SIDC Weekly Bulletin

Issued: 2020 Jul 28 1000 UTC
Product: documentation at www.sidc.be/products/bul
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SIDC Weekly bulletin on Solar and Geomagnetic activity #
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WEEK 1021 from 2020 Jul 20
SOLAR ACTIVITY
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The solar activity was quiet over the past week. A unipolar sunspot (Catania sunspot group 37, NOAA Active 2767) emerged on July 22. It remained stable and did not produce any flaring activity. The X-ray flux remained below C-class flare level for the whole week.

An Earth-directed partial halo Coronal Mass Ejection was observed in both STEREO/COR2 on July 19 around 4:00 UTC and SOHO/LASCO-C2 on July 19 around 12:00 UTC. It was a slow-moving ejecta with an initial deprojected speed of about 210 km/s into a slow background solar wind speed (320 km/s). A coronal dimming was visible on the surface close to the origin of the ejecta (near 32 degree latitude north and 32 degree longitude east).

The greater than 10 MeV proton flux was at background levels over the past week. The greater than 2 MeV electron flux was from nominal to Moderate levels over the past week.
GEOMAGNETIC ACTIVITY
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The solar wind conditions were at nominal levels at the beginning of the week, with the solar wind speed ranging between 276 km/s and 366 km/s (from DSCOVR data). On July 24, the solar wind parameters became enhanced due to the arrival of combined effects from the CME impact and the solar wind coming from the negative polarity equatorial coronal holes that crossed the central meridian on July 20. The solar wind speed Increased up to 443 km/s, the interplanetary magnetic field reached 11.3 nT and the magnetic component Bz fluctuated between 9.6 nT and 10.2 nT (from DSCOVR data).

The geomagnetic conditions were quiet with short periods of unsettled conditions in the beginning of the week. In response to the CME impact and arrival of the solar wind associated with the coronal hole, periods of active geomagnetic condition were observed on July 25 and 26.
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DAILY INDICES
DATE RC EISN 10CM Ak BKG M X
2020 Jul 20 000 000 069 004 A1.2 0 0
2020 Jul 21 000 005 070 006 A1.2 0 0
2020 Jul 22 011 010 070 004 A1.0 0 0
2020 Jul 23 011 010 070 004 A1.0 0 0
2020 Jul 24 011 010 070 014 A1.0 0 0
2020 Jul 25 /// 010 070 015 A2.0 0 0
2020 Jul 26 /// 011 071 004 A2.0 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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