The details for April 18, 2016 can be viewed here.
Noise was reported to be high during the session from storms in the central and southern US but transcontinental openings were also noted by many of “the faithful” that showed up in spite of noise and storms. Afternoon storms here in North Texas resulted in a power outage that went into the night.
We are still waiting for elevated geomagnetic conditions from a coronal hole that is supposedly geoeffective but so far the magnetic field has remained quiet. The Bz has not changed much and continues to point slightly to the South. The same can be said about solar wind velocities which consistently remain in the low category, averaging near 322 km/s. DST values made significant increases overnight, pushing strongly into positive territory. I’m not going to guess what happens next.
Trans-Atlantic propagation has either been really poor or masked by seasonal noise. WG2XPJ continues to take advantage of these high latitude openings. Report details can be viewed here.
WG2XPJ -> G8HUH, LA2XPA/2
Al, K2BLA / WI2XBV, reported that he decoded five WSPR stations in relatively high noise. He was decoded by eighteen unique stations including WH2XCR.
Dave, N4DB, indicates that the session was not poor. He decoded fourteen WSPR stations including WD2XSH/20 located in Oregon.
Trans-Pacific report details, excluding KL7 and KH6, can be viewed here.
Roger, VK4YB, reported, “Moderate but intermittent QRN from within VK. ZL was clear and they made good use of it. The big 4 were strong early. Then the mid evening slump before a good second opening.” Roger received reports from 7L1RLL4, CF7MM, JA3TVF, JE1JDL, VE7BDQ, VE7SL, W7IUV, WH2XGP, WI2XJQ, WE2XPQ, and WH2XCR. He provided reports for WG2XXM, WH2XGP, WH2XXP, and WD2XSH/20. Roger was monitoring propagation to VE7SL for a possible CW QSO attempt and notes that he was “…receiving long, but my tx sigs are not getting beyond Hawaii. Later I will hear nothing except Merv and everyone will hear me. Very strong diode effect which is fine for WSPR but not good for 2xCW. Also QRN is coming from storms in NSW. There are decent length gaps in between.” All of the variables have to line up and it can be tough!
John, VK2XGJ, reported a trifecta of early evening reports at his QTH:
Ken, K5DNL / WG2XXM, indicates the he provided reports for seven WSPR stations and he was decoded by 55 unique stations including VK4YB, ZL2AFP, WE2XPQ and WH2XCR.
Rudy, N6LF / WD2XSH/20, provided reports for six WSPR stations and he received reports from forty unique stations including VK4YB, VK2XGJ, and ZL2BCG.
Ward, K7PO / WH2XXP, received reports from 56 unique stations including VK4YB, VK2XGJ, JA3TVF, ZL2BCG, and ZL2AFP.
Larry, W7IUV / WH2XGP, provided reports for eight WSPR stations including VK4YB and he was reported by 49 unique stations including VK4YB, VK2XGJ, ZL2AFP, and ZL2BCG. As W7IUV, Larry provided reports for eight WSPR stations including VK4YB. Larry indicates that he “…managed to stay on air all night by disabling SWR protect circuit. Good path to VK/ZL. Not so good to SE USA/ZF.”
Rick, W7RNB / WI2XJQ, indicates that Pacific band conditions must be improving as he had netted VK4YB twice in one week. He provided reports for eight WSPR stations including VK4YB and he was decoded by nineteen unique stations. Rick’s unique report details can be viewed here.
Regional and continental WSPR breakdowns follow:
Eden, ZF1EJ, provided reports for five WSPR stations and he was reported by thirteen WSPR stations. This session was down by a significant margin for Eden.
Laurence, KL7L / WE2XPQ, reported that his transmitter was off overnight for some reason. His investigation has turned up a blown fuse. Laurence provided reports for VK4YB and WH2XCR. Report details can be viewed here.
Merv, K9FD/KH6 / WH2XCR, experienced a moderately down session as JA was cutoff again and Oceania, or at least Australia, was less robust than recently observed. Merv shared two-way reports with VK4YB and he received reports from VK2XGJ, ZL2AFP, and ZL2BCG. The eastern US was lean with Merv providing reports only for WI2XBV. DX report details can be viewed here.
Jim, W5EST, presents, “MAILBAG: SUNRISE AT ALTITUDE EXPLAINS PRE-SUNRISE FREQUENCY DEPARTURE ON 600KHz?”:
“Roger VE7VV: Hi Jim, thanks for the April 12 blog . http://njdtechnologies.net/041217/ Re your blog statement, ‘The results puzzle me for several reasons. First, the early onset of the frequency departure occurred about 13 minutes before sunrise time 3/28 at the reflection point 40 km east of midpath. (The white dashed vertical lines on first illustration indicate the timing).’
