Physics
Scientific paper
Oct 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002soph..209..233k&link_type=abstract
Solar Physics, v. 209, Issue 2, p. 233-245 (2002).
Physics
5
Scientific paper
The 1968-2000 data on the mean magnetic field (MMF, longitudinal component) of the Sun are analysed to study long-time trends of the Sun's magnetic field and to check MMF calibration. It is found that, within the error limits, the mean intensity of photospheric magnetic field (the MMF strength, |H|), did not change over the last 33 years. It clearly shows, however, the presence of an 11-year periodicity caused by the solar activity cycle. Time variations of |H| correlate well with those of the radial component, |Br|, of the interplanetary magnetic field (IMF). This correlation (r=0.69) appears to be significantly higher than that between |Br| and the results of a potential source-surface extrapolation, to the Earth's orbit, of synoptic magnetic charts of the photosphere (using the so-called `saturation' factor δ-1 for magnetograph measurements performed in the line Fei λ525.0 nm Wang and Sheeley, 1995). It seems therefore that the true source surface of IMF is the `quiet' photosphere - background fields and coronal holes, like those for MMF. The average `effective' magnetic strength of the photospheric field is determined to be about 1.9 G. It is also shown that there is an approximate linear relation between |Br| and MMF intensity |H| (in gauss), |Br|~α(H0)min×(1+C|H|), where α=1.5×10-5 normalizes the photospheric field strength to 1 AU distance from the Sun, (H0)min=1.2 G is some minimal `effective' intensity of photospheric background fields and C=1.3 G-1 an empirical constant. It is noted that good correlation between time variations of |H| and |Br| makes suspicious a correction of the photospheric magnetic fields with the use of saturation factor δ-1.
Kotov S. V.
Kotov Valerii A.
Setyaev V. V.
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