Solar Conditions
The mostly calm propagation conditions will continue and the only minor variations will be August 6-10 when the Boulder 'A' index will peak at 8. Things will then settle down to the recent 'norm' of A=5 and K=2. The Solar Flux should also remain between 68 and 70 during this period.
We saw a run of eight days with a large sunspot during July, but none have emerged since. Unlike other recent spots, this one did not appear just for one or two days and then vanish. Sunspot numbers for July 9-15 were 15, 13, 0, 0, 0, 0 and 0 with a mean of 4. The Solar flux was 69.1, 67.8, 68.2, 68, 67.2, 66.6 and 66.5 with a mean of 67.6. The estimated planetary A indices were 6, 7, 4, 5, 10, 8 and 5 with a mean of 6.4. The estimated mid-latitude A indices were 6, 7, 2, 4, 5, 6 and 3 with a mean of 4.7.
Previous Solar Cycles
Solar Cycle 23 began in October 1996, so Solar Cycle 24 should have had an impact on Solar conditions by now, as Solar cycles typically last 11 years, but the ‘false alarms’ continue as we see the occasional burst of Solar activity followed by yet another period of ‘Quiet to Unsettled’. In October 1991, Solar Cycle 22 reached its peak in a short period, but Solar Cycles 17, 20 and 23 were very similar to each other. Here is another website which has both text and graphical charts which show this quite clearly: http://www.solen.info/solar/
The WM7d forecast is easy to understand as it gets to the point without going through too much detailed data: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml
A 45 day text based forecast can be found at: http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html
Here is yet another site dedicated to HF propagation conditions: http://dx.qsl.net/propagation/
Sunspot Numbers:
Observers around the world compute daily sunspot numbers by multiplying the number of observed sunspot groups by ten and then adding this product to his total count of individual spots. Results vary greatly, since the measurement strongly depends on observer interpretation and experience and on the stability of the Earth's atmosphere above the observing site.
Moreover, the use of Earth as a platform from which to record these numbers contributes to their variability, too, because the sun rotates and the evolving spot groups are distributed unevenly across solar longitudes.
To compensate for these limitations, each daily international number is computed as a weighted average of measurements made from a network of cooperating observatories. Sunspot counts rise and fall approximately every 11.1 years. The cycle, though, is not symmetrical, for the spot count takes on the average about 4.8 years to rise from a minimum to a maximum and another 6.2 years to fall to a minimum once again. The largest annual mean number (190.2) occurred in 1957.
There is a comprehensive FAQ’s page about Sunspot numbers and Space Weather in general at: http://www.space.com/spacewatch/solar_faq.html#g1
ASAP Software
Bradford University have a software download called ASAP (Automated Solar Activity Prediction) which shows real time Solar data on your PC, although I haven’t tried it yet. Details at: http://spaceweather.inf.brad.ac.uk/asap.html
Thanks to Mike Terry and Ken Fletcher for regular updates.
Thursday, 23 July 2009
Friday, 19 June 2009
July '09
Propagation Forecast
The Boulder A, and K indices will remain at their ‘norm’ of 5 and 2 until the end of June when there will be a disturbance on the 30th with the ‘A’ at 5 and the ‘K’ at 3. Things should return to normal by 2nd July with the A and the K back to 5 and 2 respectively. The Solar Flux however, will go from 68 to 70 around 26 June, dropping back to 68 by July 10th.
Mystery of the Missing Sunspots, Solved?
The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why.
At an American Astronomical Society press conference in Boulder, Colorado, researchers announced that a jet stream deep inside the sun is migrating slower than usual through the star's interior, giving rise to the current lack of sunspots. Rachel Howe and Frank Hill of the National Solar Observatory (NSO) in Tucson, Arizona, used a technique called Helioseismology to detect and track the jet stream down to depths of 7,000 km below the surface of the sun. The sun generates new jet streams near its poles every 11 years, they explained to a room full of reporters and fellow scientists. The streams migrate slowly from the poles to the equator and when a jet stream reaches the critical latitude of 22 degrees, new-cycle sunspots begin to appear. Howe and Hill found that the stream associated with the next solar cycle has moved sluggishly, taking three years to cover a 10 degree range in latitude compared to only two years for the previous solar cycle. The jet stream is now, finally, reaching the critical latitude, heralding a return of solar activity in the months and years ahead.
"It is exciting to see", says Hill, "that just as this sluggish stream reaches the usual active latitude of 22 degrees, a year late. We finally begin to see new groups of sunspots emerging." The current solar minimum has been so long and deep, some scientists speculated that the sun might enter a long period with no sunspot activity at all, akin to the Maunder Minimum of the 17th century. This new result dispels those concerns. The sun's internal magnetic dynamo is still operating, and the sunspot cycle is not "broken." (NASA Science News 17 June 2009)
CQ Magazine Propagation editor challenges Solar cycle 24 Predictions
CQ magazine's Propagation Editor is challenging the accuracy of the newest predictions on Solar Cycle 24. The revised prediction, issued in late May by a panel of solar experts, suggests a weak sunspot cycle with a peak in 2013. But CQ Propagation Editor Tomas Hood, NW7US, is asking "How Credible Are These 'Experts'?"
