Viewing archive of Thursday, 23 April 2015

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2015 Apr 23 1230 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

Active conditions expected (A>=20 or K=4)

Solar protons

Quiet

	10cm flux	Ap
23 Apr 2015	152	023
24 Apr 2015	152	016
25 Apr 2015	152	007

Bulletin

Solar flaring activity was mainly low but reached moderate levels with an M1.1 flare originating from Catania group 28 (NOAA 2322) from beyond the West limb peaking at 10:07 UT. Some further low level C flaring was observed from Catania groups 31 and 32 (NOAA 2326 and 2324 respectively). Most regions on disc appear mostly stable or in decay and not too remarkable. We expect C flaring over the next days. No Earth directed CME's were observed in the available coronagraph images. Solar wind conditions showed the decline of the positive polarity coronal hole high speed stream. Solar wind speed decreased from around 560 km/s at the start of the reporting period to around 440 km/s presently. Total magnetic field was around 4-5 nT with a short excursion up to 7 nT. Bz was variable remaining above -5nT. The magnetic field phi angle was stable in the outward sector. The were no clearly identifiable signs of the arrival of the April 18 CME. There remains a possibility for the CME to arrive later today or otherwise its effects have been covered up by the high speed stream effects. Geomagnetic conditions were quiet to unsettled with an isolated active period at planetary level (NOAA Kp 2-4, local K Dourbes 0-3). Solar wind is expected to further stabilize to nominal condition over the next days, but there remains a possibility for agitated conditions if the April 18 CME still arrives. Correspondingly, quiet to unsettled geomagnetic conditions are expected, with possibly active to minor storm conditions in case of CME arrival.

Today's estimated international sunspot number (ISN): 087, based on 22 stations.

Solar indices for 22 Apr 2015

Wolf number Catania	181
10cm solar flux	150
AK Chambon La Forêt	018
AK Wingst	011
Estimated Ap	012
Estimated international sunspot number	105 - Based on 29 stations

Noticeable events summary

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

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