CORE VERSION OF JOP9 (as of May 1995) ----------------------------- SOHO observations programs 1) Prominence diagnostics and dynamics Contributors: J. Fontenla, J.-C. Vial, F. Paletou The purpose of this project is to understand the structure of prominences from the standpoint of the physics involved in the energy and force balance processes that make them form, endure and dissapear. For this we need to evaluate the importance, effects, and quantitative description of basic physical processes, and then combine them into a full, consistent, physical picture. These processes involve at least the following: a) particle transport along and accross the magnetic field, basically mass and energy exchange through the prominence-corona interface (or prominence- corona transition region); b) optically thin radiative losses, both in the prominence-corona interface and in the core of a forming condensation illuminated by solar radiation; c) radiative transfer between prominence and solar atmosphere (mainly the chromosphere where the incident radiation forms), and between various parts of the prominence, this involves interactions between prominence threads, Doppler shifts of incident with respect to local profile, and multidimensional radiative transfer; d) MHD processes that determine the force balance in both the local and global scale, these involve considering the background magnetic field configuration, the local electric current distribution, and the magnetic interactions between various parts of the prominence. These points are critical to all phases of prominences, but the detailed treatement depends on which phase is studied. Many of these processes have been studied in other contexts and few of them have been studied for prominences (e.g., the prominence-corona interface was recently studied by FRVG (Fontenla, Rovira, Vial and Gouttebroze), the radiative transfer was investigated by HVG (Heinzel, Vial and Gouttebroze), the multidimensional radiative transfer was investigated by PAV (Paletou, Auer and Vial)). These results will be used and extended with quantitative evaluations of particular prominences that will be observed to determine particular aspects in individual cases. The basic scheme of the project is to set important questions, develop observational sequences, and interpret quantitatively the results and how they answer the questions. Few examples in which we want to concentrate follow: *) Formation: Observations have revealed that cold and warm dynamic material seen in Lyman alpha and C IV, respectively, is abundant on the corona apart from prominences, specially at heights below 10 arcsec above the chromosphere. - How much of this material is at each temperature and density range, and how this distribution relates to the photospheric magnetic fields? - How the distribution and shapes of the often observed loops relate to the network (are the footpointS in the cells or lanes, in high field)? - Why is this material in motion and whether and how it becomes almost homogeneous in temperature? - What is the actual size and geometry of such features, are they loops, what about plasmoids, are there both? - What is the footpoint signature of the dynamic loops, if any? - What is the interface between the dynamic loops and the corona (on the sides), are there current sheets? - If there are current sheets, how are they formed and maintained, are they in equilibrium, do they produce significant heating? - Where is gas and magnetic pressure lower: inside or outside the loops, do the two pressures balance or is there significant tension force? - Can the dynamic material be caught into magnetic traps and be the inital core of a prominence? - Once the initial core is formed, would it be stable, could it accumulate more mass, under which conditions? - As the initial core fills with mass, would the temperature drop or not, if it drops how fast and to which value, which are the net radiative losses? - How does the prominence formation relate to the cavity above, is there a relationship between prominence mass and cavity depletion or size? - Which electric currents develop