In an online commentary posted on the CQ magazine website, Hood notes that this same group of so-called "experts" has issued multiple predictions for this cycle already, all of which they now say are wrong, and asks why we should believe they're right this time.
Hood points out that, while the Sun itself is millions of years old, scientists have been tracking solar activity for just a few hundred years. "In my view," he says, "it is pretty arrogant to postulate that mankind has any real understanding and handle on what the Sun might do next. If none of the models are totally correct, how are they making this current prediction with such dismal expectations? I'm not holding my breath in favour of supporting any of the predictions at this point." He also points out that there are already signs of "an awakening Solar Cycle 24," and encourages hams to "enjoy the unique propagation opportunities currently presenting themselves during this quiet phase," and to "prepare now for whatever the sun will do by honing your radio skills."
( http://www.cq-amateur-radio.com Via Southgate ARC http://www.southgatearc.org and Mike Terry)
HUF, MUF and LUF Charts
Ken Fletcher sent me a link to some useful charts of the Highest, Medium and Lowest useable frequency charts which can be downloaded from the ARRL website in PDF format. These regional charts are based on average readings for June ’09, and some may remember similar charts being published in Wireless World. http://www.arrl.org/qst/propcharts/2009/06/East-Coast.pdf. Charts can also be found at: http://www.dxzone.com/catalog/Propagation/
Links to these articles can be found at: www.jameswelsh.org.uk
The Boulder A, and K indices will remain at their ‘norm’ of 5 and 2 until the end of June when there will be a disturbance on the 30th with the ‘A’ at 5 and the ‘K’ at 3. Things should return to normal by 2nd July with the A and the K back to 5 and 2 respectively. The Solar Flux however, will go from 68 to 70 around 26 June, dropping back to 68 by July 10th.
Mystery of the Missing Sunspots, Solved?
The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why.
At an American Astronomical Society press conference in Boulder, Colorado, researchers announced that a jet stream deep inside the sun is migrating slower than usual through the star's interior, giving rise to the current lack of sunspots. Rachel Howe and Frank Hill of the National Solar Observatory (NSO) in Tucson, Arizona, used a technique called Helioseismology to detect and track the jet stream down to depths of 7,000 km below the surface of the sun. The sun generates new jet streams near its poles every 11 years, they explained to a room full of reporters and fellow scientists. The streams migrate slowly from the poles to the equator and when a jet stream reaches the critical latitude of 22 degrees, new-cycle sunspots begin to appear. Howe and Hill found that the stream associated with the next solar cycle has moved sluggishly, taking three years to cover a 10 degree range in latitude compared to only two years for the previous solar cycle. The jet stream is now, finally, reaching the critical latitude, heralding a return of solar activity in the months and years ahead.
"It is exciting to see", says Hill, "that just as this sluggish stream reaches the usual active latitude of 22 degrees, a year late. We finally begin to see new groups of sunspots emerging." The current solar minimum has been so long and deep, some scientists speculated that the sun might enter a long period with no sunspot activity at all, akin to the Maunder Minimum of the 17th century. This new result dispels those concerns. The sun's internal magnetic dynamo is still operating, and the sunspot cycle is not "broken." (NASA Science News 17 June 2009)
CQ Magazine Propagation editor challenges Solar cycle 24 Predictions
CQ magazine's Propagation Editor is challenging the accuracy of the newest predictions on Solar Cycle 24. The revised prediction, issued in late May by a panel of solar experts, suggests a weak sunspot cycle with a peak in 2013. But CQ Propagation Editor Tomas Hood, NW7US, is asking "How Credible Are These 'Experts'?"
In an online commentary posted on the CQ magazine website, Hood notes that this same group of so-called "experts" has issued multiple predictions for this cycle already, all of which they now say are wrong, and asks why we should believe they're right this time.
Hood points out that, while the Sun itself is millions of years old, scientists have been tracking solar activity for just a few hundred years. "In my view," he says, "it is pretty arrogant to postulate that mankind has any real understanding and handle on what the Sun might do next. If none of the models are totally correct, how are they making this current prediction with such dismal expectations? I'm not holding my breath in favour of supporting any of the predictions at this point." He also points out that there are already signs of "an awakening Solar Cycle 24," and encourages hams to "enjoy the unique propagation opportunities currently presenting themselves during this quiet phase," and to "prepare now for whatever the sun will do by honing your radio skills."
