[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 8, 2013 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA Average daily sunspot numbers hardly changed from last week and the week prior, but average daily solar flux bounced back to about the level it was from two weeks ago. Average daily sunspot numbers were down five points to 50.7, and average daily solar flux was up 7.7 points to 106.4. Predicted solar flux values are 105 on February 8-10, 110 and 105 on February 11-12, 100 on February 13-14, 110, 115 and 110 on February 15-17, 115 on February 18-19, 110 on February 20-21, 105 on February 22, 115 on February 23-24, then 110, 105 and 100 on February 25-27, 95 on February 28 through March 2, 115 on March 3-4, 120 on March 5-6, and 125 on March 7-8. The predicted planetary A index is 22, 15 and 10 on February 8-10, 5 on February 11-18, 8 on February 19, 5 on February 20-21, then 15, 10 and 8 on February 22-24, 5 on February 25-28, 10 and 8 on March 1-2, 5 on March 3-7, and 8 on March 8-9. OK1HH says geomagnetic activity should be quiet to unsettled on February 8, quiet to active February 9-10, quiet to unsettled February 11-12, quiet to active February 13-14, quiet to February 15-16, quiet February 17-21, active to disturbed February 22-23, quiet to unsettled February 24-25, quiet on February 26-27, mostly quiet February 28, quiet to active March 1, quiet to unsettled March 2, and mostly quiet on March 3. I've been looking at the predictions for planetary A index and solar flux, and it is interesting to note how they change over time. The planetary A index prediction for February 3 for over a month was a value of 5, until January 31, when it changed to 18. Then on February 1 it was 15, and the same on February 2. But on February 3, the actual value was 4. A similar thing happened with the February 4 prediction. It was 5 up until January 31, when it changed to 15, then for March 1 and 2 it was 12, then it changed back to 15 on March 3. The following day, March 4, the actual value was 4 again, just as it was the day earlier. On February 7 the planetary A index prediction for February 8 is 22, and on February 6 the prediction for February 8 was 8. Prior to that it was 5. We will see the actual value at the end of the day today, February 8. We heard from Fabrizio Valdirosa, a shortwave listener in Italy, who inquired about the average sunspot number for all of 2011. We mentioned recently that it was 29.9, but Fabrizio thought this was too low while looking at the monthly averages at, http://www.swpc.noaa.gov/ftpdir/weekly/RecentIndices.txt. I recalculated by again totaling all of the daily sunspot numbers for 2011, which is 29,239. Divide that by 365 days, and we get an average daily sunspot number for that year of 80.1. I have no idea how 29.9 was previously calculated, except that I somehow came up with a total for the year of 10,913 instead of 29,239 and it was my own error. So the average yearly sunspot numbers for 2008-2012 were 4.7, 5.1, 25.5, 80.1 and 82.3. Don Street, HS0ZEE wrote to ask about seasonal variations mentioned in the bulletin, and asked, Here in Asia, Spring and Fall are not so well defined, perhaps for reader like me it would be helpful to mention which month you refer to. We are just referring to the seasons as the time between Equinox and Solstice, Solstice to Equinox, etc. This page gives the dates for the seasonal changes: http://wwp.greenwichmeantime.com/longest-day/equinox-solstice-2010-2019.htm. Don also likes the HAP charts for HF propagation produced by the Australian government and notes, I find the charts near to actual band conditions. Unfortunately they are based on the previous hours observed conditions, but still very useful. Here is the link Don refers to: http://www.ips.gov.au/HF_Systems/6/6/1. Bill Bliss, W1WBB of Portsmouth, Rhode Island wrote: Don't believe I've seen these two new forecast products from the SWPC mentioned in your weekly column, found via link on their home page: http://www.swpc.noaa.gov/index.html They are issued twice daily and I've found them helpful as an additional tool for predicting near-term propagation on the HF/MF amateur bands. Links for feedback on both the 3-Day Forecast and the Forecast Discussion are also provided. Positive feedback on these 'experimental' products from the amateur community (accepted up through Feb. 12) may help ensure they become a permanent part of SWPC's Data and Products area. If you would like to make a comment or have a tip for our readers, email the author at, k...