Transcript Are We Headed Toward Another Maunder Minimum? And What

A Long Overdue Review of
Gray Line Propagation on the
Low Bands
Carl Luetzelschwab K9LA
e-mail: [email protected]
web site: http://k9la.us
WWROF Webinar - Sept 2014 - K9LA
Thanks to WWROF
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Topics
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Quick status of Cycle 24
Origin of ‘gray line’ propagation
Some confusion with gray line
Common explanation for gray line propagation
Doubts about the explanation
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YB1A QSO on 40m vs IONCAP
Topband reflector comment
3Y0X DXpedition QSOs to JA on 160m
Ray tracing software
The ionization process
What I think is really happening
This presentation challenges some long-held beliefs
And it gets into physics deeper than usual
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Cycle 24 - Where We Are
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We’re in the second peak of Cycle 24
Contesting on the higher bands should be good this fall
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Disappearing Sunspots
original
data
updated data: end of 2013
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This is what I presented in my “Maunder Minimum” webinar
in April 2014
Updated data at that time was only through end of 2013
WWROF Webinar - Sept 2014 - K9LA
maximum smoothed sunspot
number
Latest Data
250
200
150
100
50
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
solar cycle number
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Latest data shows the magnetic field strength has leveled off
This suggests we aren’t headed for a Maunder-type Minimum
It may just be a period of small cycles as seen before
WWROF Webinar - Sept 2014 - K9LA
First Known Mention of Gray line
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Article by K6UA and W6NLZ,
with editing by K6SSS
CQ magazine, Sept 1975
Worked mostly EU, AF and
Mideast via long path on
80m SSB
At morning sunrise and
evening sunset
from article: gray line is “long path
opening that exists between two points
on the Earth which are experiencing
simultaneous sunrise and sunset”
WWROF Webinar - Sept 2014 - K9LA
Example from CQ Article
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W6NLZ to OJ0AM
January 28, 1974
1457 UTC
• W6 sunrise
• OJ0 sunset
Long path over
Antarctica and up
across eastern Africa
and the Mideast
thanks W6ELProp
from article: “signals travel along the edge of the
band or ring of twilight encircling the Earth”
WWROF Webinar - Sept 2014 - K9LA
this may
be a
problem
Some Confusion
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Sometimes the term
‘gray line’ has been
used for a
sunrise/sunset
enhancement path
I subscribe to gray
line = follows the
terminator
Sunrise/sunset
enhancement is on a
path going away
from the terminator
thanks W6ELProp
• perpendicular is best
K9LA to STØRY, March 28 (2003), 0330 UTC,
160m, signal well out of noise from 0320-0340
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Sunrise/Sunset Enhancement
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Believed to be due
to ducting in the
electron density
valley above the E
region peak in the
dark ionosphere
Valley not well
developed along the
terminator
Pretty much nonexistent in the
daytime ionosphere
WWROF Webinar - Sept 2014 - K9LA
valley in
the dark
ionosphere
ray trace
in the dark
ionosphere
showing
ducting
Comparison
thanks W6ELProp
this is gray line
thanks W6ELProp
this is NOT gray line
WWROF Webinar - Sept 2014 - K9LA
Explanation of Gray Line
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The explanation is rooted in the concept
that before sunrise the F2 region is
formed prior to the D region
Similarly, after sunset the D region goes
away prior to the F2 region going away
Thus there’s a band along the terminator
of F region ionization without D region
ionization (low or no absorption)
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How Does This Happen?
Using spherical geometry, we can work out how long before
sunrise an ionospheric height becomes illuminated by the Sun
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And the Results Are . . .
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Top image: Earthionosphere system 69
minutes before K9LA
sunrise
Middle image: Earthionosphere system 35
minutes before K9LA
sunrise
Bottom image: Earthionosphere system at
K9LA sunrise
Thus the F2 region of the
ionosphere is illuminated
34 minutes before the D
region is illuminated
WWROF Webinar - Sept 2014 - K9LA
The Present Explanation
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Gray line propagation allegedly happens
because:
• Before sunrise there’s an F2 region but no D region
• After sunset there’s an F2 region but no D region
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This occurs all along the terminator
In my mind, several doubts have crept in
over the years . . . .
