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: 2021 Jan 18 1653 UTC
:Product: documentation at
# SIDC Weekly bulletin on Solar and Geomagnetic activity             #
WEEK 1046 from 2021 Jan 11
The solar activity was at very low levels over the entire week. The visible
solar disk was spotless until Jan 15th when a new faint sunspot group
emerged, which was later numbered and classified as NOAA AR 2796 (beta).
This active region remained quiet for the rest of the week. The flaring
activity throughout the entire week was very low with only a few isolated
B-class flares at the end of the week. The X-ray flux remained below
C-class flare level for the whole week.

A slow back-sided CME was ejected from the east limb around 22 UTC on Jan
16th. It was probably related to low-level flaring activity from NOAA AR
2795. No Earth-directed Coronal Mass Ejections (CMEs) were observed in the
available chronograph imagery for the entire week. 

The greater than 10 MeV proton flux remained at background levels over the
entire week. The greater than 2 MeV electron flux was under the 1000 pfu
threshold and the electron fluence was at nominal levels.
The solar wind conditions (based on DSCOVR and ACE data) were elevated at
the beginning of the week under the combined influence of an ICME, related
to the south-west CME ejected by the Sun on Jan 8th, and a CIR followed by
a high speed stream (HSS) emanating from a positive polarity coronal hole.
Due to the combined effect of the ICME and the CIR the maximum registered
interplanetary magnetic field reached 20.2 nT on Jan 11th with a
corresponding minimum of the north-south Bz component reaching -18.3 nT.
The HSS related to the geo-effective positive polarity coronal hole was
characterised with moderate speeds below 500km/s on Jan 11th and Jan 12th.
On Jan 13th the solar wind conditions started to return back to nominal
slow solar wind and remained at background levels throughout the rest of
the week.

The geomagnetic conditions were mostly quiet over the week. The arrival of
the ICME and the CIR/HSS brought globally active conditions on Jan 11th and
Jan 12th and locally three periods with minor geomagnetic storms (from 16
to 18 UTC on Jan 11th and from 02 - 03 UTC on Jan 12th). On Jan 13th the
geomagnetic conditions returned back to quiet and remained quiet throughout
the rest of the week.
DATE           RC   EISN  10CM   Ak   BKG    M   X
2021 Jan 11   000    000   073   ///   ////   0   0   
2021 Jan 12   000    000   073   ///   ////   0   0   
2021 Jan 13   000    000   073   ///   ////   0   0   
2021 Jan 14   000    004   074   ///   A1.4   0   0   
2021 Jan 15   ///    016   073   ///   A1.4   0   0   
2021 Jan 16   ///    013   078   ///   A3.1   0   0   
2021 Jan 17   ///    015   077   ///   A4.1   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)

# Solar Influences Data analysis Center - RWC Belgium                #
# Royal Observatory of Belgium                                       #
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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.