\n<\/p>\n
\u00a0Solar activity went from low to high this week. Activity was<\/p>\n
dominated by Region 4455, which produced frequent C-class flares
\nalongside three significant flare events: an M9.3\/Sf on June 1; as
\nwell as an M7.7\/1b and an X1.0\/1n on June 3.\u00a0
\n\u00a0
\nThere are eight numbered regions on the visible disk. Region 4455
\nremains complex, maintaining its anti-Hale configuration and
\ndisplaying a newly developed delta structure. Continuous flux
\nemergence and spot growth with penumbral development were observed
\njust ahead of its mature, positive polarity lead spot. Regions 4458
\nand 4459 both showed growth and consolidation, with Region 4459
\nshowing rapid spot development in its trailing area and gaining a
\nmixed-polarity gamma configuration. Region 4461 also showed flux
\nemergence driving a gamma configuration, though extreme
\nforeshortening near the limb limits high-confidence analysis of its
\noverall complexity. Region 4462 consolidated and showed increased
\nseparation between its poles. The remaining regions were stable or in
\ndecline.
\nSeveral eruptive events occurred during the reporting period. An
\nM9.3\/Sf flare June 1 was accompanied by wideband radio emissions,
\nincluding a Type IV radio sweep with an estimated shock velocity of
\n253 km\/s, and a 10.7-cm radio burst. An associated coronal mass
\nejection (CME) became visible in LASCO C2 imagery on June 2. While
\nfaint in coronagraph imagery, GOES\/SUVI imagery implies a partial to
\nfull halo profile, and COR2 triangulation confirms an Earth-directed
\ncomponent. Modeling indicates this event is the most Earth-directed
\nCME of the period\u2019s events.
\nThe M7.7\/1B flare on June 3 was accompanied by wideband radio
\nemissions, including a Type IV sweep, a Type II sweep with an
\nestimated shock velocity of 313 km\/s, and a prominent three-minute
\n10.7-cm radio burst. The associated CME was first seen in LASCO C2 on
\nJune 3. GOES\/SUVI 304 imagery shows much of the ejecta was deflected
\nsignificantly northward by an adjacent positive polarity coronal
\nhole. STEREO COR2 imagery and modeling shows that, while it retains
\nan Earth-directed glancing component, it is the least
\ndirectly-targeted event of the period.
\nSolar activity is expected to be at moderate to high levels through
\nJune 6. M-class (R1-R2\/minor-moderate) flaring remains likely, with a
\nslight chance for X-class (R3\/strong or greater) events, primarily
\ndue to the eruptive capabilities of Regions 4455, 4458, and 4459.
\nSolar wind parameters continued to be slightly elevated with
\nconditions reflecting possible embedded transient influences. Wind
\nspeeds held steady near 400 km\/s for most of the period before a
\ndistinct increase to near 450 km\/s late in the period. The phi angle
\nshowed a distinct transition into the positive (away from the Sun)
\nsector late in the period.\u00a0
\n\u00a0
\nMild enhancements are expected early on June 4 under the initial
\nonset of positive polarity high-speed stream (+CH HSS) influences.
\nConditions will escalate dramatically mid-to-late on June 4 with the
\narrival of the multiple June 3 CMEs. These significant enhancements
\nare expected to persist through June 5 with elevated conditions
\npersisting through June 6.
\n\u00a0
\nWeekly Commentary on the Sun, the Magnetosphere, and the Earth’s
\nIonosphere, June 4, 2026, by F. K. Janda, OK1HH:
\n\u00a0
\nOn May 28, a large sunspot group, AR 4455, began to emerge on the
\nnortheastern limb of the solar disk. Its activity had already been
\nmonitored in the preceding days by the Solar Orbiter spacecraft,
\nwhile we were also aware of it thanks to helioseismological
\nobservations. In the first days of June, AR 4455 gradually grew,
\nwhile its configuration pointed to future growth in eruptive
\nactivity. A series of moderately energetic eruption eruptions on June
\n2 turned out to be precursors. The main event, featuring four
\nenergetically significant eruptions, took place on June 3, with at
\nleast two of them accompanied by a coronal mass ejection (CME), while
\nat least one of which was headed directly toward Earth.\u00a0
\n\u00a0
\nThese lines you are currently reading are being written on June 4 at
\naround 16:00 UT, just before more than one particle cloud is expected
\nto hit Earth, marking the start of a geomagnetic disturbance. The
\ndisturbance is expected to intensify on June 5 and is likely to
\ncontinue, albeit with lower intensity, on June 6.
\n\u00a0
\nThe latest development in solar activity therefore differs
\nsignificantly from what we witnessed in May, during the previous
\nsolar rotation, when solar activity was low and the magnetosphere
\nremained calm in the following days.\u00a0
\n\u00a0
\nConclusion: Ionospheric propagation conditions during the first
\nweekend of June will be variable and generally poor, with low MUF
\nvalues. Although a noticeable improvement is expected in the coming
\ndays due to increased solar activity, another geomagnetic disturbance
\ncan be expected as early as June 10. The only certainty is change!
\n\u00a0
\nThe Predicted Planetary A Index for June 6 to June 12 is 8, 5, 5, 5,
\n5, 30, and 25 with a mean of 11.9. The Predicted Planetary K Index is
\n3, 2, 2, 2, 2, 6, and 5 with a mean of 3.1. 10.7 centimeter flux is
\n125, 125, 120, 120, 130, 135, and 135 with a mean of 127.1.
\n\u00a0
\nFor more information concerning shortwave radio propagation, see<\/span>
<\/span>and the ARRL Technical Information<\/span>
Service web page at, <\/span><\/span>http:\/\/arrl.org\/propagation-of-rf-signals. For<\/span>
an explanation of numbers used in this bulletin, see<\/span>
<\/span>. Information and<\/span>
tutorials on propagation can be found at, <\/span><\/span> <\/span>.<\/span><\/p>\n