SIDC Weekly Bulletin

:Issued: 2025 Jul 01 2140 UTC
:Product: documentation at http://www.sidc.be/products/bul
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# SIDC Weekly bulletin on Solar and Geomagnetic activity             #
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WEEK 1278 from 2025 Jun 23

Solar Active Regions (ARs) and flares
---------------
Solar flaring activity was low over the past week, with only C-class flares
identified. The largest flare was a C5.0 flare (SIDC Flare 4739) peaking at
12:23 UTC on June 23, which was produced by SIDC Sunspot Group 523 (NOAA
Active Region 4114). During the flare, the source region (SIDC 523) of the
flare had beta configuration of its photospheric magnetic field. There were
16 numbered active regions on the visible solar disk throughout the week.
SIDC Sunspot Groups 527 and 530 (NOAA Active Regions 4118 and 4120) were
the most complex regions with their beta-gamma magnetic configurations. At
the end of the week, 10 sunspot groups were visible on the solar disk.

Coronal mass ejections
---------------------
Narrow coronal mass ejections (CME) were observed on NW limb in
SOHO/LASCO-C2 on Jun 25 and Jun 27. They were associated with filament
eruptions on NW quadrant of the Sun, which was part of an extended filament
in the northern hemisphere. These CMEs did not arrive at Earth. A partial
halo CME was observed in SOHO/LASCO-C2 images around 21:00 UTC on Jun 28
with a projected speed of about 500 km/s. It was associated with the C4.0
flare (SIDC Flare 4771, N06 W21, peaked at 19:54 UTC on June 28) produced
by SIDC Sunspot Group 537 (NOAA Active Region 4126).

Coronal Holes
---------------------
At the beginning of the past week, recurrent negative polarity coronal hole
(SIDC Coronal Hole 116) which spanned from 20 S to 30 N crossed the central
meridian during Jun 21-25. A CIR and following high speed streams related
to this coronal hole enhanced the solar wind parameters near Earth during
Jun 25-29. Another recurrent negative polarity coronal hole (SIDC Coronal
Hole 111) which spanned from 20 to 40 S started to cross the central
meridian on Jun 29.

Proton flux levels
---------------------
The greater than 10 MeV GOES proton flux was at nominal levels throughout
the entire week.

Electron fluxes at GEO
---------------------
The greater than 2 MeV electron flux, as measured by GOES-19, briefly
exceeded the 1000 pfu alert threshold level daily until Jun 25. The greater
than 2 MeV electron flux, as measured by GOES-18 satellite, was above the
threshold levels daily for few hours until Jun 25. Both the electron fluxes
were below the threshold level on Jun 26. From Jun 27, the greater than 2
MeV electron flux, as measured by GOES-19 and GOES-18 satellites, remained
above the 1000 pfu threshold level during most of the time. This was due to
the high solar wind speed associated with the SIDC Coronal Hole 116 which
crossed the central meridian during Jun 21-25.

Solar wind
---------------------
At the beginning of the past week, the solar wind parameters were
transitioning from fast to slow solar wind until Jun 24. A CIR and
following high speed streams (HSSs), related to the negative-polarity
coronal hole (SIDC Coronal Hole 116) that crossed the central meridian
during Jun 21-25, enhanced the solar wind parameters near Earth during Jun
25-29. During the entire past week, the solar wind speed ranged from 355
km/s to 850 km/s. The North-South component (Bz) ranged between -12 nT and
14 nT. The interplanetary magnetic field ranged between 1 nT and 17 nT.

Geomagnetism
---------------------
At the start of the past week, geomagnetic conditions were at quiet to
unsettled conditions (NOAA Kp and K_BEL 1 to 3) both globally and locally.
With the arrival of high speed streams (HSSs) associated to the
negative-polarity coronal hole (SIDC Coronal Hole 116) that crossed the
central meridian during Jun 21-25, geomagnetic conditions were globally at
unsettlled to minor storm conditions (NOAA Kp 3 to 5) during Jun 25-27, and
locally it was at unsettled to active conditions (K_BEL 3 to 4). At the end
of the past week, geomagnetic conditions were at quiet to unsettled
conditions (NOAA Kp and K_BEL 1 to 3) both globally and locally.

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DAILY INDICES
DATE           RC   EISN  10CM   Ak   BKG    M   X
2025 Jun 23   143    094   122   009   B6.7   0   0   
2025 Jun 24   089    085   120   013   B6.0   0   0   
2025 Jun 25   113    096   117   016   B4.8   0   0   
2025 Jun 26   100    105   117   031   B4.9   0   0   
2025 Jun 27   114    118   118   024   B5.1   0   0   
2025 Jun 28   ///    137   122   011   B5.1   0   0   
2025 Jun 29   ///    152   128   010   B6.3   0   0   
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# RC   : Sunspot index (Wolf Number) from Catania Observatory (Italy)
# EISN : Estimated International Sunspot Number
# 10cm : 10.7 cm  radioflux (DRAO, Canada)
# Ak   : Ak Index Wingst (Germany)
# BKG  : Background GOES X-ray level (NOAA, USA)
# M,X  : Number of X-ray flares in M and X class, see below (NOAA, USA)
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NOTICEABLE EVENTS SUMMARY
DAY BEGIN MAX  END  LOC    XRAY OP  10CM Catania/NOAA RADIO_BURST_TYPES 
NONE
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