( http://www.cq-amateur-radio.com Via Southgate ARC http://www.southgatearc.org and Mike Terry)
HUF, MUF and LUF Charts
Ken Fletcher sent me a link to some useful charts of the Highest, Medium and Lowest useable frequency charts which can be downloaded from the ARRL website in PDF format. These regional charts are based on average readings for June ’09, and some may remember similar charts being published in Wireless World. http://www.arrl.org/qst/propcharts/2009/06/East-Coast.pdf. Charts can also be found at: http://www.dxzone.com/catalog/Propagation/
Links to these articles can be found at: www.jameswelsh.org.uk
Friday, 22 May 2009
Propagation June '09
Propagation Forecast
The Boulder 'A' index has remained at a steady 5 and the K index at 2. The first half of June will see 2 fluctuations in these figures. The first one being June 1 – 4 with the A index peaking at 10 and the K index at 4 on June 4th, and again 10th June with the A index peaking at 8 and the K index at 3. The Solar Flux is also starting to vary. June will start out at 70 but this will rise to 72 by Jun 4th and to 74 by the 8th, where it will remain until at least June 13th.
Solar Cycle 24 Prediction Update: Solar Minimum Was December 2008
The Solar Cycle 24 Prediction Panel has reached a consensus decision on the prediction of the next solar cycle (Cycle 24). First, the panel has agreed that solar minimum occurred in December, 2008. This still qualifies as a prediction since the smoothed sunspot number is only valid through September, 2008. The panel has decided that the next solar cycle will be below average in intensity, with a maximum sunspot number of 90. Given the predicted date of solar minimum and the predicted maximum intensity, solar maximum is now expected to occur in May, 2013. Note, this is a consensus opinion, not a unanimous decision. A supermajority of the panel did agree to this prediction. See: http://www.swpc.noaa.gov/SolarCycle/SC24/
This contradicts a report in March 2006 when Dr David Hathaway of the National Space Science and Technology Centre (NSSTC) announced that solar minimum had already arrived and that Solar Maximum would peak in 2010-2011 and would be 30% to 50% stronger than the historic solar maximum of 1958.
In 2006, researchers announced that the most intense storm in 50 years was coming. The prediction came from a team led by Mausamu Dikpati of the National Centre for Atmospheric Research (NCAR). The next sunspot cycle was predicted to be 30% to 50% stronger than the historic solar max of 1958.
From: http://www.nasa.gov/vision/universe/solarsystem/10mar_stormwarning.html
The 1958 Solar Maximum
In 1958 satellites were in their infancy with the Russian Sputnik being launched in October and also Explorer 1, the first US satellite was launched that year. Even so, people knew something was happening when the Northern Lights were sighted 3 times over Mexico. If a similar maximum happened today, it would be noticed by its effect on mobile phones, weather satellites and possibly domestic TV satellites.
The Conveyor Belt Effect
Dr David Hathaway of the NSSTC also has a theory about the ‘Conveyor Belt’ effect which is caused by revolving magnetic fields which carry sunspots away from the sun and back again when they lose their energy.
When the belt is turning "fast," it means that lots of magnetic fields are being swept up, and that a future sunspot cycle is going to be intense. This is a basis for forecasting: "The belt was turning fast in 1986-1996," says Hathaway. "Old magnetic fields swept up then should re-appear as big sunspots. All this happens with massive slowness and a loop can last between 30 and 50 years, so predictability is still variable. Pictures at: http://www.nasa.gov/vision/universe/solarsystem/10mar_stormwarning.html
Historical Solar data Charts Solar charts from 1954 to 2006 from the World Data Centre are available at http://www.solen.info/solar/history/
Thanks to Mike Terry and Ken Fletcher for regular updates. Links to these articles can be found at www.jameswelsh.org.uk
The Boulder 'A' index has remained at a steady 5 and the K index at 2. The first half of June will see 2 fluctuations in these figures. The first one being June 1 – 4 with the A index peaking at 10 and the K index at 4 on June 4th, and again 10th June with the A index peaking at 8 and the K index at 3. The Solar Flux is also starting to vary. June will start out at 70 but this will rise to 72 by Jun 4th and to 74 by the 8th, where it will remain until at least June 13th.
Solar Cycle 24 Prediction Update: Solar Minimum Was December 2008
The Solar Cycle 24 Prediction Panel has reached a consensus decision on the prediction of the next solar cycle (Cycle 24). First, the panel has agreed that solar minimum occurred in December, 2008. This still qualifies as a prediction since the smoothed sunspot number is only valid through September, 2008. The panel has decided that the next solar cycle will be below average in intensity, with a maximum sunspot number of 90. Given the predicted date of solar minimum and the predicted maximum intensity, solar maximum is now expected to occur in May, 2013. Note, this is a consensus opinion, not a unanimous decision. A supermajority of the panel did agree to this prediction. See: http://www.swpc.noaa.gov/SolarCycle/SC24/
This contradicts a report in March 2006 when Dr David Hathaway of the National Space Science and Technology Centre (NSSTC) announced that solar minimum had already arrived and that Solar Maximum would peak in 2010-2011 and would be 30% to 50% stronger than the historic solar maximum of 1958.
In 2006, researchers announced that the most intense storm in 50 years was coming. The prediction came from a team led by Mausamu Dikpati of the National Centre for Atmospheric Research (NCAR). The next sunspot cycle was predicted to be 30% to 50% stronger than the historic solar max of 1958.