@arrl.net. For more information concerning radio propagation, see the ARRL Technical Information Service web page at http://arrl.org/propagation-of-rf-signals. For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 11, 2011 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA Seven different sunspot groups were visible over the past week. The high sunspot number in the past seven days was 71 on Tuesday, and the average daily sunspot number more than doubled, rising over 24 points to 44.3. Average daily solar flux was up nearly three points to 83.5. 71 is the highest sunspot number since May 5, 2010 when it was 77. Coincidentally, both February 8, 2010 and February 8, 2011 had a sunspot number of 71, and between those dates it was never higher except for 77 on May 5. The NOAA/USAF prediction for solar flux for the near term improved considerably from what was reported in yesterday's ARRL Letter. Solar flux is predicted at 90 on February 11-18, then for February 19-25, 88, 88, 86, 84, 84, 80 and 80. They predict a constant planetary A index of 5 through the end of the month, then 7, 10, 10 and 7 on March 1-4. Even though NOAA sees a constant and quiet geomagnetic environment through the end of the month, Geophysical Institute Prague sees it a little differently for February 11-17. They predict quiet on February 11-12, quiet to unsettled February 13, unsettled February 14-16, and quiet to unsettled February 17. There are a couple of sobering items concerning progress of solar Cycle 24 and predictions for the peak, now centered around February through July in 2013. The latest predicted smoothed sunspot numbers are in this week's Preliminary Report and Forecast #1849 at http://www.swpc.noaa.gov/weekly/pdf/prf1849.pdf. Dick Wiltgen, K8RBW of Chicago sent an article from NASA on the latest solar cycle prediction. Read it at http://solarscience.msfc.nasa.gov/predict.shtml. Note they are using International Sunspot Numbers, which are lower than the Boulder numbers we use in this bulletin, and reported in the Preliminary Report and Forecast. Also, at this stage in Cycle 24, predictions are more reliable. Among others, the article cites recent work by Joan Feynman, daughter of the remarkable Nobel Prize winning physicist Richard Feynman. Ray Perrin, VE3FN of Ottawa, Ontario sent in a very interesting report of propagation at the start of high geomagnetic activity on February 4. Ray wrote, Just before 2000Z on Feb 4, I was tuning across 15 meters and was surprised to hear a strong signal from a Finnish station on CW. I tuned up the band a bit and heard another Finnish station -- Marko OH3XR -- working a station in Ohio. I was surprised that I was able to hear the Ohio station as it is very short skip from my QTH (Ottawa) in eastern Ontario (grid FN25). But I noticed the signal from the Ohio station was not pure T9. It also had some slight hiss which I normally associate with auroral propagation. I then worked Marko OH3XR and he reported that there was a large aurora in progress. This seemed to confirm that I had indeed heard the Ohio station via aurora -- besides, I believe the path was much too short to have been F Layer. Marko's signal was pure T9 and I am unsure as to the mechanism that propagated our signals. My first assumption was that it was Auroral E. However, I believe that F-layer propagation can be enhanced after an aurora -- primarily on north - south paths. But my guess is that it was Auroral E. After our QSO, I checked the NOAA Space Weather Now site. It was still showing that the auroral zone was fairly quiet and the K index was low. But a little later, it showed an active auroral zone, a K index of 6, and that there was a G1 storm in progress. It is interesting to look at geomagnetic indices on that date, particularly planetary A and K index, at http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt. In last week's bulletin (see http://snurl.com/20vmqo) was a report from Tamas, HA5PT and he sent along some links, including a sound file to augment his report. See http://www.ha5hrk.hu/files/ut7uj.mp3 and http://www.ha5hrk.hu/files/ut7uj_first_dash.jpg. If you would like to make a comment or have a tip for our readers, email the author at, k...@arrl.net. For more information concerning radio propagation, see the ARRL Technical Information Service web page at http://arrl.org/propagation-of-rf-signals. For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. Find more good information and tutorials on propagation at http://mysite.ncnetwork.net/k9la/index.html. Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation. Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins. Sunspot numbers for February 3 through 9 were 32, 45, 26, 41, 28, 71, and 67, with
