicated the Es ionization is sometimes tilted, as much as 10°, with respect to the ground.
Additionally, J.D. Whitehead’s work of 1978 on the shape of Es ionization indicates that odd
shapes even form – frequently concave on the underside.
The implication of this is that again, errors can be injected into some of the theoretical modeling
of Es, and identification of midpoints. Additionally, ionosonde data can be misleading. Since
ionosondes rely on reflection of vertically incident waves, tilted clouds could result in a signal not
being reflected, despite ionization being more than adequate.

In some respects, many advances have been made over the last 30 years in the study of
sporadic-E. We have a better understanding of the composition of the ionosphere and Es
ionization itself. Interactions between the ionosphere and weather are beginning to be
discovered and understood. The wind-shear theory has withstood years of validation and tests.
However, in most ways practical to DX'ers, little has been accomplished since the characteristics
of Es were first documented in the late 1950's.

And one question still stands: Would DX'ers lose more than they gain by being able to predict

Comments may be sent to
Grayer, G.H., Sporadic E and 50 MHz Transatlantic Propagation During 1987, Ham Radio, 10-35, July, 1988
Mathews, J.D., Sporadic E: current views and recent progress, Journal of Atmospheric and Solar-Terrestrial Physics, 60, 413-435, 1998
Neubeck, Ken, Sporadic-E and aurora propagation, Worldradio, 19-28, March 1993
Pocock, E and Dyer, P.J., Eleven Years of Sporadic E, QST, 23-28, March 1992
Smith, E.K., Worldwide Occurrence of Sporadic E, National Bureau of Standards Circular 582, 1957
Smith, E.K., Temperate zone sporadic-E maps (foEs > 7 MHz), Radio Science, 13, 571-575, 1978
Spokes, G.N., Technical Correspondence: Sporadic E Causes, QST, April 1993
Thomas, J.A. and Smith, E.K., A survey of the present knowledge of sporadic-E ionization, Journal of Atmospheric and Terrestrial Physics, 13, 295-314, 1959
Whitehead, J.D., The formation of the sporadic-E layer in the temperate zones, Journal of Atmospheric and Terrestrial Physics, 20, 49-58, 1961
Whitehead, J.D., Difficulty Associated with Wind-Shear Theory of Sporadic E, Journal of Geophysical Research, 76, 3127-3135, 1971
Whitehead, J.D., On the peculiar shape of sporadic-E clouds, Journal of Atmospheric and Terrestrial
Physics, 40, 1025-1028, 1978
Whitehead, J.D., Recent work on mid-latitude and equatorial sporadic-E, Journal of Atmospheric and
Terrestrial Physics, 51, 401-424, 1989
Wilson, M., Midlatitude Intense Sporadic-E Propagation, QST, December 1970 and March 1971

Tim M0BEW.

Wednesday, 27 June 2018

25/06/2018 50MHz FT8 Activity from PSKR M0BEW

25/06/2018 50MHz FT8 Activity from PSKR M0BEW.

Overall M0BEW heard.

Overall heard Europe.

Scandinavian Es.

UK Activity heard.

Iceland TF flurry.


Tim M0BEW.

24/06/2018 50MHz FT8 Activity from PSKR M0BEW

24/06/2018 50MHz FT8 Activity from PSKR M0BEW.

Overall activity.

Europe heard.

Asia heard.

West Africa heard.

East coast opening 1.

East coast opening 2. 

Overall M0BEW heard.


Tim M0BEW.

Friday, 22 June 2018

19/06/2018 50MHz FT8 Activity from PSKR M0BEW

19/06/2018 50MHz FT8 Activity from PSKR M0BEW .

Overall heard.

UK activity heard.

Europe wide heard.

Middle East.


Tim M0BEW.

50MHz Trophy Contest 2018 M0BEW

50MHz Trophy Contest 2018 M0BEW.

Contest         : IARU R1 6M CONTEST
Callsign        : M0BEW
Mode            : MIXED
Category        : Single operator
Overlay         : ---
Band(s)         : 50
Class           : Low
Grid square     : IO82RJ
Operating time  : 04h 29m

   50  60   3 20310 339  20566
TOTAL  60   3 20310 339  20566
      FINAL SCORE: 20 566

Got on a bit here and there when had a free moments.
Software not scoring.
CW could be really intresting on this band if the activity was there.
Band seemed fairly OK. There were qsos to be had via Es if you looked for them.
My simple 6m system doesn't punch much weight to run successfully.

Tim M0BEW.

18/06/2018 50MHz FT8 Activity from PSKR M0BEW

18/06/2018 50MHz FT8 Activity from PSKR M0BEW.

 Overall Heard.

Europewide heard.

M0BEW heard.

West Africa heard.

Middle East heard.

Europe heard.

UK activity.


Tim M0BEW.

Thursday, 21 June 2018

RBN Data CQ WPX CW 2018 M0BEW Day 2 80m

RBN Data CQ WPX CW 2018 M0BEW Day 2 80m.


Tim M0BEW.