as the prominence mass increases, - How does a prominence growth affect the background magnetic field, does a prominence change the background field (e.g., produces image current) in a particular way? *) maintenance - Are prominences thermally stable or is the material being refilled through the corona, if so is it by coronal condensation or syphon from the chromosphere? - If there is refill, how are prominences loosing and gaining mass by ejections, by slow or fast drift, along or accross the fieldlines, does ambipolar diffusion transport accross the field play a role? - Why the prominences have fine structure, what size does this structure have, is it fixed or changing, dynamic or static, homogenoeus or varies with altitude or at the edges? - How does this structure affect the support and energy balance? - What is the interface between the prominences and the corona, are there current sheets, what are the roles of diffusion and heat conduction? - Which are the differences in density and temperature at the greater height and edges of prominence slabs? Why are there such differences? - How does a prominence maintain its temperature and density, are they constant vary slowly or fluctuate in time? - Why all prominences have similar parameters, are they really similar, or what is the variability? - Are the temperature and pressure almost homogeneous or vary a lot, if so in which temporal and spatial scale, is this related to the fine structure or not (the fine structure is just density variation), how does this relate to the field, does the magnetic field vary a lot or is it mostly homogeneous, and what about the electric currents? *)DISAPPEARANCE - How prominences heat up and disapear, what is the difference that makes them stable or unstable to heating? - How are prominences being ejected, are there changes in the internal structure, how these changes relate to electric current changes, are there changes in the background field, how is the external field changed and how external changes affect the prominence structure? - Why some changes of the field may trigger prominence eruptions, others give heating and others don't affect them, are there specific type of changes, do they relate to specific prominence temperature and or density changes? - Are there strong incoming waves when prominences disappear, or is the prominence source of waves when disappearing? This long list is just a summary of basic things we need to answer for claiming we understand prominences. Many more questions can be posed too. To date few observations have addressed these points, mainly because ground-based optical data are not good enough to answer most of them. Next we will ellaborate on experiments that can provide answers to many of these questions. Of course, the answers from some experiments will change others and inspire new ones. Some specific experiments we propose are as follows: *) Use magnetograms (e.g., Kitt Peak) from previous days to compute potential fields (vector fields are better and we will coordinate with ground based observations of such), determine locations at the West limb with a few typical configurations (also look for non-potentiality as a configuration parameter). We will also coordinate with priminence polarization measurements. Use the strong available lines, preferable temperature sensitive, covering the whole temperature range from coronal to as low as possible, idealy: Si XII 499, Mg X 625, O VI 1038, O V 630, Ne VIII 770, Ly c 912, C III 977, C IV 1548, Si IV 1394, C III 977, Si III 1206, He I 584, Si II 1265 and 1197, Si I 1257, Ly beta 1026, and Ly alpha 1216. Infer the amount of material, at each temperature range, as function of position and field configuration (both local and global). *) The same as before but using density sensitive pairs of lines, initially: N III 772,989,1752,989, O IV 625,790,1401,1404,1407, Ne VI 562,999,1006,1010. (See Vernazza and Mason 1978, ApJ 226, 720). Infer the electron density at each temperature range and then the pressure as function of position and magnetic configuration.We will try to combine this with optical measurements