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by
John White
VA7JW
Revision 1 -11 April 2012
Rev 1 -11 Apr 2012 HF OPS 1

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 Part 1 – The Sun
 Solar 11 year cycle
 Solar ultraviolet radiation
 Solar Wind – charged particles flowing out from sun
 Solar Flares – x-rays, energetic particles
 Part 2 – The Earth
 Ionospheric Review
 Ionospheric Storms
 Solar Indices
Rev 1 -11 Apr 2012 HF OPS 2

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 Ultraviolet radiation ionizes rarified upper atmosphere
50 – 500 km
 Creates a “layer” of free electrons, “e”
 Electromagnetic radiation (RF) interacts with the electrons
 Electric field causes electron to “vibrate” at the radio frequency
 Vibrating electrons coherently re-radiate the energy
 Hence the radio wave propagates within the ionosphere
Rev 1 -11 Apr 2012 HF OPS 3

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
 Highly refractive
 Enables long skip being highest altitude
 Make possible world wide communications
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 Refractive for short skip being lower altitude
 Typically useful on lower bands
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 Non refractive
 Absorptive to lower frequencies
 Higher frequencies are able to penetrate
Rev 1 -11 Apr 2012 HF OPS 4

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 Starting at high altitude, the total electron count increases with decreasing altitude even as IONOGRAM
though air density increases
 Ionization peaks ~ 300 km
 Due to continued absorption,
electron production decreases
further down since UV is “consumed”
 Electron production ceases at
about 50 km D Layer E Layer F Layer
 Residual UV creates the Ozone layer at about 20 km
Rev 1 -11 Apr 2012 HF OPS 5

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 Ionization gradient, “e” increases with altitude
 If “e” density was same everywhere the radio wave would be “bent” just once, like air-water refraction, and not be returned earthward
 The increasing “e” density with height causes continual bending of the EM wave and hence the return to earth
 The higher the operating frequency , the greater the “e” density has to be to refract. This is Maximum Operating Frequency – MUF
 At solar minimum, reduced uV does not produce sufficient electron density to refract higher frequencies back to earth. Hi bands close
Rev 1 -11 Apr 2012 HF OPS 6

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 Earth has a magnetic field
 Field surrounding the planet is
called the MAGNETOSPHERE
 The magnetosphere is very important in that it deflects and shields the surface of the Earth from harmful high energy particle bombardment dangerous to life.
Rev 1 -11 Apr 2012 HF OPS 7

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 Solar Wind - negative electrons and positive protons
 Just as charged particles interact with Sun’s
magnetic field, so with Earth’s
 Particles travelling along the magnetic lines of force are effectively captured
B = magnetic line v = velocity of particle
F = force applied to particle
 Path becomes a spiral
 Earths magnetic field “traps“ these particles along the magnetic field line
Rev 1 -11 Apr 2012 HF OPS 8

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 Magnetosphere is distorted by the pressure of the Solar Wind
 Solar wind particle flow is fended off by the “bow wave”
 Electrons are particularly captured
 Protons not captured to same extent
 Some charge is captured at the bow wave
 Some of the charge is captured in the tail
 Some of the charge is diverted past Earth
 Captured charge flows in to the polar regions at the North and
South pole cusps
 This defines the auroral zone
Rev 1 -11 Apr 2012 HF OPS 9

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 Solar wind has an embedded magnetic field sense based on Suns field & particularly CME’s
 Wind field aligned with Earth’s (same direction) particles deflected around Earth and can be deposited in the “tail”
 Wind field opposite to Earth’s particles can couple into field directly from the front
S
Solar Wind
Field
Direction
N
Earth
Field
Direction
N
S
Rev 1 -11 Apr 2012
N
HF OPS
S
10

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 Solar Wind and the Magnetosphere
 Fields aligned http://youtu.be/lxWBlJ1kB7Q
 particles go into magneto-tail and then are guided in to the polar
Ionospheric regions from the “rear”
 Fields opposite
 particles coupled directly into polar Ionospheric regions from the front
 Either way, Ionosphere is GREATLY affected by precipitation of particles introduced into the polar regions
 Depending on the intensity & quantity, ionospheric effects can migrate southward and northward
Rev 1 -11 Apr 2012 HF OPS 11

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 Uniform ionization that follows the 11 year solar cycle smoothly through from the solar minimum to the solar maximum and back to the minimum
 Rather like the ideal weather temperature pattern, cool in winter smoothly warming to summer and smoothly cooling off towards winter
 Unfortunately for both, storms occur. Weather conditions change rapidly and unpredictably as does the ionosphere.
Rev 1 -11 Apr 2012 HF OPS 12

