1. WWROF Webinar - Sept 2014 - K9LA A Long Overdue Review of Gray Line Propagation on the Low Bands Carl Luetzelschwab K9LA e-mail: k9la@arrl.net web site: http://k9la.us

2. WWROF Webinar - Sept 2014 - K9LA Thanks to WWROF http://wwrof.org World Wide Radio Operators Foundation “Dedicated to improving the skills pf amateur radio operators around the world, utilizing education, competition, advancement of technology and scientific research, promoting international friendship and goodwill, and preparing them to better serve society in times of communication need.”

3. WWROF Webinar - Sept 2014 - K9LA Topics Quick status of Cycle 24 Quick status of Cycle 24 Origin of ‘gray line’ propagation Origin of ‘gray line’ propagation Some confusion with gray line Some confusion with gray line Common explanation for gray line propagation Common explanation for gray line propagation Doubts about the explanation Doubts about the explanation YB1A QSO on 40m vs IONCAPYB1A QSO on 40m vs IONCAP Topband reflector commentTopband reflector comment 3Y0X DXpedition QSOs to JA on 160m3Y0X DXpedition QSOs to JA on 160m Ray tracing softwareRay tracing software The ionization process The ionization process What I think is really happening What I think is really happening This presentation challenges some long-held beliefs And it gets into physics deeper than usual

4. WWROF Webinar - Sept 2014 - K9LA Cycle 24 - Where We Are We’re in the second peak of Cycle 24 We’re in the second peak of Cycle 24 Contesting on the higher bands should be good this fall Contesting on the higher bands should be good this fall

5. WWROF Webinar - Sept 2014 - K9LA Disappearing Sunspots This is what I presented in my “Maunder Minimum” webinar in April 2014 This is what I presented in my “Maunder Minimum” webinar in April 2014 Updated data at that time was only through end of 2013 Updated data at that time was only through end of 2013 original data updated data: end of 2013

6. WWROF Webinar - Sept 2014 - K9LA Latest Data Latest data shows the magnetic field strength has leveled off Latest data shows the magnetic field strength has leveled off This suggests we aren’t headed for a Maunder-type Minimum This suggests we aren’t headed for a Maunder-type Minimum It may just be a period of small cycles as seen before It may just be a period of small cycles as seen before

7. WWROF Webinar - Sept 2014 - K9LA First Known Mention of Gray line Article by K6UA and W6NLZ, with editing by K6SSS Article by K6UA and W6NLZ, with editing by K6SSS CQ magazine, Sept 1975 CQ magazine, Sept 1975 Worked mostly EU, AF and Mideast via long path on 80m SSB Worked mostly EU, AF and Mideast via long path on 80m SSB At morning sunrise and evening sunset 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”

8. WWROF Webinar - Sept 2014 - K9LA Example from CQ Article W6NLZ to OJ0AM W6NLZ to OJ0AM January 28, 1974 January 28, 1974 1457 UTC 1457 UTC W6 sunriseW6 sunrise OJ0 sunsetOJ0 sunset Long path over Antarctica and up across eastern Africa and the Mideast Long path over Antarctica and up across eastern Africa and the Mideast from article: “signals travel along the edge of the band or ring of twilight encircling the Earth” thanks W6ELProp this may be a problem

9. WWROF Webinar - Sept 2014 - K9LA Some Confusion Sometimes the term ‘gray line’ has been used for a sunrise/sunset enhancement path Sometimes the term ‘gray line’ has been used for a sunrise/sunset enhancement path I subscribe to gray line = follows the terminator I subscribe to gray line = follows the terminator Sunrise/sunset enhancement is on a path going away from the terminator Sunrise/sunset enhancement is on a path going away from the terminator perpendicular is bestperpendicular is best K9LA to STØRY, March 28 (2003), 0330 UTC, 160m, signal well out of noise from 0320-0340 thanks W6ELProp

