Wilcox Solar Observatory Source Surface Synoptic Charts

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The coronal magnetic field is calculated from photospheric field observations with a potential field model. The field is forced to be radial at the source surface to approximate the effect of the accelerating solar wind on the field configuration. Results for two methods are presented here.
The *classic* computation locates the source surface at 2.5 solar radii, assumes that the photospheric field has a meridional component and requires a somewhat ad hoc polar field correction to more closely match the observations of the IMF structure at Earth. The *radial* computation assumes the field in the photosphere is radial; results presented here locate the source surface at 2.5 Rs or 3.25 Rs. This model requires no polar field correction. The Rs=3.25 computation matched the latitudinal extent observed by Ulysses in 1994 as it went southward. However, using the lower radius gives a significantly better overall match to the structure of the inner corona and subsequent estimations of the maximum inclination of the HCS to the ecliptic.		A quarter-size sample of CR 1642 (June 1976) is shown above. Blue, light shading shows the positive regions. The neutral line is black.
The classic and radial models give very similar results for the location of the neutral line at the source surface that is observed to be a good indicator of the source of the heliospheric current sheet. Neither model should be used to predict the magnitude of the field above the source surface. The Rs = 2.5 radial model is probably the preferred choice overall, if only because of its simplicity.
		K.H. Schatten, J.M. Wilcox, and N.F. Ness, Solar Physics, 6, 442, 1969. M.D. Altschuler, and G. Newkirk, Jr., Solar Physics, 9, 131, 1969. J.T. Hoeksema, J.M. Wilcox, & P.H. Scherrer, JGR, 88, 9910, 1983.

CR 1614 begins 1974:04:24.Classic 250: [gif] : [ps] : [txt]Radial 250: [gif] : [ps] : [txt]Radial 325 :[gif] : [ps] : [txt]

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