[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 12, 2010 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA Increasing sunspot activity continues. A glance at the image from the STEREO mission (http://stereo.gsfc.nasa.gov/) shows a string of active regions in the Sun's northern hemisphere, both visible and over the horizon on the far side. The high sunspot number for the week was 71 on February 8, and the average for the week was 43.3. We haven't reported a weekly average that high since the week of March 27 through April 4 in 2008, when it was 43.6. The daily sunspot number hasn't been as high as 71 since May 28, 2006 when it was 78. The earlier reading that reached that level or more was 105 on April 6, 2006. On February 8 when the daily sunspot number was 71, the total area covered by sunspot activity was 460 millionths of a solar hemisphere. That measure hasn't been that high since the same earlier week in 2008 that had a high sunspot number average. The dates were March 26-27, 2008 when the area of sunspots was 520 and 510. You can find continuous records of these old indices going back through 1994 at, http://www.swpc.noaa.gov/ftpdir/indices/old_indices. The latest forecast has the solar flux index for today, February 12 at 90, followed by 92 on February 13, 94 on February 14-16, 93 on February 17-18. Predicted planetary A index for February 12-18 is 10, 8, 8, 7, 8, 8 and 5. Geophysical Institute Prague sees unsettled conditions February 12-13, unsettled to active February 14, unsettled February 15, quiet to unsettled February 16, and quiet February 17-18. A number of people have inquired about short versus long skip on 75-80 meters, and why short skip is often non-existent but long skip is enhanced. Dennis Carlson, K9ZMI of Arlington Heights, Illinois provides an explanation: As I understand it, the effect we are seeing is that the F-layer ionization is weak because of low sunspot activity. A weakly ionized layer has a low index of refraction (a term used in optics) which impacts the amount of bending of the HF radio wave impinging on it. Low index of refraction equals not much bending. So an HF radio wave leaving an antenna is typically headed toward outer space but is bent back (refracted) towards Earth when it reaches the ionized layers above Earth. The amount of bending depends on the index of refraction and, for a given index of refraction, the angle of impingement determines if the radio wave will return to Earth or not. HF radio signals impinging on the weakly ionized layer at a high angle (necessary for short skip communications between stations close to each other) are not refracted enough to be turned back to Earth and they simply radiate into space. Signals impinging on the weakly ionized layer at a low angle are refracted enough to be turned back to Earth and they appear at a large distance from the signal's origin, which is long skip. Thank you, Dennis. Look at ionosonde data for Boulder, Colorado on the web at http://www.swpc.noaa.gov/ftpdir/lists/iono_day/Boulder_iono.txt. A glance at the foF2 column is instructive. This is the highest frequency that bounces back a signal from the ionosphere directly above, with a signal beaming straight up. For reliable short-skip communications on 75 meters, we need the foF2 to be at least 4 MHz. It may be different by the time you see it, but starting at z on February 11, I see the foF2 dipping below 4 MHz from 0115-1115z, 1145-1330z, and on February 12 0115-0515z, 0600-0615z, 0700-0715z, and so on. On February 12 the approximate sunrise at the ionosonde is at 1402z and sunset at 0028z. It appears that roughly after sunset until sunrise, possibly there isn't enough sunlight to support short skip on 75 meters. On Thursday, Bob Marston, K6TR sent this: Today, Feb 11th, NASA successfully launched the Solar Dynamics Observatory at 10:23 AM EST from Launch Complex 41 at Cape Canaveral Air Force Station in Florida. After completing its second burn 90 minutes after liftoff, the Atlas Centaur booster released SDO in a 1900 by 21,000 mile elliptical Geostationary Transfer Orbit. Through a series of burns over the next three weeks SDO's propulsion system will circularize the orbit. First light from the observatory can be expected in 60 Days. Full calibration of the satellite will be completed in early July. Carried on board SDO is the Extreme Ultraviolet Variability Experiment which will render data of importance to ham radio operators interested in HF Propagation. EVE will sample Solar Radiation in the 304 Angstrom Range which composes half of all radiation that goes into ionizing the F Layer of the Ionosphere. The 304A number represents a tighter real-time correlation to F Layer Ionization that the Smooth Sunspot Number (SSN) or the 2800 MHz Solar Flux Number. According to news reports, the
