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1、PVRC Webinar Mar 9, 2011 K9LAWhat Well Cover in This SessionAn 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 Cycle 23An interesting anomaly not sure what it says yetIonosphere-Ionosphere ModesTh

2、eres more than multi-hop out there第1頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAAn Update on Cycle 24第2頁，共35頁。PVRC Webinar Mar 9, 2011 K9LALatest DataminimumSmoothed 10.7 cm solar flux is still rising第3頁，共35頁。PVRC Webinar Mar 9, 2011 K9LALatest Dataminimum第4頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAReview of the

3、PredictionsThese are from the Solar Cycle 24 PredictionPanel (NOAA, NASA, ISES, and other personnel)1409090第5頁，共35頁。The Latest PredictionThere may be an updated prediction (lower) from the Solar Cycle 24 Prediction PanelPVRC Webinar Mar 9, 2011 K9LA第6頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAMarshall Spac

4、e Flight CenterSimilar prediction to Kane, “Size of the coming solar cycle 24 based onOhls Precursor Method, final estimate”, Annales Geophysicae, July 201059A lot of evidence pointing to small Cycle 24第7頁，共35頁。But . . . . . . .Not everyone agrees that Cycle 24 will be so smallRecent prediction in S

5、olar 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 is a sm

6、all one, though, 6m F2 propagation will take the biggest hitThank goodness for summer E region propagationPVRC Webinar Mar 9, 2011 K9LA第8頁，共35頁。Predictions in GeneralOver 60 predictions for Cycle 24Maximum smoothed sunspot number from 40 to 185Common forecasting methodsStatistical methods: length of

7、 Cycle 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 pre

8、cursor method: 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 2

9、4, the first integrated solar cycle in the new millennium, Annales Geophysicae, 29, 341-348, 2011PVRC Webinar Mar 9, 2011 K9LA第9頁，共35頁。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 th

10、e physics right for all three 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 numberPVRC Webinar Mar 9, 2011 K9LAKeep an eye on

11、 NASA Headline News, , , and /science-news/science-at-nasa/2011/02mar_spotlesssun/第10頁，共35頁。ARRL DX CW and PHPVRC Webinar Mar 9, 2011 K9LA1 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 8FebMarIts headed in the right direction!ARRL DX CWARRL DX PH第11頁，共35頁。AR

12、RL DX CW and PHPVRC Webinar Mar 9, 2011 K9LARecent solar activity helped ARRL DX PH the mostARRL DX CWARRL DX PHred line is one-day running average1 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 8FebMar28 MHz21 MHz第12頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAThe M-

13、FactorNo, not this M第13頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAWhat 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-

14、Factor 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 angleIf the angle = 90o (vertically incident), then the M-Factor equals 1 and the MUF = the critical frequencyionosphere第14頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAApp

15、ly It To The IonosphereionosphereEarthThus the M-Factor = 1 sine (1o) = 57Wow 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第15頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAThe Real Earth-Ionosphere SystemionosphereEar

16、thheight now matters lets assume 300 kmNow the M-Factor = 1 sine (17.5o) = 3.3MUF for this F2 region scenario is about 3 times the critical frequency = 1o = 17.5o第16頁，共35頁。M-Factor vs Height and AnglePVRC Webinar Mar 9, 2011 K9LAThis calculation assumes specular (mirror-like) reflection over an infi

17、nitely short distance the real-world is refraction over a spherical distance height distance M-Factor100 km0 deg2243 km 10.1 deg5.75 deg1389 km 11.3 deg5.110 deg 927 km 14.2 deg4.125 deg 408 km 26.8 deg2.2200 km0 deg3152 km 14.2 deg4.15 deg2226 km 15.0 deg3.910 deg1620 km 17.3 deg3.425 deg 781 km 28

18、.5 deg2.1300km0 deg3836 km 17.3 deg3.45 deg2877 km 17.9 deg3.310 deg2193 km 19.9 deg2.925 deg1124 km 30.1 deg2.0400 km0 deg4401 km 19.8 deg3.05 deg3422 km 20.4 deg2.910 deg2687 km 22.1 deg2.725 deg1412 km 31.4 deg1.9The higher the layer, the longer the hop distance for a given angle But the higher t

