1. Flare Prediction and the Background Corona Coronal Diagnostic Spectrometer Wolter-Schwarzschild Type 2 telescope Two separate spectrometers- the Normal Incidence Spectrometer (NIS) and the Grazing Incidence Spectrometer (GIS) NIS has two wavelength ranges of sensitivity (308 - 381 Å, 513 - 630 Å) Slit sizes (2 x 240´´, 4 x 240´´, and 90 x 240´´ ) Transition Region and Coronal Explorer Cassegrain telescope with 30 cm aperture 1024 x 1024 pixel CCD, 8 x 8´ FOV, 1.0´´ resolution Four channels: –3 EUV 173 Å, 195 Å, 284 Å –UV / White light Average exposure ≈ 20 s Joint Observing Program 146 Requested observations of Solar Active Regions using multiple space-based observing platforms CDS : Raster scans using 5 - 42 pass-bands with varying exposure times and step sizes TRACE : Narrow band EUV images using 1 - 3 of the EUV filters SXT and EIT data were also collected. Five campaigns to date. Now implemented as a ‘standard’ NASA/SoHO observing routine when a target is available. Flaring Active Region 9628 Intensity vs. Altitude AR 10001 TRACE images were made using 173 Å channel only 13 CDS passbands Restricted field-of- view in CDS to limit time to develop raster No flares were recorded for the AR. AR 10249 TRACE images collected using all three EUV filters. 20 CDS spectral passbands No flares recorded for AR No Loops visible in 284 Å channel. Few loops were evident in 195 Å Quiescent Active Regions Visible at east limb 09/18/2001 Produced M 1.4 Flare as recorded by GOES 8 with onset at 17:04 UT Many post-flare loops were visible in TRACE 173 Å. Numerous EUV loops were also observed that were stationary. Strongly emitted in many EUV spectral lines formed over the temperature range 0.075 - 3 MK Discovery of the precursors to flare onset are paramount to the increased need for accurate space weather prediction. A potential indicator for flaring activity may be the temperature structure of the Active Region background emission. The active region background, or unresolved active region corona (UARC), can be modeled using a magneto-hydrostatic model for the density stratification as a function of altitude. Exponential decreases in the intensity of EUV emission above the limb and within active regions have been used by Cirtain (2005) to determine the scale height temperature of the UARC. Presently this analysis has been completed for a limited set of active regions. `Quiescent' active region data was examined and the scale height temperature determined was found to be isothermal, constant in time and slowly decreasing with distance from the center of the Active Region. `Flaring' active region emission was found to be quite different. Prior to the onset of the flare the estimated scale height temperature was nearly isothermal. Just before the peak in the GOES 8 X-ray flux it was determined to be multi-thermal, varying over 1 MK for the multiple spectral lines observed. The temperatures found from the emission of multiple spectral lines were all observed to increase approximately an hour before the flare and reached a maximum subsequent to the GOES 8 X-ray peak. The current state-of-the-art in active region flare prediction tools falls into two categories: complexity of magnetic field as measured in the photosphere, and the "sigmoidalness" (i.e., twistiness) of bright loops observed in EUV and X-ray emission. Both of these measures rely on well-resolved data. This work proposes to investigate a new category of prediction which uses the coronal emission from unresolved structures. While this emission is commonly eliminated as background "noise", Cirtain (2005) has demonstrated that this may be a fruitful area of research (even with current instruments), for which there may be robust applications. We plan to determine the UARC scale height temperature characteristics for an extended sample of flaring and quiescent active regions to determine the validity of the forecasting competence of this observational technique. J. Cirtain 1, M. Weber 1, A. Davey 2, J. Raymond 1 1 Smithsonian-Center for Astrophysics 60 Garden St. Cambridge, MA 02138 U.S.A. 2 Southwest Research Institue 1050 Walnut St., Suite 400, Boulder, CO 80302, U.S.A. Intensity in units of ergs cm -2 s -1 arcsec -2 is determined for all pixels along multiple radial lines Three different functions are fit to the intensity variation with altitude Reduced chi-squared calculations for the curve fits are used to select the best fit function and the associated parameters, such as the initial value at the lowest altitude pixel and exponent The value of the exponent from the best fit is used to calculated the temperature from an equation for the hydrostatic scale height. The scale height temperature is compared to the formation temperature as a check of the validity of the technique The temperatures derived from the curve fits for the ‘quiescent’ active regions are nearly constant in time. Results are invariant with respect to the ion used to determine the scale height temperature Temperatures determined from the curve fit routine are consistent with the temperatures derived from line ratio technique and emission measure analysis Scale height temperature showed marginal variation from ‘core’ of active region to ‘edge’ of the active region. For active region 10249, a spherical geometry model of the atmosphere is used to determine the scale height model and is found to be a reasonable match to the data Conclusions from ‘Quiescent’ Active Region Study Conclusions from ‘Flaring’ Active Region 9628 Substantial increase in measure scale height temperature prior to the onset of the flare Measured scale height temperatures are multi- thermal Measured scale height temperature increases throughout active region without regard to area responsible for the flare ‘Relaxes’ to pre-flare conditions several hours after the flare Future Work We have compiled an extended set of coronal active region spectroscopic data 15 ‘Flaring’ active regions > 40 ‘quiescent’ active regions We will determine how the emission from ions formed at transition region and coronal temperatures varies with time Compare variations for different sizes/morphologies for flares Develop tools for prediction of flares as found feasible from results of large sample survey