The K7RA Solar Update

SEATTLE, WA, Jan 14, 2005--For the second reporting week of 2005 (January 6-12) solar flux and sunspot numbers were down, as expressed in the weekly averages of the daily numbers. Average daily sunspot numbers declined more than 9 points to 31.6, and average daily solar flux was down more than 5 points to 89.9. These are not big point spreads, but at this low level of solar activity there isn't much room for decline. Over the next two years we eventually will see increasing periods of consecutive days with a sunspot count of zero and solar flux less than 70.

The daily solar flux value is an expression of the noontime 2.8 GHz energy detected at a sun-pointing receiving antenna at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, British Columbia. Canada. Details and a history of this daily observation are on the DRAO Web site. According to my records, the lowest daily solar flux value measured over the past decade was 64.9 on July 9, 1996. This was during a time when the sunspot number was zero.

Solar activity has been rising over the past week. Right after the Solar Update was posted a week ago, the interplanetary magnetic field near Earth dropped sharply to the south, which made Earth vulnerable to geomagnetic storms. The geomagnetic indices (A and K indices) rose sharply from very quiet to very stormy on January 7 and 8. A few days later Earth was inside a high-speed solar wind, and conditions were stormy again on January 12. Fast-growing sunspot 720 emerged, and this should increase the sunspot number and solar flux over the next few days.

Solar flux is predicted at 120 for January 14-15, and around 125 for January 16-20. This is a sharp increase over the average daily value of 89.9 for the past week and 95.4 for the previous week. Solar flux values around 120-125 suggest daily sunspot numbers rising toward (but not reaching) 100. Unsettled to active geomagnetic conditions are predicted for January 14, and quiet conditions for the following week.

We neglected last week to say anything about disturbed conditions in the first hours and days of 2005. There was a powerful solar flare around 40 minutes into the new year on January 1 (UTC). The high latitude and planetary A and K indices rose dramatically over the next two days. This produced disturbed HF conditions. On January 2, the high latitude college A index (in Alaska) rose to 64, and it was 44 and 41 over the next two days. The planetary A index was up to 33 on January 2, indicating a geomagnetic storm.

For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page.

Sunspot numbers for January 6 through 12 were 14, 22, 34, 28, 40, 25 and 58, with a mean of 31.6. The 10.7 cm flux was 83.2, 83.5, 88.5, 87.5, 90.1, 94.2 and 102.1, with a mean of 89.9. Estimated planetary A indices were 4, 37, 30, 4, 6, 14 and 30, with a mean of 17.9. Estimated mid-latitude A indices were 4, 21, 20, 3, 4, 9 and 18, with a mean of 11.3.

Amateur solar observer Tad Cook, K7RA, Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Frida,y and an abbreviated version also appears in The ARRL Letter. Readers may contact the author via e-mail.

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