Some properties of solar magnetic fields as deduced from NSO/KP data and from calculations

Abstract

In this paper we carry out a correlative analysis of the measurements of the photospheric magnetic field Bd (the magnetic component along the line of sight) from NSO/KP, and of the calculations of the field components on the visible solar disk from these measurements using Rudenko's (2001) potential field approximation method. The analysis revealed the following features: (1) near the equator the character of variation of langle|Bd| rangle(ρ) varies with the range of the values of |Bd| used in the analysis (here the brackets langle rangle denote an averaging over time and over the area of the portion of the size 10°×10°, and ρ is the angle between this portion and the central meridian (CM)); (2) generally near the equator there is a relatively small field `radiality': the value of langle|BR| rangle/ langle|BF| rangle near the CM varies over the range 1.25–0.9 and increases from the CM to the limb (here BR and BF are the calculated radial and toroidal field components); (3) the magnetic field measurements near the equator are different for different longitudes; (4) in the region of coronal holes (He i λ10 830 A) and at the calculated bases of open magnetic tubes (OMT) there is an increased `radiality' of the magnetic field in comparison with solar disk areas near the equator. The largest recorded values of the ratios of area-averaged coronal holes (CH) and OMT of the moduli of the radial and transverse field components were 9.2 in CH, and 4 in OMT.