SIDC Ursigram

:Issued: 2026 May 16 1231 UTC
:Product: documentation at http://www.sidc.be/products/meu
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# DAILY BULLETIN ON SOLAR AND GEOMAGNETIC ACTIVITY from the SIDC     #
# (RWC Belgium)                                                      #
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SIDC URSIGRAM 60516
SIDC SOLAR BULLETIN 16 May 2026, 1230UT
SIDC FORECAST 
SOLAR FLARES  : C-class flares expected, (probability >=50%)
GEOMAGNETISM  : Minor storm expected (A>=30 or K=5)
SOLAR PROTONS : Quiet
PREDICTIONS FOR 16 May 2026  10CM FLUX: 101 / AP: 034
PREDICTIONS FOR 17 May 2026  10CM FLUX: 104 / AP: 015
PREDICTIONS FOR 18 May 2026  10CM FLUX: 105 / AP: 006

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 C9.5
flare (SIDC Flare 7709), peaking at 16:14 UTC on May 15, which was
associated with SIDC Sunspot Group 844 (NOAA Active Region 4435, magnetic
type beta). There are currently five numbered active regions on the solar
disk. SIDC Sunspot Groups 844 and 867 (NOAA Active Regions 4435 and 4438)
are the most complex groups with magnetic type beta. SIDC Sunspot Groups
868 and 869 (both magnetic type alpha) have rotated on disk from the east
limb. The solar flaring activity is expected to be low over the next 24
hours, with C-class flares very likely and a chance for M-class flares.

Coronal mass ejections: Two faint Coronal Mass Ejections (SIDC CME 654 and
SIDC CME 655) were observed in SOHO/LASCO-C2 imagery on May 15, directed
toward the west/northwest. SIDC CME 654 was first observed around 13:48 UTC
and was associated with a C6.7 flare peaking at 13:13 UTC from SIDC Sunspot
Group 844 (NOAA Active Region 4435), with possibly associated Type II radio
emissions detected at 13:44 UTC. SIDC CME 655 was first observed around
16:36 UTC and was associated with a C9.5 flare peaking at 16:14 UTC from
the same region, with possibly associated Type II radio emissions detected
at 16:16 UTC. As detected and measured by the CACTus tool, both CMEs were
relatively narrow and slow, with projected speeds around 340–360 km/s,
and
are not considered Earth-directed. No other Earth-directed CMEs were
observed in the available coronagraph imagery.

Solar wind: Over the past 24 hours, the solar wind parameters (ACE)
reflected enhanced solar wind conditions under the influence of the high-
speed stream from the large, negative polarity transequatorial coronal hole
(returning SIDC Coronal Hole 147). The solar wind speed increased up to
approximately 810 km/s. The interplanetary magnetic field reached up to
about 17 nT, while the Bz component reached values down to -11 nT. The
interplanetary magnetic field angle was mostly in the negative sector.
Further enhanced solar wind conditions are expected over the next 24 hours
due to the continuous influence of the high-speed stream.

Geomagnetism: Geomagnetic conditions globally reached moderate storm levels
between 21:00 UTC on May 15 and 00:00 UTC on May 16 (NOAA Kp 6 +). Locally,
several intervals of minor storm conditions were observed, with K BEL
reaching 5. Further active to minor storm conditions, with possible
isolated intervals of moderate storm conditions, may persist over the next
24 hours due to the continuous influence of the high-speed stream,
depending on the evolution of the interplanetary magnetic field,
particularly the Bz orientation.

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 GEO: 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 be below the 1000 pfu
threshold over 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 ISN  : 054, BASED ON 13 STATIONS.

SOLAR INDICES FOR 15 May 2026
WOLF NUMBER CATANIA    : ///
10CM SOLAR FLUX        : 101
AK CHAMBON LA FORET    : 053
AK WINGST              : 033
ESTIMATED AP           : 034
ESTIMATED ISN          : 048, BASED ON 19 STATIONS.

NOTICEABLE EVENTS SUMMARY
DAY BEGIN MAX  END  LOC    XRAY OP  10CM Catania/NOAA RADIO_BURST_TYPES 
NONE
END

BT
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