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: 2020 Nov 24 1552 UTC
:Product: documentation at
# SIDC Weekly bulletin on Solar and Geomagnetic activity             #
WEEK 1038 from 2020 Nov 16
The solar activity was at low levels over the past week with 23-B class and
5 C-class flares recorded. In the beginning of the week the solar disk was
spotless with 1 page region, previously NOAA 2872. By Nov 17th a new active
region (NOAA 2783 alpha) rotated from the east limb, which remained quiet
and stable throughout Nov 19th. On Nov 20th NOAA 2783 produced a C1.9 class
flare (peak at 17:03UTC) and another C1 class flare was produced (peak at
18:44 UTC) by an active region hidden behind the east limb. On Nov 21st a
new active region appeared on the solar disk, namely NOAA 2874 (beta),
which remained quiet until the end of the week. On Nov 22nd the active
region NOAA 2875 (alpha), previously hidden behind the east limb, appeared
on the solar disk and produced two C1.3 flares (peaks at 09:27 UTC and
14:32 UTC), as well as a C3.3 class flare (peak at 17:31 UTC). 

No Earth-directed CMEs were identified in the available coronagraph imagery
for the entire week. Nevertheless multiple CMEs were ejected from the east
limb on Nov 18th, Nov 19th, Nov 20th and Nov 21st. It is unlikely, but
remains possible that a slow deflected CME from Nov 19th and a slow CME
from Nov 21st had an Earth-directed component. One filament eruption from
the north-east part of the solar disk resulted in a fast east-ward CME
estimated to have no Earth-directed component. A couple minor CMEs were
detected from the west limb.

Over the past week the greater than 10 MeV proton flux remained at
background levels for the entire week. The greater than 2 MeV electron flux
was below the 1000 pfu alert threshold until the afternoon on Nov 22nd when
it increased and reached the 1000 pfu threshold under the influence a the
high speed stream solar wind.
The solar wind conditions as measured by DSCOVR and ACE were at very low
levels at the beginning of the week. The solar wind speed was fluctuating
around 300 km/s until late evening of Nov 19th. During the night of Nov
19th a solar wind disturbance was detected, possibly due to the arrival of
a weak CME or the influence of an enhanced solar wind stream originating
from a patchy extension of the northern polar coronal hole facing the Earth
since Nov 17th. This caused an increase in the solar wind speed to about
400 km/s and short periods of geomagnetically unsettled conditions in the
morning of Nov 20th. The solar conditions then remained quiet until the
afternoon of Nov 21st when a high speed stream from another low-latitude
extension of the northern polar coronal hole reached the Earth. This caused
unsettled to active geomagnetic conditions as the solar wind speed
increased towards 500 km/s with prolonged periods of negative Bz reaching
down to -10 nT. Active conditions prevailed on Nov 22nd and a minor
geomagnetic storm was registered in the afternoon as the solar wind speed
reached 650 km/s.
DATE           RC   EISN  10CM   Ak   BKG    M   X
2020 Nov 16   000    000   077   000   A9.0   0   0   
2020 Nov 17   ///    010   079   002   A5.5   0   0   
2020 Nov 18   012    010   077   004   A4.4   0   0   
2020 Nov 19   ///    010   077   003   A6.0   0   0   
2020 Nov 20   011    010   082   008   A7.9   0   0   
2020 Nov 21   ///    022   085   015   B1.8   0   0   
2020 Nov 22   ///    028   088   032   B3.0   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)

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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.