Monthly T Indices
These T Indices apply when you are making a prediction using ASAPS or the on line tools and are planning to use the prediction later on (ie on a monthly basis). The observed T indices are computed from global foF2 data. The predicted T indices are based on the observed data and show the expected behaviour of the global ionosphere as the Sun progresses through its solar cycle.
The monthly predicted T indices may be used to compute predictions between locations anywhere in the world. Note that predictions based on monthly T indices will not account for ionospheric storms that are the result of sudden solar activity.
The monthly T indices shown below are also available as a text file.
(last updated 21 Dec 2024 17:20 UT)
IPS Monthly Observed and Predicted Smoothed T indices Prepared at 2321 UT on 01 Dec 2024 YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ============================================================================= 1938 133 149 145 136 124 124 137 147 128 135 144 137 1939 134 128 102 95 119 125 113 116 135 131 119 106 1940 88 89 96 91 78 82 90 91 101 97 87 75 1941 74 67 52 44 39 49 55 65 59 56 47 57 1942 53 47 58 57 54 30 23 19 22 18 26 29 1943 24 25 31 30 23 19 16 16 10 5 8 19 1944 17 9 15 6 2 5 6 11 18 20 18 23 1945 31 34 28 34 35 48 48 42 41 64 66 56 1946 51 84 104 93 88 97 109 118 108 120 130 134 1947 145 163 155 152 161 160 161 161 158 166 161 146 1948 139 126 131 149 152 158 150 138 136 128 133 126 1949 137 162 159 157 137 125 127 120 144 138 139 136 1950 123 117 116 115 113 112 93 77 56 57 54 57 1951 59 58 54 64 72 71 71 61 60 58 57 54 1952 49 42 29 31 27 33 33 35 32 20 19 23 1953 25 18 10 16 12 12 8 7 12 9 4 5 1954 8 4 4 3 0 -5 -4 -2 -1 5 6 7 1955 16 18 10 12 19 28 30 29 42 57 68 84 1956 86 98 125 125 119 115 120 142 155 163 162 167 1957 166 155 156 148 151 159 162 151 157 176 176 174 1958 193 171 164 165 165 160 154 170 183 182 177 170 1959 180 167 167 154 153 152 153 151 145 133 127 132 1960 152 147 123 113 111 117 116 117 131 105 97 94 1961 78 66 67 61 55 60 65 72 57 52 41 39 1962 35 42 52 44 46 44 32 24 33 34 32 24 1963 25 22 23 20 26 22 19 18 15 18 21 13 1964 12 12 19 13 5 3 1 1 4 6 6 11 1965 18 15 20 13 14 17 13 11 11 15 13 10 1966 29 25 30 36 46 47 53 54 44 54 60 69 1967 91 105 124 108 92 81 87 97 100 107 98 105 1968 125 122 110 103 103 101 91 92 99 110 95 99 1969 101 108 122 115 101 111 101 102 97 98 101 98 1970 115 128 125 120 120 117 112 99 107 107 113 103 1971 97 92 82 74 68 62 66 53 52 49 62 68 1972 67 83 96 88 75 84 82 81 83 75 56 52 1973 49 52 43 41 43 38 30 26 43 30 21 22 1974 24 20 26 23 30 27 27 25 24 32 30 24 1975 20 15 10 8 7 5 10 19 23 13 10 12 1976 10 8 11 12 9 7 2 5 10 11 4 11 1977 15 26 22 20 22 29 25 27 32 43 44 47 1978 59 81 99 95 96 98 104 81 104 128 114 117 1979 141 165 164 145 138 131 130 133 145 164 166 155 1980 151 152 161 155 155 155 146 139 142 158 154 151 1981 138 157 167 161 149 132 125 137 174 168 165 153 1982 141 142 158 130 109 102 98 105 104 123 118 123 1983 97 78 76 65 79 87 80 77 63 63 51 47 1984 50 66 77 66 56 55 42 28 22 10 10 13 1985 16 14 12 9 14 13 12 6 6 1 6 7 1986 12 15 17 11 9 0 1 -2 1 12 12 10 1987 11 13 12 21 27 17 18 26 24 29 42 40 1988 48 46 60 74 75 86 84 97 114 131 115 127 1989 149 157 139 139 139 155 160 150 145 159 160 153 1990 154 131 138 130 129 140 138 143 143 136 124 133 1991 144 169 168 158 139 126 143 131 136 132 121 130 1992 154 167 156 134 99 83 90 70 70 71 85 93 1993 77 77 85 66 66 65 62 49 35 39 35 44 1994 58 45 44 30 22 16 28 18 18 20 21 23 1995 25 36 25 16 11 14 14 9 9 9 13 9 1996 15 8 5 4 10 3 5 5 5 3 7 13 1997 14 15 13 12 13 10 10 17 32 28 31 37 1998 41 44 49 59 51 59 81 78 88 74 79 93 1999 97 88 95 82 107 127 123 110 92 98 123 117 2000 110 126 157 149 130 133 148 141 120 127 132 135 2001 132 133 135 126 114 137 111 118 142 150 155 154 2002 171 172 161 140 135 118 110 123 129 106 107 115 2003 105 95 86 82 70 71 76 68 62 63 68 69 2004 59 61 60 58 52 52 51 55 52 51 46 41 2005 42 43 41 34 36 34 38 33 28 21 18 27 2006 26 23 14 23 23 14 17 6 14 5 10 13 2007 20 16 11 9 9 10 7 1 0 -2 -7 -1 2008 6 4 6 2 -5 -11 -6 -7 -5 -9 -8 -9 2009 -2 -1 -2 0 2 -3 -4 -7 -2 -3 -3 -2 2010 12 28 31 21 13 7 18 24 29 20 19 23 2011 22 32 51 63 53 48 44 49 65 85 102 92 2012 81 65 64 69 77 74 70 80 86 75 65 65 2013 74 62 69 84 92 82 81 76 68 76 86 90 2014 91 108 130 114 96 84 86 81 90 94 98 103 2015 92 101 91 97 85 79 71 48 40 43 53 50 2016 52 57 46 30 34 28 26 25 28 17 12 10 2017 14 19 11 8 2 2 0 3 16 13 5 6 2018 8 2 3 -2 -6 -3 -3 -8 -6 -10 -15 -9 2019 -5 -3 -4 -4 -9 -14 -11 -14 -11 -14 -16 -12 2020 -2 -5 2 -1 -7 -7 -9 -2 -6 -6 7 12 2021 12 4 9 6 6 12 21 12 23 23 17 28 2022 41 52 63 71 81 65 67 56 72 75 65 71 2023 107 114 119 105 101 110 118 118 107 113 97 95 2024 122 123 117 113 114 126 141 143 137 133 122* 120^ 2025 117^ 113^ 110^ 107^ 104^ 101^ 100^ 99^ 98^ 96^ 95^ 94^ 2026 93^ 92^ 91^ 89^ 88^ 86^ 83^ 80^ 77^ 74^ 70^ 66^ ============================================================================= YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC * = New observed data. T index value may have changed. ^ = Predicted smoothed T index.