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 How to measure the state of the ionosphere
 Is it quiet, unsettled, disturbed, stormy etc ?
 Direct measurements of the ionosphere
 Height, critical frequencies etc by echo sounding (ionogram)
 Direct measurements of non-ionospheric parameters that affect the state of the ionosphere (ground and satellite based observations)
 Propagation forecasts are typically based on the indirect ionospheric measurements that infer ionospheric conditions
Rev 1 -11 Apr 2012 HF OPS 13

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 An Ionospheric Storm is a disturbance occurring in the ionosphere that alters propagation, generally for the worse
 Ionospheric storms directly driven by stormy “weather” on the Sun, particularly at the solar maximum
 Signals may be weakened, absorbed, subjected to erratic fading, multipath distortions, unusual modulations and noise increases or decreases
 The disturbances can be gradual or sudden, minor to severe, of short and log duration, and not altogether predictable
Rev 1 -11 Apr 2012 HF OPS 14

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 Think of ionosphere as weather clouds, highly variable, lumpy, moving, vary by location etc
 Storms will cause ionization densities to change
 Change not the same everywhere
 Polar, sunlit, local regions all differ
 All cause degrees of disruption to the steady state properties
 Extent of disruption depends on intensity of the storm
Rev 1 -11 Apr 2012 HF OPS 15

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 Ionospheric Earth Storms result from a Stormy Sun
 Ionospheric storms classified by NOAA
(National Oceanic and
Atmospheric Administration) according to the disturbing mechanism
(G) Geomagnetic Storms due to Solar Wind
(R) Radio Blackout Storms due to X-ray Flares
(S) Solar Radiation Storms due to High Energy Protons
Rev 1 -11 Apr 2012 HF OPS 16

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 Disturbances to the magnetosphere occur due to particle charge and magnetic fields carried by the solar wind
 Solar Wind most common purveyor of disturbances due to the constancy of the wind as compared to unpredictable eruptive events
 Drives aurora phenomena
 Geomagnetic events typically commence within hours can last for days; sometimes onset is sudden
Rev 1 -11 Apr 2012 HF OPS 17

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 Storm properties as affects HF radio
 A Geomagnetic Storm is designated by letter “G”
Rev 1 -11 Apr 2012 HF OPS 18

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 A Blackout is a near to complete loss of HF propagation
 Disturbances are caused by high energy X-rays illuminating the sunlit side of Earth
 X-rays are produced by Flares
 Onset of degradation is quick, within minutes
 X-rays penetrate deeply into the ionosphere
 D layer absorption attenuates signals to the extent that propagation can fail altogether
Rev 1 -11 Apr 2012 HF OPS 19

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 Storm properties as affects HF radio
 A Radio Blackout Storm is designated by letter “R”
Rev 1 -11 Apr 2012 HF OPS 20

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 Solar protons normally have insufficient energy to penetrate earths magnetic field
 Disturbances are caused by numerous and highly energetic protons entering the ionosphere in the polar regions
 High energy particles are able to penetrate to the D layer and result in over-dense ionization
 Increased electron density causes greater chaotic collisions increasing RF absorption
 Loss of paths through the N and S polar regions
 Depending on the intensity, the disturbance will move further towards the equator from both North and South direction
Rev 1 -11 Apr 2012 HF OPS 21

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 Storm properties as affects HF radio
 Solar Radiation Storm is designated by letter “S”
Rev 1 -11 Apr 2012 HF OPS 22

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 The following are the Major Solar Indices defining prevailing conditions,
 Solar Flux index - SFI
 Sun Spot Number - SSN
 “a” and “K” index
 Solar Wind parameters
 X Ray flux
 Protons
 Aurora activity
 MUF map
 Solar Images
 Current Conditions
 Forecast
Rev 1 -11 Apr 2012 HF OPS 23

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• http://dx.qsl.net/propagation/
 This site is installed on NSARC HF Stations
 Line by Line explanation of reported parameters
 There are many other forecast web sites
 Google “ HF Propagation” pick your own source …
Rev 1 -11 Apr 2012 HF OPS 24

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 SFI is a measure of the energy radiated by the Sun at 2800 MHz
 SFI ranges from ~ 50 at solar min to > 200 at solar max
 Measured as 10 -22 watts / square meter / per Hz of bandwidth
 Correlates very well with the level of uV radiation and hence the level of ionization state of the ionosphere
 Increased ionization supports high MUF’s; better DX opportunities and opening of higher bands
 SFI is the guide as to overall ionization levels linked to solar cycle
Rev 1 -11 Apr 2012 HF OPS 25

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 SSN can be used in same
way as SFI, your choice
 Observed number of sun spots is
statistically related to SFI
 Different measurement, much
the same indication for
propagation purposes
Rev 1 -11 Apr 2012 HF OPS 26

