Quasi-periodic Line-of-Sight Velocity Variations at the Bases of Polar Coronal Holes

Details Quasi-periodic Line-of-Sight Velocity Variations at the Bases of Polar Coronal Holes Quasi-periodic Line-of-Sight Velocity Variations at the Bases of Polar Coronal Holes

Nov 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003arep...47..946k&link_type=abstract

Astronomy Reports, vol. 47, Issue 11, p.946-952

Astronomy and Astrophysics

Astronomy

Scientific paper

Spatial and temporal variations in the line-of-sight velocities and brightnesses measured in the Hα and FeI 6564 Å Hβ and FeI 4864 Å NiI 4857 Å lines at the bases of polar coronal holes are analyzed. Time series with durations of 43 120 min were recorded using a CCD strip (3700 pixels 200×7 µm in size) and a CCD array (256×1024 pixels 24 µm in size). Quasi-stationary upward flows (with radial velocities reaching 3 km/s in the photosphere and 12 15 km/s in the chromosphere) were observed near dark points at the boundaries of the chromospheric network. The acoustic 3-min and 5-min oscillations are amplified in the coronal hole, and reach 1 km/s in the photosphere and 3 4 km/s in the chromosphere. The spectra of fluctuations of the line-of-sight velocity exhibit significant maxima at low frequencies, clustering near 0.4, 0.75, and 1 mHz.

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