{"id":132045,"date":"2026-07-20T10:51:22","date_gmt":"2026-07-20T10:51:22","guid":{"rendered":"https:\/\/www.europesays.com\/dk\/132045\/"},"modified":"2026-07-20T10:51:22","modified_gmt":"2026-07-20T10:51:22","slug":"coronal-hole-to-push-solar-wind-past-700-km-s-bringing-possible-aurora-to-seattle-and-oslo","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/dk\/132045\/","title":{"rendered":"Coronal Hole to Push Solar Wind Past 700 km\/s, Bringing Possible Aurora to Seattle and Oslo"},"content":{"rendered":"

A transequatorial coronal hole \u2014 one of the largest to rotate into Earth-facing geometry in months \u2014 is forecast to more than double the speed of the solar wind reaching Earth by Tuesday, July 22, creating the most actionable aurora opportunity of the summer for observers in Seattle, Edinburgh, Oslo, and other mid-latitude cities while giving satellite and grid operators a multi-day head start to prepare for elevated geomagnetic conditions, according to EarthSky’s July 19 report<\/a> by NASA Goddard solar astrophysicist C. Alex Young.<\/p>\n

That forecast is a reminder of something the recent run of space weather stories has largely buried: coronal hole events are the only category of geomagnetic disturbance for which forecasters can issue reliable multi-day warnings before the storm arrives \u2014 a structural advantage that the Bz-blind CME forecasts that drove July 4’s surprise G3 storm cannot match.<\/p>\n

The solar wind is currently averaging approximately 325 km\/s. The arriving coronal hole stream could push that to roughly 700 km\/s, representing more than twice the baseline speed, according to modeling by NOAA’s Space Weather Prediction Center (SWPC)<\/a> referenced in EarthSky’s July 19 report. If the stream peaks near that level, conditions could escalate from G1 (minor) on July 21 to G2 (moderate) intervals on July 22.<\/p>\n

AR4491 Made Its Entrance: Then Went Quiet<\/p>\n

The week’s other headline-grabber, newly designated sunspot region AR4491, had been building anticipation since mid-July. The region made its first appearance as a small dark sunspot near the southeastern limb of the solar disk on July 17, when NASA’s Solar Dynamics Observatory (SDO) captured visible-light imagery and a magnetic-field map<\/a> showing patches of opposite polarity.<\/p>\n

Before it even received an official number, the incoming region was already the Sun’s leading flare producer, firing the day’s strongest burst for two consecutive days \u2014 not bad for a region still hidden behind the solar horizon. Its strongest pre-designation flare reached C8.9, just shy of the M-class threshold<\/a>.<\/p>\n

Once AR4491 cleared the limb, however, the picture became more modest. Forecasters assigned it an alpha magnetic configuration<\/a> \u2014 the simplest classification, with limited flare potential \u2014 and noted that the region appeared smaller than initially expected, though limb-proximity distortion may be inflating that impression. By July 18\u201319, AR4491 had stayed stable and quiet. As it rotates toward disk center over the coming days, its full magnetic structure will become easier to assess. For now, it is a watch-and-wait story, not an alarm.<\/p>\n

There is also an additional wildcard: at least one unnumbered region is rotating onto the northeast limb near solar latitude N15, generating multiple C-class flares<\/a> \u2014 suggesting it may carry more magnetic complexity than can currently be assessed. It should become fully analyzable within the next one to two days.<\/p>\n

What a Coronal Hole Actually Is<\/p>\n

A coronal hole is not a hole in the conventional sense \u2014 it is a region of the Sun’s outer atmosphere, the corona, where the plasma is cooler and less dense than its surroundings, and where the magnetic field lines extend open into interplanetary space rather than looping back to the solar surface. First identified unambiguously from soft X-ray images taken during the 1973 Skylab mission<\/a>, coronal holes appear dark in extreme-ultraviolet imagery for the same reason: less hot, less dense plasma emits less light.<\/p>\n

Those open field lines are the key. Plasma escaping along them \u2014 accelerated by wave-driven turbulent heating and Alfv\u00e9n-wave pressure<\/a> \u2014 can reach 650 to 800 km\/s by the time it crosses Earth’s orbital distance, roughly twice the speed of the slow solar wind that fills the space between active regions. That speed differential is what drives the storm.<\/p>\n

