AAVSO Sudden Ionospheric Disturbance Report September 1990 Observers: A-01 A-09 A-19 A-40 A-50 A-52 A-61 A-62 A-63 A-64 A-65 A-66 A-67 A-68 A-69 A-70 A-71 YYMMDD Event Peak (UT) Importance 900901 0708 1+ 900901 1717U 3 900901 2221 1- 900903 0742 1- 900903 0947 2+ 900903 1345 1+ 900903 1935 2 900904 0810 2+ 900904 1446 3 900905 0437 2+ 900905 1552 2+ 900905 1927 1 900905 2200 1 900906 1600 2+ 900906 2130 2+ 900907 0531 2+ 900907 0756 2 900908 2217 2+ 900912 1905 2+ 900913 1409 2 900913 1755 2 900914 0416 2 900914 1335 3 900914 2014 2+ 900915 0751 1 900915 0815 1 900915 1841 1 900916 1424 2 900917 1330 1- 900917 1347 2+ 900917 1409 2 900917 1801 1- 900917 1853 2+ 900917 2158 2+ 900918 2037 1- 900919 0910 1+ 900919 1416 1- 900919 1639 2 900919 2058 1- 900920 0624 2 900920 1324 1+ 900920 1525 2 900920 1721 1 900920 1859 3 900921 1305 1 900922 1926 2 900922 2245 2+ 900923 1312 2+ 900924 1352 1 900924 1612 2 900924 1859 2+ 900925 1036 1+ 900926 1330 2+ 900926 1434 1 900926 1602 2 900926 1841 1+ 900928 1412 1- 900929 0408 1+ 900929 2313 1+ 900930 0745 2 ******************************************* Importance Summary September 1990 1- events: 8 1 events: 9 1+ events: 8 2 events: 14 2+ events: 17 3 events: 4 3+ events: 0 Total events: 60