Did you take into account the sunrise time at the height of the ionosphere vs. at the earth’s surface? Could this account for your 13 minute discrepancy? Illumination at 100 km happens sooner and lasts longer than at the surface. Compare after-sunset seen from the ground: Clouds overhead and then towards the west remain illuminated making for nice sunset glows, and then satellites at higher altitudes remain brightly illuminated in the dark night sky for some time afterwards.
Jim W5EST: I’m seeing your question goes beyond mere idle curiosity about unexplained 13 minutes. If we could clarify this pre-SR topic, it would help us go on to estimate potential time durations of MF pre-SR signal enhancement at various latitudes, path distances and path azimuths, and seasons.
In reply, you may have hit upon an approach to an explanation. See today’s illustration. Starting from your suggestion, may I merely investigate a somewhat higher-altitude geometry by which the nearly horizontal sunlight (orange) there would graze the E-region (gray) and penetrate a depth d of a few km. See E-region between solar rays i and ii. Would ionizing rays reach and ionize horizontally for 295 km into and across the E-region westward high above what’s pre-dawn at ground level? (Endnote 1*).
The tilt of the slanted ionosphere is shown dotted in red to the west of surface sunrise. Compared to the 4/12 blog post, that tilt looks a lot less mysterious when drawn over spherical earth. The tilt more nearly hugs the straight line of the solar ionizing radiation arriving from the east (right side of illustration). At night the E-region is thin, like the blue dotted line to the west. Then the pre-SR tilt is only somewhat more inclined than the sun’s rays through the lower part of the thickened E-region eastward.
Roger VE7VV: By my simple geometry calculations, the E-region at 110 km would have first illumination (i.e. it’s “sunrise”) just grazing the ozone layer top (at 40 km) prior to at least a half-hour before ground sunrise directly underneath. The 70 km downward bulging E-region’s “sunrise” would be about 10 minutes or so later. The “slope” implied by a 10 minute top to bottom illumination front would extend 228 km at your 22.8 km/minute terminator speed. I see that the steepest slope in your “compressed” graph (12 April blog), from 110 to 85 km, extends about this distance.
Also, note that the initial illumination of the ionosphere would actually be from bottom up. Suppose sun ray iv just grazes horizontally above the ozone layer at ~40km, then ascends to enter the E-region ionosphere from the bottom side. On the way from grazing the ozone layer at 40 km up it would pass through the D-region and then the lower E-region to reach this point.
Jim W5EST: Our readers can see various web sites and references that this conversation turned up. (Endnote 2**). This is surely a complicated subject. I’m struggling with March 28’s screenshot where the frequency departure curve, which leads to the tilt, straddled either side of sunrise, see April 12 blog, instead of preceding by roughly a half-hour.
At the various altitudes each layer at least partially absorbs particular ionizing wavelengths. Other wavelengths are left to ionize a lower layer, like solar radiation through F then E then D region. And then, as to your topic, will wavelengths remain that can ionize going from D bottom up to E westward? We should also beware assuming D-region timing of absorption of ionizing radiation is similar to D-region radio absorption timing at MF.
Enough ionizing solar radiation penetrates the E-region after sunrise at wavelengths to ionize the D-region then and make it MF-absorbent. So, at higher altitude, does enough ionizing solar radiation like ray iii penetrate the E-region almost horizontally and on across westward into the E-region itself with the right wavelengths strong enough to ionize E-region there? My distance calculations support that idea, ignoring the wavelength issue. (Endnote 3***)
Roger VE7VV: My, very non-expert, understanding of the ionization chemistry leads me to believe that the hard UV rays that ionize E-region would not be absorbed in the D-region (which is ionized by different wavelengths) and most would pass through the lower E-region. We know that in the normal top/down situation UV passes through the E and D regions to reach the ozone layer which then blocks it. Thus, the idea that the E-region can, during a very brief period around its sunrise, be illuminated with ionizing UV radiation from below seems worth considering.
Jim W5EST: You have gotten me started thinking about sun ray geometry inside the E-region analogous to your bottom-up underside illumination idea, just with the geometry higher up in altitude. Whether it stands up to the acid test of all considerations and all the data from the 600 KHz, we’ll see.
For instance, I’m still uncertain about the origin of April 12 blog’s initial steepest tilt in E-region altitude in the westward areas. Would weakened solar ionizing radiation that far west produce that steeper tilt or decline and achieve the 180 mHz frequency departure seen on ARGO QRSS600 March 28? We likely would have to do physics calculations to resolve that issue.