As the coronal hole’s fast wind overtakes the slower ambient solar wind ahead of it, the two streams collide and compress into a structure called a corotating interaction region, or CIR<\/a>. The CIR’s compressed magnetic field is what interacts with Earth’s magnetosphere to produce geomagnetic activity. According to the scientific literature on coronal holes, the majority of moderate-intensity geomagnetic storms originate from CIRs \u2014 not from coronal mass ejections (CMEs), which tend to produce the rarer but more dramatic sudden-onset events.<\/p>\n

The current hole is transequatorial, spanning both the northern and southern hemispheres of the Sun<\/a> and connecting across its equator. Its geometry makes it particularly effective at targeting Earth’s orbital plane with a sustained fast-wind stream rather than a briefly grazing one.<\/p>\n

How Forecasters Know the Wind Is Coming: and When<\/p>\n

The forecasting mechanism behind the July 21\u201322 prediction is worth understanding, because it illustrates the key structural difference between this event and the surprise G3 storm that produced Independence Day aurora for 30 states on July 4.<\/p>\n

For CME-driven storms, the most critical variable \u2014 the north-south orientation (Bz) of the interplanetary magnetic field embedded inside the approaching plasma cloud \u2014 cannot be measured until the storm reaches the L1 Lagrange point about 1.5 million kilometers from Earth, giving forecasters only 15 to 60 minutes of advance warning at that stage. That measurement gap is why NOAA forecast G1 for the July 4 event and got G3.<\/p>\n

Coronal hole streams are different. Because the hole is visible in EUV imagery days before its fast wind arrives at Earth, and because the Wang-Sheeley-Arge (WSA) model can convert synoptic solar magnetograms into solar-wind boundary conditions that feed the three-dimensional Enlil heliospheric model<\/a>, forecasters can predict when the stream will arrive and estimate its peak speed with multi-day lead time. The July 22 G1\u2013G2 forecast is the product of exactly this modeling chain.<\/p>\n

The recurrence advantage adds another layer: because coronal holes can persist for multiple solar rotations, the same structure that sends a fast-wind stream toward Earth this week could return roughly 27 days later. This is why CIR-driven storms are described as “recurring geomagnetic activity” rather than one-time events in the heliophysics literature.<\/p>\n

Modern convolutional neural networks are now being deployed to automatically detect and track coronal hole boundaries in EUV images from SDO and other spacecraft, improving the ensemble forecast reliability for exactly these events.<\/p>\n

Forecast: Unsettled July 21, Best Storm Chance July 22<\/p>\n

Conditions on July 20, as of publication, remain quiet to unsettled, with the solar wind near baseline levels and Earth’s magnetic field at Kp 0\u20132.<\/p>\n

July 21 is expected to bring unsettled-to-active conditions (Kp 3\u20135) as the coronal hole high-speed stream begins arriving, with wind speeds potentially reaching approximately 450 km\/s and a chance of G1 (minor) storm intervals. Minor auroral enhancements are possible at high latitudes \u2014 northern Scotland, southern Alaska, and similar magnetic latitudes \u2014 but very short midsummer darkness hours in the Northern Hemisphere will significantly constrain visibility.<\/p>\n

July 22 carries the highest space weather potential. Active to G1 (minor) storm conditions are likely, with a chance of G2 (moderate) intervals if the fast wind peaks near 700 km\/s, as some models suggest. If conditions align, aurora could become visible over Seattle, Edinburgh, Oslo, and similar latitudes<\/a>.<\/p>\n

What G1 and G2 Storms Mean for Infrastructure<\/p>\n

For aurora watchers, the language of G-scale storm intensity translates to a viewing latitude question: G1 reaches down to roughly 60\u00b0 magnetic latitude (northern Scotland, Alaska), while G2 can bring aurora to cities like Seattle, New York, and Oslo. What the G-scale communicates less visibly is its operational significance for technology infrastructure.<\/p>\n

