ARLP005 Propagation de KT7H: February 3, 1996

Propagation Forecast Bulletin 5 ARLP005
From Tad Cook, KT7H
Seattle, WA February 3, 1996
To all radio amateurs

ARLP005 Propagation de KT7H

This bulletin was delayed by one day due to a delay in getting solar data.

Solar activity is still very low. We are very close to the solar minimum. The latest projections show the 10.7 cm solar flux reaching minimum around a year from now, during January and February 1997. But similar projections show the sunspot number reaching minimum during April through June of this year, and a big increase starting late in 1997. The sunspot number is derived by counting visible dark spots on the Sun and factoring in their area. Solar flux is derived by measuring 10.7 cm radiation from the Sun, and this seems to correlate with density of ionization in the ionosphere.

The most disturbed day over the past week was January 29, when the A index reached 18, and the K index was as high as five. Otherwise geomagnetic conditions were quiet over this period. Solar flux should head down toward 70 by a week from now and then back above the mid-seventies late in the month.

Chuck Sherman writes that he found a good source of historical solar data on the internet via ftp at

Some versions of last week's bulletin ARLP004 had a wrong email address for the author of this bulletin. The correct address is

Sunspot Numbers for January 25 through 31 were 11, 11, 11, 11, 12, 26 and 14, with a mean of 13.7. 10.7 cm flux was 73.9, 73.8, 73.8, 73.6, 74, 74.7 and 76.7, with a mean of 74.4.