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 GEOMAGNETIC storm indicators
 Electric currents flow within the D and E layers as belts around the earth (electrojets) which in turn, generate a magnetic field
 Electrojet magnetic field is imposed on Earths field
 Changes in the current are due to solar wind disturbances
 “a” and “K“ measure the disturbance of Earths’ magnetic field to infer Ionospheric disturbance
 The value of the “a” index measures the change in value of
Earth’s magnetic field intensity
Rev 1 -11 Apr 2012 HF OPS 27

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 “a” and K are measured every 3 hours world wide
 “a” is an average of the last 8 readings over the last 24 hours
 “K” is the 3 hour reading advising us of change “now” taking place
Rev 1 -11 Apr 2012 HF OPS 28

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 “a” & “K” reports magnetic change impacting ionospheric disturbance
 a = 0 and K= 0 indicates a stable, quiet ionosphere
 Bands free of Geomagnetic disturbances
 Increased values of “a” and K, i,e. a=25 / K=3, will indicate disturbed conditions
 High values of “a” and K, i.e. a = 50, K=5, propagation will become difficult to impossible
 Bands unstable to closed.
Rev 1 -11 Apr 2012 HF OPS 29

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 Orientation of magnetic field
indicates coupling of particles
into ionosphere
 Wind speed variations reflect
Solar conditions; higher velocities
infer eruptions, flares, coronal
holes
 Pressure related to velocities
Rev 1 -11 Apr 2012 HF OPS 30

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 Flares produce x-rays
 X-rays are measured continuously by satellite and graphed according to their intensity
 X-rays are energetic and penetrate deep down into the D layer increasing absorption, leading to fades and Blackouts
 Sudden Ionospheric Disturbance or “SID”
GOES = Geostationary Operational Environmental Satellite
Rev 1 -11 Apr 2012 HF OPS 31

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 Flares rated by the intensity of emitted X-rays
 A, B and C class of little consequence, M class may be noticeable
 X class is very noticeable – higher bands go suddenly dead
Rev 1 -11 Apr 2012 HF OPS 32

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 Proton flux measured by satellite
 High energy protons produced by energetic flares
 Major component of Solar Radiation
Storm
 Polar blackouts known as Polar Cap
Absorptions, “PCA” events
Rev 1 -11 Apr 2012 HF OPS 33

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 Concentrated particle “precipitation” occurs at the poles where the magnetic field lines converge
 Particles enter the ionosphere. Energetic particles increase ionization levels and increase RF absorption
 Auroras result from intensive, ongoing ionization where light is emitted when recombination occurs
 Occurs in the lower E and D layers
 The extent (southward width) of the aurora indicates the magnitude of the particle activity and hence disturbance
Rev 1 -11 Apr 2012 HF OPS 34

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 A near real time MUF map
 MUF given in MHz
 Contours of equal MUF
 Gray Line
 Auroral zone- green lines
 Sun’s position
 Not a great circle map
 MUF is based on a 3000 km hop
 To use, look for DX location and estimate if MUF is sufficient over the path at operating freq
 Contours ~ 1 to 2 MHz
 Lowest Useable Frequency LUF are red lines (D absorption)
 frequencies < LUF will be absorbed
Rev 1 -11 Apr 2012 HF OPS 35

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 Current images of Sun state
 Double click on any image
to load a large detained image
 Useful for catching a quick
visual image of Sun activity
 Refer to Part 1 this presentation for interpretations http://umbra.nascom.nasa.gov/images/latest_aia_171.gif
Rev 1 -11 Apr 2012 HF OPS 36

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 Solar Flux is very good
 Bands ought to be open
As reported on
DX cluster Oct 23
At 00:36 UTC
 Geomagnetic Field (GMF)
 Quiet, ought to be good
 Radio Blackout
 Extended M1.3 flare
 X-Ray absorption
 Observation
 20m was dead; 10 m was open
 Lower frequencies being
absorbed but high SFI supports higher frequency propagation
Rev 1 -11 Apr 2012 HF OPS 37

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 Forecasts are based on Solar observations, such as eruptive
Sun spots
 New spots rotating into view, old ones rotating out of view
 Ability of satellites to look on far side to see what’s coming…
Rev 1 -11 Apr 2012 HF OPS 38

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…in a few words …..
With apologies to Jerry Lee Lewis
Rev 1 -11 Apr 2012 HF OPS 39

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 http://softwaves.net/sun/sun-now.html
 http://www.swpc.noaa.gov/NOAAscales/
 http://www.qsl.net/w2vtm/hf_solar.html
Good DX to all
Rev 1 -11 Apr 2012 HF OPS 40