NDLI: Towards Calibration of the Mean Magnetic Field of the sun

Content Provider	Springer Nature Link
Author	Kotov, V.A. Kotov, S.V. Setyaev, V.V.
Copyright Year	2002
Abstract	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, \|B $_{r}$\|, of the interplanetary magnetic field (IMF). This correlation (r=0.69) appears to be significantly higher than that between \|B $_{r}$\| 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 Fe i 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 \|B $_{r}$\| and MMF intensity \|H\| (in gauss)\|B $_{r}$\|≈α(H $_{0}$)$_{min}$×(1+C\|H\|)where α=1.5×10$^{−5}$ normalizes the photospheric field strength to 1 AU distance from the Sun, (H $_{0}$)$_{min}$=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 \|B $_{r}$\| makes suspicious a correction of the photospheric magnetic fields with the use of saturation factor δ$^{−1}$.
Starting Page	233
Ending Page	245
Page Count	13
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	209
Issue Number	2
e-ISSN	1573093X
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	2002-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astrophysics
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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