Latest Propagation Report dated 6th August 2008

The text below is a rolling forecast and report of long distance propagation conditions as I see them. The most recent addition to the report is in red.

Kyoto real-time Dst extimates are now reliable again and compare with historic values. I am still relying mthore on the Colorado data for my estimates. Colorado gives a Dst value between 10 and 20 nT lower than Kyoto, so anything consistently above about -20nT can be regarded as an indicator of good LF propagation, or at least low excess absorption (attenuation) at night. Note that unfavourable multi-path fading can produce poor local conditions for some paths.

Geomagnetic activity remains quiet (31st) though some small disturbance is forecast for tomorrow. Propagation conditions at LF and MF remain good and should not be significantly affected by the predicted disturbance tomorrow.Steve's plots of DCF39 and HGA22 are still off-line. There is a slight sign of some "turbulance" in the solar wind this morning (1st) but it has not yet affected the Kp index, though the Dst at Colorado has climbed to +4nT. I do not expect thiiis event to significantly affect LF / MF radio propagation. Geomagnetic activity should quieten again tomorrow. Steve's plots are still off-air. There are signs on the Colorado Dst estimate plots of some slight disturbance (2nd) in geomagnetic activity but it is very small and virtually insignificant so far in radio terms. Steve's plots are still off-air, so there is no data for the assessment but I believe that LF/MF propagtions should be good to very good. Those conditions should carry through into the begining of next week. Geomagnetic activity is very quiet (3rd), and the Colorado Dst estimate has climbed to a steady -2nT. Solar X-ray background is also very low with the flux recorded by the Geos satellites bumping along on the least significant bit of they ADCs (technically A0 ). NOAA forecast it to continue quiet until the 5th. Steve W3EEE's plot of DCF39 and HGA22 is still disconneted, so there is no radio data on conditions, but Henny PA3CPM is reporting captures of Joe (VO1NA) 186kHz QRP LowFer beacon. These are weak but consistent.The indexes (4th) suggest quiet geomagnetic conditions, but there was a slight "glitch" late on 2nd, which seemed to lead to a short term fade out. NOAA had no significant data, but Kiruna showed some activity and there was a small dip in the Dst estimate from Colorado. I wonder whether this could be a small "sub-storm" event mainly affecting high latitudes. More generally LF and MF propagations looks good, though Steve W3EEE's plots are still down. Geomagnetic activity is quiet (5th) and predicted to stay that way for the next two days with unsettled conditions occuring on the 7th. Steve's plots are still not available, so there is no practical measure of propagation at present. However LF / MF propagation should remain good to very good for the next three days. Geomagnetic activity remains quiet as predicted (6th) After a long relatively quiet period like we have just experienced it is possible that the E-layer may become somewhat depleted. I have previously seen evidence what could be an increase in LF signals leaking through, and not being returned to ground at normal good strength. If this starts to occur there may start to be slightly lower levels of night-time signals received. The situation is soon reversed by some minor disturbance which tops-up the ionisation again. Henny PA3CPM reports copy of Joe VO1NAs 186kHz LowFer beacon again.

Note the table below. I have included a row for the value of Dst. This can be considered as a measure of the strength of the "Equatorial Ring Current". I believe good conditions will return about two days after this returns close to zero. The value given is the lowest, i.e.the most "stormy", value of the day, because I believe this is an indication of the maximum level of ions and electrons available for injection into the ionosphere. It is possible that peak values in either direction could be a measure of the transient effect of the distortion of the static geomagnetic field by a shock wave, and so may not be so pertinent to the actual content of the ring current..It is interesting to see the Dst level improving whilst the Kp index is "static" at 3, mimicking the steady return of better propagation conditions after a storm. The Dst index seems to be continually refined as more data becomes available, so expect changes for the most recent days.

Table of Kp and Dst values in nT (Dst values in red are negative ..storm -400, quiet -10 to +30 )

Dst Figures from Kyoto available again (1st. Nov 2006), The Colorado site can be viewed at http://lasp.colorado.edu/space_weather/dsttemerin/dsttemerin.html John W1TAG suggests using the menu page http://swdcwww.kugi.kyoto-u.ac.jp/dstdir/dst1/quick.html to go to the Kyoto real-time text file page. They seem to be including the month number in the file address which would ease archiving, but will mean the URL changes every month.

W3EEE Plot of DCF39 (locator FN10sg)

The red box shows the normal levels experienced from DCF39 (Magdeburg) over a few very good nights in mid-January 2006 as a benchmark to compare with the recorded value for last night.(check the date/time on the axis). This is a path of about 6500km, passing through the English-Scottish border, the northern tip of Newfoundland, and skirting Boston. The most northerly lattitude is 56.5 degrees so it is usually well south of the auroral circle. This long path is very sensitive to increases in absorption because it makes three excursions through the ionosphere. Steve's web pages are at http://www.w3eee.com/ The "darkness path" window is short in summer so the rise and fall of the signal draws in away from the winter template. Steve will disconnect when threatened by local thunderstorms. The HGA22 trace is from Lakihegy (Budpast) which is slightly fiurther away from Steve, but a very similar path.

Click here for an archive of DCF39 and HGA22 plots from W3EEE in Mount Gretna, Pennsylvania, USA

Dst

The Dst index (in nT) is an estimated value from Kyoto University, based on a formula. Big negative values after a severe or major geomagnetic storm indicate a high "equatorial ring current". I believe that this is the "reservoir" which acts as the source of precipitated ions and electrons, which lead to high night-time absorption, during the (radio) recovery phase after a geomagnetic storm. I still believe that there is about a 2 day diffusion time ( dependent on latitude) from the injection point at high latitudes to the position of mid latitude path. If this hypothesis is correct, good propagation conditions should occur about two days after the Dst value returns near to zero or becomes positive. Note the very good conditions around the 5th Jan 2003 correspond to "worst" values of zero, a condition not see again right through to the end of October 2003.

Alan Melia G3NYK in locator JO02PB

(c) A.J.Melia G3NYK 2008

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