From: http://www.nasa.gov/vision/universe/solarsystem/10mar_stormwarning.html
The 1958 Solar Maximum
In 1958 satellites were in their infancy with the Russian Sputnik being launched in October and also Explorer 1, the first US satellite was launched that year. Even so, people knew something was happening when the Northern Lights were sighted 3 times over Mexico. If a similar maximum happened today, it would be noticed by its effect on mobile phones, weather satellites and possibly domestic TV satellites.
The Conveyor Belt Effect
Dr David Hathaway of the NSSTC also has a theory about the ‘Conveyor Belt’ effect which is caused by revolving magnetic fields which carry sunspots away from the sun and back again when they lose their energy.
When the belt is turning "fast," it means that lots of magnetic fields are being swept up, and that a future sunspot cycle is going to be intense. This is a basis for forecasting: "The belt was turning fast in 1986-1996," says Hathaway. "Old magnetic fields swept up then should re-appear as big sunspots. All this happens with massive slowness and a loop can last between 30 and 50 years, so predictability is still variable. Pictures at: http://www.nasa.gov/vision/universe/solarsystem/10mar_stormwarning.html
Historical Solar data Charts Solar charts from 1954 to 2006 from the World Data Centre are available at http://www.solen.info/solar/history/
Thanks to Mike Terry and Ken Fletcher for regular updates. Links to these articles can be found at www.jameswelsh.org.uk
Friday, 24 April 2009
May '09
Propagation Forecast
April has been fairly constant with the A index mostly at 5 and the K index mainly at 2. These conditions are likely to continue in May except for a fluctuation on the 6th, with the A index peaking at 15 and the K index at 4. This should drop back to the norm of A5 and K2 by 11 May. The Solar Flux should remain at a steady 70 during this period.
Deep Solar Minimum. The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower. 2008 was a bear. There were no sunspots observed on 266 of the year's 366 days (73%). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008. Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year's 90 days (87%).
It adds up to one inescapable conclusion: "We're experiencing a very deep solar minimum," says solar physicist Dean Pesnell of the Goddard Space Flight Centre.
"This is the quietest sun we've seen in almost a century," agrees sunspot expert David Hathaway of the Marshall Space Flight Centre. Quiet suns come along every 11 years or so. It's a natural part of the sunspot cycle, discovered by German astronomer Heinrich Schwabe in the mid-1800s. Sunspots are planet-sized islands of magnetism on the surface of the sun; they are sources of solar flares, coronal mass ejections and intense UV radiation. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm—a clockwork pattern that has held true for more than 200 years. The current solar minimum is part of that pattern. In fact, it's right on time. "We're due for a bit of quiet—and here it is," says Pesnell.
But is it supposed to be this quiet? In 2008, the sun set the following records:
A 50-year low in solar wind pressure: Measurements by the Ulysses spacecraft reveal a 20% drop in solar wind pressure since the mid-1990s—the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays are permitted to enter, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.
A 12-year low in solar "irradiance": Careful measurements by several NASA spacecraft show that the sun's brightness has dropped by 0.02% at visible wavelengths and 6% at extreme UV wavelengths since the solar minimum of 1996. The changes so far are not enough to reverse the course of global warming, but there are some other significant side-effects: Earth's upper atmosphere is heated less by the sun and it is therefore less "puffed up." Satellites in low Earth orbit experience less atmospheric drag, extending their operational lifetimes. Unfortunately, space junk also remains longer in Earth orbit, increasing hazards to spacecraft and satellites.
A 55-year low in solar radio emissions: After World War II, astronomers began keeping records of the sun's brightness at radio wavelengths. Records of 10.7 cm flux extend back all the way to the early 1950s. Radio telescopes are now recording the dimmest "radio sun" since 1955. Some researchers believe that the lessening of radio emissions is an indication of weakness in the sun's global magnetic field. No one is certain, however, because the source of these long-monitored radio emissions is not fully understood. (NASA Science News 1 April 2009)
NASA Discuss The Anatomy Of Solar Storms NASA held a Science Update on April 14, to present new findings and three-dimensional views revealing the inner workings of solar storms known as coronal mass ejections. The data will improve the ability to predict how and when these solar tsunamis impact Earth, affecting communication systems, power grids, and other technology. It is available on NASA TV at: http://www.nasa.gov/multimedia/nasatv/ Acknowledgements to Ken Fletcher and Mike Terry
Links to these articles and more can be found at: www.jameswelsh.org.uk
April has been fairly constant with the A index mostly at 5 and the K index mainly at 2. These conditions are likely to continue in May except for a fluctuation on the 6th, with the A index peaking at 15 and the K index at 4. This should drop back to the norm of A5 and K2 by 11 May. The Solar Flux should remain at a steady 70 during this period.
Deep Solar Minimum. The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower. 2008 was a bear. There were no sunspots observed on 266 of the year's 366 days (73%). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008. Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year's 90 days (87%).
It adds up to one inescapable conclusion: "We're experiencing a very deep solar minimum," says solar physicist Dean Pesnell of the Goddard Space Flight Centre.
