% The Homogenized aa indices % % These annual mean aa index data have been corrected for % secular changes in the geomagnetic field and the stations % re-calibrated. % Indices have been scaled to match the am index over 2012-2017. % % column 1 year number % column 2 date % column 3 aa_H = (aa_HN+aa_HS)/2 – the homogenised aa index % column 4 aa_HN – northern hemisphere homogenised aa index % column 5 aa_HS – southern hemisphere homogenised aa index % column 6 aa = (aa_N+aa_S)/2 – the old classic aa index % column 7 aa_N – the old classic northern hemisphere aa index % column 8 aa_S – the old classic southern hemisphere aa index % column 9 difference Daa = aaH - aa % column 10 difference Daa_N = aa_HN - aa_N % column 11 difference Daa_S = aa_HS - aa_S % % Please cite: % Lockwood, M., A. Chambodut, L.A. Barnard, M.J. Owens, and E. Clarke (2018) % A homogeneous aa index: 1. Secular variation % J. Space Weather & Space Climate, 2018 % % data fields % Date New homogenized aa indices Old ("classic") aa indices deltas (new aa minus old aa) % 1 2 3 4 5 6 7 8 9 10 11 % # date aa_H aa_HN aa_HS aa aa_N aa_S Daa Daa_N Daa_S % (nT) (nT) (nT) (nT) (nT) (nT) (nT) (nT) (nT) 1 1868.5 16.4459 16.9047 15.9870 18.2088 19.9580 16.4597 -1.7630 -3.0533 -0.4727 2 1869.5 18.8600 19.4557 18.2643 20.8276 22.7247 18.9305 -1.9676 -3.2690 -0.6662 3 1870.5 20.0079 20.1374 19.8784 22.2240 23.7127 20.7353 -2.2161 -3.5753 -0.8569 4 1871.5 19.3592 19.2667 19.4517 21.3455 22.5685 20.1226 -1.9864 -3.3018 -0.6709 5 1872.5 21.2234 21.4500 20.9968 23.6662 25.4901 21.8422 -2.4428 -4.0401 -0.8454 6 1873.5 18.3172 18.7690 17.8654 20.2000 22.1007 18.2993 -1.8828 -3.3316 -0.4339 7 1874.5 13.3434 13.2934 13.3935 14.5877 15.5764 13.5990 -1.2442 -2.2830 -0.2055 8 1875.5 10.4309 9.7611 11.1007 11.1880 11.2366 11.1394 -0.7571 -1.4755 -0.0387 9 1876.5 8.9256 8.3328 9.5184 9.5048 9.6766 9.3330 -0.5791 -1.3437 0.1854 10 1877.5 8.3792 7.7889 8.9695 8.8882 8.9188 8.8575 -0.5090 -1.1299 0.1120 11 1878.5 6.8927 6.4518 7.3336 7.1842 7.3024 7.0661 -0.2916 -0.8506 0.2675 12 1879.5 6.6935 5.9478 7.4392 6.9358 6.7586 7.1130 -0.2423 -0.8108 0.3262 13 1880.5 10.7067 10.1822 11.2312 11.5120 11.8227 11.2012 -0.8052 -1.6405 0.0300 14 1881.5 12.4873 12.3300 12.6446 13.5604 14.3781 12.7428 -1.0731 -2.0481 -0.0982 15 1882.5 20.7463 21.3407 20.1519 22.8841 24.7017 21.0664 -2.1378 -3.3611 -0.9145 16 1883.5 15.9211 16.7948 15.0474 17.5017 19.6349 15.3685 -1.5806 -2.8402 -0.3211 17 1884.5 12.9652 12.9813 12.9491 14.0678 14.9402 13.1954 -1.1026 -1.9590 -0.2463 18 1885.5 14.0663 14.2466 13.8860 15.3771 16.5229 14.2312 -1.3107 -2.2763 -0.3451 19 1886.5 18.7849 18.9637 18.6062 20.5950 21.8000 19.3901 -1.8101 -2.8363 -0.7839 20 1887.5 14.9707 14.4778 15.4637 16.3586 16.7349 15.9822 -1.3878 -2.2571 -0.5185 21 1888.5 14.0879 13.4765 14.6993 15.3581 15.5297 15.1865 -1.2702 -2.0532 -0.4872 22 1889.5 11.5255 10.7871 12.2638 12.4471 12.4236 12.4705 -0.9216 -1.6365 -0.2068 23 1890.5 9.8570 9.7189 9.9950 10.6221 11.2390 10.0051 -0.7651 -1.5201 -0.0102 24 1891.5 15.5734 15.5479 15.5990 17.0217 17.6784 16.3651 -1.4483 -2.1306 -0.7661 25 1892.5 21.9427 22.1549 21.7305 24.1834 25.6755 22.6913 -2.2407 -3.5207 -0.9608 26 1893.5 15.4329 15.4615 15.4042 16.9411 17.9675 15.9147 -1.5082 -2.5059 -0.5106 27 1894.5 18.7880 19.2731 18.3029 20.6512 22.2562 19.0462 -1.8632 -2.9830 -0.7434 28 1895.5 16.3964 17.3614 15.4315 18.0342 19.9486 16.1199 -1.6378 -2.5872 -0.6884 29 1896.5 16.3524 16.8000 15.9049 17.9267 19.2811 16.5724 -1.5743 -2.4811 -0.6675 30 1897.5 12.4998 13.0161 11.9835 13.5185 14.6360 12.4010 -1.0187 -1.6198 -0.4176 31 1898.5 13.8402 13.2685 14.4119 15.0644 15.1634 14.9654 -1.2242 -1.8949 -0.5536 32 1899.5 12.0755 12.0022 12.1489 13.0454 13.5658 12.5250 -0.9698 -1.5635 -0.3761 33 1900.5 7.0960 6.9910 7.2009 7.4452 7.8226 7.0678 -0.3492 -0.8316 0.1331 34 1901.5 5.8173 5.6448 5.9898 5.9966 6.2877 5.7055 -0.1792 -0.6428 0.2843 35 1902.5 6.2225 5.6239 6.8212 6.4445 6.2360 6.6531 -0.2220 -0.6120 0.1681 36 1903.5 10.9252 10.8665 10.9839 11.9070 12.4860 11.3281 -0.9818 -1.6195 -0.3441 37 1904.5 10.7022 10.4353 10.9691 11.5610 11.8439 11.2780 -0.8588 -1.4087 -0.3089 38 1905.5 13.6869 12.8888 14.4850 14.9176 14.7260 15.1092 -1.2307 -1.8372 -0.6243 39 1906.5 11.5109 10.9364 12.0854 12.4238 12.3370 12.5106 -0.9129 -1.4006 -0.4252 40 1907.5 14.5796 13.6940 15.4651 15.9820 15.6805 16.2836 -1.4025 -1.9864 -0.8185 41 1908.5 15.5221 15.0158 16.0284 17.0314 16.9573 17.1055 -1.5093 -1.9415 -1.0771 42 1909.5 15.5931 14.4730 16.7132 17.1068 16.4380 17.7757 -1.5138 -1.9650 -1.0625 43 1910.5 15.9474 15.1262 16.7686 17.5283 17.0610 17.9955 -1.5808 -1.9347 -1.2269 44 1911.5 14.4544 14.0606 14.8483 15.7933 15.7740 15.8127 -1.3389 -1.7134 -0.9644 45 1912.5 8.2528 7.7700 8.7356 8.7874 8.6469 8.9279 -0.5346 -0.8768 -0.1923 46 1913.5 8.0470 7.3715 8.7225 8.5416 8.1479 8.9353 -0.4946 -0.7764 -0.2128 47 1914.5 10.0669 9.6145 10.5192 10.8920 10.8688 10.9151 -0.8251 -1.2543 -0.3958 48 1915.5 14.0382 14.6518 13.4247 15.5298 16.6798 14.3798 -1.4916 -2.0280 -0.9551 49 1916.5 17.9076 18.1587 17.6564 19.8224 20.5652 19.0796 -1.9148 -2.4065 -1.4231 50 1917.5 16.4862 16.6345 16.3379 18.1991 19.0243 17.3740 -1.7129 -2.3898 -1.0360 51 1918.5 19.3817 19.8317 18.9318 21.5182 22.5651 20.4712 -2.1364 -2.7334 -1.5395 52 1919.5 20.2044 20.0672 20.3417 22.4207 22.6592 22.1822 -2.2163 -2.5921 -1.8404 53 