Premium
Slow twists of solar magnetic flux tubes and the polar magnetic field of the Sun
Author(s) -
Hollweg Joseph V.,
Lee Martin A.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i008p00919
Subject(s) - physics , poynting vector , wkb approximation , heliospheric current sheet , flux (metallurgy) , solar wind , magnetic flux , magnetic field , solar rotation , magnetohydrodynamics , alfvén wave , computational physics , classical mechanics , quantum electrodynamics , interplanetary magnetic field , astrophysics , solar physics , quantum mechanics , materials science , metallurgy
The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric magnetic field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). Magnetic field components transverse to r do not in general grow to dominate the radial component at large r. Our analysis also yields expressions for the Poynting flux associated with the steady twists. These results are regarded as indicative of the Poynting flux associated with very low frequency Alfven waves, and it is shown how the Poynting flux and the spatial evolution of the wave amplitude differ from the usual WKB result. It is found that the low‐frequency Poynting flux at the base of a coronal hole can be about 50 percent larger than the WKB flux inferred from spectral observations of coronal motions (e.g., Hassler et al., 1988).