Solar Activity Alerts

Space Weather Message Code: ALTK04 Serial Number: 2694 Issue Time: 2026 Oct 23 1955 UTC ALERT: Geomagnetic K-index of 4 Threshold Reached: 2026 Oct 23 1953 UTC Synoptic Period: 1800-2100 Active Warning: YES Comment: NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

Space Weather Message Code: WARK04 Serial Number: 5443 Issue Time: 2026 Oct 23 1927 UTC WARNING: Geomagnetic K-index of 4 expected Valid From: 2026 Oct 23 1926 UTC Valid To: 2026 Oct 24 0900 UTC Warning Conditions: Onset Comment: NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

:Product: Forecast Discussion :Issued: 2026 Oct 23 1230 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center # Solar Activity .24 hr Summary... Solar activity continued at low levels with the largest flare, a C3.3/Sf at 23/0542 UTC from Region 4560 (N13W51, Eai/beta-gamma). The only other active on the visible solar disk is Region 4557 (N07W75, Cao/beta), who was responsible for few C-class flares, including a C1.3 at 23/0355 UTC associated with an eruption observed first by GOES-19/SUVI and later by the operational coronagraphs (first imagery from LASCO/C2 at 23/0428 UTC). Preliminary analysis indicate that the trajectory of this CME will not intercept the Geospace. No new Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to remain at low levels through 25 Oct, with a slight chance for isolated M-class flares (R1-R2, Minor-Moderate), mostly due to the flare potential of Region 4560. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux reached high levels at 23/1140 UTC. The greater than 10 MeV proton flux remained steady at background levels. .Forecast... The greater than 2 MeV electron flux is expected to continue reaching high levels on 23-25 Oct. The greater than 10 MeV proton flux is anticipated to persist at background levels through 25 Oct. Solar Wind .24 hr Summary... Solar wind parameters reflected diminishing positive polarity CH HSS influences. Total magnetic field strength (Bt) was about 5 nT with a north-south (Bz) component oscillating between -/+ 6 nT during the period. Solar wind speeds slowly decreased from 450 km/s level to about 400 km/s late in the period. The phi angle remained predominantly in the positive sector (away from the Sun). .Forecast... Undisturbed solar wind conditions are expected early 24 Oct with enhancements returning on 25 Oct due to the combined influences of a negative polarity CH HSS and possible glancing CME effects from the 21 Oct eruptions. Geospace .24 hr Summary... The geomagnetic activity decreased from active to quiet levels during the past 24h. .Forecast... Quiet to unsettled conditions are expected on 23 Oct as CH HSS influences wane, transitioning to mostly quiet levels on 24 Oct. A return to active levels, with a chance for geomagnetic storming, is anticipated on 25 Oct due to low-confidence combined effects from a recently emerged negative polarity coronal hole and potential glancing CME impacts.

Space Weather Message Code: ALTEF3 Serial Number: 3755 Issue Time: 2026 Oct 23 1147 UTC ALERT: Electron 2MeV Integral Flux exceeded 1,000pfu Threshold Reached: 2026 Oct 23 1140 UTC Station: GOES-19 Comment:

:Product: Forecast Discussion :Issued: 2026 Oct 23 0030 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center # Solar Activity .24 hr Summary... Solar activity continued at low levels. There are two numbered sunspot regions on the visible disk: Region 4557 (N07W68, Dao/beta) showed modest new flux emergence in its intermediate spots following a period of decay, producing a C1.4/Sf flare at 22/1733 UTC. Region 4560 (N13W42, Eai/beta-gamma) was the primary driver of flaring, producing the largest event of the period-a C3.5 flare at 22/0309 UTC. The region continued to undergo flux emergence in its intermediate portions and briefly developed a delta magnetic configuration alongside its mixed gamma polarities. No new Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to remain at low levels through 25 Oct, with a slight chance for isolated M-class flares (R1-R2, Minor-Moderate), primarily due to the flare potential and ongoing development of Region 4560. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux was at moderate to high levels, briefly exceeding the 1,000 pfu threshold for a single reading before returning below high levels. The greater than 10 MeV proton flux remained steady at background levels. .Forecast... The greater than 2 MeV electron flux is expected to reach high levels on 23-25 Oct in response to coronal hole high-speed stream (CH HSS) influences. The greater than 10 MeV proton flux is anticipated to persist at background levels through 25 Oct. Solar Wind .24 hr Summary... Solar wind parameters reflected diminishing positive polarity CH HSS influences. Total magnetic field strength (Bt) steadily declined over the period, moving from 9 nT down to 5 nT. The North-South (Bz) component exhibited multiple extended southward deflections, reaching peak negative values between -5 nT and -7 nT. Solar wind speeds gradually drifted downward from early values around 480-490 km/s to around 430-440 km/s late in the period. The phi angle remained predominantly positive (away from the Sun). .Forecast... Positive polarity CH HSS influences are anticipated to continue waning through 23 Oct, returning to mostly background-like conditions by early 24 Oct. Enhancements are likely to return on 25 Oct due to the combined influences of a negative polarity CH HSS and possible glancing CME effects from the 21 Oct eruptions. Geospace .24 hr Summary... The geomagnetic field reached mostly active levels due to ongoing positive polarity CH HSS influences. .Forecast... Quiet to unsettled conditions are expected on 23 Oct as CH HSS influences wane, transitioning to mostly quiet levels on 24 Oct. A return to active levels, with a chance for geomagnetic storming, is expected on 25 Oct due to low-confidence combined effects from a recently emerged negative polarity coronal hole and potential glancing CME impacts.