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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 May 18 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
18 May 2025	118	029
19 May 2025	119	010
20 May 2025	119	011

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares. The strongest flare was a C2.2 flare (SIDC Flare 4409) peaking at 20:00 UTC on May 17, from beyond the west limb. There are currently four numbered active regions on the solar disk. The most complex one is SIDC Sunspot Group 496 (NOAA Active Region 4087, magnetic type beta-delta). SIDC Sunspot Group 500 (NOAA Active Region 4091, magnetic type beta) has emerged in the southeast quadrant, west of SIDC Sunspot Group (NOAA Active Region 4090). SIDC Sunspot Group 498 has decayed into plage. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares likely and a small chance for M-class flares.

Espulsioni di massa coronale

No Earth-directed Coronal Mass Ejections (CMEs) were observed in the available coronagraph imagery in the last 24 hours.

Fori coronali

An elongated, mid-latitude, positive polarity coronal hole (SIDC Coronal Hole 104) continues to cross the central meridian since May 15.

Vento solare

The solar wind conditions (ACE and DSCOVR) were enhanced over the last 24 hours, likely due to the arrival of a high-speed stream from the elongated, mid-latitude, positive polarity coronal hole (SIDC Coronal Hole 104). Speed values increased up to 700 km/s. The interplanetary magnetic field values were between 6 nT and 19 nT. The Bz component varied between -14 nT and 13 nT. The interplanetary magnetic field angle phi was mostly in the positive sector. Further enhancements in the solar wind conditions may be expected over the next 24 hours, under the continuous influence of the high-speed stream from the elongated, mid-latitude, positive polarity coronal hole (SIDC Coronal Hole 104).

Geomagnetism

Geomagnetic conditions globally reached active levels (NOAA Kp 4+ ) between 06:00 UTC and 09:00 UTC on May 18. Geomagnetic conditions locally were mostly at unsettled to active levels (K BEL 3 to 4). Active conditions are expected over the next 24 hours, under the continuous influence of the high-speed stream from the elongated, mid-latitude, positive polarity coronal hole (SIDC Coronal Hole 104).

Proton flux levels

The greater than 10 MeV proton flux was below the 10 pfu threshold level over the past 24 hours. It is expected to remain below the threshold level over the next 24 hours.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 and GOES 19 was below the 1000 pfu threshold in the last 24 hours. The greater than 2 MeV electron flux is expected to remain below the 1000 pfu threshold the next 24 hours. The 24-hour electron fluence is presently at normal levels and is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 056, based on 14 stations.

Solar indices for 17 May 2025

Wolf number Catania	///
10cm solar flux	117
AK Chambon La Forêt	035
AK Wingst	037
Estimated Ap	040
Estimated international sunspot number	055 - Based on 25 stations

Noticeable events summary

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

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