QST de W1AW
Propagation Forecast Bulletin 6 ARLP006
From Tad Cook, K7VVV
Seattle, WA February 6, 1998
To all radio amateurs
SB PROP ARL ARLP006
ARLP006 Propagation de K7VVV
This solar cycle seems to be in the doldrums. Average sunspot number last week was less than half what it was the week before, and average solar flux was down about nine points. The ninety day average for solar flux drifted down from 97 to 96, and flux values were below that level on every day, indicating a general downward trend over the short term.
Even more disturbing though is the regression in solar activity over the past few months. Average solar flux for November, 1997 was 99.5, for December it was 98.7, and for January it was 93.4. This new cycle was already showing progress slower and later than expected, and now it seems to be gradually retreating rather than progressing. The NOAA prediction for those three months was that the smoothed solar flux would be 102, 109 and 116, and this month would be 122.
Last week geomagnetic activity was running a bit higher. The worst day was Friday, January 30, when Planetary A index was 19 and the K index went as high as five.
For the short term the solar flux is expected to gradually increase to around the mid-nineties by February 10, then drift back around 90 after mid-month, then possibly mid-nineties or above by February 22, then back to 90 by month's end. No geomagnetic disturbances are predicted, although unsettled conditions could return around February 26-28. The predicted solar flux for February 6-8 is 86 for each day.
W6PYK wrote to ask if we take into account the sun's rotational period in forecasting conditions. The paragraph above is based upon projections by NOAA which use the solar rotation to try to predict when active regions may come into view again.
N0EG wrote to point out an interesting website at http://www.dxlc.com, operated by the DX Listener's Club of Norway. This site has some nice graphs of sunspot numbers, solar flux and planetary A indices, as well as daily solar data, all selectable in either English or Norwegian. N0EG wanted to know what the references such as ''K indices: 3322 3211'' meant. Each digit is a single K index value for each three hour period in a 24-hour day. The grouping in four digits has no significance, except that each group represents 12 hours out of a day.
Sunspot Numbers for January 29 through February 4 were 71, 41, 37, 25, 23, 39 and 26 with a mean of 37.4. 10.7 cm flux was 93.6, 91, 89.4, 90.7, 89.1, 88.8 and 89.1, with a mean of 90.2, and estimated planetary A indices were 8, 19, 9, 7, 3, 3, and 8, with a mean of 8.1.