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Daily bulletin on solar and geomagnetic activity from the SIDC

Випущено: 2017 Sep 23 1234 UTC

SIDC Forecast

Сонячні спалахи

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

Geomagnetism

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

Сонячні протони

Quiet

	10cm flux	Ap
23 Sep 2017	076	010
24 Sep 2017	079	022
25 Sep 2017	081	007

Bulletin

Over the past 24 hours the solar activity was very low, only a small B-class flare was recorded. Catania sunspot groups 56 (NOAA active regions 2681) remained stable showing no flaring activity. Catania sunspot group 55 (NOAA active region 2680) is currently turning over the west solar limb. The top of the loops from the returning region Catania sunspot group 46 (NOAA active region 2673), from which a B3.0-class flare (Sept 23 at 06:03 UT) is attributed, is now visible at the east solar limb. We expect the solar activity to increase due to this returning region with C-class flares. As this region was very active with several X-class flares during the previous solar rotation, we cannot exclude the possibility of M to X-class flares to occur. Once the foot-points of the loops will be visible, a better estimation of its magnetic complexity will be made and we will be able to better estimate the probability of flaring activity.

No Earth directed CMEs have been observed and the solar protons remained at background level over the past 24 hours.

The Earth remained inside a slow solar wind flow with de speed lower than 400 Km/s. The interplanetary magnetic field magnitude remained below 6 nT and the Bz component fluctuated between -4 and 4 nT being mainly negative. The associated fast solar wind to the small equatorial coronal hole that has crossed the central meridian on Sept 20 is expected to arrive at Earth today around midnight UT time.

Geomagnetic conditions were mostly quiet to unsettled with Kp (NOAA) and local K (Dourbes) indexes ranging between 1-2 and 0-3 respectively. While the solar wind remained in its nominal condition, the local K (Dourbs) sowed an unexpected short duration maximum (K=4) at 22:00 UT due to the Bz components being mostly negative. The geomagnetic conditions are expected to remain quiet to unsettled until Sept 23 when the fast solar will reach Earth.

Today's estimated international sunspot number (ISN): 012, based on 21 stations.

Solar indices for 22 Sep 2017

Wolf number Catania	022
10cm solar flux	078
AK Chambon La Forêt	012
AK Wingst	008
Estimated Ap	006
Estimated international sunspot number	018 - Based on 29 stations

Noticeable events summary

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

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