HARMONICS OF THE 25-DAY PERIODICITY IN SEQUENCES OF SOLAR-X-RAY EVENTS

I analyzed the data of measurements of the solu X-ray flux in the rang e 1-8 angstrom, obtained on the SOLRAD 9 and 10 space vehicles in 1969 - 1974. Time intervals were found from 3 to 6 months long, which had a quasiperiodic burst component; the periods varied between =98 h (196 9) and =33 h (1972). The corresponding frequencies form a sequence tha t can be interpreted, with an equal degree of probability, as a set of harmonics of the fundamental frequency f0 = 465 +/- 10 nHz (a period of 24.9 +/- 0.05 days) and f0 = 415 +/- 10 nHz (a period of 27.9 +/- 0 .6 days). The harmonic pulsations could result from modulation of the burst-like noise by a 25-day periodic process; e.g., rotation of the a ctive longitude of the oblique rotator, predicted by Bai and Sturrock (1993), which is located in the interior of the Sun.