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Relation Between Coronal Hole Areas on the Sun and the Solar Wind Parameters at 1 AU
Ist Teil von
Solar physics, 2012-12, Vol.281 (2), p.793-813
Ort / Verlag
Dordrecht: Springer Netherlands
Erscheinungsjahr
2012
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
We analyze the relationship between the coronal hole (CH) characteristics on the Sun (area, position, and intensity levels) and the corresponding solar wind parameters (solar wind speed
v
, proton temperature
T
, proton density
n
, and magnetic field strength
B
) measured
in situ
at 1 AU with a 6-h time resolution. We developed a histogram-based intensity thresholding method to obtain fractional CH areas from SOHO/EIT 195 Å images. The algorithm was applied to 6-h cadence EIT 195 Å images for the year 2005, which were characterized by a low solar activity. In calculating well-defined peaks of the solar wind parameters corresponding to the peaks in CH area, we found that the solar wind speed
v
shows a high correlation with correlation coefficient cc=0.78, medium correlation for
T
and
B
with cc=0.41 and cc=0.41. No significant correlation was found with the proton density
n
. Applying an intensity-weighted CH area did not improve the relations, since the size and the mean intensity of the CH areas are not independent parameters but strongly correlated (cc=− 0.72). Comparison of the fractional CH areas derived from GOES/SXI and SOHO/EIT and the related solar wind predictions shows no systematic differences (cc=0.79).