:Issued: 2026 May 01 08:35 UTC :Product: documentation at http://www.sidc.be/products/ri #-------------------------------------------------------------# # MONTHLY TABLE OF THE INTERNATIONAL TOTAL SUNSPOT NUMBER # # AND 12-MONTH PREDICTIONS from the World Data Center SILSO # #-------------------------------------------------------------# Provisional International monthly mean Sunspot Number for April 2026 : 79.3 (seventy-nine point three) Maximum : 135 on 30 // Minimum : 28 on 10 Provisional daily International Sunspot Numbers for April 2026 : 1..129 6.. 97 11.. 39 16.. 50 21.. 50 26..115 2..133 7.. 89 12.. 38 17.. 48 22.. 71 27..117 3..120 8.. 70 13.. 53 18.. 41 23.. 68 28..128 4..106 9.. 59 14.. 53 19.. 36 24.. 94 29..123 5.. 89 10.. 28 15.. 49 20.. 37 25..114 30..135 68 cooperating stations on May 1, 09 UT Predictions of the monthly smoothed Sunspot Number using the last provisional value, calculated for October 2025 : 108.3 (+-5%) SM CM SM CM SM CM 2025 Nov 109 108 2026 May 91 107 2026 Nov 77 99 Dec 105 109 Jun 89 106 Dec 75 95 2026 Jan 98 110 Jul 87 103 2027 Jan 72 92 Feb 97 110 Aug 85 102 Feb 69 88 Mar 95 110 Sep 83 101 Mar 66 85 Apr 93 109 Oct 80 100 Apr 64 82 SM : SIDC classical method : based on an interpolation of Waldmeier's standard curves; the estimated error ranges from 7% (first month) to 35% (last month) CM : Combined method : the combined method is a regression technique coupling a dynamo-based estimator with Waldmeier's idea of standard curves, due to K. Denkmayr. ref. : K. Denkmayr, P. Cugnon, 1997 : "About Sunspot Number Medium-Term Predictions", in "Solar-Terrestrial Prediction Workshop V", eds. G. Heckman et al., Hiraiso Solar Terrestrial Research Center, Japan, 103 #--------------------------------------------------------------------# # World Data Center SILSO # # Sunspot Index and Long-term Solar Observations # # Royal Observatory of Belgium # # Tel.: ../32/(0)2/373 02 33 Fax : ../32/(0)2/374 98 22 # # Please do not reply directly to this message # # For more information, contact: silso.info@oma.be # # or visit first our Web site at: http://www.sidc.be/silso # # To unsubscribe, visit http://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 | ----------------------------------------------------------------------