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1、PVRC Webinar Mar 9,2011 K9LA,Selected Topics in Propagation,Carl Luetzelschwab K9LA,PVRC Webinar Mar 9,2011 K9LA,What Well Cover in This Session,An Update on Cycle 24Will it be an underachiever?The M-FactorSome theory about one of the basic parameters of the ionosphereSunspots and Solar Flux During
2、Cycle 23An interesting anomaly not sure what it says yetIonosphere-Ionosphere ModesTheres more than multi-hop out there,PVRC Webinar Mar 9,2011 K9LA,An Update on Cycle 24,PVRC Webinar Mar 9,2011 K9LA,Latest Data,minimum,Smoothed 10.7 cm solar flux is still rising,PVRC Webinar Mar 9,2011 K9LA,Latest
3、Data,minimum,PVRC Webinar Mar 9,2011 K9LA,Review of the Predictions,These are from the Solar Cycle 24 PredictionPanel(NOAA,NASA,ISES,and other personnel),140,90,90,The Latest Prediction,There may be an updated prediction(lower)from the Solar Cycle 24 Prediction Panel,PVRC Webinar Mar 9,2011 K9LA,PVR
4、C Webinar Mar 9,2011 K9LA,Marshall Space Flight Center,Similar prediction to Kane,“Size of the coming solar cycle 24 based onOhls Precursor Method,final estimate”,Annales Geophysicae,July 2010,59,A lot of evidence pointing to small Cycle 24,But.,Not everyone agrees that Cycle 24 will be so smallRece
5、nt prediction in Solar PhysicsMaximum of 131+/-20Maximum in July 2012+/-4 monthsFrom R.S.Dabas and Kavita Sharma,Prediction of Cycle 24 Using Geomagnetic Precursors:Validation and Update,Solar Physics,Vol 266 No 2,pp 391-403,July 2010This would be good for the higher bands and for 6m F2If Cycle 24 i
6、s a small one,though,6m F2 propagation will take the biggest hitThank goodness for summer E region propagation,PVRC Webinar Mar 9,2011 K9LA,Predictions in General,Over 60 predictions for Cycle 24Maximum smoothed sunspot number from 40 to 185Common forecasting methodsStatistical methods:length of Cyc
7、le n correlated to maximum of Cycle n+1,maximum R12 correlated to minimum R12Generally gives low Cycle 24Geomagnetic precursor methods:Ap,aa,and number of magnetically disturbed days correlate to next maximumUnfortunately can give widely varied answers depending on assumptionsPolar field precursor m
8、ethod:strength of Suns polar field correlates to next cycleGives small Cycle 24Solar dynamo method:the conveyor belt theoryUnfortunately can give widely varied answers depending on assumptionsSummary of forecasting methods from K.J.Li,et al,A brief review on the presentation of cycle 24,the first in
9、tegrated solar cycle in the new millennium,Annales Geophysicae,29,341-348,2011,PVRC Webinar Mar 9,2011 K9LA,Recent NASA News,“Researchers Crack the Mystery of the Missing Sunspots”Solar scientists claim theyve developed a new computer model of the suns interior that gets the physics right for all th
10、ree aspects of the sunspot generation process-the magnetic dynamo,the conveyor belt,and the buoyant evolution of sunspot magnetic fieldsMaybe this will help narrow down the range of the forecasted maximum smoothed sunspot number,PVRC Webinar Mar 9,2011 K9LA,Keep an eye on NASA Headline News,http:/,h
11、ttp:/www.swpc.noaa.gov,and http:/,http:/science.nasa.gov/science-news/science-at-nasa/2011/02mar_spotlesssun/,ARRL DX CW and PH,PVRC Webinar Mar 9,2011 K9LA,1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 1 2 3 4 5 6 7 8,Feb,Mar,Its headed in the right direction!,ARRL DX C
12、W,ARRL DX PH,ARRL DX CW and PH,PVRC Webinar Mar 9,2011 K9LA,Recent solar activity helped ARRL DX PH the most,ARRL DX CW,ARRL DX PH,red line is one-day running average,1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 1 2 3 4 5 6 7 8,Feb,Mar,28 MHz,21 MHz,PVRC Webinar Mar 9,2
