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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Aug 16 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
16 Aug 2025	120	007
17 Aug 2025	120	007
18 Aug 2025	120	013

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares identified. A total of 9 numbered sunspot groups were observed on the solar disk. Several of the SIDC Sunspot Groups have Alpha magnetic configurations and did not produce any flaring activity. The most productive region was SIDC Sunspot Group 590 (NOAA Active Region 4172), currently located at N09W78, which has a Beta magnetic configuration and was decreasing over the past 24 hours. This region produced the largest flare, a C7.7 flare (SIDC Flare 5156), peaking on August 15 at 21:22 UTC. Solar flaring activity is expected to remain low over the next 24 hours, with C-class flares very likely.

Espulsioni di massa coronale

No Earth-directed coronal mass ejections (CMEs) were observed over the past 24 hours. Only a very small number of minor CMEs were detected, none of which are expected to impact Earth. Moreover there are few large filaments visible on the disc, however they appear the remain stable.

Fori coronali

The recurring SIDC Coronal Hole 104 (polar-south, positive polarity) reached the central meridian on August 14. The SIDC Coronal Hole 116, a mid-latitude coronal hole with negative polarity, first reached the central meridian on August 15, continues its transit across the central meridian.

Vento solare

Solar wind parameters indicate a return to a slow solar wind regime. Solar wind speed varied between 340 and 450 km/s. The total interplanetary magnetic field (Bt) remained around 5 nT, and the southward interplanetary magnetic field (Bz) component fluctuated between -4.0 nT and 3.6 nT. The high-speed streams associated with SIDC Coronal Hole 116, a mid-latitude coronal hole with negative polarity now facing Earth, are forecast to influence solar wind conditions on August 18-19.

Geomagnetism

Geomagnetic activity was quiet over the past 24 hours, with NOAA Kp indices between 1 and 2, and the Belgian K-index also between 1 and 2. In response to the expected arrival of high-speed streams associated with SIDC Coronal Hole 116, minor geomagnetic disturbances or active conditions are possible on August 18-19.

Proton flux levels

Proton flux remained below 10 pfu over the past 24 hours. A slight enhancement cannot be fully excluded due to the number of sunspot groups on the solar disk but is considered unlikely.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 and GOES 19 remains above the 1000 pfu threshold in response to high-speed streams associated with SIDC Coronal Hole 123 observed over the past days. Electron flux levels are expected to fluctuate around the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence remains at moderate levels and is expected to return to normal levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 129, based on 08 stations.

Solar indices for 15 Aug 2025

Wolf number Catania	///
10cm solar flux	123
AK Chambon La Forêt	012
AK Wingst	010
Estimated Ap	010
Estimated international sunspot number	144 - Based on 25 stations

Noticeable events summary

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

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