Tad "I swayed my leaves and flowers in the Sun" Cook, K7RA, this week reports:
Sunspot 998 emerged this week, another old Solar Cycle 23 sunspot near the Sun's equator. Daily sunspot numbers for June 10-12 were 14, 11 and 13. Last Sunday, June 8, had the lowest 10.7 cm solar flux value I've ever seen -- 64.9 -- at the observatory in Penticton. The noon reading is the official daily sunspot number; the value observed that morning at 1700 UTC was actually a tiny bit lower at 64.8. The only value this low I have in my records was almost a dozen years ago near the last solar minimum, July 19, 1996.
The 10.7 cm solar flux is a measurement of energy at 2.8 GHz gathered by an antenna in British Columbia. The facility is the Dominion Radio Astrophysical Observatory (DRAO) that sits 168 miles northeast of my Seattle location at approximately 49.322 degrees north latitude, 119.621 degrees west longitude. The solar flux value is a general indicator of solar activity, but not as useful as sunspot numbers for predicting propagation.
Geophysical Institute Prague expects quiet conditions for June 13, quiet to unsettled June 14, unsettled June 15-18 and quiet to unsettled June 19.
Sunspot numbers for June 5-11 were 0, 0, 0, 0, 0, 14 and 11 with a mean of 3.6. The 10.7 cm flux was 66.4, 65.9, 65.6, 64.9, 66, 66.2, and 65.7 with a mean of 65.8. Estimated planetary A indices were 2, 8, 12, 7, 5, 4 and 4 with a mean of 6. Estimated mid-latitude A indices were 3, 7, 10, 5, 2, 1 and 3, with a mean of 4.4.
NASA predicts more of the same quiet conditions, with slight possible unsettled conditions on June 18, with a planetary A index of 12. They expect solar flux to stay below 70 until mid-July.
For more information concerning radio propagation, visit the ARRL Technical Information Service Propagation page <http://www.arrl.org/tis/info/propagation.html>. To read this week's Solar Report in its entirety, check out the W1AW Propagation Bulletin page <http://www.arrl.org/w1aw/prop/>.
| Notes | This solar update is brought to you courtesy of the American Radio Relay League's ARRL Letter. |