CAOSP abstracts, Volume: 27, No.: 2, year: 1997
- Author(s): JAKIMIEC, M.; STORINI, M.; ANTALOVA, A.
- Journal: Contributions of the Astronomical Observatory Skalnate Pleso,
vol. 27, no. 2, p. 104-114.
- Date: 10/1997
- Title: Solar soft X-ray parameters: 1969-1976 autocorrelation functions
- Keyword(s): THE SUN, FLARES, NONFLARE (XBG) SOFT X-RAY PARAMETER
- Pages: 104 -- 114
Abstract:
The autocorrelation analysis of solar soft X-ray parameters was performed
with a time lag ranging from 1 to 32 days (acf_j, with j=1, ..., 32) for the
1969-76 period. Consecutive sequences containing daily data for a 2-year
interval were considered. From the comparison of the autocorrelation functions
for both flare (TOT) and nonflare (XBG) soft X-ray variables we selected the
different recurrent tendency over the years. During the maximum (1969-71) and
minimum (1975-76) phases of the 20th solar cycle the recurrency of all the SXR
parameters is included between 18 and 23 days, but during the decreasing
activity phase (1972-74) recurrencies approach the expected 27-day synodic
rate of rotation. The nonflare X-ray corona has a particularly stable 27-day
recurrency (from 1971-72 to 1974-75), but the flare TOT variable displays the
27-day recurrency only in the 1972-73 sequence (Figure 5). The most stable
25-day TOT recurrency was observed in 1973-75. Our results of the atypical
"solar periodicity" of TOT values (i.e., acf_lm < 27 days) are in agreement
with past findings based on other solar activity indices and cycles. However,
we have also noted, on a short time scale (1 day), that there exists a strong
coherence (acf_1 ~ 0.8) of the XBG variables for all the investigated
intervals. While this coherence is high (acf_1 ~ 0.7) in the TOT variable only
for 1973-75, when long-lived coronal holes covered a large fraction of the
solar surface, in the other periods the parameter acf_1(TOT) =< 0.55. The
above findings were never explicitly emphasized in solar soft X-ray studies.
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