[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 6, 2009 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA K7RA is on the road this week from Charleston, South Carolina. Still no hint of sunspots or sunspots to come. We did see some geomagnetic activity on February 4 from a possible coronal mass ejection. This raised the planetary A index to 16 that day. Current prediction is for quiet conditions. Geophysical Institute Prague predicts quiet conditions for February 6-12. NOAA and USAF predict quiet geomagnetic conditions with planetary A index at 5, but it jumps to 8 on February 15, then back to 5 until February 22-24, which has a predicted planetary A index of 10, 8 and 8. While we don't see much excitement at the high end of the HF spectrum, the quiet conditions and winter nights are great for the lower frequencies. There were many comments on the fascinating several decades old letter from Ed Tilton, W1HDQ, the editor of this bulletin until 1991. I've never learned when this bulletin began, and if Ed always wrote it. I remember copying it on CW from W1AW as a boy in the mid 1960s, and it was written by W1HDQ then. No one currently at ARRL HQ seems to know either. Starting out as a 12-year-old ham in the 1960s, I was always accustomed to having some source for info from an older ham. For instance, if I wanted to know how experimenters set up spark stations in the early 20th century, there were plenty of people still around in the late 20th century who had done it themselves when they were younger, and could lend me their first-hand knowledge. But now after 44 years as a ham, there aren't that many people older than me who I can ask these sorts of questions. Jim Muiter, N6TP of San Mateo, California commented on the W1HDQ letter. Jim wrote, Ed's letter pointed out there are many layers to ten-meter propagation and the selection of the date for the ten-meter contest was no accident. The three hundred mile path makes good sense. I believe the British Chain Home Radar system of Battle of Britain fame used frequencies in that range, perhaps 30 to 50 MHz. In effect it was partially an over the horizon radar and may have relied on tropo inadvertently. Just after last week's bulletin, Jeff Hartley, N8II of Shepherdstown, West Virginia wrote, The highlight of the week was Monday (January 26) working FW8DX on 75 meters at sunrise. 17 meters was barely open to Europe all week long except on Monday conditions were good enough for a brief opening on 15 meters to F/EA/sw DL from 1510-1545Z. He continues, I heard double hop Es on 10 meters Sunday evening (January 25) into New Mexico and Arizona, but no QSOs as they were fairly weak here and they had a good opening going with the SE USA with S9 reports. Jeff goes on to say, By all accounts, the CQ WW 160 had the best conditions ever; I was too tired to operate past my normal bedtime, but did manage to work over 1000 QSOs and 51 DXCC countries with 6W/DL2MDU being a new one. Conditions were so good that many East Coast stations worked UA9 and several caught EY8MM. Mike Schaffer, KA3JAW of Tampa, Florida likes to hunt commercial broadcast television DX, and reports that last winter he didn't see any, but on January 25 he reported, I just snagged my initial 2009 winter season television DX on channel two coming from HIJB Tele Antillas, Santo Domingo, Dominican Republic. I saw the station logo (TA) several minutes before 17:00 GMT. The audio level was about equal to the video quality in this case, but normally the audio is loud compared to the video level. The distance from me here in Tampa, Florida to Santo Domingo city is 1,045 miles. Half this distance, 523 miles, would place the Es plasma cloud near south-west of George Town, Bahamas. Mike copied the signal for less than 3 minutes. Later that same day he copied WKAQ on channel 2 at 2313z from San Juan, Puerto Rico, 1,232 miles away. He said the sporadic-E opening that day ran from 1530-2320z. The next day, also on channel 2 he copied a TV station in Managua, Nicaragua. A new month began since the last bulletin, so we can calculate another 3-month average of daily sunspot numbers. This new one will be centered on December 2008, and includes data from November 1 2008 through January 31 2009. We were of course hoping for an uptick, but the new average is 3.7, lower than the previous average of 4.4. Jan 07 22.7 Feb 07 18.5 Mar 07 11.2 Apr 07 12.2 May 07 15.8 Jun 07 18.7 Jul 07 15.4 Aug 07 10.2 Sep 07 5.4 Oct 07 3.0 Nov 07 6.9 Dec 07 8.1 Jan 08 8.5 Feb 08 8.4 Mar 08 8.4 Apr 08 8.9 May 08 5.0 Jun 08 3.7 Jul 08 2.0 Aug 08 1.1 Sep 08 2.5 Oct 08 4.5 Nov 08 4.4 Dec 08 3.7 Bill Van Alstyne, W5WVO of Rio Rancho, New Mexico had some information and comments after this bulletin mentioned some weak signal methods for VHF. Bill said the