of 10830, He I 5876, Na D, Mg b, Balmer and Ca lines. *) Observe cool material in the filament channels where no H alpha filament is observed. Look at sequences of line profiles in Ly alpha and beta, and He I 584, and compare with neighboring regions find whether there is, and how much, cool absorbing material in the channeLs, whether the profiles are static or have any typical velocities and widths, find out if there is dynamic material only or if there is evidence of trapping. Compare channels that are mostly potential with others that are highly sheared. Some line modeling will be needed here. *) Similar to previous but carried on near disk center neutral lines where H alpha filament is observed, and where the field is apparently changing as seen in H alpha and idealLy magnetograms, find relation between changes and line asymmetry and or broadening. This will also require line modeling. *) On the limb, use the brightest previous lines, together with highest spatial and temporal resolution, find fluctuations in profiles (intensities, shapes, widths and shifts), relate to position in prominence and magnetic configuration as inferred from potential field from previous or posterior magnetograms. Look also for inclined profiles where rotation may occur. *) As many of the above for comparing active region with quiet Sun prominences. Here the field may evolve faster, and filaments are easy targets. *) Select few quiescent prominences to compare two or more pairs of density sensitive lines, formed in the same temperature range, between two isoelectronic sequences, one pair should be highly sensitive to temperature and the other insensitive, e.g., B and Li seqs. The comparison would show departures from local ionization equilibria. Also look for correlations between velocity and density variations. One can evaluate the diffusion or flow accross that temperature range, in relation to the temperature gradient and density. We are working on the theory of these effects, and will study several species to compareinferred mass flows and diffusion velocities form them. Check for ionization degree dependence, this gives relationship with electric field and with classical Coulomb collision processes. I.A PROMINENCE EMISSION MEASURE Operational Sequence Initial pointing selected limb position at the slit center Slit 1x120 arcsec^2 Scan Area 120 arcsec^2 Step Size 0.76 arcsec; 4 STEPS OVER 2S Resulting Number of Scan Locations 160 ELEMENTARY steps; 40 EXPOSURES Dwell Time 10 s Duration of Scan 6 MIN 40 S Number of Scans 2 Number of Scan Mirror Settings 3 Repointing none Total Duration 8 MIN Line Selection 1/ CIV (1548A AND 1550A), NE VIII (770 & 780) 2/ SI IV (1394 & 1401), O IV (1401 & 1404) 3/ NV (1238 & 1242), MG X(625), O V (630) Bins Accross Line 25 Estimated Reduction Factor * Selection 1/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) 2/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) 3/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) * Compression BYTESCALE 1 * Reduction Co-operation Requirements CDS (SEE THE CME PROGRAM JOP3) I. B LYMAN ALPHA EMISSION IN LIMB PROMINENCE Operational Sequence Initial pointing selected limb position at the slit center (SAME AS ABOVE) Slit 1x120 arcsec^2 Scan Area 120 arcsec^2 Step Size 0.76 arcsec; 4 STEPS OVER 2S Resulting Number of Scan Locations 160 ELEMENTARY steps; 40 EXPOSURES Dwell Time 4 s Duration of Scan 2 MIN 40 S Number of Scans 2 Number of Scan Mirror Settings 1 Repointing none Total Duration 2 MIN 40S Line Selection Ly alpha (1216.7A) (ON THE BARE MCP) Bins Accross Line 50 pixelS Estimated Reduction Factor * Selection 1x50x24 (AVERAGE OVER 5 SPATIAL PIXELS) * Compression NONE * Reduction Co-operation Requirements CDS (SEE THE CME PROGRAM JOP3) I. C PROMINENCE EMISSION MEASURE Operational Sequence Initial pointing selected limb position at the slit center (SAME AS ABOVE) Slit 1x120 arcsec^2 Scan Area 120 arcsec^2 Step Size 0.76 arcsec; 4 STEPS OVER 2S Resulting Number of Scan Locations 160 ELEMENTARY steps; 40 EXPOSURES Dwell Time 10 s Duration of Scan 6 MIN 40 S Number of Scans 2 Number of Scan Mirror