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The Sun, the Ionosphere and HF Propagation

The Sun, the Ionosphere and HF Propagation. Carl Luetzelschwab K9LA k9la@arrl.net http://k9la.us. Who Is K9LA?. Received Novice license (WN9AVT) in Oct 1961 Selected K9LA in 1977 Interests include Propagation DXing Contesting Playing with antennas Vintage equipment

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The Sun, the Ionosphere and HF Propagation

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  1. The Sun, the Ionosphere and HF Propagation Carl Luetzelschwab K9LA k9la@arrl.net http://k9la.us Kamloops ARC Nov 2015 K9LA

  2. Who Is K9LA? • Received Novice license (WN9AVT) in Oct 1961 • Selected K9LA in 1977 • Interests include • Propagation • DXing • Contesting • Playing with antennas • Vintage equipment • DXpeditions include YK9A (Syria, 2001), OJ0 (Market Reef, 2002) and ZF (Cayman Islands, many times) • Wife is Vicky AE9YL/ZF2YL Viking Ranger II HQ-170A Kamloops ARC Nov 2015 K9LA

  3. Some of My Favorite Movie Stars Kamloops ARC Nov 2015 K9LA

  4. But This Is My Favorite Star Kamloops ARC Nov 2015 K9LA

  5. Some Facts About the Sun Ionizing wavelengths .1 to 100 nm • Radiates energy at many wavelengths • Highest intensity is at visible light wavelengths (400-700 nm) • Wavelengths that ionize the atmosphere (.1-100 nm) are much shorter than visible light • Visible light has nothing to do with the ionization process – not enough energy • Same for 10.7 cm solar flux Solar Radiation Spectrum 10.7 cm intensity 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 wavelength in nm The shorter the wavelength, the more the energy (Planck’s Law) Kamloops ARC Nov 2015 K9LA

  6. Early Ionospheric Studies • 1901 – Marconi hears Poldhu • 1902 – Kennelly (US) & Heaviside (UK) independently suggest that the Earth’s upper atmosphere consists of an electrically conducting region (the Kennelly-Heaviside layer) • 1925 – Appleton finds conclusive evidence of a conducting region by measuring arrival angles of nearby transmitter • 1925 – Breit and Tuve confirm existence of reflecting region with the first ionosonde(swept-frequency upward-looking radar) • 1926 - Watson-Watt coins the term “ionosphere” • 1927 – Sharp decrease in critical frequency (measured by an ionosonde) seen during solar eclipse – deduce that solar radiation forms the ionosphere • 1928 – Pettit ties sunspots to solar radiation – the more sunspots, the more radiation Kamloops ARC Nov 2015 K9LA

  7. Sunspots • Sunspots are the result of magnetic fields in the Sun that erupt through the surface, forming a huge magnetic loop • The solar surface in this area cools significantly, causing this area to be darker • The area around the sunspot emits radiation at wavelengths that ionize the atmosphere • Sunspots (and 10.7 cm solar flux) are a proxy for the true ionizing radiation Kamloops ARC Nov 2015 K9LA

  8. Solar Cycle • Average length (A to C) is 11 years • Average rise time (A to B) is 4 years • Average fall time (B to C) is 7 years • Solar cycle may have two peaks • We measure solar cycles using a smoothed solar index to “smooth out” the spikiness of daily and monthly mean values • The maximum value varies Smoothed solar index could be smoothed sunspot number or smoothed 10.7 cm solar flux Kamloops ARC Nov 2015 K9LA

  9. Two Peaks • Cycles 21, 22, 23 and now 24 had a second peak • What does this mean? • Good question! Kamloops ARC Nov 2015 K9LA

  10. Recorded History • Three periods of large cycles, two periods of small cycles • Looks like we’re headed for some small solar cycles • Corroborating evidence is cycle max vs duration of previous min Dalton minimum Cycle 1 began in 1755 Kamloops ARC Nov 2015 K9LA

  11. Duration of Cycle Minimums • On the left is the duration of solar minimums • Out-of-phase with plot on previous slide • On the right is a scatter diagram of months at solar minimum vs magnitude of next peak • The longer the duration of solar minimum, the smaller the next cycle Kamloops ARC Nov 2015 K9LA

  12. Early History Positive 14C is solar minimum Negative 14C is solar maximum the most well known minimum (~ 1645-1715) • Carbon-14 (and Beryllium-10) are proxies for solar activity • Tied to galactic cosmic rays • Are we headed for another Maunder Minimum? • Some say yes, most say no – duration of minimum between Cycle 24 and 25 should give us a hint of where we’re headed Cycles 5,6 ,7 Kamloops ARC Nov 2015 K9LA

  13. Solar Cycle 24 Status • Blue vertical bars are monthly means • Red line is smoothed value • First peak in early 2012 – second peak in mid 2014 Kamloops ARC Nov 2015 K9LA

  14. The Atmosphere • Atmosphere is most often defined by temperature (yellow line) • Terrestrial weather is in the troposphere and lower stratosphere • Ionosphere starts in the mesosphere Kamloops ARC Nov 2015 K9LA