[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 8, 2008 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA After a solid week of sunspots (January 29 to February 4), the following three days have been blank. February 2 was an active geomagnetic day, with a solar wind stream spewing from a coronal hole near sunspot 982. Another solar windstream from a coronal hole is expected to strike Earth on Sunday, February 10, causing unsettled conditions. The predicted planetary A index for February 8 through 15 is 8, 12, 15, 10, 10, 10, 10 and 5. That was from NOAA and the U.S. Air Force, and Geophysical Institute Prague predicts unsettled conditions February 8, unsettled to active February 9-10, and unsettled again on February 11-14. The Australian Space Forecast Centre's geomagnetic forecast expects mostly unsettled to active conditions with storm periods possible at high latitudes on February 9, and mostly unsettled with isolated active periods and storm levels at high latitudes on February 10. Following this weekend, NOAA predicts the next active conditions around February 28-29. Their prediction for solar flux is flat at 70 for each of the next 45 days, and this probably indicates little or no sunspot activity. Bob Leo, W7LR of Bozeman, Montana and IS0/YO3RA (Sardinia) have been trying for several years to make contact on 160 meters. Bob claims 228 countries on 160, but says Sardinia seems to be ''a black hole'', even though both have what he calls ''reasonable stations'' for that band. With some acreage for antennas, Bob runs full power, has various receiving antennas pointed toward different directions, and even a two-element transmit array toward Europe with 4.5 db gain. He asked what time would be best to work Sardinia on 160, and frankly, I didn't know, except I would expect darkness at both ends of the path when successfully making contact. The propagation modeling programs generally don't work below 3 MHz. I noted that this weekend darkness should extend over both locations from 0036-0629z, or at least the sunset in Bozeman will be 0036z and sunrise in Sardinia is at 0629z. Bob emailed back, and said he finally heard YO3RA at 0510z. He hopes to work him this season before YO3RA departs Sardinia on February 15. Several readers wrote to ask about the recent sunspot mentioned in last week's bulletin, hoping it was a cycle 24 spot. Alas, sunspot 982 had cycle 23 polarity. Any cycle 24 spots in the near future will be reported here. Stan Tacker, N5OHM of Tulsa, Oklahoma writes that the absence of sunspots and geomagnetic activity is great for 160 meters, but creates problems for AM broadcast stations. He operates one in Northeast Oklahoma on 1.57 MHz (which is 191 meters), and that is a portion of the AM broadcast band where stations run low power, sometimes 250 watts during the day, and as little as 6-8 watts at night. There is also a Mexican ''border blaster'' station on this frequency, and his station is experiencing QRM well into mid to late morning, hours after sunrise. Stan's station is running 1 KW, and broadcasting in the daytime only. Chuck Zabriskie, KE5HPY in Houston, Texas wrote on February 2 that the 60 meter shortwave broadcast band (4.4-5.1 MHz) was jumping on January 29-31 from 0300-0500z. He heard African stations ''that rarely rise above the noise at this QTH''. He copied Angola, Madagascar, Chad, South Africa, Swaziland and Botswana, all as loud as Midwest AM broadcast stations. Regarding the 60 meter ham band, check out a web page devoted to that band at http://www.60meters.info/. If you would like to make a comment or have a tip for our readers, email the author at, [EMAIL PROTECTED] For more information concerning radio propagation, see the ARRL Technical Information Service at http://www.arrl.org/tis/info/propagation.html. For a detailed explanation of the numbers used in this bulletin, see http://www.arrl.org/tis/info/k9la-prop.html. An archive of past propagation bulletins is at http://www.arrl.org/w1aw/prop/. Monthly propagation charts between four USA regions and twelve overseas locations are at http://www.arrl.org/qst/propcharts/. Sunspot numbers for January 31 through February 6 were 15, 19, 16, 14, 14, 0 and 0 with a mean of 11.1. 10.7 cm flux was 72, 71.1, 71.8, 71, 71.3, 70.5, and 71.6 with a mean of 71.3. Estimated planetary A indices were 5, 18, 19, 12, 6, 3 and 4 with a mean of 9.6. Estimated mid-latitude A indices were 3, 10, 19, 10, 6, 2 and 2, with a mean of 7.4. /EX -- Archives http://www.mail-archive.com/dx-news@njdxa.org THE DXR is sponsored by the North Jersey DX Association. Please visit our website: http://www.njdxa.org/index.php To subscribe/unsubscribe, please send request to [EMAIL PROTECTED] and allow a few hours for acknowledgement
[DX-NEWS] ARLP006 Propagation de K7RA
