SB PROP @ ARL $ARLP025<br />ARLP025 Propagation de K7RA<br /><br />ZCZC AP25<br />QST de W1AW <br />Propagation Forecast Bulletin 25 ARLP025<br />>From Tad Cook, K7RA<br />Seattle, WA June 20, 2003<br />To all radio amateurs <br /><br />SB PROP ARL ARLP025<br />ARLP025 Propagation de K7RA<br /><br />Low sunspot numbers and geomagnetic disturbances in the<br />over-the-hill portion of the solar cycle continue. There are enough<br />sunspots for some good HF propagation, but we are about three years<br />past the cycle peak and about three and a half years ahead of the<br />next sunspot minimum. Complicating the situation is continued high<br />solar wind and flares, causing constant disturbance to geomagnetic<br />conditions. HF operators generally want stable geomagnetic indices,<br />such as a K index at 3 or below and a daily A index of 10 or less.<br /><br />A chart in the recent NOAA Preliminary Report and Forecast of Solar<br />Geophysical Data at
http://www.sec.noaa.gov/weekly/pdf/prf1450.pdf<br />shows the enhanced geomagnetic activity following the peak of a<br />solar cycle. Go to the last page of the report, and look at the bar<br />graphs for severe storm conditions, expressed as a planetary A index<br />over 100.<br /><br />Note that for a few years after high solar activity the geomagnetic<br />indices are higher. Another report from last week at<br />
http://www.sec.noaa.gov/weekly/pdf/prf1449.pdf projects our position<br />in the current cycle. Look at the last page, and see a rising<br />historical planetary A index. Look at the previous few pages, and<br />see the smoothed sunspot and solar flux projections.<br /><br />The next minimum appears sometime around the end of 2006. By the<br />way, this publication is full of interesting information and appears<br />weekly at
http://www.sec.noaa.gov/weekly/index.html.<br /><br />William Hartman, N6FB forwarded a question from the eHam.net forum<br />about the relation between A and K indices, as well as a few other<br />questions. The K index is a measure of geomagnetic stability at<br />various magnetometers around the globe. During periods of activity,<br />the higher latitudes tend to have higher K indices. For mid-latitude<br />K values, an index of 3 is normal. Below 3 is nice and quiet, and<br />above is disturbed. Each point in the K index, which is published<br />every three hours, represents a big change. It is a non-linear<br />system.<br /><br />The A index is published daily, and is made up of the eight K<br />indices over 24 hours. It is a linear scale, so a one point change<br />doesn't represent a big jump in activity. For instance, if you had a<br />constant K index of 2 for 24 hours this would produce an A index of<br />7. A constant K index of 3 is equal to an A of 15, and K of 4 equals<br />27. The K usually changes every three hours, so the A is somewhere<br />in between the values shown here. A web page that shows the<br />relationship is at
http://www.ngdc.noaa.gov/stp/GEOMAG/kp_ap.html.<br /><br />You can see recent mid-latitude, high and planetary A and K indices<br />at
http://www.sec.noaa.gov/ftpdir/indices/DGD.txt. Note that on June<br />17 and 18, 2003 we had a planetary A index of 50 and 54, which is<br />very high.<br /><br />June 17 and 18 activity was significant, and Al Olcott, K7ICW sent<br />an email commenting that the recent sporadic E skip on 144 and 222<br />MHz was of historic importance. He is in Las Vegas, and on June 17th<br />on 222 MHz, he worked K7MAC in Idaho. K7MAC was S7, and on 144 MHz<br />he was S9 into Nevada, a 544-mile path.<br /><br />The June 17 and 18 numbers were the result of yet another robust<br />interplanetary shock wave, which swept over the earth around 0500z<br />on June 18. It was probably from a coronal mass ejection hurled from<br />sunspot 365 on June 15, the day that this sunspot reappeared. In<br />May that same spot released two X-class solar flares, big ones.<br /><br />Mark Williams, KF6YU wrote about an unusual experience on June 14<br />around 0000z. He was vacationing in Payson, Arizona and an AM<br />broadcast station he was listening to in his truck abruptly<br />disappeared. He switched to FM to listen to a Phoenix station, and<br />instead heard one in Sioux City, Iowa on that frequency. When he got<br />back to his cabin, he listened to dead air on HF, and the whole<br />phenomenon was over in about 30 minutes.<br /><br />Someone had a question about what Carl Luetzelschwab, K9LA meant<br />when he referred to IMF in an email quoted in last week's bulletin.<br />IMF in this context doesn't refer to global banking or third-world<br />debt, but the Interplanetary Magnetic Field. When a strong solar<br />wind or interplanetary shock wave from the sun blasts earth, the IMF<br />tends to point south. This has been covered several times in this<br />bulletin over the past year, but now may be a good time to review<br />the IMF and its significance at<br />
http://spaceweather.com/glossary/imf.html.<br /><br />In addition, in last week's bulletin we hoped to come up with some<br />images showing the effects on the spectrograph at Project JOVE<br />during an x-ray event on June 9. Jim Sky, KH6SKY sent the link,<br />
http://radiosky.com/wccro_spec_030609.html. The strip charts were<br />produced with Radio-Skypipe software. Check<br />
http://radiosky.com/skypipeishere.html for information.<br /><br />Back to recent indices as well as a projection for the next few<br />days, we had average sunspot numbers drop nearly 37 points from last<br />week to 112.7 this week. Solar flux was also down. Not surprisingly<br />given the conditions and all the reports, the average planetary A<br />index increased from 21 to 30. Space weather was remarkably mild on<br />Thursday, June 19 with mid latitude and planetary K indices down to<br />2 or 3. However, the forecast shows more of the same enhanced<br />activity over the next few days, with a planetary A index of 25, 25,<br />20 and 20 for June 20-23. Solar flux should remain around 125 on<br />those days. On June 20 we should enter a solar wind stream flowing<br />from a coronal hole, which should cause those high A indices.<br /><br />Sunspot numbers for June 12 through 18 were 168, 149, 91, 111, 91,<br />80, and 99, with a mean of 112.7. 10.7 cm flux was 163.5, 151,<br />133.5, 128.7, 122.6, 121.9, and 120.4, with a mean of 134.5.<br />Estimated planetary A indices were 11, 11, 32, 20, 32, 50, and 54,<br />with a mean of 30.<br />NNNN<br />/EX
