Extended time series of Solar Activity Indices (ESAI) is database including observational, synthetic and simulated sets to study Solar magnetic field variations and their influence on the Earth. ESAI extend the ordinary lengths of some traditional indices of solar activity: sunspot areas, Wolf numbers (equatorial component of magnetic field of the Sun), polar faculae numbers (polar component), mean latitudes, N-S asymmetry of hemispheres (location of activity).

Series Conventional time interval ESAI time interval
monthly sunspot areas (Greenwich general system) 1874-1976 1821-1989
yearly sunspot areas (Greenwich general system) for N- and S- hemispheres 1874-1976 1821-1994
yearly mean latitudes of sunspots for N- and S- hemispheres 1874-1976 1854-1985
yearly polar faculae numbers (Mt.Wilson general system) for N- and S- hemispheres 1906-1991 1837-1999
yearly Wolf numbers (International general system) 1700-2002 1090-2002
yearly polar faculae numbers (Mt.Wilson general system) 1906-1991 1705-1999

ESAI monthly sunspot areas (1821-1989), yearly sunspot areas (1821-1994) and yearly mean latitudes of sunspots (1854-1985) were created by compilation of pre-Greenwich observational data sets (by Schwabe, Carrington, De La Rue, Sporer) and post-Greenwich observations (Gnevysheva) to Greenwich general system.
Ref: Nagovitsyn Yu. A. The series of total sunspot area index in the Greenwich general system (1821-1989). // "Solnechnye dannye. 1995-1996" Bulletin. PP.38-48. 1997. (in Russian).

Yearly polar faculae numbers were constructed by synthesis of different data series: Mt.Wilson, Greenwich, Lyon, Kodaykanal, Tokyo, Zurich, Kislovodsk observations of polar facula and observations of polar coronal structures during solar eclipses.
Ref: Nagovitsyn Yu.A. A synthetic series of yearly means of polar faculae numbers for 1847-1979. // "Solnechnye dannye" Bulletin. No 8. PP. 88-95. 1988. (in Russian).

Series of yearly Wolf numbers for 1090-2002. Based on Krylov-Bogolyubov's approach to the description of weakly nonlinear oscillatory processes, the nonstationary frequency-amplitude structure of the Wolf numbers (1700-1995) was analyzed. Using the nonlinear description and well-known Schove's data on the epochs of extrema of 11-yr solar cycles in the past, the yearly average Wolf numbers in 1090-1699 were reconstructed.
Ref. Nagovitsyn Yu.A. A nonlinear mathematical model for the Solar cyclicity and prospects for reconstructing the Solar activity in the Past.// Astronomy Letters. Vol. 23. No. 6. PP. 742-748. 1997.

Yearly polar faculae numbers for 1705-1999 were created by procedure similar to one used for the Wolf numbers reconstruction (in assumption that 11-yr cycles of polar faculae develop in exact antiphase to sunspot cycles).
Ref. Nagovitsyn Yu.A. The Solar cyclicity on the large time scale. // Proceedings of conference "New cycle of Solar activity: observational and theoretical aspects". Pulkovo. 1998. PP.321-324 (in Russian).

GRAPHICS. The figures show variations of the mentioned above indices. Time intervals of ESAI-extension of solar activity parameters are marked by the blue colour.