19、he layer, the lower the M-Factor (lower MUF) for a given angle 第17頁，共35頁。PVRC Webinar Mar 9, 2011 K9LARule of 3 and Rule of 5For the F2 region with low angles, the MUF is approximately 3 times the critical frequencyIonosondes report the M-Factor for a 3000 km hopM(3000)F2 or M(D) where D = 3000 kmFo

20、r the E region with low angles, the MUF is approximately 5 times the critical frequencyClose enough for sporadic E, tooAllows you to estimate the MUF only knowing the critical frequency第18頁，共35頁。PVRC Webinar Mar 9, 2011 K9LASunspots and Solar FluxDuring Cycle 23第19頁，共35頁。PVRC Webinar Mar 9, 2011 K9L

21、AWhy 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 through a smoothed solar index - this is the basis on which the statistical mode

22、l of the ionosphere for our propagation predictions was developed第20頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAEarly CorrelationEquation from texts on the ionosphere: SF12 = 63.75 + .728 SSN12 + .00089 SSN122 (the “12” subscript denotes smoothed values)Side note - there is very little correlation between d

23、aily 10.7 cm solar flux and daily sunspot number第21頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAMore DataSome more scatter about the trend line, but still pretty good.第22頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAInclude Cycle 23In terms of smoothed sunspot number, second peak is a bit lowerIn terms of smoothed sol

24、ar flux, second peak is definitely higherWe had much better 6m F2 propagation during the second peakCycle 23 dataApril 2000Nov 2001第23頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAWhy The Anomaly?Dr. Leif Svalgaard (member of the Cycle 24 Prediction Panel) has several opinionsThe sunspot counting procedure or

25、 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 Changes in Sunspot Umbra

26、l 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 in an undercount o

27、f sunspotsNo definite answer (yet!)Visit /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 this/WRO is free !第24頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAIonosphere-Ionosphere Modes第25頁，共35頁。PVRC Web

28、inar Mar 9, 2011 K9LAMulti-Hop Can Have LimitsOn 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 spaceionosphereEarth第26頁，共35頁。PVRC Webinar Mar

29、 9, 2011 K9LAHigher MUF & Less AbsorptionAre there modes that could give a higher MUF and/or lesser absorption?Yes - there appear to be three of themChordal hopDuctPedersen Raychordal hopunaffected by the ionospherein between refraction pointsductconsecutive refractionsbetween E and F regions Peders

30、en Rayhigh angle ray, close to MUF,parallels the Earth第27頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAChordal HopExample TEP (trans-equatorial propagation)K6QXY to ZL on 6mRay trace from Proplab Promonthly median resultsHigh density of electrons on either side of geomagnetic equatorExtremely long hop approxi

31、mately twice a normal hopOnly two transits through the absorbing regionNo ground reflectionsLiterature says MUF is approximately 1.5 times normal F2 hoprefractionrefractionhelps MUF and absorptionarea of higher electron densityarea of higher electron density第28頁，共35頁。PVRC Webinar Mar 9, 2011 K9LADuc

32、tRequires upper and lower boundary for successive refractionsNeed entry and exit criteria - small range of anglesNo transits through the absorbing regionNo ground reflectionsLow grazing angles with ionosphere higher MUFBelieved to allow extremely long distance QSOs on 160mhelps MUF and absorption第29

33、頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAPedersen RayNot a lot in the literature on the Pedersen RayComment from Ionospheric Radio (Davies, 1990)Across the North Atlantic, occurrence tends to peak near noon at the midpointOne would surmise that the ionosphere needs to be very stable for a ray to exactly

34、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 losseshelps absorption1 and 2 are “l(fā)ow-angle” paths3 is “medium-angle” path4 and 5 are “high-angle” Pedersen Ray

35、paths6 goes thru the ionosphere第30頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAA Detailed 20m AnalysisK2MO (AA2AE at the time) to ZS5BBO on July 5, 2003 at 1230 UTC on 20m SSB via long pathK2MO reported that ZS5BBOs signal was around S7 ( -83 dBm)Long path from W2 starts off in daylight, goes into darkness,

36、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 S7Short path 12,700 kmLong path 27,300 km第31頁，共35頁。PVRC Webinar Mar 9, 2011 K9LAThe Ionosphere Along the LPNote the tilts in the ionosphere at dawn (W2 end) and at dusk (ZS end)Tilt can refract the ray so that it