WWROF Webinar - Sept 2014 - K9LA
Doubt #1 - YB1A on 40m CW
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December 3, 2002 at 2231
UTC (my sunset)
thanks W6ELProp
• YB1A was S8 = -78 dBm on
my calibrated S-meter
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My inv-vee can’t tell if it was
short path or long path
Most experienced DXers
would say it was long path
Long path
• 153 degrees, 24,467 km
• -180 dBm predicted by
IONCAP assuming YB1A at 1
kW and +3 dBi antennas
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Short path
• 333 degrees, 15,565 km
• -130 dBm predicted
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Even assuming short path, is
IONCAP off by 52 dB?
WWROF Webinar - Sept 2014 - K9LA
Doubt #2 - Topband Reflector
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I posted a message to the topband reflector in early
April 2005
It commented on the F2 region forming before the D
region as sunrise approached
Mike K1MK responded personally with an interesting
comment:
“While illumination by visible light to which the
atmosphere is transparent will start prior to groundlevel sunrise and continue after ground-level sunset,
direct solar ionizing flux would be expected to appear
and disappear at all altitudes simultaneously with
ground-level sunrise/sunset.”
WWROF Webinar - Sept 2014 - K9LA
Doubt #3 – 3Y0X
thanks W6ELProp
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0210 UTC
thanks W6ELProp
0901 UTC
February 2006 DXpedition to Peter I
On 160-Meters they worked 764 US stations between
0210 UTC and 0901 UTC
• Note that the paths get away from the terminator
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Doubt #3 continued – 3Y0X
thanks W6ELProp
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Nice gray line to JA via short
path at 15,263 km
IONCAP says MUF okay but
absorption prohibitive on 160m
QSOs – 1 JA during the entire
DXpedition
If gray line via long path is so
efficient, why isn’t short path?
I’ve never seen a report of
fantastic short path gray line
• G0KYA monitored VP8NO in
November 2002 on 40m
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3-6 dB average enhancement
30 minutes before mutual
sunrise – why not the entire
gray line period?
Is propagation along the terminator
efficient as is commonly believed?
WWROF Webinar - Sept 2014 - K9LA
Comments About Absorption
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At HF, absorption is proportional to electron
density times collision frequency (Davies, 1990)
• Electron density increases as altitude increases
• Collision frequency decreases as altitude increases
electron density
collision frequency
altitude ->
• Expect a maximum in absorption where they intersect
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Absorption occurs in the D region during the day
Absorption occurs in the lower E region at night
WWROF Webinar - Sept 2014 - K9LA
Comments About Absorption
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Absorption does not go to zero in the dark
ionosphere on 160m
On 160m at night, there’s still about 10 dB
of absorption per hop
• This limits multi-hop to about 10,000 km with
1000 W into +0 dBi antennas assuming external
noise limits sensitivity (not your receiver)
• This is why ducting is likely for the longer paths
on 160m
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Ionospheric text books give an equation for
absorption that is tied to the solar zenith
angle
• Nice smooth function, but probably doesn’t
represent the real-world around sunrise and
sunset
WWROF Webinar - Sept 2014 - K9LA
The Problem
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Is the explanation of gray line
propagation correct?
• RF follows the terminator where there’s
an advantageous band of ionization
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Or is our model of the ionosphere
correct?
• Propagation along the terminator is not
efficient
• Something else is going on
WWROF Webinar - Sept 2014 - K9LA
Who’s Right and Who’s Wrong?
