SIDC Weekly Bulletin

Review of past solar and geomagnetic activity.
Source SIDC (RWC-Belgium)
Frequency Weekly
Format Plain text
Mail header SIDC Weekly Bulletin
SIDC code bul


Latest issue

:Issued: 2022 May 18 2249 UTC
:Product: documentation at
# SIDC Weekly bulletin on Solar and Geomagnetic activity             #
WEEK 1115 from 2022 May 09
Over the past week the solar activity was at low to high levels. There were
eleven numbered active regions on the visible solar disc and two unnumbered
regions which rotated over the north-east limb at the end of the week. The
beginning of the week started with NOAA AR 3004 (beta-delta) and a few
other simple regions approaching the west limb and high C-class flaring
activity from NOAA AR 3007 (beta). The flaring activity reached high levels
on May 10th with an X1.5 class flare (start time 13:50 UTC, peak time 13:55
UTC, end time 13:59 UTC) from active region NOAA AR 3006 in the south-west
quadrant, which had grown in size, sunspot number and complexity and was
classified as magnetic type beta-gamma-delta. The solar activity was at
moderate levels on May 11th with an M1.5-class flare, peak time 16:49 UTC,
produced by NOAA AR 3007 near the central meridian, which developed into
beta-gamma-delta, while NOAA AR 3006 decreased its complexity. Further low
M-class flaring was observed from behind the west limb, most probably from
NOAA AR 3004 and high C-class flaring was produced from the east limb. The
solar flaring activity remained at moderate levels on May 12th with a
single M1.3-class flare, peak time 20:19 UTC, from behind the north-east
limb. NOAA AR 3007 (beta-gamma-delta) further increased its sunspots and
approached the central meridian. Few other simple active regions developed
on the visible disk and NOAA AR 3010 (beta) rotated from the east limb,
producing low levels of flaring activity. Flaring activity was at low
levels on May 13th and returned to moderate levels on May 14th with
background C-class flaring and an isolated M2.2-flare (peak time 00:09 UTC
on May 15th) from the north-east limb. 

The solar disc was streaked with filaments throughout the entire week and
has a few filament eruptions, none of which produced an Earth-directed CME.
Several partial halo CMEs were detected in the LASCO C2 coronagraph data,
most of which were back-sided. An on-disc partial halo CME related to the
X1.5-class and earlier C4.7-class flaring was first observed by LASCO C2 at
14:24 UTC on May 10th. A minor flank from this CME was estimated to
possibly affect Earth during the night of May 13th or early on May 14th. No
other Earth-directed CMEs were detected in the available coronagraph
imagery throughout the week.

A large patchy positive polarity coronal crossed the central meridian in
the UTC afternoon on May 12th and the related high speed stream (HSS) was
expected to reach Earth early on May 16th. 

The greater than 10 MeV proton flux was below radiation storm thresholds
throughout the entire week. The 10 MeV proton flux was elevated on May 11th
following the M-class flaring produced by NOAA 3007 and NOAA 3004 and
related coronal eruptions. The 10 MeV proton flux values returned to
background values on May 13th and remained at nominal levels thereafter.
The greater than 2 MeV electron flux briefly crossed the 1000 pfu threshold
in the UTC afternoon of May 08th. It returned to background values after a
few hours and remained so throughout the remaining of the week. The
electron fluence was at nominal levels throughout the entire week.
The solar wind parameters as registered by ACE and DSCOVR were at
background slow solar wind levels throughout most of the week. On May 14th
the solar wind parameters registered the early arrival of  a CIR and a HSS
from the positive polarity coronal, which crossed the central meridian on
May 12th. The magnitude of the interplanetary magnetic field increased to
20.7 nT. The Bz component reached a minimum of 10.2 nT. On May 15th the
solar wind speed approached 580 km/s. The expected flank arrival from the
CME related to the X1.5- and C4.7-class flaring on May 10th did not arrive
to Earth and was not detected in the solar wind data throughout the week.

The geomagnetic conditions were locally quiet to unsettled throughout the
entire week and globally quiet to unsettled with two isolated active
periods in the early UTC morning on May 15th while the Earth was influenced
by the CIR and the early HSS arrival.
DATE           RC   EISN  10CM   Ak   BKG    M   X
2022 May 09   ///    069   117   008   B5.8   0   0   
2022 May 10   071    055   116   004   B7.6   0   1   
2022 May 11   098    081   133   007   C1.1   3   0   
2022 May 12   139    113   133   010   C1.0   1   0   
2022 May 13   173    122   150   008   C1.2   0   0   
2022 May 14   ///    129   153   008   C1.1   1   0   
2022 May 15   ///    144   154   014   C1.0   0   0   
# 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)

10  1350  1355 1359 S30W04 X1.5 1B       01/3006      II/3 

11  1635  1649 1658 S24E41 M1.6 1N       02/3007      

11  1813  1858 1927 ////// M2.6     82   ///////      II/2IV/2 

11  1927  1931 1935 S25E37 M2.2 SF       ///////      

12  2004  2019 2027 ////// M1.3          ///////      

14  2358  0008 0017 ////// M2.2          ///////      

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This report is sent once a week, typically on a monday.
The weekly bulletin gives an overview of solar and geomagnetic activity of the past week and includes a noticeable solar events list.
Check the ISES code book for information on ISES codes.