Regarding D-region absorption on 630m, see example SNRs for WH2XXP as decoded at N6SKM. SNR decline got very steep at and after XXP SR (eastward station). http://njdtechnologies.net/120116/ (1st illust.) Does some ionizing radiation get through eastward sunlit D-region to reach westward underside of E-region, albeit attenuated?
Roger VE7VV: N6SKM has a good RX location. He is my best “DX” at around 1200 km getting decodes of my 1 W output WSPR transmissions some nights. For the D-region I estimate XXP-n6skm absorption increase times to be about the same as was shown on your graphs if one takes into account that the D-region has its “sunrise” about 25 minutes before ground sunrise (calculation available on request).
Jim W5EST: Roger, thanks for your digging and your efforts to think this through and share them!”
*W5EST ENDNOTE 1: Let’s try this formula:
Depth d = (RE+Y) [ 1 – cos( v Tpre / kRE) ]
where terminator velocity v =22.75km/minute here at 35 N latitude, Pre-SR onset time Tpre = 13 minutes, and Earth radius RE=6371km. Altitude “Y” is my guess for nighttime E-region altitude: Y=110km. Fudge factor k is the fraction of actual penetration like 295 km divided by the full geometric horizontal distance across the top of the E-region at depth d.
Depth d = 6.9 km if w1 = 295 km horizontal penetration of ray ii crosses the entire post-SR half-top of the E-region. (k=1.0). That depth and width are plausible values in the E-region, which gets bathed in solar radiation by SR. Presumably the solar radiation penetrated another 295 km even farther westward as shown for ray ii and tilt-reflected MF RF 13 minutes pre-SR March 28.
Is it plausible that such an ionizing “underside effect” would be strong enough to produce the initial 180 mHz of frequency departure that represents such an initially abrupt decrease in E-region altitude as the model calculated? At 295 km west of surface SR, the ionized thickness would be near zero 0.0 km when k=1.0. So I think more depth than 6.9 km is involved and k is say 5/6 or so, which leads to Depth d = 10km or more.
**W5EST ENDNOTE 2: For regions in the comprehensive atmosphere, see: https://scied.ucar.edu/ionosphere; https://en.wikipedia.org/wiki/Ozone_layer
Robert Brown’s The Big Gun’s Guide to Low-Band_Propagation tells that solar UV radiation is necessary to establish D layer absorption in daylight and the ozone layer is about 40 km above ground level (p. 95). Ionizing wavelengths are tabulated and discussed at p. 20-21.
Due to accumulated absorption of ionizing radiation by E and D and finally the ozone layer, hard UV and soft x-rays don’t reach Earth’s surface, and so can’t then ascend from the Earth’s surface bottom-up to the ionosphere to ionize it far westward from there. Carl K9LA discusses ionization timing: http://k9la.us/Jun15_When_Does_A_Layer_Ionize.pdf
Ascending from the top of a layer such as ozone layer, or from the top of the D-region, or merely from a depth inside the E-region to ionize the E-region far westward, occupies today’s blog’s calculations instead.
**W5EST ENDNOTE 3:
Further, let hD = 60km be guesstimated D-region top altitude. Inspect the illustration for ray iii to see:
cos β = (RE+hD)/(RE+Y) = (6371 + 60)/(6371 + 110) =.9923
Then I estimate width w2 across the E-region from 4/12 blogged thickness u ~ 36 km and cos β calculated from above.
w2 = u / sin β, which can use the cos β formula this way:
w2 =u / sqrt(1 – cos2β) = 36km / sqrt(1-.99232) = 290km.
Width w2 is similar to width w1 so it’s reasonable to think some radiation would traverse the eastward E-region and could cross over westward bottom-up and ionize the E-region even earlier than 13 minutes pre-SR on this path—indeed 35 minutes pre-SR:
TpreD = β (radians) x (6371km/22.75km/min) = 35 minutes.
If ionizing radiation grazes top of the ozone layer and gets up through D-region, the bottom-up E-region timing is even earlier:
TpreOzoneE110 = arccos(6371 + 40)/(6371 + 110) x (6371km/22.75km/min) = 41 minutes.
If such radiation were strong enough to bulge E-region down to Apr. 12 blog’s 76km, then:
TpreOzoneE76 = arccos(6371 + 40)/(6371 + 76) x (6371km/22.75km/min) = 29 minutes (i.e. 12 minutes later).
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).