SOHO JOP074 A Study of Filaments and their Environments using VLA, SOHO & Yohkoh N. Gopalswamy (Catholic U.), Y. Hanaoka, K. Shibasaki (Nobeyama), J. R. Lemen (Lockheed), R. Howard (NRL) and J. B. Gurman (EIT) Objective: The main objective of this proposal is to determine the Structure and evolution of filaments and prominences using radio, X-ray and EUV observations. These characteristics are important to understand the onset phase of coronal mass ejections. We seek the eruption signatures in the filaments and their environments. This can be achieved by observing the filament and its surrounding at multiple wavelengths so that plasmas at many different temperatures can be probed. We will be able to answer several related questions such as the temperature structure of the filaments, relationship of the prominence cavity seen in radio X-ray and EUV and the extent of corona affected during an eruption. VLA & Nobeyama: The filament and its environment can be probed at radio wavelengths. The Very Large Array (VLA) can be used at short wavelengths (2, 3.6 and 6 cm) to acquire information on the filament, filament cavity and the filament-corona transition region. At longer wavelengths, we can probe the filament cavity (20 cm) and the overlying streamer (90 cm). Thus the three part structure of the pre-eruption state of a CME can be imaged by a combination of these wavelengths. In addition to the VLA observations, the Nobeyama radioheliograph can provide information on the filament at 1.7 cm. The filament is optically thick at this wavelength and thus directly gives the temperature of the filament. SOHO: The SOHO instruments can provide information on filaments and their environments at various spectral lines corresponding to temperatures below about 2 MK down to about 10,000 K, somewhat similar to the information obtained in radio and hence we can get a better picture of the evolution of the filament. In addition, the Yohkoh/SXT observations can provide information on the higher temperature plasma overlying the filament. What we need from SOHO: High cadence observations at 304 and 195 angstrom; CDS observations in lower temperature lines; basic synoptic MDI observations; LASCO synoptic observations to look for halo CMEs if a filament eruption occurs. We need about 9 arcmin X 9 arcmin images every 10 min where possible. Note: This program overlaps with JOPs 3 and 4. We have additional radio and X-ray inputs.