Settings 4 Repointing none Total Duration 11 min Line Selection 1/ Ly beta (1026A), O VI (1032 & 1036) 2/ SI XII (499), N III (992), C III (977), LY GAMMA (973) 3/ LY DELTA, LY EPSILON, LY 6, LY 7 (926) 4/ LY CONT (912), C II (904), NE VII (895), LY CONT (880) Bins Accross Line 25 pixelS Estimated Reduction Factor * Selection 1/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) 2/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) 3/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) 4/ 4x25x24 ((AVERAGE OVER 5 SPATIAL PIXELS)) * Compression BYTESCALE 1 * Reduction Co-operation Requirements CDS (SEE THE CME PROGRAM JOP3) II. DENSITY IN PROMINENCE NOTE THAT PROGRAM I.A. (SCAN 2) ALLOWS A DENSITY MEASUREMENT AT O IV TEMPERATURE (1.7 E5) IT IS DIFFICULT TO BUILD AN EFFICIENT PROGRAM ALLOWING FOR Ç SIMULTANEOUS È MEAUREMENTS IN THE TWO LINES INVOLVED. IF THIS SIMULTANEITY IS NOT CRITICAL, ONE CAN RECORD THE LINES WHICH ARE NEEDED FOR DENSITY DIAGNOSTIC DURING THE SPECTRAL SCAN ABOVE (TOTAL DURATION: 21 MINUTES III. FILAMENT CHANNELS AND IV FILAMENTS: Operational Sequence Initial pointing selected FILAMENT OR FILAMENT CHANNEL at the slit center Slit 0.3x120 arcsec^2 Scan Area 120 arcsec^2 Step Size 0.38 arcsec; 8 STEPS OVER 2S Resulting Number of Scan Locations 320 ELEMENTARY steps; 40 EXPOSURES Dwell Time 8 s Duration of Scan 5 MIN 20 S Number of Scans 2 Number of Scan Mirror Settings 3 Repointing SOLAR CORRECTION Total Duration 8 MIN Line Selection 1/ Ly alpha (1216.7A) (ON THE BARE MCP) 2/ HE I (584) 3/ LY BETA (1025) Bins Accross Line 50 pixelS Estimated Reduction Factor * Selection 1/ 1x50x24 (AVERAGE OVER 5 SPATIAL PIXELS) 2/ 1x50x24 (AVERAGE OVER 5 SPATIAL PIXELS) 3/ 1x50x24 (AVERAGE OVER 5 SPATIAL PIXELS) * Compression NONE * Reduction Co-operation Requirements CDS (SEE THE CME EARTH-ORIENTED PROGRAM) V. HIGH RESOLUTION QUIET PROMINENCE THE PROGRAM IS IDENTICAL TO PROGRAM IV EXCEPT THAT ONE NEEDS NOW A VERY HIGH COMPRESSION RATE AND/OR DATA SELECTION Operational Sequence Initial pointing selected PROMINENCE at the slit center Slit 0.3x120 arcsec^2 Scan Area 120 arcsec^2 Step Size 0.38 arcsec (2 STEPS FOR ONE EXPOSURE) Resulting Number of Scan Locations 320 ELEMENTARY steps; 160 EXPOSURES Dwell Time 2 s Duration of Scan 5 MIN 20 S Number of Scans 2 Number of Scan Mirror Settings 3 Repointing SOLAR CORRECTION Total Duration 16 MIN Line Selection 1/ Ly alpha (1216.7A) (ON THE BARE MCP) 2/ HE I (584) 3/ LY BETA (1025) Bins Accross Line 50 pixelS Estimated Reduction Factor * Selection 1/ 1x50x120 2/ 1x25x120 3/ 1x25x120 ACCUMULATION OF DATA DURING SCANS AND TRANSMISSION OF EXCESS DATA (ABOUT 4 MBYTES) LATER ON. * Compression BYTESCALE 1 * Reduction Co-operation Requirements CDS VI SAME AS ABOVE FOR ACTIVE REGION PROMINENCE VI DEPARTURES FROM LOCAL IONIZATION EQUILIBRIA IF TIME IS NOT CRITICAL, WE CAN USE SEQUENCES I.A AND I.C ABOVE FOR LINES OF O IV (B LIKE), O VI (LI LIKE): IN THIS CASE IT IS NECESSARY THAT CDS RECORDS O VI (173 A). ___________________________________________________________________________ 2) The composition of the dynamic low-altitude layers above the limb. Contributors: J. Fontenla, J.-C. Vial, K. Bocchialini Scientific Justification Material above the limb has been observed in various wavelengths and the observations are not explained by traditional sphericAlly symmetric chromosphere-transition region models. Early observations showed spicules at about 10^4 K (e.g. Beckers ), UVSP data showed a "cloud layer" of dynamic material in the range of heights <~10,000 km (Fontenla et al 1987), other UV data showed macro-spicules, and recently X-ray data from NIXT showed an absorption rim. The range in temperatures where this material is seen covers 10^4-10^5 K, and the velocities are tens of km/s. The Lyman alpha data showed a very different profile as soon as the limb is crossed, and the central reversal disAPPEARs. Also, the N V and C IV showed THAT this material is above the bright rim in these lines. The can /SUPPRESSnSUPPRESS: onical X-ray absorption, and the UV interpretation advanced BY by Orrall and Schmall (19..), invoke neutral Hydrogen