Weekly Bulletin on Solar and Geomagnetic Activity Highlights on 12 - 18.04.2021, Forecast on 19 - 26.04.2021, Carrington Rotation 2242, 2243 (14,23.04; 11,47.05.2021) Earth out of ecliptic (-6.1 - -5.6) deg. (S35 - N25 is zone of geoeffectiveness) THE SUNSPOT-FORMING SOLAR ACTIVITY REMAINED ON VERY LOW LEVEL. ESTIMATED, MOST LIKELY WEEKLY AVERAGE VALUE OF THE SUNSPOT NUM- BER IN THE INTERNATIONAL SYSTEM (old) FOR PERIOD W = 14+12/-5 (Wn= 23+21/-8). THERE ARE THREE SMALL SUNSPOT GROUP ON SOUTHERN HEMISPHERE HAVE BEEN OBSERWED, ONE IS STABLE. NEXT WEEK SUNSPOT ACTIVITY WILL BE ON VERY LOW LEVEL. WEEKLY AVERAGE VALUE OF THE RELATIVE SUNSPOT NUMBER IN THE INTERNATI- ONAL SYSTEM (old) FOR NEXT WEEK IS W=020+10/-10. FLARE ACTIVITY WAS AT LOW LEVEL. 39 SOLAR FLARE OF X-RAY CLASS "B", 43 -CLASS "A" AND 9 CORONAL MASS EJECTIONS (12, 13, 15-18. 04) WAS 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 to te localization l deg. Fl AR CME/to -------------------------------------------------------------------- NEXT WEEK THE FLARE ACTIVITY IS EXPECTED AT VERY LOW LEVEL. ON THE VISIBLE SOLAR DISK THE FOLLOWING CORONAL HOLES WERE OBSERVED: --------------------------------------------------------------------- sign N end E end S end W end Sch EE R G Sp/craft CH - S22L342 S40L010 S50L340 S35L330 ~4% 16-17.04 3 G1 SOHO,SDO... CH* - N00L291 S05L301 S21L296 S05L261 ~4% 21.04 3 - SOHO,SDO... * - 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. ---------------------------------------------------------------------- AFTER 15.04/0340 UT THE EARTH IS IN THE "-" SECTOR OF THE INTER- PLANETARY MAGNETIC FIELD. THE FOLLOWING SECTOR BOUNDARY "-/+" IT CAN BE EXPECT 1.05. ---------------------------------------------------------------------- APRIL 12 13 14 15 16 17 18 APRIL Wus 016 016 017 022 044 028 015 F10.7 083 073 074 072 077 075 078 èbcg A2.7 A2.5 A3.7 á4.7 A4.8 A4.4 A7.4 GOES Sp 010 030 090 050 110 030 050 msh N 1 2 IMF ~ ~ ~ +/- - - - DSCOVR Å>2 1.5E+6 1.2å+6 1.1E+6 1.3E+6 1.2E+6 3.0å+7 3.5E+8 GOES Ie>2 376 126 178 164 134 1092 14078 pfu Ap 5 5 7 13 19 29 16 nô Dst nô KIOTO Amsc 7 5 6 11 17 23 16 nô 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 RECURRENT ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT BEGUN 17.04/1715 UT AND WAS OBSERVED 17-18.04. NEXT WEEK THE GREATER THAN 2 MeV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS EXPECTED 19-23.04. MINOR MAGNETIC STORM (G1, Ams=37, dur.=21 h) ACCORDING OF CENTER IN BOULDER DATA AND (G1, Ams=30, dur.=15 h) ACCORDING OF IZMIRAN DATA WAS REGISTERED 16-17.04 DUE TO THE EARTH's PASSAGE OF HIGH- SPEED STREAM FROM CORONAL HOLE ("-") OF SOUTHERN HEMISPHERE. GEO- MAGNETIC CONDITION OF OTHER DAYS REMAINED QUIET AND UNSETTLED. IN THE NEXT WEEK THE MOST PROBABLE IS EXPECTED A QUITE AND UNSET- TLED GEOMAGNETIC CONDITION. 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