25 CYCLE OF SOLAR ACTIVITY, THE BRANCH OF RISE: THE PHASE OF MINIMUM Weekly Bulletin on Solar and Geomagnetic Activity Highlights on 19 - 24.10.2021, Forecast on 25 - 31.10.2021 Carrington Rotations 2249, 2250 (24,59.09; 21,88.10.2021) Earth out of ecliptic (-1.5 - -1.9) deg. (S30 - N30 is zone of geoeffectiveness) THE SUNSPOT-FORMING SOLAR ACTIVITY WAS ON VERY LOW AND LOW LE- VELS. 18.10 THE SUN WAS SPOTLESS (2021 total: 60 days - 21%). ESTIMATED MOST LIKELY WEEKLY AVERAGE VALUE OF THE SUNSPOT NUM- BER IN THE INTERNATIONAL SYSTEM (old) FOR PERIOD IS W=12+16/-5 (Wn= 20+26/-9). THERE WERE THREE SUNSPOT GROUPS ON VISIBLE SO- LAR DISK: ONE MIDDLE SIZE AND 2 - SMALL, ALL ON S-HEMISPHERES HAS BEEN OBSERVED. NEXT WEEK SUNSPOT ACTIVITY WILL BE ON LOW AND MIDDLE LEVELS. WEEKLY AVERAGE VALUE OF THE RELATIVE SUNSPOT NUMBER IN THE IN- TERNATIONAL SYSTEM (old) FOR NEXT WEEK IS W=040+20/-20. FLARE ACTIVITY WAS AT LOW AND VERY LOW LEVELS. 50 FLARES OF X- RAY CLASS "B", ONE SOLAR FILAMENT EJECTIONS AND 17 CORONAL MASS EJECTIONS (18, 19, 21-23.10) HAVE BEEN OBSERVED. ------------------------------------------------------------------- FLARES >M1 X-RAY CLASSES to tm te local. Class E(1-8A) AR RII/IV CME X-ray/Ïp J/m-2 DSF (EPL) to te localization l deg. Fl AR CME/to 21.10 0536 0625 N24W43L 7 -------------------------------------------------------------------- NEXT WEEK THE FLARE ACTIVITY IS EXPECTED AT VERY LOW AND LOW LEVELS. ON THE VISIBLE SOLAR DISK THE FOLLOWING CORONAL HOLES WERE OBSERVED: --------------------------------------------------------------------- sign N end E end S end W end Sch EE R G Spacecraft * - low geoeffectivity, the substorms with duration <6 h. only. Sch - CH area in % solar hemisphere near the central meridian on https://www.solarmonitor.org/; n/d - no data; R - solar rotations; EE-date of possible geomagnetic disturbance in the Earth's environment. G(0-5)-geoeffectivity in last solar rotation on the middle latitudes. A-active geomagnetic condition. ---------------------------------------------------------------------- 20.10/14 UT THE EARTH IS IN THE "-" SECTOR OF THE INTERPLANETARY MAG- NETIC FIELD. FOLLOWING SECTOR BOUNDARY "-/+" IT CAN BE EXPECT 25.10. ----------------------------------------------------------------------- OCTOBER 18 19 20 21 22 23 24 OCTOBER Wus 000 011 011 011 028 032 046 F10.7 077 076 076 082 087 087 093 èbcg á4.0 á2.6 á4.2 ÷1.3 ÷1.7 ÷1.9 ÷2.3 GOES Sp 170 185 130 100 250 540 570 msh N 1 1 1 IMF + +/- - - - - - DSCOVR Å>2 4.6E+6 1.9E+6 1.6E+6 1.2E+6 1.5å+6 1.7E+6 1.4E+6 GOES Ie>2 432 198 155 144 154 140 151 pfu Ap 10 14 6 6 4 3 4 nô Dst nô KIOTO Amsc 8 17 5 6 4 3 4 IZMIRAN ------------------------------------------------------------------------ Å>2 - Daily Electron Fluency e/(cm2-ster-day) with E>2 MeV. Ie>2 - the maximum intensity of electron flux in geostationary or- bits in days according to GOES-15 in (electrons/cm2.s.sr) for events > 1000 pfu. THE GREATER THAN 2 MeV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT NOT OBSERVED. NEXT WEEK THE GREATER THAN 2 MeV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS CAN NOT EXPECTED. THE GEOMAGNENIC CONDITION REMAIND QUITE AND UNSETTLED ALL DAYS EX- CEPT 19.10, WHEN THE 6-hour SUBSTORM INTENCITY G1 WAS OBSERVED AC- CORDING IZMIRAN DATA. ACCORDING TO THE CENTER IN BOULDER DATA THIS SUBSTORM INTENCITY WAS G0. THIS GEOMAGNETIC DISTURBANCE WAS ASSOCI- ATED WITH THE PASSAGE OF SOLAR WIND HIGH-SPEED STREAM FROM WEAK CO- RONAL HOLE OF THE S-HEMISPHERE. THE NEXT WEEK MOST PROBABLE QUIET AND UNSETTLED GEOMAGNETIC CONDI- TION. HIGHLIGHT AND FORECAST COMPOSED FROM DATA: NOAA SWPC, BOULDER, USA http://www.swpc.noaa.gov, THE SOLAR INFLUENCES DATA ANALYSIS CENTRE, SIDC, BRUSSELS, BELGIUM http://sidc.oma.be/index.php3, THE IZMIRAN, MOSCOW, TROITSK, RUSSIA http://www.izmiran.ru V. Ishkov