Summary and Forecast
Solar Summary
(last updated 18 Apr 2026 23:30 UT)
Activity 18 Apr: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 18 Apr: 106/55
Solar Forecast
(last updated 18 Apr 2026 23:30 UT)
19 Apr 20 Apr 21 Apr Activity R0 R0 R0 Fadeouts None expected None expected None expected 10.7cm/SSN 105/54 105/54 110/60 COMMENT: Solar flare activity was at the R0 level on UT day 18-Apr, with no M-class or greater flares observed. There are currently two active regions on the visible solar disk, with Active Region (AR) 4419 (N13E02, beta) being the largest and most magnetically complex. Both this region, and AR 4415 (S18W62, alpha) have remained stable over the past 24 hours. Solar flare activity is forecast to remain at the R0 level through 19-21 Apr. S0 solar proton conditions were observed throughout UT day 18-Apr, with solar proton flux consistent with background levels. S0 solar proton conditions are expected over 19-21 Apr. No geoeffective coronal mass ejections (CMEs) were observed over the last 24 hours. A filament eruption, visible in GONG Halpha imaging, was observed centred on S28E28 at 18/0732UT. A low-velocity, south-east-directed CME was subsequently observed in SOHO/LASCO imagery from 18/0848UT. The CME was modelled to pass ahead and below Earth, so is not considered geoeffective. The solar wind speed on UT day 18-Apr was initially light, ranging from 330-370 km/s early in the UT day. A subsequent increase in the solar wind speed and temperature, and decrease in the solar wind density at 18/0125UT signified a connection to a coronal hole high speed wind stream. The solar wind speed continued to increase, reaching a maximum of approximately 600 km/s, and is currently ranging between 520 and 560 km/s. The interplanetary magnetic field strength (IMF, Bt) also rose after the connection to the high speed wind stream, peaking at 18 nT, with the north-south component (Bz) ranging between -14 and +14 nT over the UT day. An extended period of southward Bz was also recorded between 18/0308-0714UT. The solar wind is expected to remain elevated over 19-20 Apr due to ongoing effects of this high speed wind stream, before starting to decline by 21-Apr.
Solar Activity levels are explained in the SWS Solar Terrestrial Glossary.
