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Session 86 - Coronal Activity.
Oral session, Thursday, June 13
Wisconsin Center,

[86.08] The Quasi-Stationary Behavior of Solar Activity Indices: International Sunspot Numbers and F10.7cm Radio Flux Densities

P. C. Crane (NRL/Interferometrics Inc.)

Studies of solar activity on the time scale of the nominally eleven-year solar cycle and of the subtle differences between cycles of activity require long-term consistent measurements of solar activity indices, with daily sampling because solar rotation modulates the observed activity on time scales of a few days. The longest series of daily indices are for the daily international sunspot number R defined by J.R. Wolfe in 1848 and the solar radio flux density F10.7cm at 2800 MHz which has been measured almost daily since 1947 February 14. Both are available from the National Geophysical Data Center (R since 1932 January 1).

The DFT/CLEAN technique (Roberts et al. 1987, Astron. J., 93, 968; Roberts and Lehar 1994, private communication) has been applied to the available data for both indices. CLEANed Fourier transforms have been calculated for the full time ranges and for individual cycles (six of R and five of F10.7cm). The quasi-stationary behavior within each cycle and for each index is shown by "dynamic" short-period Fourier transforms calculated after detrending with the long-period Fourier components (>90 days) for each cycle.

The results for each index have been compared for the different cycles and with those for the other index.

Program listing for Thursday