  15. The Ionosphere • Remember that ionizing radiation is at wavelengths between .1 and 100 nm • The shorter the wavelength, the more the energy • The more the energy, the lower it gets into the atmosphere • F region above ~ 160 km • 10-100 nm wavelengths (EUV) • E region from ~ 90-160 km • 1-10 nm wavelengths (soft x-rays) • D region from ~ 70-90 km • .1-1 nm wavelengths (hard x-rays) R is the smoothed sunspot number R=0 is solar minimum R=200 is solar maximum Kamloops ARC Nov 2015 K9LA

  16. Critical Frequency and MUF • Ionosondes measure the critical frequencies of the ionosphere • Critical frequency of a region is the frequency at which the RF pulse does not return to Earth (it goes through the region) • Ionosondes report critical frequencies for the E, F1 and F2 regions (and sporadic E when present) • Using spherical geometry, we can estimate the maximum frequency that will propagate over a given path at a given time Kamloops ARC Nov 2015 K9LA

  17. Critical Frequency Example • As the elevation angle is lowered from 90o, higher frequencies are refracted back to Earth • The highest frequency that is refracted back to Earth when launched at a low elevation angle is about 3 times the critical frequency • This is the maximum useable frequency (MUF) • In this example, the MUF would be about 24 MHz F region ionosonde varies its frequency 3 MHz 8 MHz Kamloops ARC Nov 2015 K9LA

  18. Variability of the Ionosphere • The ionosphere varies significantly • Over a solar cycle - most ionization at solar maximum • Monthly – Fall months best in northern hemisphere • Throughout the day – max around noon, min before dawn • The ionosphere is affected by disturbances to propagation • Our understanding of the ionosphere is statistical in nature over a month’s time frame • Thus our propagation predictions are statistical in nature over a month’s time frame • We do not have a daily model of the ionosphere Kamloops ARC Nov 2015 K9LA

  19. The Bands • Our bands fall into three categories • 160m, 80m, 40m: these bands are very dependent on ionospheric absorption • Best during the night and best at solar minimum • 15m, 12m, 10m: these bands are very dependent on the MUF • Best during the day and best at solar maximum • 30m, 20m, 17m: these are transition bands • Not entirely dependent on absorption • Not entirely dependent on MUF • Hold up well throughout a solar cycle Kamloops ARC Nov 2015 K9LA

  20. Space Weather www.qrz.com Current weather parameters and assessment of band conditions Kamloops ARC Nov 2015 K9LA

  21. What We Desire • Solar activity • In general we desire a high sunspot number (0-200) and a high 10.7 cm solar flux (65-300) • Openings vs 10.7 cm solar flux • 10m: long-term solar flux > 100 • 12m: long-term solar flux > 75 • 15m: long-term solar flux > 50 • Geomagnetic field activity • In general we desire A < 7 and K < 2 • A and K are measures of the deviation of the Earth’s magnetic field from quiet conditions • A is a daily index, K is a 3-hour index Kamloops ARC Nov 2015 K9LA

  22. What Bands Are Open? • Since we don’t have a daily model of the ionosphere, knowing the 10.7 cm solar flux does not pin down the MUF for a given path at a given time • We can use propagation predictions to give a statistical view of what the best band would be for the desired path • W6ELProp is a user-friendly propagation prediction program that is a free download • Visit the Tutorials link at http://k9la.us for info about W6ELProp (how to download it, set it up and interpret the results) Kamloops ARC Nov 2015 K9LA

  23. Listen Real-Time! • The IARU/NCDXF beacon project has a beacon on 20m, 17m, 15m, 12m and 10m in 18 countries worldwide • Each beacon transmits for 10 seconds – so in 3 minutes you can assess worldwide openings on a band • http://www.ncdxf.org/pages/beacons.html for details Kamloops ARC Nov 2015 K9LA

  24. Use Real-Time Spots • Select LF-HF or VHF & up • Select band • Select geographical area • Spots are shown for the designated time period from www.dxmaps.com Kamloops ARC Nov 2015 K9LA

  25. Modes of Propagation • Most of our HF QSOs are made via the true great circle short path • Other HF propagation modes exist • Long path • Skewed path • Scatter path (implies loss = weak signal) • Path could be via F region, E region, Es region, auroral ionization, equatorial ionization (TEP), etc Kamloops ARC Nov 2015 K9LA

  26. Noise • Usually a problem on the lower bands (160m and 80m) • Two categories • Man-made • Atmospheric • Mitigation for • Man-made noise – check your house and neighbor’s house, work with power company • Atmospheric noise – use low-noise receive antennas Kamloops ARC Nov 2015 K9LA

  27. Disturbances to Propagation Kamloops ARC Nov 2015 K9LA

  28. Disturbances – The Big Picture • Worst is geomagnetic storm – several days to a week • Caused by CME or coronal hole • Solar radiation storm – couple days • Radio blackout – couple hours both caused by big solar flare Kamloops ARC Nov 2015 K9LA

  29. Solar Flares • Emit lots of radiation at x-ray wavelengths (very short) • Biggest is X-Class • Next down is M-Class • Next down is C-Class • Least is B-Class • Visit http://www.swpc.noaa.gov/noaa-scales-explanation for details of disturbances to propagation Kamloops ARC Nov 2015 K9LA

  30. Summary • The Sun radiates at many wavelengths • .1-100 nm is important for the ionosphere • Looks like we’re headed for some smaller solar cycles • How small is the question • Ionosphere varies significantly day-to-day • Forces us to use a statistical model • Several ways to assess band conditions • Use them to help your operating habits Kamloops ARC Nov 2015 K9LA

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