Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2026 Apr 18 1231 UTC

SIDC Forecast

Solar flares

C-class flares expected, (probability >=50%)

Geomagnetism

Moderate (ISES: Major) magstorm expected (A>=50 or K=6)

Solar protons

Quiet

	10cm flux	Ap
18 Apr 2026	107	047
19 Apr 2026	107	028
20 Apr 2026	107	007

Solar Active Regions and flaring

A total of 3 numbered sunspot groups were identified on the disk over the past 24 hours. There was only 1 C-class flare detected in the last 24 hours, peaking at 07:04 UTC from SIDC Sunspot Group 844 (NOAA Active Region 4416), currently located at N19W77 and with a Beta magnetic configuration. More C-class falres can be expected in the coming 24 hours.

Coronal mass ejections

No Earth directed CMEs were observed in the past 24 hours.

Coronal holes

There is a large equatorial coronal hole with negative polarity in the western hemisphere (SIDC Coronal Hole 147).

Solar wind

The fast solar wind stream from SIDC Coronal Hole 147 is arriving to the Earth. The solar wind speed rose to 550 km/s, the interplanetary magnetic field magnitude has reached 17 nT with Bz down to -14 nT. This is a large coronal hole that has increased in size since the last rotation, we can expect high speeds probably reaching 700 km/s in the coming hours. There are low chances of also observing a glancing blow from the CME that left the Sun on 15 April.

Geomagnetism

Geomagnetic conditions have reached minor storm levels locally with K_Bel up to 5 and moderate storm levels at planetary scale with Kp up to 6-. More disturbed periods are expected in the next 24 hours (up to moderate storm levels).

Proton flux levels

The greater than 10 MeV proton flux, as measured by GOES-18, was below the 10 pfu threshold level over the past 24 hours and is expected to remain so for the next 24 hours.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux, as measured by GOES-18 and GOES-19 was above the 1000 pfu alert threshold in the past 24 hours. The flux is expected to fluctuate around the alert threshold over the next 24 hours. The 24-hour electron fluence was at normal to moderate levels over the past 24 hours and is expected to remain at these levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 047, based on 17 stations.

Solar indices for 17 Apr 2026

Wolf number Catania	///
10cm solar flux	107
AK Chambon La Forêt	020
AK Wingst	006
Estimated Ap	005
Estimated international sunspot number	052 - Based on 27 stations

Noticeable events summary

Provided by the Solar Influences Data analysis Center© - SIDC - Processed by SpaceWeatherLive