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Selected Topics in PropagationPowerPoint Presentation

Selected Topics in Propagation

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Presentation Transcript

What We’ll Cover in This Session

- An Update on Cycle 24
- Will it be an underachiever?

- The M-Factor
- Some theory about one of the basic parameters of the ionosphere

- Sunspots and Solar Flux During Cycle 23
- An interesting anomaly – not sure what it says yet

- Ionosphere-Ionosphere Modes
- There’s more than multi-hop out there

PVRC Webinar Mar 9, 2011 K9LA

An Update on Cycle 24

PVRC Webinar Mar 9, 2011 K9LA

Review of the Predictions

140

90

90

These are from the Solar Cycle 24 Prediction

Panel (NOAA, NASA, ISES, and other personnel)

PVRC Webinar Mar 9, 2011 K9LA

The Latest Prediction

There may be an updated prediction (lower) from the Solar Cycle 24 Prediction Panel

PVRC Webinar Mar 9, 2011 K9LA

Marshall Space Flight Center

Similar prediction to Kane, “Size of the coming solar cycle 24 based on

Ohl’s Precursor Method, final estimate”, AnnalesGeophysicae, July 2010

59

A lot of evidence pointing to small Cycle 24

PVRC Webinar Mar 9, 2011 K9LA

But . . . . . . .

- Not everyone agrees that Cycle 24 will be so small
- Recent prediction in Solar Physics
- Maximum of 131 +/- 20
- Maximum in July 2012 +/- 4 months
- From 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 2010

- This would be good for the higher bands – and for 6m F2
- If Cycle 24 is a small one, though, 6m F2 propagation will take the biggest hit
- Thank goodness for summer E region propagation

PVRC Webinar Mar 9, 2011 K9LA

Predictions in General

- Over 60 predictions for Cycle 24
- Maximum smoothed sunspot number from 40 to 185

- Common forecasting methods
- Statistical methods: length of Cycle n correlated to maximum of Cycle n+1, maximum R12 correlated to minimum R12
- Generally gives low Cycle 24

- Geomagnetic precursor methods: Ap, aa, and number of magnetically disturbed days correlate to next maximum
- Unfortunately can give widely varied answers depending on assumptions

- Polar field precursor method: strength of Sun’s polar field correlates to next cycle
- Gives small Cycle 24

- Solar dynamo method: the conveyor belt theory
- Unfortunately can give widely varied answers depending on assumptions

- Statistical methods: length of Cycle n correlated to maximum of Cycle n+1, maximum R12 correlated to minimum R12
- Summary of forecasting methods from K. J. Li, et al, A brief review on the presentation of cycle 24, the first integrated solar cycle in the new millennium, AnnalesGeophysicae, 29, 341-348, 2011

PVRC Webinar Mar 9, 2011 K9LA

Recent NASA News

- “Researchers Crack the Mystery of the Missing Sunspots”
- Solar scientists claim they’ve developed a new computer model of the sun's interior that gets the physics right for all three aspects of the sunspot generation process --the magnetic dynamo, the conveyor belt, and the buoyant evolution of sunspot magnetic fields

- Maybe this will help narrow down the range of the forecasted maximum smoothed sunspot number

http://science.nasa.gov/science-news/science-at-nasa/2011/02mar_spotlesssun/

- Keep an eye on NASA Headline News, http://www.solarcycle24.com, http://www.swpc.noaa.gov, and http://spaceweather.com

PVRC Webinar Mar 9, 2011 K9LA

ARRL DX CW and PH

ARRL DX PH

ARRL DX CW

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

It’s headed in the right direction!

PVRC Webinar Mar 9, 2011 K9LA

ARRL DX CW and PH

ARRL DX PH

red line is one-day running average

ARRL DX CW

28 MHz

21 MHz

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

Recent solar activity helped ARRL DX PH the most

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 frequency
- MUF = M-Factor x Critical Frequency
- M-Factor and critical frequency (along with other parameters) are measured by ionosondes

- M-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)

ionosphere

sine of this angle

If the angle = 90o (vertically incident), then the M-Factor equals 1 and the MUF = the critical frequency

PVRC Webinar Mar 9, 2011 K9LA

Apply It To The Ionosphere

- Wow – if the critical frequency is 5 MHz, then the MUF would be 285 MHz
- But hold on – the Earth-ionosphere system isn’t flat – it’s spherical

ionosphere

Ω = 1o

= 1o

Earth

Thus the M-Factor = 1

sine (1o)

= 57

PVRC Webinar Mar 9, 2011 K9LA

The Real Earth-Ionosphere System

Ω = 17.5o

= 1o

ionosphere

height now matters – let’s assume 300 km

Earth

Now the M-Factor = 1

sine (17.5o)

