SIDC Ursigram

:Issued: 2025 Apr 20 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 50420
SIDC SOLAR BULLETIN 20 Apr 2025, 1230UT
SIDC FORECAST 
SOLAR FLARES  : M-class flares expected (probability >=50%)
GEOMAGNETISM  : Active conditions expected (A>=20 or K=4)
SOLAR PROTONS : Quiet
PREDICTIONS FOR 20 Apr 2025  10CM FLUX: 159 / AP: 011
PREDICTIONS FOR 21 Apr 2025  10CM FLUX: 161 / AP: 017
PREDICTIONS FOR 22 Apr 2025  10CM FLUX: 163 / AP: 016

Solar Active Regions and flaring: Solar flaring activity over the last 24
hours has been low, with few C-class flares. The strongest flare was a C4.3
flare (SIDC Flare 4158) peaking at 16:28 UTC on April 19, associated with
SIDC Sunspot Group 476 (NOAA Active Region 4065, magnetic type beta). There
are currently seven numbered active regions on the solar disk. The most
complex one is SIDC Sunspot Group 473 (NOAA Active Region 4062, magnetic
type beta-gamma). A new, currently unnumbered active region (SIDC Sunspot
Group 479, magnetic type beta) has emerged in the southwest quadrant. A
new, currently unnumbered active region (SIDC Sunspot Group 480) is
rotating on disc from the southeast limb. The solar flaring activity is
expected to be low to moderate over the next 24 hours, with C-class flares
expected and M-class flares probable.

Coronal mass ejections: A filament eruption was observed in SDO/AIA 304
data around 15:20 UTC on April 19 in the northeast quadrant, north of SIDC
Sunspot Group 473 (NOAA Active Region 4062). No associated Coronal Mass
Ejection (CME) was observed in the available coronagraph imagery. No other
Earth-directed CMEs were observed in the available coronagraph imagery.

Coronal holes: The southern, mid-latitude, positive polarity coronal hole
(SIDC Coronal Hole 104) continues to cross the central meridian since April
17.

Solar wind: The solar wind conditions (ACE and DSCOVR) were enhanced during
the past 24 hours, likely due to the arrival of a high-speed stream from
the southern, positive polarity coronal hole (SIDC Coronal Hole 104). The
solar wind speed reached 450 km/s. The interplanetary magnetic field
increased from 6 nT to 10 nT. The Bz component initially was mostly
negative, between -5 nT and -7 nT, before flipping to positive around 23:00
UTC on April 19, with values between 3 nT and 5 nT. The interplanetary
magnetic field angle was in the negative sector until 23:00 UTC on April
19, when it flipped to the positive sector. Further enhancements in the
solar wind conditions may be expected over the next 24-48 hours, under the
continuous influence of the high-speed stream from the southern, positive
polarity coronal hole (SIDC Coronal Hole 104) and the possible arrival of
the high-speed stream from the equatorial, positive polarity coronal hole
(returning SIDC Coronal Hole 82).

Geomagnetism: Geomagnetic conditions globally and locally reached minor
storm levels (NOAA Kp 5) between 00:00 UTC and 03:00 UTC on April 20.
Mostly unsettled to active levels, with possible minor storm intervals
(NOAA Kp 3 to 5, K BEL 3 to 5), are expected globally and locally over the
next 24-48 hours, under the continuous influence of the high-speed stream
from the southern, positive polarity coronal hole (SIDC Coronal Hole 104)
and the possible arrival of the high-speed stream from the equatorial,
positive polarity coronal hole (returning SIDC Coronal Hole 82).

Proton flux levels: The greater than 10 MeV proton flux was below the
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 was over the threshold between 20:15 UTC and 21:25 UTC on April 19.
The greater than 2 MeV electron flux measured by GOES 19 was below the
threshold over the past 24 hours. The greater than 2 MeV electron flux is
expected to remain below the 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  : 125, BASED ON 15 STATIONS.

SOLAR INDICES FOR 19 Apr 2025
WOLF NUMBER CATANIA    : ///
10CM SOLAR FLUX        : 157
AK CHAMBON LA FORET    : 032
AK WINGST              : 022
ESTIMATED AP           : 023
ESTIMATED ISN          : 111, BASED ON 15 STATIONS.

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

BT
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