Viewing archive of Wednesday, 28 April 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Apr 28 1231 UTC

SIDC Forecast

Solar flares

Quiet conditions (<50% probability of C-class flares)

Geomagnetism

Quiet (A<20 and K<4)

Solar protons

Quiet

	10cm flux	Ap
28 Apr 2021	078	006
29 Apr 2021	078	007
30 Apr 2021	077	014

Bulletin

X-ray flux has remained below C level throughout the period. All three regions on disc remained stable or in decay. In particular the trailing edge of Catania group 91 (NOAA region 2821) seems to be dissolving. X-ray flux is likely to remain below C level though an isolated C-flare is not unlikely.

No new Earth directed CMEs have been detected. Regarding the April 26 filament eruption and associated CME reported yesterday: SoHO/LASCO C2 coronagraph data now show more clearly (though faint) the CME propagating towards the South-South-West with an angular width of under 90 degrees. Nevertheless, combined with the STEREO A observations which clearly display an equatorial component, it is not excluded that Earth may see part of the passing magnetic cloud. If it reaches Earth it should be expected late on May 1.

The greater than 10 MeV proton flux was at nominal levels over the past 24 hours and is expected to remain so for the next 24 hours. The greater than 2 MeV electron flux remained under the 1000 pfu event threshold. The 24h electron fluence was at normal levels but rising. As Solar wind enhancements are now dying out, the electron fluence is expected to remain at normal levels during next days.

From just before midnight, Solar wind parameters finally showed the expected return to slow Solar wind conditions. Solar wind speed meanwhile dropped to around 375km/s while total magnetic field remained under 5nT with an unremarkable Bz component and a phi angle indicating magnetic field orientation mostly towards the Sun. By end of April 30, start of May 1 we may see Solar wind perturbations due to a combination of enhanced speed associated to the positive polarity coronal hole currently transiting the central meridian, and magnetic field perturbations due to passing magnetic clouds from first the April 25 CME and later the April 26 CME. Though likelihood and confidence for the CME arrivals is low.

Geomagnetic conditions were quiet (local K Dourbes and NOAA Kp 0-2). Geomagnetic conditions are expected to be quiet to unsettled until at least late April 30.

Today's estimated international sunspot number (ISN): 044, based on 16 stations.

Solar indices for 27 Apr 2021

Wolf number Catania	///
10cm solar flux	079
AK Chambon La Forêt	006
AK Wingst	007
Estimated Ap	007
Estimated international sunspot number	053 - Based on 30 stations

Noticeable events summary

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

All times in UTC

<< Go to daily overview page