Does ACE IMF Polarity Come from Bz Data?

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IMF Polarity Predictions:
Comparison of real-time ACE IMF polarity data (solid black line) with Wang-Sheeley-Arge model predictions (colored dots). The three sets of predictions (i.e., red, green, and blue dots) are based on data from, respectively, Wilcox (WSO), Mount Wilson (MWO) and SOLIS (NSO) solar observatories. The solid black line is the real-time (9-hour-averaged) ACE IMF values normalized to equal unit value. A positive (negative) polarity indicates that the IMF is directed radially outward (inward) from the Sun to the Earth. Each 9-hour interval of real-time ACE data corresponds to 9 individual (hourly averaged) values when there are no gaps in coverage. If two-thirds of the 9 values have positive (negative) sign, they are assigned a polarity of +1 (-1). If less than two-thirds are of a particular sign, that time interval is assigned a polarity of zero, implying mixed or indeterminate polarity. Source : http://www.swpc.noaa.gov/ws/predimf_3d.html

Referring to above image, based on data from Bz, 8 out of 9 numbers are positive polarity, but ACE shows negative polarity, I would like to confirm whether ACE IMF polarity come from data of Bz or not.

Does anyone have any suggestions?

Thanks in advance for any suggestions :>

 

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Does anyone have any suggestions?