SB PROP @ ARL $ARLP006 ARLP006 Propagation de K7RA ZCZC AP06 QST de W1AW Propagation Forecast Bulletin 6 ARLP006 From Tad Cook, K7RA Seattle, WA February 11, 2005 To all radio amateurs SB PROP ARL ARLP006 ARLP006 Propagation de K7RA All solar activity indicators rose this week, though not by much. Average daily sunspot number for the week rose 4.4 points to 41.3, average daily solar flux was up 11.6 points to 85.1, and average planetary A index rose 4 points to 15.1. Average daily mid-latitude A index rose 2.2 points to 10.6. Monday through Wednesday, February 7-9 had unsettled to active geomagnetic activity with Tuesday the most disturbed day. The planetary A index was 34 that day and mid-latitude A index was 27. At the 0300z February 8 reading, the planetary K index reached a high of 6, and the highest reading for Alaska's college K index came at 1800z that day when it reached a very high value of 8. There was a K index of 7 on the previous day, and the college A index for February 7-10 was 50, 71, 45 and 30, all high values. This is why Alaskan operators oftentimes report such poor HF conditions during periods when the rest of the United States hardly notices. For instance, between 1200-1500z on February 8, the Alaska K index readings were 6, 6, and 8, indicating a severe geomagnetic storm. But the mid-latitude K index, which affects most of the rest of us was only 2, 3 and 3, quite moderate numbers. Of course for the rest of us, a high latitude path (such as the one to Europe from Seattle) would also be affected, even though each end of the path is at a more moderate latitude. The college A and K index is measured at Fairbanks, Alaska, and the mid-latitude indices that we use are from Fredericksburg, Virginia. The planetary K and A index is the mean-standardized index from 13 geomagnetic observatories between 44 and 60 degrees northern or southern latitude. That single A index for the day is calculated from the eight K index readings, and the scales are quite different, the K index being quasi-logarithmic. A single point change in the K index is quite significant, but a several point change in the A index is not. A day with all eight K index readings of 2 would yield an A index for the day of 7, but all-day K index of 3 would produce an A of 15, and K of 4 all day would yield an A index of 27. You can check the relationship between the A and K readings on NOAA's National Geophysical Data Center site at, http://www.ngdc.noaa.gov/stp/GEOMAG/kp_ap.html. A week-long graph showing Boulder (another mid-latitude observatory), Fredericksburg, planetary and college K index is at http://www.sec.noaa.gov/alerts/k-index.html. Notice from the graphs that the Boulder measurement is often slightly higher (at least it was in the week prior to this bulletin) than the Fredericksburg values. There is only a two-degree difference in latitude, Boulder being at 40 degrees north, and Fredericksburg at 38 degrees north. The higher A and K numbers this week were caused by a robust solar wind stream. The Interplanetary Magnetic Field pointed south, so the earth was vulnerable to these particles. When the IMF points north, the earth is shielded, and it didn't point north until February 10, a quiet day. Last week this bulletin said that solar flux values should rise to 130 by February 7, and stay there for about a week. This was because of the return of sunspot 720, which was quite large the last time it faced earth. When 720 returned a few days after the bulletin, it was much smaller than before. Currently solar flux is expected to stay around 115 for February 11-12, then drop a few points for the next few days. Solar flux could drop below 100 around February 19, but the further out we look, the prediction becomes less meaningful. Roger Bonuchi, AC9Y of Plainfield, Illinois sent an email this week asking about GOES Solar X-Ray Flux as shown at, http://www.sec.noaa.gov/today.html#xray. He wonders if this relates to the 10.7 cm solar flux we report in this bulletin. They actually are measurements of electromagnetic radiation in different parts of the spectrum. X-rays have wavelengths shorter than ultraviolet light. 10.7 cm solar flux is at a much lower frequency, around 2.8 GHz. See the relative positions of x-rays, light waves and radio waves at a physics study aid at, http://www.plus2physics.com/electrons_and_photons/study_material.asp?cha pter=4. 10.7 cm solar flux correlates to some degree with sunspots, and typically the higher solar flux or sunspot numbers result in a higher MUF, or Maximum Usable Frequency. If you use a propagation program such as W6ELprop (free at http://www.qsl.net/w6elprop/), over most paths the MUF will go higher when the sunspot numbers or solar flux are higher. X-rays are correlated with events such as coronal mass ejections or solar flares, and the measurements shown in the graph that Roger sent are done by the GOES satellite. You'll notice on that same page there is a link to the
