Viewing archive of Friday, 17 September 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Sep 17 1230 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
17 Sep 2021	073	012
18 Sep 2021	072	008
19 Sep 2021	075	003

Bulletin

The solar activity was at low levels with only one detection of a C3.5 flare during the last 24 hours. There are currently no Active Regions (AR) visible from Earth, however the C-class activity came at 04:51 UT from an AR expected to soon turn into view. NOAA plage 2870 is also present on the front side of the solar disk, but did not produce any noticeable activity. For the next 24 hours more C-class activity and even an M-class flare is possible from the same AR, although it is difficult to provide a reliable estimation as its magnetic complexity is currently unknown.

No Earth-directed CMEs were detected in the available coronagraph imagery over the past 24 hours. A partial halo CME visible in SOHO/LASCO-C2 images starting from today 04:28 UT, is back-sided and not expected to be geo- effective.

The greater than 10 MeV proton flux was at nominal levels in the past 24 hours and is expected to remain so in the next 24 hours. The greater than 2MeV electron flux was below the 1000 pfu threshold and is expected to remain so in the next 24 hours. The 24h fluence for the greater than 2MeV electron flux was at nominal levels and is expected to remain so in the next 24 hours.

The Solar Wind (SW) parameters show the arrival at 01:30 UT of the CME observed on 14 Sep and predicted to arrive on 18 Sep. The SW speed varied between 290 and 410 km/s during the last 24 hours. The total magnetic field (Btot) varied between 2.7 and 8.7 nT, while the Bz component between -6.8 and 2.8 nT in the last 24 hours. The interplanetary magnetic field phi angle was in the positive sector (directed away from the Sun) until the arrival of the ICME, and varied almost equally between the two sectors since. The SW are expected to return to a typical slow solar wind regime in the next 24 hours as the ICME appears to be small and relatively slow.

Geomagnetic conditions were globally quiet to active (NOAA Kp 1-4) and locally quiet (K Dourbes 1-2). For the next 24 hours the geomagnetic conditions are expected to become active, due to the arrival of the CME detected on 14 Sep.

Today's estimated international sunspot number (ISN): 000, based on 17 stations.

Solar indices for 16 Sep 2021

Wolf number Catania	000
10cm solar flux	073
AK Chambon La Forêt	010
AK Wingst	004
Estimated Ap	002
Estimated international sunspot number	000 - Based on 29 stations

Noticeable events summary

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

All times in UTC

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