At G1, weak power grid fluctuations become possible, and satellite operations may experience minor impacts<\/a>. The mechanism is geomagnetically induced currents (GICs) \u2014 quasi-direct currents that storm-related variations in Earth’s magnetic field overlay on long transmission lines, where they can saturate transformer cores and generate unwanted heat in equipment designed for alternating current.<\/p>\n

At G2, that risk escalates to voltage alarms in high-latitude power systems, and long-duration storms at this level can cause transformer heating that concerns grid operators even if it falls well short of the catastrophic transformer damage associated with the 1989 Quebec G5 event. High-frequency (HF) radio propagation may also fade at higher latitudes, affecting polar aviation routes that depend on HF for communications.<\/p>\n

Satellites in low Earth orbit face increased atmospheric drag as geomagnetic heating expands the upper atmosphere, slightly accelerating orbital decay. At G1\u2013G2 levels, these effects are manageable with the advance notice forecasters have already issued \u2014 a very different situation from the scramble that followed the G3 surprise on July 4.<\/p>\n

Why This Storm Is Different from the July 4 Surprise<\/p>\n

The comparison to TechTimes’s July 4 coverage is instructive. That event \u2014 a G3 storm that hit two levels stronger than NOAA’s G1 forecast \u2014 traced to the Bz measurement gap: no satellite can tell forecasters how the magnetic field inside an approaching CME is oriented until it reaches L1, 15 to 60 minutes before impact. The July 4 storm was inherently difficult to predict precisely because it came from a CME.<\/p>\n

Coronal hole streams are the structural exception. The CIR builds gradually \u2014 its front takes hours to arrive and compress rather than arriving in minutes. The fast-wind component follows behind the CIR, sustaining elevated activity over a longer period. That gradual arrival, combined with the days-in-advance observational visibility of the hole itself, means the Enlil model’s forecast of arrival timing and peak speed is far more reliable for this event than it was for the July 4 CME.<\/p>\n

The July 22 G1\u2013G2 forecast is not a guess. It is the output of a physics-based model tracking a visible, measurable structure on the Sun whose behavior across prior rotations is part of the observational record.<\/p>\n

Solar Cycle 25 Context: Why Events Like This Keep Coming<\/p>\n

These developments are unfolding while our star remains near the extended maximum of Solar Cycle 25. NASA and NOAA announced on October 15, 2024 that the Sun had reached its solar maximum period<\/a>. The cycle, which began in December 2019, surprised forecasters by significantly exceeding the predicted peak \u2014 reaching a 13-month smoothed monthly sunspot value of 156.7 in August 2024<\/a>, well above the 101.8 to 125.2 range the international prediction panel had anticipated.<\/p>\n

The solar maximum is the peak of the Sun’s roughly 11-year activity cycle, during which sunspot counts, flare rates, and the frequency of geomagnetic disturbances all run elevated. But the declining phase of a solar cycle is gradual and uneven. Space weather researchers characterize the period extending through mid-2027 as a window of sustained elevated risk for satellite infrastructure and high-latitude power grids.<\/p>\n

The Parker Solar Probe’s closest approaches to the Sun in 2024 and 2025, passing directly through coronal hole interiors, detected widespread magnetic switchbacks and signatures of interchange reconnection \u2014 the mechanism by which open magnetic flux is replenished inside coronal holes \u2014 at distances as close as 9.9 solar radii from the Sun’s surface. During 2024\u20132025, a series of equatorial coronal holes generated recurring G2-level geomagnetic storms that affected terrestrial power grids over multiple solar rotations. The current event belongs to the same pattern.<\/p>\n

What Observers Should Know<\/p>\n

For aurora enthusiasts, July 22 is the window to watch, contingent on how aggressively the coronal hole’s wind stream develops. High-latitude observers in Canada, Scandinavia, Iceland, Scotland, and the northern United States have the best chance of seeing elevated auroral displays \u2014 cloud cover and local darkness permitting. The compressed darkness hours of late July significantly limit viewing windows in the Northern Hemisphere.<\/p>\n

NOAA’s Space Weather Prediction Center at swpc.noaa.gov provides continuously updated Kp index readings and geomagnetic storm-scale alerts. EarthSky’s daily solar activity reports, authored by NASA Goddard solar astrophysicist C. Alex Young and colleagues, are providing rolling coverage of AR4491’s evolution and the coronal hole’s progress.<\/p>\n