10. WWROF Webinar - Sept 2014 - K9LA Sunrise/Sunset Enhancement Believed to be due to ducting in the electron density valley above the E region peak in the dark ionosphere 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 Valley not well developed along the terminator Pretty much non- existent in the daytime ionosphere Pretty much non- existent in the daytime ionosphere valley in the dark ionosphere ray trace in the dark ionosphere showing ducting

11. WWROF Webinar - Sept 2014 - K9LA Comparison thanks W6ELProp this is gray linethis is NOT gray line

12. WWROF Webinar - Sept 2014 - K9LA Explanation of Gray Line The explanation is rooted in the concept that before sunrise the F2 region is formed prior to the D region 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 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) Thus there’s a band along the terminator of F region ionization without D region ionization (low or no absorption)

13. WWROF Webinar - Sept 2014 - K9LA How Does This Happen? Using spherical geometry, we can work out how long before sunrise an ionospheric height becomes illuminated by the Sun

14. WWROF Webinar - Sept 2014 - K9LA And the Results Are... Top image: Earth- ionosphere system 69 minutes before K9LA sunrise Top image: Earth- ionosphere system 69 minutes before K9LA sunrise Middle image: Earth- ionosphere system 35 minutes before K9LA sunrise Middle image: Earth- ionosphere system 35 minutes before K9LA sunrise Bottom image: Earth- ionosphere system at K9LA sunrise Bottom image: Earth- ionosphere system at K9LA sunrise Thus the F2 region of the ionosphere is illuminated 34 minutes before the D region is illuminated Thus the F2 region of the ionosphere is illuminated 34 minutes before the D region is illuminated

15. WWROF Webinar - Sept 2014 - K9LA The Present Explanation Gray line propagation allegedly happens because: Gray line propagation allegedly happens because: Before sunrise there’s an F2 region but no D regionBefore sunrise there’s an F2 region but no D region After sunset there’s an F2 region but no D regionAfter sunset there’s an F2 region but no D region This occurs all along the terminator This occurs all along the terminator In my mind, several doubts have crept in over the years.... In my mind, several doubts have crept in over the years....

16. WWROF Webinar - Sept 2014 - K9LA Doubt #1 - YB1A on 40m CW December 3, 2002 at 2231 UTC (my sunset) December 3, 2002 at 2231 UTC (my sunset) YB1A was S8 = -78 dBm on my calibrated S-meterYB1A was S8 = -78 dBm on my calibrated S-meter My inv-vee can’t tell if it was short path or long path My inv-vee can’t tell if it was short path or long path Most experienced DXers would say it was long path Most experienced DXers would say it was long path Long path Long path 153 degrees, 24,467 km153 degrees, 24,467 km -180 dBm predicted by IONCAP assuming YB1A at 1 kW and +3 dBi antennas-180 dBm predicted by IONCAP assuming YB1A at 1 kW and +3 dBi antennas Short path Short path 333 degrees, 15,565 km333 degrees, 15,565 km -130 dBm predicted-130 dBm predicted Even assuming short path, is IONCAP off by 52 dB? Even assuming short path, is IONCAP off by 52 dB? thanks W6ELProp

17. WWROF Webinar - Sept 2014 - K9LA Doubt #2 - Topband Reflector I posted a message to the topband reflector in early April 2005 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 It commented on the F2 region forming before the D region as sunrise approached Mike K1MK responded personally with an interesting comment: Mike K1MK responded personally with an interesting comment: “While illumination by visible light to which the atmosphere is transparent will start prior to ground- level 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.”

