:Issued: 2023 May 31 2120 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1169 from 2023 May 22 Solar Active Regions (ARs) and flares --------------- The solar flaring activity throughout the week was at low to moderate levels with multiple C-class flaring and one or up to two low M-class flares per day. There were eleven numbered active regions on the visible solar disc. The week started at moderate levels with an M2.6-flare, peak time 16:04 UTC on May 21st, from the most complex and most active region in the first half of the week, NOAA AR 3311 (beta-gamma-delta). Multiple low to high C-class flaring was also produced by NOAA AR 3305 (beta) from near the west limb. Active region NOAA 3310 (beta) was large enough to be seen by protected eye and produced multiple C-class flaring. The second half of the week was governed by activity from NOAA AR 3315, which towards the end of the week developed a beta-gamma-delta magnetic type configuration becoming the most complex region on the visible disc as NOAA AR 3311 decreased its complexity to beta-gamma. Coronal mass ejections --------------------- Multiple filament and prominence eruptions were observed throughout the week, none of it resulted in an Earth-directed coronal mass ejection (CME). Low chances were given for a weak glancing blow arrival late on May 25th or May 26th related to low M-class flare-driven CME on May 22nd with accossiated on-disc dimming, but no ICME arrival was confirmed by the solar wind data later. Two back-sided fast full halo CMEs were observed on May 22nd and May 23rd with no expected arrival at Earth. No other Earth-directed CMEs were observed in the available coronagraph imagery. Coronal Holes --------------------- A negative polarity equatorial coronal hole crossed the central meridian on May 21st and related high speed stream was expected to arrive at Earth as early as May 23rd. 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 was below the 1000 pfu threshold at the start of the week and frequently exceeded the thresholds for prolonged periods of time until May 28th, when it returned back to background values. The corresponding electron fluence started at nominal levels and quickly increased towards moderate levels. It dropped back to nominal levels at the end of the week. Solar wind --------------------- The solar wind parameters as measured by ACE and DSCOVR at the beginning of the week were under the mixed influence of a high speed stream (HSS) arrival from a negative polarity coronal hole and a weak ICME arrival related to the flare-driven CME from May 17th. The corresponding solar wind velocity reached up to 657 km/s on May 22nd with enhanced interplanetary magnetic field values of up to 13.22 nT and minimum Bz of -10.57 nT. Enhanced solar wind parameters due to continuous HSS influence with solar wind speeds exceeding 600 km/s (and reaching as high as 688 km/s) persisted throughout May 25th and started to wane from May 26th onwards to reach mostly slow solar wind conditions at the end of the week. Geomagnetism --------------------- The geomagnetic conditions globally started at moderate storm levels at the beginning of the week due to the mixed influence of a HSS and an ICME arrivals. Locally in Belgium only mostly active conditions were observed with a single isolated minor storm period late UTC on May 21st. The geomagnetic conditions were mostly quiet to active throughout May 22nd, May 23rd and quiet to unsettled thereafter. The week ended at quiet levels. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2023 May 22 /// 130 162 023 C1.5 2 0 2023 May 23 156 121 155 016 C1.2 1 0 2023 May 24 190 146 164 012 C1.0 3 0 2023 May 25 /// 145 152 014 B8.7 1 0 2023 May 26 171 141 149 007 B6.4 0 0 2023 May 27 /// 137 157 004 B8.5 0 0 2023 May 28 /// 143 151 011 B8.3 1 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) --------------------------------------------------------------------------- NOTICEABLE EVENTS SUMMARY DAY BEGIN MAX END LOC XRAY OP 10CM Catania/NOAA RADIO_BURST_TYPES 22 1331 1337 1343 N18E24 M1.9 SF 110 ///3311 VI/2III/2II/2 22 1330 1337 0655 ////// M1.9 /////// VI/2 23 1207 1213 1217 ////// M3.0 97/3311 III/1 24 0951 0958 1002 N18W00 M1.0 SN 97/3311 24 1704 1721 1748 N18W03 M1.8 1F 97/3311 24 1753 1800 1818 S17E38 M1.0 SF 01/3315 25 1437 1446 1453 S25W04 M1.1 1N 98/3312 III/2 28 1021 1036 1055 S15W11 M1.0 1N 01/3315 III/1 #--------------------------------------------------------------------# # Solar Influences Data analysis Center - RWC Belgium # # Royal Observatory of Belgium # # # # Website http://www.sidc.be. # # E-mail sidc-support@oma.be # # To unsubscribe http://www.sidc.be/registration/unsub.php # # # # Legal notices: # # - Intellectual Property Rights: # # http://www.astro.oma.be/common/internet/en/data-policy-en.pdf # # - Liability Disclaimer: # # http://www.astro.oma.be/common/internet/en/disclaimer-en.pdf # # - Use and processing of your personal information: # # http://www.astro.oma.be/common/internet/en/privacy-policy-en.pdf # #--------------------------------------------------------------------#