An erupting active region filament: Three-dimensional trajectory and hydrogen column density

From 15:33 through 16:02 UT on 13 June 1998, observations of an erupting fi lament as it crossed solar disk center were obtained with the NSO/KPVT and SOHO/CDS instruments as part of the SOHO Joint Observing Program 70. Contex t observations show that this event was the eruption of the north-east sect ion of a small active region filament associated with NOAA 8237, that the p hotospheric magnetic field was changing in this active region between 12-14 June 1998, and that a coronal Moreton-wave disk event occurred, as well as a white-light CME off the south-west solar limb. The NSO/KPVT imaging spec troscopy data covered 512 x 512 are sec of the disk center and were spectra lly centered at the He I 1083 nm line and captured +/- 1.0 nm of surroundin g solar spectrum. The He I absorption line is seen blue-shifted to velociti es of between 200 and 300 km s(-1). The true solar trajectory of the erupti on is obtained by using the projected solar coordinates and by integrating the Doppler velocity. The filament travels with a total velocity of about 3 00 km s(-1) along a path inclined roughly 49 deg to the solar surface and r ises to a height of just over 1.5 solar radii before it becomes too diffuse to follow. The filament also shows internal motions with multiple Doppler components shifted by +/- 25 km s(-1). Finally, the KPVT data show no Stoke s V profiles in the Doppler-shifted He I 1083.03 nm absorption to a limit o f roughly 3 x 10(-3) times the continuum intensity. The SOHO/CDS scanned th e center of the KPVT FOV using seven EUV lines; Doppler-shifted filament em ission is seen in lines from He I 58.4 nm, He II 30.4 nm, O IV 55.5 nm, O V 63.0 nm, Ne VI 56.3 nm, and Mg x 61.0 nm representing temperatures from ab out 2 x 10(4)K through 1 x 10(6)K. Bound-free continuum absorption from H I , without confusion from foreground emission and line emission, is seen as the filament obscures underlying chromospheric emission. A fit to the wavel ength dependence of the absorption from five lines between 55.5 to 63.0 nm yields a column density xiH I = 4.8 +/- 2.5 x 10(17) cm(-2). Spatial maps s how that this filament absorption is more confined than the regions which s how emission.