Coronal Magnetic-Field Configuration Associated with Pseudostreamer and Slow Solar Wind

The global distribution of the solar wind speed $V$ $V$ is closely related to the configuration of the coronal magnetic-field, and the expansion factor $f$ $f$ of the flux tube is known as a parameter for determining $V$ $V$ . However, the inverse relation between $f$ $f$ and $V$ $V$ does not hold for pseudostreamers, which separate open-field regions with the same polarity. In the present study, we examined the magnetic-field configuration of pseudostreamers using the potential field (PF) model analysis of magnetograph observations for six Carrington rotations (CRs) in Cycle 23 and compared it with $V$ $V$ data derived from interplanetary scintillation observations. We calculated the parameter $S$ $S$ , which represents the relative angular distance of foot points on the photosphere magnetically connected to adjacent pixels on the source surface and $f$ $f$ from PF model analysis and discriminated areas of helmet and pseudostreamers on the source surface by selecting large values of $S$ $S$ . Although the overall correlation between $S$ $S$ and $V$ $V$ was very poor, helmet and pseudostreamers with large $S$ $S$ values were exclusively associated with slow $V$ $V$ . Furthermore, helmet and pseudostreamers were associated with large and small values of $f$ $f$ , respectively. This suggests that $S$ $S$ enables a better discrimination of slow-wind sources associated with pseudostreamers than $f$ $f$ . We calculated the distance from the streamer boundary (DSTB) on the source surface using data of helmet and pseudostreamers to compare with $V$ $V$ data. Calculated DSTB data exhibited significant correlations with $V$ $V$ data except for the solar maximum period. The average of correlation coefficients between DSTB and $V$ $V$ over five CRs excluding one at the solar maximum were 0.69, higher than that between the distance from the coronal hole boundary (DCHB) and $V$ $V$ . This suggests that DSTB acts as a better parameter for determining $V$ $V$ than DCHB. We demonstrated that $f$ $f$ for pseudostreamers tended to reach a maximum at a height lower than the source surface (2.5 $R_{\odot }$ $R_{\odot }$ ). This provides important insight into the formation process of the slow solar wind in pseudostreamers.