18. WWROF Webinar - Sept 2014 - K9LA Doubt #3 – 3Y0X February 2006 DXpedition to Peter I February 2006 DXpedition to Peter I On 160-Meters they worked 764 US stations between 0210 UTC and 0901 UTC On 160-Meters they worked 764 US stations between 0210 UTC and 0901 UTC Note that the paths get away from the terminatorNote that the paths get away from the terminator thanks W6ELProp 0210 UTC0901 UTC

19. WWROF Webinar - Sept 2014 - K9LA Doubt #3 continued – 3Y0X Nice gray line to JA via short path at 15,263 km Nice gray line to JA via short path at 15,263 km IONCAP says MUF okay but absorption prohibitive on 160m IONCAP says MUF okay but absorption prohibitive on 160m QSOs – 1 JA during the entire DXpedition QSOs – 1 JA during the entire DXpedition If gray line via long path is so efficient, why isn’t short path? 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 I’ve never seen a report of fantastic short path gray line G0KYA monitored VP8NO in November 2002 on 40mG0KYA monitored VP8NO in November 2002 on 40m 3-6 dB average enhancement 30 minutes before mutual sunrise – why not the entire gray line period? 3-6 dB average enhancement 30 minutes before mutual sunrise – why not the entire gray line period? thanks W6ELProp Is propagation along the terminator efficient as is commonly believed?

20. WWROF Webinar - Sept 2014 - K9LA Comments About Absorption At HF, absorption is proportional to electron density times collision frequency (Davies, 1990) At HF, absorption is proportional to electron density times collision frequency (Davies, 1990) Electron density increases as altitude increasesElectron density increases as altitude increases Collision frequency decreases as altitude increasesCollision frequency decreases as altitude increases Expect a maximum in absorption where they intersectExpect a maximum in absorption where they intersect Absorption occurs in the D region during the day Absorption occurs in the D region during the day Absorption occurs in the lower E region at night Absorption occurs in the lower E region at night altitude -> electron density collision frequency

21. WWROF Webinar - Sept 2014 - K9LA Comments About Absorption Absorption does not go to zero in the dark ionosphere on 160m 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 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 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 160mThis is why ducting is likely for the longer paths on 160m Ionospheric text books give an equation for absorption that is tied to the solar zenith angle 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 sunsetNice smooth function, but probably doesn’t represent the real-world around sunrise and sunset

22. WWROF Webinar - Sept 2014 - K9LA The Problem Is the explanation of gray line propagation correct? Is the explanation of gray line propagation correct? RF follows the terminator where there’s an advantageous band of ionizationRF follows the terminator where there’s an advantageous band of ionization Or is our model of the ionosphere correct? Or is our model of the ionosphere correct? Propagation along the terminator is not efficientPropagation along the terminator is not efficient Something else is going onSomething else is going on

23. WWROF Webinar - Sept 2014 - K9LA Who’s Right and Who’s Wrong? The figure assumes that ionizing radiation can go thru the atmosphere TWICE to ionize the F2 region in the dark ionosphere 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 Let’s look at the ionization process from article: “signals travel along the edge of the band or ring of twilight encircling the Earth” I believe this is a problem from slide 5 atmosphere here and here

24. WWROF Webinar - Sept 2014 - K9LA It’s All About Energy More than 50% of the F2 region is due to EUV (extreme ultraviolet) radiation at wavelengths between 26 and 34 nm More than 50% of the F2 region is due to EUV (extreme ultraviolet) radiation at wavelengths between 26 and 34 nm Ionizes atomic oxygenIonizes atomic oxygen We’ll use 30 nm for the following analysisWe’ll use 30 nm for the following analysis From Planck’s Law, the energy of one photon at 30 nm is 41 eV 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 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 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 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 Thus the F2 region ionizing radiation can’t even get thru the atmosphere ONCE This is why we can’t measure EUV at ground levelThis is why we can’t measure EUV at ground level

25. WWROF Webinar - Sept 2014 - K9LA What About the D Region? There are two sources of ionizing radiation for the D region There are two sources of ionizing radiation for the D region 0.1-1.0 nm that ionizes all atmospheric species at D region altitudes0.1-1.0 nm that ionizes all atmospheric species at D region altitudes 121.5 nm that ionizes nitric oxide (NO) at D region altitudes121.5 nm that ionizes nitric oxide (NO) at D region altitudes The same conclusion results as for the F2 region The same conclusion results as for the F2 region The energy of the ionizing radiation is used up before it gets to ground level 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 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 levelThis is why we can’t measure D region ionizing radiation at ground level