1920.5 16.5325 16.7195 16.3456 17.5850 18.7923 16.3777 -1.0525 -2.0728 -0.0322 54 1921.5 15.7674 15.9349 15.6000 16.6214 17.6548 15.5880 -0.8540 -1.7199 0.0119 55 1922.5 17.5002 16.5237 18.4767 18.7452 18.6551 18.8353 -1.2450 -2.1314 -0.3586 56 1923.5 9.9008 9.2087 10.5929 10.2582 10.3332 10.1832 -0.3574 -1.1245 0.4097 57 1924.5 9.7842 9.1073 10.4611 10.1894 10.3012 10.0775 -0.4052 -1.1940 0.3836 58 1925.5 12.3135 11.6153 13.0117 13.1005 13.2938 12.9072 -0.7870 -1.6785 0.1046 59 1926.5 18.6925 18.0044 19.3805 19.8652 20.0329 19.6976 -1.1728 -2.0284 -0.3171 60 1927.5 15.6212 14.9904 16.2520 16.6226 16.7462 16.4990 -1.0014 -1.7558 -0.2470 61 1928.5 16.4588 16.3210 16.5966 17.6332 18.3859 16.8805 -1.1744 -2.0649 -0.2839 62 1929.5 18.0824 18.2173 17.9475 19.3587 20.4257 18.2918 -1.2764 -2.2084 -0.3443 63 1930.5 26.4032 26.1530 26.6533 28.5387 29.1442 27.9332 -2.1355 -2.9912 -1.2799 64 1931.5 15.7461 16.0336 15.4587 16.7899 17.9168 15.6630 -1.0438 -1.8832 -0.2044 65 1932.5 17.8145 17.8106 17.8184 18.9973 19.8091 18.1855 -1.1828 -1.9985 -0.3671 66 1933.5 15.3420 15.2084 15.4757 16.3050 16.9140 15.6959 -0.9629 -1.7057 -0.2202 67 1934.5 12.6259 12.7969 12.4549 13.3817 14.3527 12.4106 -0.7558 -1.5559 0.0442 68 1935.5 14.6899 15.0034 14.3765 15.6231 16.7897 14.4565 -0.9332 -1.7863 -0.0800 69 1936.5 15.2571 15.0987 15.4155 16.2269 16.8774 15.5765 -0.9698 -1.7787 -0.1610 70 1937.5 17.7461 18.0933 17.3989 18.9762 20.1014 17.8510 -1.2301 -2.0081 -0.4521 71 1938.5 21.9059 22.4741 21.3377 23.5740 25.0110 22.1370 -1.6681 -2.5368 -0.7993 72 1939.5 21.5265 23.0757 19.9773 23.1878 25.5945 20.7812 -1.6613 -2.5188 -0.8039 73 1940.5 21.8103 22.8720 20.7486 23.4925 25.4635 21.5215 -1.6822 -2.5915 -0.7730 74 1941.5 22.9141 23.4987 22.3294 24.8620 26.3435 23.3805 -1.9479 -2.8448 -1.0510 75 1942.5 20.0909 21.5992 18.5825 21.7260 24.1010 19.3510 -1.6352 -2.5018 -0.7685 76 1943.5 23.7474 24.9423 22.5525 25.8396 27.8000 23.8791 -2.0921 -2.8577 -1.3266 77 1944.5 16.5708 17.2903 15.8513 17.7529 19.2510 16.2548 -1.1821 -1.9607 -0.4035 78 1945.5 15.2870 15.7493 14.8247 16.3368 17.5562 15.1175 -1.0498 -1.8069 -0.2928 79 1946.5 23.2602 24.3400 22.1805 25.2531 27.1377 23.3685 -1.9929 -2.7977 -1.1880 80 1947.5 23.1216 24.2543 21.9889 25.1822 27.1281 23.2363 -2.0606 -2.8738 -1.2474 81 1948.5 20.8659 21.0401 20.6916 22.5695 23.4054 21.7336 -1.7036 -2.3653 -1.0420 82 1949.5 19.6270 19.9210 19.3331 21.1522 22.1651 20.1394 -1.5252 -2.2441 -0.8063 83 1950.5 22.4877 22.2837 22.6917 24.4014 24.7572 24.0455 -1.9137 -2.4735 -1.3538 84 1951.5 26.3666 27.0734 25.6598 28.6728 29.9805 27.3651 -2.3062 -2.9071 -1.7052 85 1952.5 25.6508 25.9563 25.3454 27.8123 28.7240 26.9006 -2.1615 -2.7677 -1.5552 86 1953.5 20.4065 20.2996 20.5135 22.1300 22.5661 21.6938 -1.7234 -2.2665 -1.1803 87 1954.5 16.0287 15.9455 16.1120 17.2123 17.6979 16.7267 -1.1836 -1.7525 -0.6147 88 1955.5 16.3731 15.9423 16.8038 17.5416 17.6408 17.4425 -1.1685 -1.6984 -0.6386 89 1956.5 22.8122 22.2767 23.3478 24.6644 24.5663 24.7626 -1.8522 -2.2896 -1.4149 90 1957.5 25.4387 25.5600 25.3173 29.2875 31.5702 27.0048 -3.8488 -6.0102 -1.6875 91 1958.5 24.6312 24.5419 24.7205 28.3467 30.3390 26.3545 -3.7155 -5.7972 -1.6339 92 1959.5 26.1067 26.3881 25.8252 30.1406 32.4616 27.8195 -4.0339 -6.0735 -1.9943 93 1960.5 28.5800 28.4535 28.7065 32.8658 34.8415 30.8900 -4.2858 -6.3880 -2.1835 94 1961.5 19.3674 18.8979 19.8369 22.3464 23.6466 21.0462 -2.9790 -4.7487 -1.2093 95 1962.5 18.5754 18.7873 18.3634 21.4646 23.4942 19.4349 -2.8892 -4.7069 -1.0715 96 1963.5 18.3646 18.9747 17.7546 21.2146 23.6914 18.7377 -2.8499 -4.7168 -0.9831 97 1964.5 14.8570 15.2051 14.5088 17.1424 19.2794 15.0055 -2.2855 -4.0743 -0.4967 98 1965.5 12.0895 12.3764 11.8026 13.9943 15.9671 12.0216 -1.9048 -3.5907 -0.2190 99 1966.5 14.9996 15.2753 14.7239 17.3296 19.3192 15.3401 -2.3300 -4.0439 -0.6162 100 1967.5 17.1863 17.2551 17.1176 19.7498 21.5973 17.9024 -2.5635 -4.3422 -0.7848 101 1968.5 19.5768 19.9128 19.2407 22.4824 24.6561 20.3087 -2.9057 -4.7432 -1.0681 102 1969.5 17.3324 16.9782 17.6867 19.9060 21.2284 18.5836 -2.5736 -4.2502 -0.8969 103 1970.5 17.3015 16.5624 18.0406 19.9380 20.7209 19.1551 -2.6365 -4.1585 -1.1145 104 1971.5 17.4513 16.9979 17.9048 20.0329 21.1986 18.8671 -2.5816 -4.2008 -0.9623 105 1972.5 17.8718 17.5142 18.2294 20.5796 21.7664 19.3928 -2.7078 -4.2522 -1.1633 106 1973.5 23.3478 22.5719 24.1237 26.7327 27.5699 25.8955 -3.3849 -4.9979 -1.7719 107 1974.5 26.4830 25.7800 27.1860 30.3649 31.2267 29.5031 -3.8819 -5.4468 -2.3170 108 1975.5 20.7055 20.3716 21.0395 23.7067 24.9716 22.4418 -3.0011 -4.6000 -1.4023 109 1976.5 19.4078 18.4836 20.3320 22.2169 22.7739 21.6598 -2.8091 -4.2903 -1.3279 110 1977.5 17.5606 16.8905 18.2307 20.2034 20.9192 19.4877 -2.6428 -4.0287 -1.2570 111 1978.5 22.2849 21.8548 22.7149 25.5101 26.5849 24.4353 -3.2252 -4.7301 -1.7204 112 1979.5 19.5721 19.8072 19.3371 22.4272 24.2140 20.6404 -2.8551 -4.4069 -1.3033 113 1980.5 16.4663 15.9406 16.9920 18.4151 19.7678 17.0625 -1.9488 -3.8271 -0.0705 114 1981.5 22.5007 21.7641 23.2373 24.8702 26.4048 23.3356 -2.3695 -4.6407 -0.0983 115 1982.5 30.9743 30.3366 31.6119 33.9598 36.1695 31.7500 -2.9855 -5.8329 -0.1381 116 1983.5 26.8648 27.1563 26.5732 29.6065 32.5140 26.6990 -2.7417 -5.3577 -0.1258 117 1984.5 26.3011 26.9957 25.6064 29.0193 32.3064 25.7322 -2.7182 -5.3107 -0.1258 118 1985.5 20.3341 21.2277 