Joint Observing Program 188: Prominence Mass Composition and Variability Study Authors: Gary Kilper, Holly Gilbert, Therese Kucera, Joseph Gurman, David Alexander Revised Fourth Draft, 6/28/07 Instruments: SOHO-EIT, SOHO-CDS, SOHO-MDI, TRACE, STEREO-EUVI, Hinode-SOT, MLSO Purpose: To study the relative abundances of hydrogen and helium in prominences and find trends in its spatial distribution and variability over time by measuring the continuum absorption due to photoionization for EUV observations (e.g. JOP63, ref:Kucera98, ref:Gilbert05) and the absorption in H-alpha (6563 A) and He I (10830 A). This study is primarily motivated by our findings from analyzing absorption due to filaments in H-alpha and He I MLSO observations (ref:Gilbert07). The results of that study and the preliminary results of our current, ongoing analysis of continuum absorption in archived EUV data from CDS, EIT, and TRACE show similar trends: stable (i.e. relatively unchanging) prominences have a relative helium surplus (compared to the average ratio of He to H) in the lower part and a relative helium deficit in the upper part, while more variable prominences (including those that are pre-eruption) have a homogenized spatial distribution of helium relative to hydrogen. Further study needs to be done to find the scale heights of the H and He distribution and the time scales over which they change, but the ability to study more highly varying material requires co-temporal observations with better cadence and spatial resolution (via the newer observatories) than is currently available in the archived data of CDS, EIT, and TRACE. Note that coordinated observations are necessary to compare the simultaneous distributions of H0, He0, and He+. References: JOP63: Absorption by H and He Continua in Prominences, au: T. Kucera, V. Andretta, A. Poland, J. Gurman Kucera98: Kucera, T.A., Andretta, V., & Poland, A.I. 1998, SoPh, 183, 107 Gilbert05: Gilbert, H.R., Holzer, T.E., & MacQueen, R.M. 2005, ApJ, 618, 524 Gilbert07: Gilbert, H., Kilper, G., & Alexander, D., to be submitted to ApJ Instrument Operations: The targets are prominences with at least some prominence material on disk, and some material extending over the limb (from the Earth-Sun line-of-sight). An ideal target would have no (or very little) material behind the limb, hidden from view. A priority would be to observe a pre-eruption prominence, starting at least two days before the eruption occurs. Additional observations would also be desired when a prominence is near the limb, but entirely on the disk. Filaments on the disk and not near the limb would be good secondary targets. Additional observations with SOT and MLSO of the targets crossing the disk would be very beneficial. It should be possible to identify targets quickly enough to observe them at the East limb, although the West limb has a higher probability of providing ideal targets. In order to increase the warning time, target selection will be aided by using the latest SECCHI beacon EUVI 195 A images from the Behind STEREO spacecraft. 1. CDS: Observe the prominence region using the same observing program as POBS1_2/v46 (e.g. program 24990, 2002/05/29). The duration of each raster would be about 68 minutes, with a rastered-image size of 120"x240". If a prominence is larger than the field of view, multiple rasters would be combined to create a mosaic of the prominence. Note that the CDS observations showing the distribution of neutral H on its own do not need to have such high cadence since the neutral H is expected to vary slowly, and it is more important to get good spatial resolution. 2. EIT: Observe the full disk every 12 minutes in Fe XII (195 A) with 1024x1024 image size (2.625 arcsec/pixel), with context images in Fe XV (284 A), Fe IX/X (171 A), and He II (304 A) taken every six hours, as per the regular observing schedule. The EIT observations will be used to test the accuracy of the mass-determination method in the current study using EIT observations, and to test for effects resulting from analyzing a larger vs. a smaller pixel size. 3. MDI: Take a full disk Continuum observation whenever possible, depending on the rate of telemetry, as per the regular observing schedule. A Continuum observation every hour (or every 96 minutes) would be ideal, although stretching that up to a four hour cadence would still be okay. Having only the synoptic Continuum images (with eight hour cadence) may pose a problem, but this can be worked around and compensated for. The sunspots in the Continuum images will be used to align TRACE with SOHO. Note that if there are no sunspots present within the TRACE White Light field-of-view, then aligning the continuum images is impossible and we won't need observations from MDI. 4. TRACE: Observe the prominence region every 155 seconds (or whatever is necessary to get good signal-to-noise) in Fe XII (195 A) with 768x768 image size (384"x384", 0.5 arcsec/pixel), and take White Light and Fe IX/X (171 A) every two hours. The sunspots in the White Light images will be used to align TRACE with SOHO pointing (through MDI Continuum observations). 5. EUVI: Observe the full disk every 10 minutes in Fe XII (195 A) with 2048x2048 image size (1.588 arcsec/pixel), every 2.5 minutes in Fe IX/X (171 A), in He II (304 A) every 10 minutes, and in Fe XV (284 A) every 20 minutes. Higher cadence data (or a shift in observing sequence to switch the timings of 195 A and 171 A observations) during the observing time has been requested for 18:00 UT to 24:00 UT. It is hoped that there will be enough separation between the A and B spacecraft and the instruments on the Earth-Sun line such that a good 3-D perspective of the prominences is formed by the observations from the three viewpoints combined. The STEREO observations are also important in providing estimates on the amount of mass hidden behind the disk (from the Earth-Sun line-of-sight). 6. SOT: Observe the prominence region every minute in H-alpha (6563 A), and interspersing observations in Ca II H (3968 A) and in the G-band (4305 A). Additional observations using SOT and MLSO of the target prominences as they cross the disk (as filaments) would be used to advance the previous study of absorption in H-alpha and He I. 7. Mauna Loa: Take full-disk observations in H-alpha (6563 A, PICS disk and limb) and He I (10830 A, CHIP intensity and velocity) with three minute cadence whenever possible, as per the regular observing schedule. Note that the ability to take observations depends on the weather at Mauna Kea, and would only occur during daylight observing hours -- between 17:00 and 02:00 UT (more or less).