Weekly Bulletin on Solar and Geomagnetic Activity Highlights on 19 - 25.04.2021, Forecast on 26.04 - 02.05.2021, Carrington Rotation 2243 (11,47.05.2021) Earth out of ecliptic (-5.6 - -5.1) deg. (S35 - N25 is zone of geoeffectiveness) THE SUNSPOT-FORMING SOLAR ACTIVITY REMAINED ON LOW AND MIDDLE LEVEL. ESTIMATED, MOST LIKELY WEEKLY AVERAGE VALUE OF THE SUN- SPOT NUMBER IN THE INTERNATIONAL SYSTEM (old) FOR PERIOD W=19+ 15/-2 (Wn= 32+25/-3). FIVE SMALL SUNSPOT GROUPS WERE OBSERVED ON THE SOLAR VISIBLE DISK AND THREE OF THEM IN THE CENTRAL ZO- NE OF THE SOUTHERN HEMISPHERE FORMED A COMPLEX OF ACTIVE RE- GIONS. 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+20/-10. FLARE ACTIVITY WAS AT MIDDLE AND LOW LEVELS. ONE SOLAR FLARE M1.1 OF X-RAY CLASS, 19 -CLASS "C", 95 -CLASS "B" AND 16 CORO- NAL MASS EJECTIONS (19, 20, 22-25.04) 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 19.04 2319 2359 2342 S24E23L264 M1.1 12816 DSF to te localization l deg. Fl AR CME/to 25.04 <1336 S37E56L262 23 CME/1336 -------------------------------------------------------------------- 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* - N00L291 S05L301 S21L296 S05L261 ~4% 21.04 3 - SOHO,SDO... CH* + N10L230 S05L235 S12L225 N09L219 ~5% 29.04 >5 - 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 21.04/11 UT THE EARTH IS IN THE "-" SECTOR OF THE INTERPLANE- TARY MAGNETIC FIELD. THE FOLLOWING SECTOR BOUNDARY "-/+" IT CAN BE EXPECT 1.05. ---------------------------------------------------------------------- APRIL 19 20 21 22 23 24 25 áðòåìø Wus 036 054 047 042 029 062 057 F10.7 086 080 078 084 077 079 079 èbcg B1.1 B4.0 B1.2 B2.3 B2.3 B1.3 A6.6 GOES Sp 180 340 220 240 100 150 160 msh N 1 1 2 1 IMF - - -/+ ~ - - - DSCOVR Å>2 2.1E+8 4.7å+8 5.5E+8 6.9E+8 5.0E+8 4.3å+8 1.8E+7 GOES Ie>2 10148 12719 15548 12293 4918 23082 pfu Ap 18 13 7 5 15 10 20 nô Dst nô KIOTO Amsc 16 13 8 4 15 18 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 17-25.04. NEXT WEEK THE GREATER THAN 2 MeV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS EXPECTED 26-30.04. GEOMAGNETIC CONDITION VARY FROM ACTIVE TO QUITE. SUBSTORMS INTEN- SITY G0-G1 and duration of 9 - 3 h. MARKED 19, 23, and 25.09, IN RESPONSE TO PASS EARTH OF HIGH SPEED STEAM FROM A WEAK GEOEFFEC- TIVE CORONAL HOLES. 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