26. WWROF Webinar - Sept 2014 - K9LA Measuring Ionizing Radiation Prior to World War II, we couldn’t measure ionizing radiation Prior to World War II, we couldn’t measure ionizing radiation It does not get through the atmosphere to the groundIt does not get through the atmosphere to the ground We had to wait for rocket flights and eventually satellites We had to wait for rocket flights and eventually satellites

27. WWROF Webinar - Sept 2014 - K9LA “Illumination” Yes, before sunrise the F2 region and D region are illuminated by the Sun Yes, before sunrise the F2 region and D region are illuminated by the Sun This illumination is by visible light This illumination is by visible light Visible light has nothing to do with the ionization process 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 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 bagVisible light couldn’t ionize its way out of a paper bag That’s why visible light gets thru the atmosphere unimpeded – it does not do any ionization That’s why visible light gets thru the atmosphere unimpeded – it does not do any ionization Just like 10.7 cm solar fluxJust like 10.7 cm solar flux

28. WWROF Webinar - Sept 2014 - K9LA When Does the F2 Region Ionize? Around sunrise - just like K1MK said

29. WWROF Webinar - Sept 2014 - K9LA When Does the D Region Ionize? Electron density over Arecibo from incoherent scatter radar Electron density over Arecibo from incoherent scatter radar Local sunrise at 0602 (AST) Local sunrise at 0602 (AST) Look at D region altitude of 80 km Look at D region altitude of 80 km Around sunrise - just like K1MK said sunrise at 0602 local

30. WWROF Webinar - Sept 2014 - K9LA Why Sunrise? Sunrise is when photons can get to the ionospheric regions without having to plow through the atmosphere twice

31. WWROF Webinar - Sept 2014 - K9LA Another Interim Summary I’m very confident that the explanation of gray line on the low bands is incorrect I’m very confident that the explanation of gray line on the low bands is incorrect propagation along the terminator is efficient This conclusion is based on an understanding of the ionization process and absorption This conclusion is based on an understanding of the ionization process and absorption The ionospheric regions begin ionizing around sunrise, not way earlier The ionospheric regions begin ionizing around sunrise, not way earlier “Around” sunrise = variability “Around” sunrise = variability Ozone layer can block ionizing radiationOzone layer can block ionizing radiation Ionosondes do not have pencil-thin beams - can receive off-zenith reflectionsIonosondes do not have pencil-thin beams - can receive off-zenith reflections Dayside E region plasma can move horizontally into the dark ionosphere via advectionDayside E region plasma can move horizontally into the dark ionosphere via advection Photons can scatter into the dark atmospherePhotons can scatter into the dark atmosphere

32. WWROF Webinar - Sept 2014 - K9LA What’s Really Happening? Just saying the current explanation is incorrect isn’t enough Just saying the current explanation is incorrect isn’t enough An alternative explanation needs to be presented An alternative explanation needs to be presented It has to mesh observations and physicsIt has to mesh observations and physics The clue is in the quote from the CQ article that was cited on slide 4 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”

33. WWROF Webinar - Sept 2014 - K9LA W6NLZ to OJ0AM Map - Again What else happens when W6NLZ and OJ0AM experience simultaneous sunrise and sunset? What else happens when W6NLZ and OJ0AM experience simultaneous sunrise and sunset? There is a dark ionosphere in between W6NLZ and OJ0AM There is a dark ionosphere in between W6NLZ and OJ0AM Gray line is “long path opening that exists between two points on the Earth which are experiencing simultaneous sunrise and sunset” thanks W6ELProp W6NLZ OJ0AM