= 3.3

MUF for this F2 region scenario is about 3 times the critical frequency

PVRC Webinar Mar 9, 2011 K9LA

heightdistanceΩM-Factor

100 km 0 deg 2243 km 10.1 deg 5.7

5 deg 1389 km 11.3 deg 5.1

10 deg 927 km 14.2 deg 4.1

25 deg 408 km 26.8 deg 2.2

200 km 0 deg 3152 km 14.2 deg 4.1

5 deg 2226 km 15.0 deg 3.9

10 deg 1620 km 17.3 deg 3.4

25 deg 781 km 28.5 deg 2.1

300km 0 deg 3836 km 17.3 deg 3.4

5 deg 2877 km 17.9 deg 3.3

10 deg 2193 km 19.9 deg 2.9

25 deg 1124 km 30.1 deg 2.0

400 km 0 deg 4401 km 19.8 deg 3.0

5 deg 3422 km 20.4 deg 2.9

10 deg 2687 km 22.1 deg 2.7

25 deg 1412 km 31.4 deg 1.9

M-Factor vs Height and AngleThis calculation assumes specular (mirror-like) reflection over an infinitely short distance – the real-world is 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 the critical frequency
- Ionosondes report the M-Factor for a 3000 km hop
- M(3000)F2 or M(D) where D = 3000 km

- Ionosondes report the M-Factor for a 3000 km hop
- For the E region with low angles, the MUF is approximately 5 times the critical frequency
- Close enough for sporadic E, too

Allows you to estimate the MUF only knowing the critical frequency

PVRC Webinar 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 what’s happening
- Reason #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 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 values)

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 peak is a bit lower
- In terms of smoothed solar flux, second peak is definitely higher
- We had much better 6m F2 propagation during the second peak

Cycle 23 data

Nov 2001

April 2000

PVRC Webinar Mar 9, 2011 K9LA

Why The Anomaly?

- Dr. Leif Svalgaard (member of the Cycle 24 Prediction Panel) has several opinions
- The 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 Sun’s corona or chromosphere accounting for additional 10.7 cm emission
- Penn and Livingston’s observations (Penn, M. J. and W. Livingston, Temporal 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 in an undercount of sunspots

- No definite answer (yet!)
- Visit http://www.leif.org/research and select item 1020 for details
- Check out my Propagation columns in the forthcoming May 2011 and June 2011 issues of WorldRadio Online for more on this
- http://www.worldradiomagazine.com/ WRO is free !

PVRC Webinar Mar 9, 2011 K9LA

Ionosphere-Ionosphere 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 weak
- On 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 Webinar 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 them
- Chordal hop
- Duct
- Pedersen Ray

chordal hop unaffected by the ionosphere

in between refraction points

duct consecutive refractions

between E and F regions

Pedersen Ray high angle ray, close to MUF,

parallels the Earth

PVRC Webinar Mar 9, 2011 K9LA

Chordal Hop

- Example – TEP (trans-equatorial propagation)

K6QXY to ZL on 6m

Ray trace from Proplab Pro

monthly median results

area of higher electron density

area of higher electron density

refraction

refraction

- High density of electrons on either side of geomagnetic equator
- Extremely long hop – approximately twice a normal hop
- Only two transits through the absorbing region
- No ground reflections
- Literature says MUF is approximately 1.5 times normal F2 hop

helps MUF and absorption

PVRC Webinar Mar 9, 2011 K9LA

Duct

- Requires upper and lower boundary for successive refractions
- Need entry and exit criteria - small range of angles
- No transits through the absorbing region
- No ground reflections
- Low grazing angles with ionosphere – higher MUF
- Believed 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 Ray
- Comment from Ionospheric Radio (Davies, 1990)
- Across the North Atlantic, occurrence tends to peak near noon at the midpoint

- One would surmise that the ionosphere needs to be very stable for a ray to exactly parallel the Earth for long distances
- Probably 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

- 1 and 2 are “low-angle” paths
- 3 is “medium-angle” path
- 4 and 5 are “high-angle” Pedersen Ray paths
- 6 goes thru the ionosphere

helps absorption

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 path
- K2MO reported that ZS5BBO’s signal was around S7 (~ -83 dBm)
- Long path from W2 starts off in daylight, goes into darkness, and ends in daylight
- Short path has high MUF but marginal signal strength due to absorption
- Long path signal strength from ZS predicted to be -125 dBm
- About 40 dB shy of S7

Short path 12,700 km

Long path 27,300 km

PVRC 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 Trace from W2 End

- Proplab Pro can only ray trace out to 20,000 km (half way around)
- Do two ray traces
- One from W2 end (pictured)
- One from ZS end (not pictured)

- Ray trace from ZS end shows similar ducting
- Signal strength now estimated to be -89 dBm
- Close to observed -83 dBm

PVRC Webinar Mar 9, 2011 K9LA

The Big Picture

- My crude picture on the left shows chordal hops as the ionosphere-ionosphere mode
- Proplab Pro data indicates the K2MO-to-ZS5BBO QSO was ducting
- Easier to draw chordal hops!
- You’ve probably seen a similar picture in the propagation literature.

Ionosphere-ionosphere modes are our friends

PVRC Webinar Mar 9, 2011 K9LA

Summary

- I hope you learned something
- This webinar will be on the PVRC web site
- http://www.pvrc.org/webinar/webinars.htm
- The slides will also be at http://mysite.ncnetwork.net/k9la

- Follow-up webinars: More Selected Topics in Propagation
- Such as noise, 10m long path, effect of the Moon on HF propagation, trans-equatorial propagation

- E-mail me if you have a specific topic
- [email protected]
- Also visit http://mysite.ncnetwork.net/k9la

- Thanks to Ken K4ZW and to the PVRC
- And now . . . . . . . . . . . Q/A

PVRC Webinar Mar 9, 2011 K9LA

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