13、011 K9LA,The M-Factor,No,not this M,PVRC Webinar Mar 9,2011 K9LA,What Is The M-Factor?,The M-Factor(MUF factor)relates the MUF(maximum useable frequency)to the critical frequencyMUF=M-Factor x Critical FrequencyM-Factor and critical frequency(along with other parameters)are measured by ionosondesM-F
14、actor is one over the sine of the angle between the ray and the ionosphere(also known as the secant law as 1/sine=secant),sine of this angle,If the angle=90o(vertically incident),then the M-Factor equals 1 and the MUF=the critical frequency,ionosphere,PVRC Webinar Mar 9,2011 K9LA,Apply It To The Ion
15、osphere,ionosphere,Earth,Thus the M-Factor=1 sine(1o),=57,Wow if the critical frequency is 5 MHz,then the MUF would be 285 MHzBut hold on the Earth-ionosphere system isnt flat its spherical,=1o,=1o,PVRC Webinar Mar 9,2011 K9LA,The Real Earth-Ionosphere System,ionosphere,Earth,height now matters lets
16、 assume 300 km,Now the M-Factor=1 sine(17.5o),=3.3,MUF for this F2 region scenario is about 3 times the critical frequency,=1o,=17.5o,M-Factor vs Height and Angle,PVRC Webinar Mar 9,2011 K9LA,This calculation assumes specular(mirror-like)reflection over an infinitely short distance the real-world is
17、 refraction over a spherical distance,The higher the layer,the longer the hop distance for a given angle But the higher the layer,the lower the M-Factor(lower MUF)for a given angle,PVRC Webinar Mar 9,2011 K9LA,Rule of 3 and Rule of 5,For the F2 region with low angles,the MUF is approximately 3 times
18、 the critical frequencyIonosondes report the M-Factor for a 3000 km hopM(3000)F2 or M(D)where D=3000 kmFor the E region with low angles,the MUF is approximately 5 times the critical frequencyClose enough for sporadic E,too,Allows you to estimate the MUF only knowing the critical frequency,PVRC Webin
19、ar Mar 9,2011 K9LA,Sunspots and Solar FluxDuring Cycle 23,PVRC Webinar Mar 9,2011 K9LA,Why Use Smoothed Solar Indices?,Reason#1:Daily data(and even monthly mean data)is spiky-hard to tell whats happeningReason#2:The best correlation between what the Sun is doing and what the ionosphere is doing is t
20、hrough a smoothed solar index-this is the basis on which the statistical model of the ionosphere for our propagation predictions was developed,PVRC Webinar Mar 9,2011 K9LA,Early Correlation,Equation from texts on the ionosphere:SF12=63.75+.728 SSN12+.00089 SSN122(the“12”subscript denotes smoothed va
21、lues),Side note-there is very little correlation between daily 10.7 cm solar flux and daily sunspot number,PVRC Webinar Mar 9,2011 K9LA,More Data,Some more scatter about the trend line,but still pretty good.,PVRC Webinar Mar 9,2011 K9LA,Include Cycle 23,In terms of smoothed sunspot number,second pea
22、k is a bit lowerIn terms of smoothed solar flux,second peak is definitely higherWe had much better 6m F2 propagation during the second peak,Cycle 23 data,April 2000,Nov 2001,PVRC Webinar Mar 9,2011 K9LA,Why The Anomaly?,Dr.Leif Svalgaard(member of the Cycle 24 Prediction Panel)has several opinionsTh
23、e sunspot counting procedure or observers have changed with resulting artificial changes of the sunspot number(as they have in the past)There are changes in the Suns corona or chromosphere accounting for additional 10.7 cm emissionPenn and Livingstons observations(Penn,M.J.and W.Livingston,Temporal
24、Changes in Sunspot Umbral Magnetic Fields and Temperatures,The Astrophysical Journal,649,L45-L48,2006 September 20)suggest that sunspots have been getting warmer during the last decade,leading to a decreased contrast with the surrounding photosphere and hence lessened visibility,possibly resulting i
25、n an undercount of sunspotsNo definite answer(yet!)Visit http:/www.leif.org/research and select item 1020 for detailsCheck out my Propagation columns in the forthcoming May 2011 and June 2011 issues of WorldRadio Online for more on thishttp:/is free!,PVRC Webinar Mar 9,2011 K9LA,Ionosphere-Ionospher