"This is the quietest sun we've seen in almost a century," agrees sunspot expert David Hathaway of the Marshall Space Flight Centre. Quiet suns come along every 11 years or so. It's a natural part of the sunspot cycle, discovered by German astronomer Heinrich Schwabe in the mid-1800s. Sunspots are planet-sized islands of magnetism on the surface of the sun; they are sources of solar flares, coronal mass ejections and intense UV radiation. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm—a clockwork pattern that has held true for more than 200 years. The current solar minimum is part of that pattern. In fact, it's right on time. "We're due for a bit of quiet—and here it is," says Pesnell.
But is it supposed to be this quiet? In 2008, the sun set the following records:
A 50-year low in solar wind pressure: Measurements by the Ulysses spacecraft reveal a 20% drop in solar wind pressure since the mid-1990s—the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays are permitted to enter, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.
A 12-year low in solar "irradiance": Careful measurements by several NASA spacecraft show that the sun's brightness has dropped by 0.02% at visible wavelengths and 6% at extreme UV wavelengths since the solar minimum of 1996. The changes so far are not enough to reverse the course of global warming, but there are some other significant side-effects: Earth's upper atmosphere is heated less by the sun and it is therefore less "puffed up." Satellites in low Earth orbit experience less atmospheric drag, extending their operational lifetimes. Unfortunately, space junk also remains longer in Earth orbit, increasing hazards to spacecraft and satellites.
A 55-year low in solar radio emissions: After World War II, astronomers began keeping records of the sun's brightness at radio wavelengths. Records of 10.7 cm flux extend back all the way to the early 1950s. Radio telescopes are now recording the dimmest "radio sun" since 1955. Some researchers believe that the lessening of radio emissions is an indication of weakness in the sun's global magnetic field. No one is certain, however, because the source of these long-monitored radio emissions is not fully understood. (NASA Science News 1 April 2009)
NASA Discuss The Anatomy Of Solar Storms NASA held a Science Update on April 14, to present new findings and three-dimensional views revealing the inner workings of solar storms known as coronal mass ejections. The data will improve the ability to predict how and when these solar tsunamis impact Earth, affecting communication systems, power grids, and other technology. It is available on NASA TV at: http://www.nasa.gov/multimedia/nasatv/ Acknowledgements to Ken Fletcher and Mike Terry
Links to these articles and more can be found at: www.jameswelsh.org.uk
Saturday, 28 March 2009
April '09
Propagation Forecast
During the second half of March, conditions have remained quite steady with the A index mostly at 5 and the K index at 2. As we enter the A09 period, things are likely to remain the same during April except for the 9th with the A index at 15 and the k index at 4. This should return to normal by April 11th. The Solar flux is likely to remain at a steady 70 during this period.
(From: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml)
Modes of propagation
Here is an interesting article explaining modes of radio propagation and how they work:
The three main modes of propagation of electromagnetic waves are:
(a) Ground (or surface) Wave
(b) Ionosphere Wave (Sky Wave)
(c) Tropospheric Wave
Ground-Wave Propagation In ground-wave propagation, the radiated wave follows the surface of the earth. It is the major mode of propagation for frequencies up to about 2MHz. Attenuation of the ground wave increases very rapidly above 2MHz and it may extend for only a few kilometers at frequencies of the order of 15- 20MHz. At very low frequencies the attenuation decreases to such an extent that reliable world-wide communication is possible at all times. The ground wave is not so affected by atmospheric effects or time of day as other modes, particularly at frequencies below about 500 kHz.
Ionospheric Propagation Ionospheric propagation is the 'refraction' (i.e. bending), and hence reflection, of radio waves back to earth by layers of ionised gases as shown in Fig 7.2. It is the normal mode of propagation over the frequency range of about 1MHz to 30MHz.
These layers are the F2 layer (height 300-400km); Fl layer (about 200km) and the E layer (about 120km). At night and in midwinter, the F1 and F2 layers tend to combine into a single layer at a height of about 250km. At about 80km there is a much less distinct layer which is generally known as the D region.
The ionised layers are the result of the ionisation of the oxygen, nitrogen and nitric oxide in the rarefied atmosphere at these heights by X-Ray and ultra-violet radiation of various wavelengths which comes from the sun.
When these gases are ionised the molecules split up into ions and free electrons, and recombine after sunset. This whole region is therefore known as the 'ionosphere'.
The solar radiation which causes the ionisation is continually varying; hence the degree of ionisation varies considerably according to season and time of day. It has also been found that the degree of ionisation is affected by the number of sunspots.
(You can read the full article at: http://www.ukradioamateur.co.uk/full/html/c7-1-2.htm)
NOAA Space Weather Prediction Centre Here is a web page featuring the latest solar weather indices including real time maps, solar wind dials and a solar cycle progression chart: http://www.swpc.noaa.gov/SWN/index.html
Thanks to Mike Terry and Ken Fletcher for updates. Links to the above articles can be found at. http://www.jameswelsh.org.uk
During the second half of March, conditions have remained quite steady with the A index mostly at 5 and the K index at 2. As we enter the A09 period, things are likely to remain the same during April except for the 9th with the A index at 15 and the k index at 4. This should return to normal by April 11th. The Solar flux is likely to remain at a steady 70 during this period.
