[600MRG] MF/LF Ionosphere at Sunrise

[James Hollander]

    SNR sequences  between TX/RX stations’ sunrises (SR) on12/6/2015 suggest  propagation-relevant SNR dynamics  for  stations  at each  end  of paths  on both 2200m and 630m. Basically, I  use  the oncoming terminator-caused  absorption  in the  D-layer  as  apoor man's way  of  looking at the  elevation  angle  distribution  of incoming RF signal rays  at MF/LF.  
    Data: Since  directive antennas  aren't available to  us  atMF/LF to  distinguish  arrivingelevation angles, the  idea is to letMother Nature help us. One focuses  onWSPR SNR data for geographic paths that  are relatively free  from storm noise  and that support SNRs strong enough to  last from sunrise SR  at the  eastwardstation until sunrise SR  at the  westward station. 
    Method: I picked 2200/ 630m TX/RXs on relatively Tstorm-free pathswith strong SNRs, even  if rainy  in Pacific NW. I subtracted consecutive SNRsto  difference those SNRs  and looked for peaks  in the  difference results. Also, I simply scrutinizedthe  original SNR sequences  for stairsteps.  
     Since WSPR slots  are 2 minutes long, the  SR-SR time interval between the  sunrises preferably encompasses  at least  ten (10) consecutive WSPR decodes  at  theTxPct used (WSPR TX duty cycle). TxPct 50% is  preferable to give good data, but not required for this work. 
     Results: I found SNR stairsteps at ¼ & ¾, one-quarterand three-quarters of the SR-SR time interval. These SNR stairsteps  indicated RF signal rays penetratingD-region ¼ & ¾ of way along paths between XND-w7iuv on 2200m  and between XXP- kk6eew 630m.  
     Conclusion: Try drawing  signal  raylines  on  an  altitude diagram from TX ground level  through the D-region one-quarter 1/4 way alonga path, and from RX ground level back up through the D-region three-quarters3/4 way along the path. The lines meet  at  a  signal reflection point lying  about twice  as high  as  theD-region altitude.  So  the  reflecting region for those 2200m and 630mpaths  apparently lies  about twice  the height of the D-region. 
    E-region: An actual reflecting region  around sunrise  at twice the D-region height means  it’s probably the E-region  of the  ionosphere  and not the  much-higher F-region.  If  that seems like old news--fair enough--it'smost  interesting nevertheless tosee  actual SNR sequences givingspecific support to  what others maytell us. 
   Further work: Moreover, I’ve seen SR-SR SNRsequences can be more complicated. Studying those sequences can lead  to  a  more realistic picture of  actual MF/LF propagation  around sunrise SR than  a  single-rayreflection picture gives.     
    If you have comments or simplywould like more information about this use of WSPR SNR information, pleasecontact me at mrsocion at aol.com.  73, Jim H W5EST