26、e Modes,PVRC Webinar Mar 9,2011 K9LA,Multi-Hop Can Have Limits,On the lower bands there may be too much absorption for multi-hop the signal is too weakOn the higher bands the MUF may not be high enough to refract the ray back to Earth for multi-hop the ray goes out into space,ionosphere,Earth,PVRC W
27、ebinar Mar 9,2011 K9LA,Higher MUF&Less Absorption,Are there modes that could give a higher MUF and/or lesser absorption?Yes-there appear to be three of themChordal hopDuctPedersen Ray,PVRC Webinar Mar 9,2011 K9LA,Chordal Hop,Example TEP(trans-equatorial propagation),K6QXY to ZL on 6mRay trace from P
28、roplab Promonthly median results,High density of electrons on either side of geomagnetic equatorExtremely long hop approximately twice a normal hopOnly two transits through the absorbing regionNo ground reflectionsLiterature says MUF is approximately 1.5 times normal F2 hop,refraction,refraction,hel
29、ps MUF and absorption,area of higher electron density,area of higher electron density,PVRC Webinar Mar 9,2011 K9LA,Duct,Requires upper and lower boundary for successive refractionsNeed entry and exit criteria-small range of anglesNo transits through the absorbing regionNo ground reflectionsLow grazi
30、ng angles with ionosphere higher MUFBelieved to allow extremely long distance QSOs on 160m,helps MUF and absorption,PVRC Webinar Mar 9,2011 K9LA,Pedersen Ray,Not a lot in the literature on the Pedersen RayComment from Ionospheric Radio(Davies,1990)Across the North Atlantic,occurrence tends to peak n
31、ear noon at the midpointOne would surmise that the ionosphere needs to be very stable for a ray to exactly parallel the Earth for long distancesProbably no help with MUF biggest advantage appears to be with lower absorption due to less transits of the absorbing region and no ground reflection losses
32、,helps absorption,1 and 2 are“low-angle”paths3 is“medium-angle”path4 and 5 are“high-angle”Pedersen Ray paths6 goes thru the ionosphere,PVRC Webinar Mar 9,2011 K9LA,A Detailed 20m Analysis,K2MO(AA2AE at the time)to ZS5BBO on July 5,2003 at 1230 UTC on 20m SSB via long pathK2MO reported that ZS5BBOs s
33、ignal was around S7(-83 dBm)Long path from W2 starts off in daylight,goes into darkness,and ends in daylightShort path has high MUF but marginal signal strength due to absorptionLong path signal strength from ZS predicted to be-125 dBmAbout 40 dB shy of S7,Short path 12,700 kmLong path 27,300 km,PVR
34、C Webinar Mar 9,2011 K9LA,The Ionosphere Along the LP,Note the tilts in the ionosphere at dawn(W2 end)and at dusk(ZS end)Tilt can refract the ray so that it encounters the ionosphere at more of a grazing angle(i.e.,a higher MUF)Good entry/exit criteria for duct,VK5,PVRC Webinar Mar 9,2011 K9LA,Ray T
35、race from W2 End,Proplab Pro can only ray trace out to 20,000 km(half way around)Do two ray tracesOne from W2 end(pictured)One from ZS end(not pictured)Ray trace from ZS end shows similar ductingSignal strength now estimated to be-89 dBmClose to observed-83 dBm,PVRC Webinar Mar 9,2011 K9LA,The Big P
36、icture,My crude picture on the left shows chordal hops as the ionosphere-ionosphere modeProplab Pro data indicates the K2MO-to-ZS5BBO QSO was ductingEasier to draw chordal hops!Youve probably seen a similar picture in the propagation literature.,Ionosphere-ionosphere modes are our friends,PVRC Webin
37、ar Mar 9,2011 K9LA,Summary,I hope you learned somethingThis webinar will be on the PVRC web sitehttp:/www.pvrc.org/webinar/webinars.htmThe slides will also be at http:/webinars:More Selected Topics in PropagationSuch as noise,10m long path,effect of the Moon on HF propagation,trans-equatorial propagationE-mail me if you have a specific Also visit http:/to Ken K4ZW and to the PVRCAnd now.Q/A,