34. WWROF Webinar - Sept 2014 - K9LA Possible Path – With a Problem Absorption is least in the dark ionosphere Absorption is least in the dark ionosphere The RF must take a short cut across the dark ionosphere – the white path 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 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 The path in white that I drew isn’t a great circle path – it’s just a sketch to show the idea There are only two great circle paths between W6NLZ and OJ0AMThere are only two great circle paths between W6NLZ and OJ0AM thanks W6ELProp W6NLZ OJ0AM

35. WWROF Webinar - Sept 2014 - K9LA The Solution – A Skewed Path Observations by those with directional antennas have resulted in the following two axioms Observations by those with directional antennas have resulted in the following two axioms Listen south-southwest at your sunriseListen south-southwest at your sunrise Listen south-southeast at your sunsetListen south-southeast at your sunset Thus the path is more “along the terminator” than “at right angles to the terminator” 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 It has to be far enough away from the terminator when it encounters the ionosphere on the first hop so that Absorption is minimumAbsorption is minimum The ducting mechanism is availableThe ducting mechanism is available Need to look at great circle paths out of both W6NLZ and OJ0AM Need to look at great circle paths out of both W6NLZ and OJ0AM

36. WWROF Webinar - Sept 2014 - K9LA Great Circle Paths from W6NLZ Great circle paths out of W6NLZ in 10 degree increments

37. 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

38. WWROF Webinar - Sept 2014 - K9LA Putting It All Together terminator (black)great circle path (red) alternative paths (green) night day skew area

39. WWROF Webinar - Sept 2014 - K9LA Possibilities for the Skew Ionospheric origin Ionospheric origin Normal ionosphere – E region or F2 regionNormal ionosphere – E region or F2 region Example: FT5ZM on 10-Meters Example: FT5ZM on 10-Meters Practical Propagation column in CQ Plus for July 2014Practical Propagation column in CQ Plus for July 2014 Electron precipitation in the auroral ovalElectron precipitation in the auroral oval Example: W4ZV to SM4CAN on 160-Meters Example: W4ZV to SM4CAN on 160-Meters “Skewed Paths to Europe on the Low bands”; K9LA; CQ August 1999“Skewed Paths to Europe on the Low bands”; K9LA; CQ August 1999 F2 region troughF2 region trough 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 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 Sea scatter “Great-Circle and Deviated-Path Observations on CW Signals Using a Simple Technique”; Silberstein and Dickson; IEEE Trans A&P; January 1965“Great-Circle and Deviated-Path Observations on CW Signals Using a Simple Technique”; Silberstein and Dickson; IEEE Trans A&P; January 1965

40. WWROF Webinar - Sept 2014 - K9LA Lack of Data 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 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 willProbably never will But physics says it is possible But physics says it is possible And most of us have experienced a similar phenomenon And most of us have experienced a similar phenomenon

41. WWROF Webinar - Sept 2014 - K9LA Thanks Bob NM7M (SK) – My mentor who insisted on applying physics to propagation 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 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 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 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 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 And the many others that I missed Many have contributed to this presentation – whether they know it or not!

42. WWROF Webinar - Sept 2014 - K9LA Let’s Wrap This Up Propagation along the terminator on the low bands does not appear to be efficient Propagation along the terminator on the low bands does not appear to be efficient Physics says there’s no magic before sunrisePhysics says there’s no magic before sunrise Our model of the ionosphere (thru IONCAP, VOACAP, W6ELProp, etc) agreesOur model of the ionosphere (thru IONCAP, VOACAP, W6ELProp, etc) agrees Low band RF takes a short cut across the dark ionosphere Low band RF takes a short cut across the dark ionosphere Far enough away from the terminator to minimize absorptionFar 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 thisNeed a skew point to kick RF off one great circle path to another great circle path - mechanisms are out there to do this You don’t have to change your operating habits You don’t have to change your operating habits South-southwest at your sunrise and south-southeast at your sunset still appliesSouth-southwest at your sunrise and south-southeast at your sunset still applies 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 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 On the higher bands, gray line is simply a MUF issue Absorption is inversely proportional to the square of the frequencyAbsorption is inversely proportional to the square of the frequency