Routine Space Environment Product (Daily)
Issued by NWS
Issued by NWS
103 FXXX12 KWNP 200031 DAYDIS :Product: Forecast Discussion :Issued: 2026 May 20 0030 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # Product description and SWPC contact on the Web # http://www.swpc.noaa.gov/wwire.html # # Forecast Discussion # Solar Activity .24 hr Summary... Solar activity continued at low levels during the reporting period. The largest events were a C2.1/Sf flare at 19/0729 UTC and a C1.1 flare at 19/1651 UTC, both from Region 4436 (N18W64, Cso/beta). This region was responsible for the majority of the periods activity, which otherwise consisted of occasional low-level B-class flaring. The notable exception was an isolated B8.2 flare from Region 4440 (N17E29, Hrx/alpha) at 19/1016 UTC. There are currently five numbered regions on the visible disk. Most regions continued to show gradual decay, with a few exhibiting localized development. Region 4436 transitioned into a well-defined bipolar group following a phase of stability, characterized by new flux emergence and consolidation within its trailing spots of opposite polarity. Region 4439 (N06E30, Cao/beta) remained mostly stable, though slight divergence was observed in its trailing spots. Region 4440 remained a stable unipolar group. Region 4441 (N07W15, Dao/beta) showed mild overall growth after new flux emerged between the leading and trailing spots, immediately consolidating with the like-polarity poles. Region 4443 (S16E37, Axx/alpha) experienced continued decay to a single unipolar spot. A CME associated with the B8.2 flare from Region 4440 was observed off the northeast limb, first appearing in LASCO C2 imagery at 19/1101 UTC. Analysis indicates this ejecta is not Earth-directed. No other Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to remain at low levels through 21 May, with a slight chance for isolated M-class flares (R1-R2/Minor-Moderate) primarily due to the complexity of Region 4441 and the recent flaring history of Region 4436. An increase in activity is anticipated starting 22 May as multiple active regions, tracked via far-side satellite and helioseismology imagery, rotate into view. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux at geosynchronous orbit remained at high levels, reaching a peak flux of 3,610 pfu observed at 19/0400 UTC. The greater than 10 MeV proton flux at geosynchronous orbit remained at background levels. .Forecast... The greater than 2 MeV electron flux is expected to return to normal to moderate levels through 21 May as current conditions wane. A return to high levels is anticipated on 22 May following the geoeffective onset of a new coronal hole high-speed stream. The greater than 10 MeV proton flux is expected to remain at background levels through 22 May. Solar Wind .24 hr Summary... Solar wind parameters initially reflected a trended toward background conditions with wind speeds around 500 km/s and total magnetic field (Bt) at 4 nT until the arrival of a CME passage at approximately 19/0630 UTC. Upon arrival, Bt spiked to a peak of 8 nT, while the north-south (Bz) component had a sustained southward deflection that reached as far as -7 nT. Solar wind speed simultaneously elevated to a peak of 655 km/s. Following this transient, parameters entered a steady decline through the remainder of the period with speeds returning to approximately 500 km/s and Bt decreasing to ~5 nT. The phi angle remained predominantly negative (towards the Sun) throughout the period. .Forecast... Solar wind parameters are expected to continue trending toward nominal conditions through early on 21 May. Mild enhancements are likely on 21 May from a solar sector boundary crossing, with more pronounced high-speed stream conditions expected on 22 May due to the onset of a positive polarity coronal hole high-speed stream (+CH HSS). Geospace .24 hr Summary... The geomagnetic field was initially quiet but responded to CME influence and increased to unsettled and active levels. .Forecast... Geomagnetic field activity is expected to be at mostly quiet to unsettled levels over 2021 May as enhancements wane. Isolated active periods are likely expected on 22 May following the onset of the approaching +CH HSS.