from slide 5
from article: “signals travel along the edge of
the band or ring of twilight encircling the Earth”
atmosphere here
and here
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WWROF Webinar - Sept 2014 - K9LA
I believe
this is a
problem
The figure
assumes that
ionizing radiation
can go thru the
atmosphere
TWICE to ionize
the F2 region in
the dark
ionosphere
Let’s look at the
ionization
process
It’s All About Energy
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More than 50% of the F2 region is due to EUV (extreme
ultraviolet) radiation at wavelengths between 26 and 34 nm
• Ionizes atomic oxygen
• We’ll use 30 nm for the following analysis
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From Planck’s Law, the energy of one photon at 30 nm is
41 eV
The ionization potential of atomic oxygen is 13.6 eV, but an
ionization efficiency issue results in needing about 34 eV to
create an electron-ion pair
Important - One photon at 30 nm creates one free electron
for the F2 region
After that its energy is too low to do any more ionization
Thus the F2 region ionizing radiation can’t even get thru the
atmosphere ONCE
• This is why we can’t measure EUV at ground level
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What About the D Region?
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There are two sources of ionizing radiation for the
D region
• 0.1-1.0 nm that ionizes all atmospheric species at D
region altitudes
• 121.5 nm that ionizes nitric oxide (NO) at D region
altitudes
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The same conclusion results as for the F2 region
The energy of the ionizing radiation is used up
before it gets to ground level
Just like the F2 region, the D region ionizing
radiation can’t get thru the atmosphere ONCE
• This is why we can’t measure D region ionizing radiation
at ground level
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Measuring Ionizing Radiation
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Prior to World War II, we couldn’t
measure ionizing radiation
• It does not get through the atmosphere
to the ground
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We had to wait for rocket flights and
eventually satellites
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“Illumination”
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Yes, before sunrise the F2 region and D region
are illuminated by the Sun
This illumination is by visible light
Visible light has nothing to do with the ionization
process
Photons of visible light (400-700 nm) have an
energy of around 2 to 3 eV
• Visible light couldn’t ionize its way out of a paper bag 
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That’s why visible light gets thru the atmosphere
unimpeded – it does not do any ionization
• Just like 10.7 cm solar flux
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When Does the F2 Region Ionize?
Around sunrise - just like K1MK said
WWROF Webinar - Sept 2014 - K9LA
When Does the D Region Ionize?
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sunrise at 0602 local
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Electron density
over Arecibo from
incoherent
scatter radar
Local sunrise at
0602 (AST)
Look at D region
altitude of 80 km
Around sunrise - just like K1MK said
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Why Sunrise?
h = 300km
(F 2 reg ion)
g round s unris e
S un
Ea
rth
Sunrise is when
photons can get
to the
ionospheric
regions without
having to plow
through the
atmosphere
twice
WWROF Webinar - Sept 2014 - K9LA
Another Interim Summary
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I’m very confident that the explanation of gray
line on the low bands is incorrect
This conclusion is based on an
propagation
understanding of the ionization
along the
process and absorption
terminator is
The ionospheric regions begin
efficient
ionizing around sunrise, not way
earlier
“Around” sunrise = variability
• Ozone layer can block ionizing radiation
• Ionosondes do not have pencil-thin beams - can
receive off-zenith reflections
• Dayside E region plasma can move horizontally
into the dark ionosphere via advection
• Photons can scatter into the dark atmosphere
WWROF Webinar - Sept 2014 - K9LA
What’s Really Happening?
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Just saying the current explanation is
incorrect isn’t enough
An alternative explanation needs to be
presented
• It has to mesh observations and physics
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The clue is in the quote from the CQ article
that was cited on slide 4
from article: gray line is “long path opening that exists
between two points on the Earth which are experiencing
simultaneous sunrise and sunset”
WWROF Webinar - Sept 2014 - K9LA
W6NLZ to OJ0AM Map - Again
thanks W6ELProp
W6NLZ
OJ0AM
Gray line is “long path opening
that exists between two points on
the Earth which are experiencing
simultaneous sunrise and sunset”
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What else happens
when W6NLZ and
OJ0AM experience
simultaneous sunrise
and sunset?
