An erupting macrospicule - Characteristics derived from SOHO-CDS spectroscopic observations

We report results from the analysis of a sequence of SOHO/CDS observations obtained off-limb in the south polar coronal hole on 6 March 1998. Three successive data sets were obtained with the Normal Incidence Spectrometer (NIS), the first of which showed a jet-like feature visible in the chromospheric and low transition region lines. The morphological characteristics of this feature suggested it was a macrospicule. The two remaining observations of the same region indicated a quiet coronal hole with a density of 10 8 cm 3 and a temperature rising from 0.95x10(6) K near the limb to 1.2x10(6) K at about 4.7x10(4) km above the limb. These data were averaged and used as "background" for the macrospicule observation. The resulting subtracted spectra showed more details of the feature. In particular, a cloud of plasma was detected at about 3x10(4) km above the limb. The macrospicule was found to have a density of the order of 10(10) cm(-3) and a temperature of about 2-3x10(5) K. The initial outflow velocity near the limb was over 80 km s(-1). This decreased to a terminal value of 26 km s(-1) above about 6x10(4) km.