(From: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml)
Modes of propagation
Here is an interesting article explaining modes of radio propagation and how they work:
The three main modes of propagation of electromagnetic waves are:
(a) Ground (or surface) Wave
(b) Ionosphere Wave (Sky Wave)
(c) Tropospheric Wave
Ground-Wave Propagation In ground-wave propagation, the radiated wave follows the surface of the earth. It is the major mode of propagation for frequencies up to about 2MHz. Attenuation of the ground wave increases very rapidly above 2MHz and it may extend for only a few kilometers at frequencies of the order of 15- 20MHz. At very low frequencies the attenuation decreases to such an extent that reliable world-wide communication is possible at all times. The ground wave is not so affected by atmospheric effects or time of day as other modes, particularly at frequencies below about 500 kHz.
Ionospheric Propagation Ionospheric propagation is the 'refraction' (i.e. bending), and hence reflection, of radio waves back to earth by layers of ionised gases as shown in Fig 7.2. It is the normal mode of propagation over the frequency range of about 1MHz to 30MHz.
These layers are the F2 layer (height 300-400km); Fl layer (about 200km) and the E layer (about 120km). At night and in midwinter, the F1 and F2 layers tend to combine into a single layer at a height of about 250km. At about 80km there is a much less distinct layer which is generally known as the D region.
The ionised layers are the result of the ionisation of the oxygen, nitrogen and nitric oxide in the rarefied atmosphere at these heights by X-Ray and ultra-violet radiation of various wavelengths which comes from the sun.
When these gases are ionised the molecules split up into ions and free electrons, and recombine after sunset. This whole region is therefore known as the 'ionosphere'.
The solar radiation which causes the ionisation is continually varying; hence the degree of ionisation varies considerably according to season and time of day. It has also been found that the degree of ionisation is affected by the number of sunspots.
(You can read the full article at: http://www.ukradioamateur.co.uk/full/html/c7-1-2.htm)
NOAA Space Weather Prediction Centre Here is a web page featuring the latest solar weather indices including real time maps, solar wind dials and a solar cycle progression chart: http://www.swpc.noaa.gov/SWN/index.html
Thanks to Mike Terry and Ken Fletcher for updates. Links to the above articles can be found at. http://www.jameswelsh.org.uk
Saturday, 28 February 2009
March'09
Propagation Forecast
During the second half of February, conditions have remained much the same with the A index at 5 and the K index at 2. This is set to continue into March, except for the 13th , when the A index will peak at 12 and the K index will reach 4. The 14th March will be much the same with the A index down to 10 and the K down to 3. Conditions will settle beck to ‘normal’ by the 15th with the A and K indices returning to 5 and 2 respectively. The Solar flux, however is forecast to stay at a steady 70 throughout this period.
(Data from: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml )
Solar Cycle 24 Update
Looking at the Sunspot trend charts on Solarcycle24.com, it seems we will not see any significant difference in HF conditions until early 2010 when sunspot activity is forecast to rise steadily until the end of 2012. This will steadily drop down towards another low period by around 2020. Detailed charts can be found at: http://solarcycle24.com/flares.htm
Online Popagation Primer
Here is an interesting website featuring Flash Media videos about how HF propagation works, which is divided into sections including The Sun, The Ionosphere and the indices, explaining how to understand the A index, the K index and the Solar Flux. You will require a Broadband connection to view these files
http://www.ae4rv.com/tn/propflash.htm See also this website explaining how shortwave propagation actually works: http://dzabcik.home.texas.net/propagation.html See also Propagation Noise and Effectiveness at: http://hfradio.org/ace-hf/ace-hf-noise.html
AM Noise Sources“The radio noise problem is as old as radio itself. Unfortunately it is getting worse as technology steadily progresses and more man-made electronic products hit the shelves. This is a direct result of mainly consumer products that generate an increasingly higher noise level. The technology behind the AM broadcast signal is very out-dated as far as current technology is concerned, not to mention that the AM broadcast band is located in the very vulnerable medium wave frequency band.”
This is an article from radiolabs.com which details the amount of devices which can cause noise on the AM bands. This article can be found at: http://www.radiolabs.com/Articles/amnoise.html
Localised Radio Interference
The number of videos on YouTube showing the interference that 'Homeplug' type devices cause to peoples' enjoyment of radio listening continues to grow. A selection of Youtube postings can be found at: http://www.southgatearc.org/news/february2009/new_plt_interference_videos.htm
There is also the UKQRM group at: http://www.ukqrm.org/ There are many features on this site including a page for identifying different sources of interference from power line adapters to electric fences: http://www.mikeandsniffy.co.uk/UKQRM/database.htm For the latest updates, you can also join their Yahoo Group at: http://tech.groups.yahoo.com/group/UKQRM/
(From Mike Terry 9 February 2009)
Links to these articles and more can be found at: http://www.jameswelsh.org.uk
During the second half of February, conditions have remained much the same with the A index at 5 and the K index at 2. This is set to continue into March, except for the 13th , when the A index will peak at 12 and the K index will reach 4. The 14th March will be much the same with the A index down to 10 and the K down to 3. Conditions will settle beck to ‘normal’ by the 15th with the A and K indices returning to 5 and 2 respectively. The Solar flux, however is forecast to stay at a steady 70 throughout this period.
