Summary: A&A 421, 339--348 (2004)
# ESO 2004
Network boundary origins of fast solar wind
seen in the low transition region?
M. D. Popescu 1,2 , J. G. Doyle 1 , and L. D. Xia 1
1 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
2 Astronomical Institute of the Romanian Academy, 75212 Bucharest 28, Romania
Received 18 September 2003 / Accepted 3 March 2004
Abstract. We present a study of a high spatial resolution raster acquired ondisk with the SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) grating spectrograph on SoHO (the Solar and Heliospheric Observatory) in a polar Coronal
Hole (CH) region. We analyse two EUV emission lines, representing the properties of solar plasma in the low transition re
gion (TR), O ### 703.87 Ċ (maximum electron temperature, T e # 8 × 10 4 K), as well as in the corona, Mg ## 706.02 Ċ
(T e # 10 6 K). For Mg ##, we find that low CH intensities correspond to negative Doppler velocities (outflows) of #5 km s -1 .
Along the quiet Sun (QS)/CH boundaries, the coronal plasma begins to be more redshifted. A coronal bright point (BP) located
within the CH is blueshifted in the coronal line. In the TR line, the outer region of the BP is redshifted at #5 km s -1 , but,