Tad "Born of Sun and shower" Cook, K7RA, this week reports:
This week several new sunspots appeared for five days, but they were all leftover spots from Solar Cycle 23, not new Cycle 24 spots. But this is okay, because at the sunspot minimum we appreciate any spots we can get.
May 16-20 saw daily sunspot numbers of 34, 23, 30, 28 and 23. Sunspot numbers for May 15- 21 were 0, 34, 23, 30, 28, 23 and 0 with a mean of 19.7. The 10.7 cm flux was 71.1, 71.6, 71.2, 71.6, 68.9, 68.6 and 69.1 with a mean of 70.3.
Estimated planetary A indices were 4, 4, 2, 3, 8, 10 and 13 with a mean of 6.3. Estimated mid-latitude A indices were 2, 3, 1, 2, 5, 7 and 9, with a mean of 4.1.
Keep in mind that a sunspot number of 34 does not mean there were 34 sunspots last Friday. Instead, the numbers represent a somewhat arcane calculation that accounts for the number of sunspot groups and the size of each group. The count gets 10 points for each sunspot group and one point for each spot within the groups, the designation of these different areas within the groups seeming somewhat arbitrary to a layman such as myself. So 34 could mean that there are three darkened areas, with one of them counting as two spots, the other two just one each. Presumably, the same number would describe the Sun with two darkened areas facing Earth, and each counting for seven spots. Thirty plus four is the same as 20 plus 14, but this week there were three areas.
Expect quiet geomagnetic conditions and another prediction for a planetary A index of 25 just before the start of summer on June 17. Geophysical Institute Prague calls for unsettled conditions May 23-24, quiet to unsettled May 25, quiet May 26, quiet to unsettled again on May 27-28 and unsettled for May 29.
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. |