Session 2 - Everything Else.
Display session, Friday, June 27
Ballroom C, Chair: Richard Canfield

## [2.73] Properties of Active and Quiescent Prominences from Mid-Infrared Line Analysis

E. S. Chang (U. Massachusetts), D. Deming (GSFC)

We have analyzed all lines in the MIR (8 to 20 micron) spectra of a quiescent(Q) and two time-frames of an active (A1 and A2) prominence. In addition to those found by Zirker(1985), we have identified a higher excitation hydrogen line and two helium recombination lines. Accounting for instrumental broadening, we can separate out the Doppler and the Stark contributions. The former yields maximum temperatures of 6200K, 34000K and 22000K and the latter electron densities (N_e) of 8, 30(3) and 14(2) in units of 10^10 cm^-3 for Q, A1 and A2 respectively. Using the same assumptions made by Zirker, namely, (1) the strongest line (7-6) is optically thin, (2) the population of the lower level(n=6) is determined by direct radiative recombination and photo-ionization, (3) the equality of proton and electron densities, and (4) the thickness of the prominence is at least 10^8 cm, we derive a new inequality, N_e \leq 1.83 \times10^8 T^0.75 e^-2195/T. Substituting our maximum temperatures into the RHS, we find upper bound N_e values of 9, 43 and 30 in the same units as above. We have now found the helium recombination spectrum which has been postulated by Tandberg-Hanssen as one of three possible ways of equilibrating the triplet/ singlet ratio. Surprisingly, it is present in the quiescent as well as the active prominence. We will report on utilizing the helium line widths to further constrain the temperature and to find the turbulence velocities. Ref. Zirker, J.B. (1985), Solar Physics, 102, 33. Tandberg-Hanssen,E. (1978) Solar Prominences.