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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 May 17 1232 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Minor storm expected (A>=30 or K=5)

Protoni solari

Quiet

	10cm flux	Ap
17 May 2025	118	029
18 May 2025	119	023
19 May 2025	120	007

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 C1.1 flare (SIDC Flare 4408) peaking at 22:41 UTC on May 16, associated with SIDC Sunspot Group 496 (NOAA Active Region 4087, magnetic type beta-delta). There are currently six numbered active regions on the solar disk. The most complex one is SIDC Sunspot Group 496 (NOAA Active Region 4087). SIDC Sunspot Group 495 (NOAA Active Region 4088) has rotated behind the west limb. SIDC Sunspot Group 482 (NOAA Active Region 4090, magnetic type alpha) has rotated on disc from the east limb, in the southeast quadrant. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares likely, a small chance for M-class flares and X-class flares unlikely.

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. An associated high-speed stream may arrive at Earth starting from May 18.

Vento solare

The solar wind conditions (ACE and DSCOVR) were enhanced over the last 24 hours, likely due to the arrival of a glancing blow, associated with the Coronal Mass Ejection (CME) observed around 23:00 UTC on May 12. The solar wind speed increased from 400 km/s to around 580 km/s. The interplanetary magnetic field values increased from 1 nT up to 20 nT. The Bz component was mostly negative, with values between -18 nT and 16 nT. The interplanetary magnetic field angle phi was in the negative sector until 04:30 UTC on May 17, when it flipped to the positive sector. Enhanced solar wind conditions are expected over the next 24 hours, due to the expected arrival of the high-speed stream from the positive polarity coronal hole (SIDC Coronal Hole 104).

Geomagnetism

The global geomagnetic conditions have escalated to moderate storm levels (NOAA Kp 6+ ) between 00:00 and 03:00 UTC on May 17 and are currently at unsettled levels (NOAA Kp 3). The geomagnetic conditions locally have reached active conditions (K BEL 4) between 00:00 and 08:00 UTC on May 17. The geomagnetic storm was most likely the result of a glancing blow arrival, associated with the Coronal Mass Ejection (CME) observed around 23:00 UTC on May 12. Further minor to moderate storm conditions are possible in the upcoming hours due to the expected arrival of the high-speed stream from the 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 marginally crossed the 1000 pfu threshold between 20:00 UTC and 21:45 UTC on May 16. The greater than 2 MeV electron flux measured by 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): 054, based on 19 stations.

Solar indices for 16 May 2025

Wolf number Catania	074
10cm solar flux	117
AK Chambon La Forêt	029
AK Wingst	012
Estimated Ap	013
Estimated international sunspot number	066 - Based on 34 stations

Noticeable events summary

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

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