(Data from: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml )
Solar Cycle 24 Update
Looking at the Sunspot trend charts on Solarcycle24.com, it seems we will not see any significant difference in HF conditions until early 2010 when sunspot activity is forecast to rise steadily until the end of 2012. This will steadily drop down towards another low period by around 2020. Detailed charts can be found at: http://solarcycle24.com/flares.htm
Online Popagation Primer
Here is an interesting website featuring Flash Media videos about how HF propagation works, which is divided into sections including The Sun, The Ionosphere and the indices, explaining how to understand the A index, the K index and the Solar Flux. You will require a Broadband connection to view these files
http://www.ae4rv.com/tn/propflash.htm See also this website explaining how shortwave propagation actually works: http://dzabcik.home.texas.net/propagation.html See also Propagation Noise and Effectiveness at: http://hfradio.org/ace-hf/ace-hf-noise.html
AM Noise Sources“The radio noise problem is as old as radio itself. Unfortunately it is getting worse as technology steadily progresses and more man-made electronic products hit the shelves. This is a direct result of mainly consumer products that generate an increasingly higher noise level. The technology behind the AM broadcast signal is very out-dated as far as current technology is concerned, not to mention that the AM broadcast band is located in the very vulnerable medium wave frequency band.”
This is an article from radiolabs.com which details the amount of devices which can cause noise on the AM bands. This article can be found at: http://www.radiolabs.com/Articles/amnoise.html
Localised Radio Interference
The number of videos on YouTube showing the interference that 'Homeplug' type devices cause to peoples' enjoyment of radio listening continues to grow. A selection of Youtube postings can be found at: http://www.southgatearc.org/news/february2009/new_plt_interference_videos.htm
There is also the UKQRM group at: http://www.ukqrm.org/ There are many features on this site including a page for identifying different sources of interference from power line adapters to electric fences: http://www.mikeandsniffy.co.uk/UKQRM/database.htm For the latest updates, you can also join their Yahoo Group at: http://tech.groups.yahoo.com/group/UKQRM/
(From Mike Terry 9 February 2009)
Links to these articles and more can be found at: http://www.jameswelsh.org.uk
Saturday, 24 January 2009
February '09
Propagation Forecast
Conditions in January have remained quiet with the A index at 5 and the K index at 2. However, January will end with a disturbance on the 27th, with 'A' index peaking at 5 and the 'K' Index at 3. The 29th should be calm followed by a lesser disturbance on the 30th, then the calm conditions will then remain until at least February 14th. From: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml
Severe Space Weather.
Severe Geomagnetic Storms can affect other things besides radio reception, according to a recent report in NASA Science News. The problem begins with the electric power grid. "Electric power is modern society's cornerstone technology on which virtually all other infrastructures and services depend," the report notes. Yet it is particularly vulnerable to bad space weather. Ground currents induced during geomagnetic storms can actually melt the copper windings of transformers at the heart of many power distribution systems. Sprawling power lines act like antennas, picking up the currents and spreading the problem over a wide area. The most famous geomagnetic power outage happened during a space storm in March 1989 when six million people in Quebec lost power for 9 hours. To estimate the scale of such a failure, report co-author John Kappenmann of the Metatech Corporation looked at the great geomagnetic storm of May 1921, which produced ground currents as much as ten times stronger than the 1989 Quebec storm, and modeled its effect on the modern power grid. He found more than 350 transformers at risk of permanent damage and 130 million people without power. The loss of electricity would ripple across the social infrastructure with "water distribution affected within several hours; perishable foods and medications lost in 12-24 hours; loss of heating/air conditioning, sewage disposal, phone service, fuel re-supply and so on. Read the full article at: http://science.nasa.gov/headlines/y2009/21jan_severespaceweather.htm
NASA'S Mission to Improve Predictions of Violent Space Weather
Sometime between the end of 2008 and the beginning 2009, NASA will launch the Solar Dynamics Observatory (SDO) to trace Solar disturbances back to their origin deep within the sun. SDO will discover how the sun builds up and explosively releases magnetic energy, which powers severe space weather.
"Right now, we can make limited space weather predictions, but they are baby steps compared to our ability to forecast weather on Earth," said Dr. Dean Pesnell of NASA's Goddard Space Flight Centre, Greenbelt, Md., Project Scientist for SDO. "SDO's instruments are designed to work together to tell us more about how solar storms form, which will improve predictions of when they are about to happen."
Heat from nuclear fusion in the sun's core makes its outer layer churn like a pot of boiling water. Solar storms are born deep in this outer layer, with tangled magnetic fields generated by the sun’s churning electrically conducting gas (plasma). Like a rubber band that has been twisted too far, solar magnetic fields can suddenly snap to a new shape, releasing tremendous energy as a solar flare or a coronal mass ejection (CME).