There is a dark
ionosphere in between
W6NLZ and OJ0AM
WWROF Webinar - Sept 2014 - K9LA
Possible Path – With a Problem
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Absorption is least in the
dark ionosphere
The RF must take a short
cut across the dark
ionosphere – the white
path
But RF follows a great
circle path unless
refracted, reflected or
scattered
The path in white that I
drew isn’t a great circle
path – it’s just a sketch to
show the idea
thanks W6ELProp
W6NLZ
• There are only two great
circle paths between
W6NLZ and OJ0AM
WWROF Webinar - Sept 2014 - K9LA
OJ0AM
The Solution – A Skewed Path
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Observations by those with directional antennas
have resulted in the following two axioms
• Listen south-southwest at your sunrise
• Listen south-southeast at your sunset
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Thus the path is more “along the terminator”
than “at right angles to the terminator”
It has to be far enough away from the terminator
when it encounters the ionosphere on the first
hop so that
• Absorption is minimum
• The ducting mechanism is available
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Need to look at great circle paths out of both
W6NLZ and OJ0AM
WWROF Webinar - Sept 2014 - K9LA
Great Circle Paths from W6NLZ
Great circle paths
out of W6NLZ in
10 degree
increments
WWROF Webinar - Sept 2014 - K9LA
Great Circle Paths from OJ0AM
Great circle paths
out of OJ0AM in
10 degree
increments
What we’re looking for:
1. Great circle paths out of W6NLZ and OJ0AM that get away
from the terminator – use 3Y0X as a guideline
2. Where these great circle path intersect
WWROF Webinar - Sept 2014 - K9LA
Putting It All Together
terminator (black)
night
great circle path (red)
day
night
skew area
alternative paths (green)
WWROF Webinar - Sept 2014 - K9LA
Possibilities for the Skew
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Ionospheric origin
• Normal ionosphere – E region or F2 region
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Example: FT5ZM on 10-Meters
• Practical Propagation column in CQ Plus for July 2014
• Electron precipitation in the auroral oval
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Example: W4ZV to SM4CAN on 160-Meters
• “Skewed Paths to Europe on the Low bands”; K9LA; CQ
August 1999
• F2 region trough
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Example: “Time of flight and direction of arrival of HF radio
signals received over a path along the midlatitude trough:
Observations”; Siddle, Stocker, Warrington; Radio Science,
Vol 39, 2004
Sea scatter
• “Great-Circle and Deviated-Path Observations on CW
Signals Using a Simple Technique”; Silberstein and
Dickson; IEEE Trans A&P; January 1965
WWROF Webinar - Sept 2014 - K9LA
Lack of Data
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For the W6-to-OJ0 path, we don’t
have a lot of data in the skew area to
ascertain which of the four
possibilities is most likely
• Probably never will
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But physics says it is possible
And most of us have experienced a
similar phenomenon
WWROF Webinar - Sept 2014 - K9LA
Thanks
Many have contributed to this presentation – whether
they know it or not!
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Bob NM7M (SK) – My mentor who insisted on applying
physics to propagation
Bill W4ZV (then WØZV) – Wrote about long path and
skewed path on the low bands in the SWL publication Fine
Tunings
Mike K1MK – Personal discussions of the physics of the
ionosphere
Ed N4II – Personal discussions of QSOs between Florida
and VK9CZ (Cocos-Keeling) on 80m – likely these are also
skewed path QSOs
JC N4IS – Personal discussions of his 160m QSOs to SE
Asia and discussions of polarization on 160m at low
latitudes
And the many others that I missed
WWROF Webinar - Sept 2014 - K9LA
Let’s Wrap This Up
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Propagation along the terminator on the low bands does
not appear to be efficient
• Physics says there’s no magic before sunrise
• Our model of the ionosphere (thru IONCAP, VOACAP,
W6ELProp, etc) agrees
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Low band RF takes a short cut across the dark ionosphere
• Far enough away from the terminator to minimize absorption
• Need a skew point to kick RF off one great circle path to
another great circle path - mechanisms are out there to do this
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You don’t have to change your operating habits
• South-southwest at your sunrise and south-southeast at your
sunset still applies
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Civil twilight, nautical twilight and astronomical twilight
have nothing to do with propagation - all that matters is
sunrise and sunset which ties into the ionization process
On the higher bands, gray line is simply a MUF issue
• Absorption is inversely proportional to the square of the
frequency
WWROF Webinar - Sept 2014 - K9LA