For satellite operators, grid managers, and HF radio network operators, the practical message is straightforward: the multi-day advance warning that coronal hole events provide is a planning advantage that CME events cannot offer. The July 22 forecast is as reliable as space weather forecasting gets. Use the lead time accordingly.<\/p>\n

Frequently Asked QuestionsWhen is the best time to watch for aurora from Seattle, Oslo, or Edinburgh?<\/p>\n

July 22 is the highest-probability night, based on NOAA’s forecast of G1 (minor) to possibly G2 (moderate) geomagnetic storm conditions as the coronal hole high-speed stream peaks. G2 conditions are what push aurora visibility down to the latitudes of Seattle (47\u00b0N), Edinburgh (56\u00b0N), and Oslo (60\u00b0N). Observers should go outside after 10 p.m. local time, face north from a dark-sky location at least 30 to 40 minutes from city lights, and monitor NOAA’s real-time Kp index at swpc.noaa.gov \u2014 storm conditions can develop quickly once the CIR arrives. Camera sensors detect faint aurora in red wavelengths before the human eye can, so a long-exposure photo north of the horizon is worth trying even if nothing is visible to the naked eye.<\/p>\n

What is a corotating interaction region, and why does it produce different storms than a CME?<\/p>\n

A corotating interaction region \u2014 or CIR \u2014 forms when the fast solar wind streaming out of a coronal hole overtakes the slower ambient solar wind ahead of it. The collision between these two streams creates a compressed, magnetically enhanced region that rotates with the Sun, arriving at Earth days after the hole becomes Earth-facing. CIR-driven storms are different from CME-driven storms in two important ways: they commence gradually over hours rather than suddenly, and they are structurally predictable in advance because the hole producing them is visible in solar imagery days before impact. That same hole can return on the next solar rotation \u2014 roughly 27 days later \u2014 making CIR events the most forecastable category of space weather disturbance.<\/p>\n

How does the July 22 forecast compare to the July 4 G3 storm TechTimes covered?<\/p>\n

The July 4 event was a CME-driven storm that reached G3 \u2014 two levels stronger than NOAA’s G1 forecast \u2014 because forecasters could not measure the magnetic orientation of the approaching plasma cloud until it was 15 to 60 minutes from Earth. The July 22 event is a coronal hole stream, which is inherently more predictable: the hole itself is visible in solar imagery, its fast wind builds gradually, and the Wang-Sheeley-Arge model has had days to run its forecast. The G1\u2013G2 prediction for July 22 is a more reliable estimate than the G1 forecast was for July 4 \u2014 not because the Sun is less active, but because the mechanism is fundamentally different. Coronal hole streams are the class of space weather event where the lead time is real.<\/p>\n

Could the unnumbered northeast limb region change the forecast before July 22?<\/p>\n

Potentially, though the current assessment is cautious. The unnumbered region near N15 on the northeast limb has been producing multiple C-class flares, suggesting more magnetic complexity than is typical for quiet periods. It should become fully analyzable within the next one to two days as it rotates into clearer view. If it carries a beta-gamma magnetic configuration, it could produce M-class or even X-class flares capable of launching a CME toward Earth \u2014 an additional space weather driver layered on top of the coronal hole stream. NOAA’s daily forecasts will update the M-class probability as the region’s magnetic structure becomes clearer.<\/p>\n","protected":false},"excerpt":{"rendered":"A transequatorial coronal hole \u2014 one of the largest to rotate into Earth-facing geometry in months \u2014 is…\n","protected":false},"author":2,"featured_media":132046,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[85],"tags":[43265,64168,64169,13689,64172,157,156,64170,64173,64171],"class_list":["post-132045","post","type-post","status-publish","format-standard","has-post-thumbnail","category-oslo","tag-aurora","tag-coronal-hole","tag-geomagnetic-storm","tag-nasa","tag-noaa","tag-norway","tag-oslo","tag-solar-cycle-25","tag-solar-wind","tag-space-weather"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@dk\/116951927225267836","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts\/132045","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/comments?post=132045"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts\/132045\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/media\/132046"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/media?parent=132045"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/categories?post=132045"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/tags?post=132045"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}