Solar flares are explosions in the sun’s atmosphere, with the largest equal to billions of one-megaton nuclear bombs. Solar magnetic energy can also blast billions of tons of plasma into space at millions of miles (kilometres) per hour as a CME. This violent solar activity often occurs near sunspots, dark regions on the sun caused by concentrated magnetic fields. Sunspots and stormy solar weather follow a cycle that repeats approximately every eleven years, from few sunspots and quiet conditions to many sunspots and active, and back again.
The key to predicting solar storms and the solar activity cycle is an understanding of the flows of plasma inside the sun. Magnetic fields are "frozen" into the solar plasma, so plasma currents within the sun transport, concentrate, and help dissipate solar magnetic fields. Currently, the Sun’s activity is at its minimum, but by the time of the SDO launch, the activity level is expected to rise significantly.
Although the general process of solar activity and its cyclic behaviour are known, many of the details are not, such as exactly what magnetic structures lead to flares and CMEs. These details need to be discovered before solar storm predictions improve, and SDO's suite of three instruments is designed to do just that. ( From: http://www.physorg.com/news123774611.html )
Thanks to Mike Terry and Ken Fletcher for regular updates.
Conditions in January have remained quiet with the A index at 5 and the K index at 2. However, January will end with a disturbance on the 27th, with 'A' index peaking at 5 and the 'K' Index at 3. The 29th should be calm followed by a lesser disturbance on the 30th, then the calm conditions will then remain until at least February 14th. From: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml
Severe Space Weather.
Severe Geomagnetic Storms can affect other things besides radio reception, according to a recent report in NASA Science News. The problem begins with the electric power grid. "Electric power is modern society's cornerstone technology on which virtually all other infrastructures and services depend," the report notes. Yet it is particularly vulnerable to bad space weather. Ground currents induced during geomagnetic storms can actually melt the copper windings of transformers at the heart of many power distribution systems. Sprawling power lines act like antennas, picking up the currents and spreading the problem over a wide area. The most famous geomagnetic power outage happened during a space storm in March 1989 when six million people in Quebec lost power for 9 hours. To estimate the scale of such a failure, report co-author John Kappenmann of the Metatech Corporation looked at the great geomagnetic storm of May 1921, which produced ground currents as much as ten times stronger than the 1989 Quebec storm, and modeled its effect on the modern power grid. He found more than 350 transformers at risk of permanent damage and 130 million people without power. The loss of electricity would ripple across the social infrastructure with "water distribution affected within several hours; perishable foods and medications lost in 12-24 hours; loss of heating/air conditioning, sewage disposal, phone service, fuel re-supply and so on. Read the full article at: http://science.nasa.gov/headlines/y2009/21jan_severespaceweather.htm
NASA'S Mission to Improve Predictions of Violent Space Weather
Sometime between the end of 2008 and the beginning 2009, NASA will launch the Solar Dynamics Observatory (SDO) to trace Solar disturbances back to their origin deep within the sun. SDO will discover how the sun builds up and explosively releases magnetic energy, which powers severe space weather.
"Right now, we can make limited space weather predictions, but they are baby steps compared to our ability to forecast weather on Earth," said Dr. Dean Pesnell of NASA's Goddard Space Flight Centre, Greenbelt, Md., Project Scientist for SDO. "SDO's instruments are designed to work together to tell us more about how solar storms form, which will improve predictions of when they are about to happen."
Heat from nuclear fusion in the sun's core makes its outer layer churn like a pot of boiling water. Solar storms are born deep in this outer layer, with tangled magnetic fields generated by the sun’s churning electrically conducting gas (plasma). Like a rubber band that has been twisted too far, solar magnetic fields can suddenly snap to a new shape, releasing tremendous energy as a solar flare or a coronal mass ejection (CME).
Solar flares are explosions in the sun’s atmosphere, with the largest equal to billions of one-megaton nuclear bombs. Solar magnetic energy can also blast billions of tons of plasma into space at millions of miles (kilometres) per hour as a CME. This violent solar activity often occurs near sunspots, dark regions on the sun caused by concentrated magnetic fields. Sunspots and stormy solar weather follow a cycle that repeats approximately every eleven years, from few sunspots and quiet conditions to many sunspots and active, and back again.
The key to predicting solar storms and the solar activity cycle is an understanding of the flows of plasma inside the sun. Magnetic fields are "frozen" into the solar plasma, so plasma currents within the sun transport, concentrate, and help dissipate solar magnetic fields. Currently, the Sun’s activity is at its minimum, but by the time of the SDO launch, the activity level is expected to rise significantly.
Although the general process of solar activity and its cyclic behaviour are known, many of the details are not, such as exactly what magnetic structures lead to flares and CMEs. These details need to be discovered before solar storm predictions improve, and SDO's suite of three instruments is designed to do just that. ( From: http://www.physorg.com/news123774611.html )
Thanks to Mike Terry and Ken Fletcher for regular updates.
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