Viewing archive of Tuesday, 28 September 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Sep 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 Sep 2021	086	007
29 Sep 2021	086	007
30 Sep 2021	086	014

Bulletin

Two active regions (ARs) present on the visible solar disk. NOAA AR 2871 (beta-gamma magnetic field configuration) produced a C1.6 flare peaking at 06:34 UT. Over the next 24 hours, more C-class flares can be expected.

The C-class flare mentioned above was related to a CME (and dimmings, type II radio bursts and an EUV wave), mostly directed towards the west, but with an Earth directed component. The CME was first seen in STEREO/COR2 at 06:52 UT (during a gap in LASCO data). Its speed is calculated to be 1050 km/s, with an expected arrival time to the Earth (glancing blow) around 16:00 UT on 30 September.

The greater than 10 MeV proton flux was at background levels in the past 24 hours, and is expected to stay there in the next 24 hours. The greater than 2 MeV electron flux remained below the 1000 pfu alert threshold, it may increase over the next 24 hours. The electron fluence was at normal levels over the past 24 hours, it may increase over the next 24 hours.

Early on 27 September we have seen the (weak) effects of an ICME arrival to the Earth, related to the CMEs that erupted on 23 September. Later on 27 September, we saw the arrival of a high speed stream from the low latitudinal extension of the northern polar coronal hole (positive polarity). Solar wind speeds have reached 540 km/s with magnetic fields up to 15 nT (with Bz mostly positive). Elevated solar wind speeds with lower magnetic field magnitudes can be expected for the next 24 hours.

Geomagnetic conditions were quiet to unsettled (NOAA Kp and K Dourbes 1-3) over the past 24 hours, similar conditions can be expected for the next 24 hours.

Today's estimated international sunspot number (ISN): 056, based on 17 stations.

Solar indices for 27 Sep 2021

Wolf number Catania	054
10cm solar flux	///
AK Chambon La Forêt	011
AK Wingst	008
Estimated Ap	008
Estimated international sunspot number	044 - Based on 22 stations

Noticeable events summary

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

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