\n<\/p>\n
Solar activity continued at moderate levels as Region 4493 produced an M3.6 flare on July 22, which was the largest event of the period and was associated with a 10.7-centimeter radio burst of 200 solar flux units (sfu). Additionally, 4493 produced a C3.4 flare on July 22, which was associated with another 10.7-cm radio burst of 150 sfu.
\u00a0
Region 4493 continued to undergo consolidation in its leading and trailing spots, but showed signs of new flux emergence in its intermediate area during the early hours of the reporting period. Region 4494 developed new, simple spots, but remained uni-polar. The remaining two numbered active regions were relatively stable and quiet.
\u00a0
A filament eruption NW of Region 4493 on July 21 was modeled and assessed to be at least partially Earth-directed. While modeling efforts suggest that a bulk of the material should pass north and ahead of Earth s orbit, this is low confidence given the faintness of this event in Sun-Earth line-focused coronagraph imagery and compounded by likely interaction with the coronal hole in the vicinity of the source location.
\u00a0
Additional M-class flare activity (R1-R2 radio blackouts) is likely through July 25 primarily due to the flare potential currently exhibited by AR 4493.
\u00a0
Solar wind parameters were mildly enhanced under a sustained negative polarity coronal hole high-speed stream (CH HSS) regime and a possible secondary Co-rotating Interaction Region (CIR). Solar wind speeds were roughly between 400 and 482 km\/s.
\u00a0
The current regime is expected to largely continue through July 25. Additional enhancements are possible beginning late on July 23 due to a coronal mass ejection (CME) that left the sun on July 20, with stronger enhancements arriving by early on July 24 with the arrival of the aforementioned CME event from July 21.<\/p>\n
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s Ionosphere,\u00a0 July 23, 2026, by F. K. Janda, OK1HH:<\/p>\n
A relatively large sunspot group, which was already very conspicuous in images from the SOLAR ORBITER spacecraft, was designated NOAA 4493 after its discovery as an active region on the northeastern limb of the solar disk. It produced class C and M flares on a daily basis. It is currently located in the northwest of the solar disk. As it grew, it disrupted a long north-south coronal hole and remains the largest and most complex sunspot group on the visible disk, accounting for most of the observed eruptive activity. The eruption observed within it on July 20 was accompanied by a CME. The ejected particles triggered a geomagnetic disturbance on the afternoon of July 23.<\/p>\n
As a result of this activity, the ionosphere is currently undergoing variable conditions, characterized albeit irregularly by a pronounced presence of the summer sporadic E layer in the Earth s northern hemisphere. In the coming days, geomagnetic activity should begin to gradually decline (no earlier than July 25). Increased solar activity will likely persist almost until the end of the month. Conditions for ionospheric radio propagation will therefore remain variable, with irregular occurrences of relatively very favorable days.<\/p>\n
The predicted Planetary A Index for July 25 to 31 is 5, 5, 5, 5, 5, 5, and 5, with a mean of 5.0. The predicted Planetary K Index is 2, 2, 2, 2, 2, 2, and 2, with a mean of 2.0. The predicted 10.7 centimeter flux is 125, 125, 120, 118, 118, 115, and 112, with a mean of 119.0.<\/p>\n
For more information concerning shortwave radio propagation, see\u00a0<\/span>http:\/\/www.arrl.org\/propagation\u00a0<\/span><\/span>and the ARRL Technical Information\u00a0<\/span>Service web page at,\u00a0<\/span><\/span><\/span>http:\/\/arrl.org\/propagation-of-rf-signals. For\u00a0<\/span>an explanation of numbers used in this bulletin, see<\/span>
http:\/\/arrl.org\/the-sun-the-earth-the-ionosphere\u00a0<\/span><\/span>. Information and<\/span>
tutorials on propagation can be found at,\u00a0<\/span><\/span><\/span>http:\/\/k9la.us\/\u00a0<\/span><\/span>.<\/span><\/p>\n