and Helium at or below 10^4 K and points that spicules are not enough, but these data cannot determine which is the temperature and the source of absorption. The observation so far indicateS that this material is very dynamic and may represent the byproduct of MHD waves that were almost Alfven type at the base of the chromosphere but brake into complex non-linear motions at the top of the chromosphere and above. Therefore, these motions can be closely associated with the magnetic energy and momentum transport through the chromosphere into the corona. The diagnostics can make possible to estimate the electric currents associated to these features, and thus the energy flow. SUMER provides the unique means for determining the height structure, and composition of these dynamic layer, and its dependence with the underlying solar features. We plan to observe the composition of this layer in coronal holes, quiet Sun, and two types of active regions (simple bipolar and complex polarity). For this we plan to observe various lines around Ly alpha, NV, Si III, CIV and , and Si IV and. The slit 1x120 or 0.3x120 arcsec^2 will be used and only a few rastering positions will be taken. Through coordination with CDS we will try to secure an image of the position observed so that we can determine the EUV morphology of the region observed. With these data we will model the statistical distribution of multi-thermal and multi-velocity material that can explain the observed profiles. Strong departures from ionization equilibrium are expected and also a distribution of densities is expected. For these regions we will analyze as many lines as possible, including allowed and intercombination lines, and a few continuum wavelengths to determine the reference height. The observations timing is not crucial, and a number of these, at least 8 will be necessary to sample the coronal hole and quiet Sun features, and another 8 to sample the two types of active regions. However, the active region program would be dependent on locating an adequate active region at the limb, and thus has scheduling constraints. I.A LIMB EMISSION MEASURE Operational Sequence Initial pointing selected limb position at the slit center Slit 1x120 arcsec^2 Scan Area 10 arcsec Step Size 0.76 arcsec Resulting Number of Scan Locations 14 steps Dwell Time 60 s Duration of Scan 14 MIN Number of Scans 2 Number of Scan Mirror Settings 3 Repointing none Total Duration 14 MIN Line Selection 1/ CIV (1548A AND 1550A), NE VIII (770 & 780) 2/ SI IV (1394 & 1401), O IV (1401 & 1404) 3/ NV (1238 & 1242), MG X(625), O V (630) Bins Accross Line 25 Estimated Reduction Factor * Selection 1/ 4x25x120 2/ 4x25x120 3/ 4x25x120 * Compression BYTESCALE 1 * Reduction Co-operation Requirements NONE I. B LYMAN ALPHA EMISSION AT LIMB Operational Sequence Initial pointing selected limb position at the slit center (SAME AS ABOVE) Slit 1x120 arcsec^2 Scan Area 10 arcsec Step Size 0.76 arcsec Resulting Number of Scan Locations 14 steps Dwell Time 10 s Duration of Scan 2 MIN 20 S Number of Scans 2 Number of Scan Mirror Settings 1 Repointing none Total Duration 4 MIN 40S Line Selection Ly alpha (1216.7A) (ON THE BARE MCP) Bins Accross Line 50 pixelS Estimated Reduction Factor * Selection 1x50x120 * Compression NONE * Reduction Co-operation Requirements NONE I. C LIMB EMISSION MEASURE Operational Sequence Initial pointing selected limb position at the slit center (AS ABOVE) Slit 1x120 arcsec^2 Scan Area 10 arcsec Step Size 0.76 arcsec Resulting Number of Scan Locations 14 steps Dwell Time 60 s Duration of Scan 14 MIN Number of Scans 2 Number of Scan Mirror Settings 4 Repointing none Total Duration 19 min Line Selection 1/ Ly beta (1026A), O VI (1032 & 1036) 2/ SI XII (499), N III (992), C III (977), LY GAMMA (973) 3/ LY DELTA, LY EPSILON, LY 6, LY 7 (926) 4/ LY CONT (912), C II (904), NE VII (895), LY CONT (880) Bins Accross Line 25 pixelS Estimated Reduction Factor * Selection 1/ 4x25x120 2/ 4x25x120 3/ 4x25x120 4/ 4x25x120 * Compression BYTESCALE 1 * Reduction Co-operation Requirements NONE ----------------------------------------------------------------