19.4405 22.6274 25.7144 19.5404 -2.2933 -4.4867 -0.0999 119 1986.5 18.8999 19.5582 18.2416 21.0664 23.7983 18.3346 -2.1666 -4.2401 -0.0930 120 1987.5 17.0855 17.6359 16.5352 19.1072 21.5966 16.6178 -2.0217 -3.9607 -0.0826 121 1988.5 20.3417 21.1441 19.5392 22.6019 25.5748 19.6291 -2.2603 -4.4307 -0.0899 122 1989.5 28.4121 28.0116 28.8126 31.1474 33.3654 28.9295 -2.7353 -5.3538 -0.1168 123 1990.5 24.1061 23.9985 24.2138 26.5471 28.7860 24.3082 -2.4409 -4.7874 -0.0945 124 1991.5 31.3878 31.9559 30.8196 34.3589 37.7945 30.9233 -2.9711 -5.8386 -0.1037 125 1992.5 24.8167 24.9586 24.6747 27.2917 29.8316 24.7517 -2.4750 -4.8730 -0.0770 126 1993.5 23.1614 23.4385 22.8842 25.5166 28.0866 22.9466 -2.3552 -4.6481 -0.0624 127 1994.5 26.8192 26.9106 26.7278 29.3918 31.9986 26.7849 -2.5726 -5.0880 -0.0571 128 1995.5 19.8774 19.8878 19.8669 21.9661 24.0288 19.9034 -2.0887 -4.1409 -0.0365 129 1996.5 16.7232 16.8892 16.5571 18.6013 20.6216 16.5809 -1.8781 -3.7323 -0.0238 130 1997.5 14.4430 13.5659 15.3201 16.0935 16.8527 15.3342 -1.6505 -3.2868 -0.0142 131 1998.5 19.2108 18.9355 19.4861 21.1969 22.9072 19.4866 -1.9861 -3.9717 -0.0005 132 1999.5 20.3217 20.3848 20.2585 22.3875 24.5295 20.2455 -2.0658 -4.1446 0.0130 133 2000.5 23.1608 23.2447 23.0770 25.3945 27.7425 23.0464 -2.2336 -4.4978 0.0305 134 2001.5 21.7802 19.8008 23.7596 23.7791 23.8442 23.7140 -1.9989 -4.0433 0.0456 135 2002.5 20.7214 21.1189 20.3240 22.7969 25.3171 20.2767 -2.0755 -4.1983 0.0473 136 2003.5 33.5645 33.1778 33.9513 36.3646 38.8873 33.8418 -2.8000 -5.7096 0.1095 137 2004.5 22.1063 21.0750 23.1375 24.1477 25.2401 23.0553 -2.0414 -4.1651 0.0822 138 2005.5 21.2271 21.0351 21.4190 23.2534 25.1774 21.3295 -2.0264 -4.1423 0.0895 139 2006.5 14.6113 14.3715 14.8512 16.2229 17.6640 14.7818 -1.6116 -3.2925 0.0693 140 2007.5 13.4857 13.0242 13.9472 15.0031 16.1346 13.8716 -1.5174 -3.1104 0.0756 141 2008.5 12.6992 12.2431 13.1554 14.1580 15.2421 13.0738 -1.4587 -2.9991 0.0816 142 2009.5 7.4723 6.9149 8.0298 8.6173 9.2555 7.9791 -1.1450 -2.3406 0.0507 143 2010.5 10.9488 10.3903 11.5074 12.2765 13.1366 11.4164 -1.3277 -2.7464 0.0909 144 2011.5 13.3970 12.7786 14.0153 14.8421 15.7959 13.8884 -1.4452 -3.0173 0.1270 145 2012.5 15.4276 14.9581 15.8972 16.9769 18.2172 15.7367 -1.5493 -3.2591 0.1605 146 2013.5 13.3584 12.8560 13.8608 14.7817 15.8534 13.7099 -1.4233 -2.9975 0.1508 147 2014.5 14.2065 13.7255 14.6874 15.6599 16.8075 14.5123 -1.4534 -3.0820 0.1751 148 2015.5 20.5847 20.1386 21.0307 22.3459 23.9377 20.7541 -1.7612 -3.7991 0.2766 149 2016.5 18.3299 18.4898 18.1700 19.9983 22.0792 17.9173 -1.6684 -3.5894 0.2527 150 2017.5 17.8730 17.5568 18.1892 19.4704 21.0205 17.9202 -1.5974 -3.4638 0.2690