Viewing archive of Sunday, 17 August 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Aug 17 1241 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

Quiet (A<20 and K<4)

Solar protons

Quiet

	10cm flux	Ap
17 Aug 2025	120	007
18 Aug 2025	120	016
19 Aug 2025	120	027

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares identified. A total of 6 numbered sunspot groups were observed on the solar disk. Several of the SIDC Sunspot Groups have Alpha magnetic configurations and did not produce any significant 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 C3.2 flare (SIDC Flare 5165), peaking on August 16 at 21:00 UTC. Solar flaring activity is expected to remain low over the next 24 hours, with C-class flares very likely.

Coronal mass ejections

Coronal mass ejections: 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.

Coronal holes

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.

Solar wind

Solar wind parameters indicate a slow solar wind regime until August 17, 04:30 UTC, after which no data are currently available. Solar wind speed varied between 307 and 400 km/s. The total interplanetary magnetic field (Bt) remained around 5 nT, and the southward interplanetary magnetic field (Bz) component fluctuated between -4.7 nT and 3.7 nT. Between August 17, 04:30 UTC and the current time (12:00 UTC), solar wind parameters are expected to remain in a slow solar wind regime under very similar conditions. 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

Geomagnetism: Geomagnetic activity was quiet over the past 24 hours, with some periods of unsettled conditions observed locally in Belgium. NOAA Kp indices ranged between 1 and 2, and the Belgian K-index between 1 and 3. 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, and it is expected to remain below for the next 24 hours.

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): 084, based on 21 stations.

Solar indices for 16 Aug 2025

Wolf number Catania	///
10cm solar flux	122
AK Chambon La Forêt	010
AK Wingst	008
Estimated Ap	007
Estimated international sunspot number	123 - Based on 13 stations

Noticeable events summary

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

All times in UTC

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