Authors: H.E. Mason, H. Hudson, B. Schmieder, K. Shibata, P.R. Young Status: Drafted July 1995, modified November 1995 Objective: To study the plasma physics involved in the formation of X-ray jets, and to learn about their physical origin. Conditions necessary: Occurrence of a suitable target region. Observations involve CDS, SUMER, MDI, and EIT, and if at the limb, LASCO and UVCS. YOHKOH data will be used to help guide the observations as necessary. Ground based observations are suggested using THEMIS and MSDP. Scientific case: Dynamic and transient phenomena have long been identified as a characteristic of the UV emission from the solar transition zone. Explosive events and jets are well documented in the observations from the High Resolution Telescope and Spectrograph (HRTS). Turbulent events (up to 250 km/s) confined in small spatial locations (<4") have been observed in the CIV emission, formed at 10^5 K (cf Dere et al, 1989). These short lived (approx 60s) phenomena are possibly associated with emerging magnetic flux (Dere et al, 1991). An apparently different class of events observed with HRTS in CIV emission are high velocity jets (Brueckner and Bartoe, 1983). These jets show upward moving material with velocities (50 - 400 km/s), sometimes in excess of the sound velocity in the solar corona (approx. 120 km/s). In the transition region emission, these are again short lived (maximum lifetime approx 80 s), with a spatial extent of approx 5" (4,000 km), some reaching an altitude of 16,000km. All jets are seen in CIV (10^5K) and SiIV (8 10^4K) emission and the strongest are also seen in a wider range of temperatures (2 10^4K - 2 10^5K). Breuckner and Bartoe interpreted the HRTS observations as exploding loops. They derived an acceleration rate of 5 km/s^2 for the leading edge of the jets, which does not decrease shortly before the jets become invisible. This suggests that the material is heated to higher coronal temperatures than the transition region temperatures observed by HRTS. From the integrated DEM and spatial extent of the jets a lower limit on the electron density was derived of around 7 10^9 cm^-3. This gives a kinetic energy of approximately 3 10^26 ergs. Recent YOHKOH SXT (Soft X-ray telescope) observations have identified several types of soft X-ray jet events (Shibata et al., 1992; Strong et al., 1992), which are highly collimated transient plasma structures occurring in particular patterns (Shimojo et al., 1994). These jets are characterised by velocities of 30 - 300 km/s, with a spatial extent of 5 10^3 - 4 10^5 km. They seem to be associated with different phenomena - flares in X-ray bright points, emerging flux, active regions etc. The temperatures derived from the ratios of the different SXT filters are around 3 10^6K, not so different from the ambient plasma. The electron densities derived from an integrated DEM and estimate of the spatial extent give a lower limit of 2 10^9 cm^-3. From the YOHKOH SXT observations, it is difficult to make a distinction between the interpretation of a jet as a real flow or as a temperature enhancement. The interpretations of these events include magnetic reconnection in the Heyvaerts-Priest-Rust geometry. The acceleration of the plasma appears to result either from the reconnection itself, or from evaporative flow driven by the energy release. Recently Kundu et al. (1995) have shown that these jets are the sites of Type III bursts, so that non-thermal activity is also a part of the phenomenon. The X-ray jets may well be related to chromospheric jets or coronal high-velocity events. The jet occurrence patterns, as revealed by the Yohkoh/SXT data, have certain characteristics that should make it possible for us to point to a likely location and to observe jets successfully both on the disk and on the limb. To fully understand all the mechanisms which produce these energetic phenomena it is important to combine these UV and X-ray space observations with some ground based observations of the magnetic field and chromospheric lines. We propose to combine the SOHO and YOHKOH observations with simultaneous measurements of the magnetic field using THEMIS and the chromospheric lines with the MSDP spectrograph (Shmieder et al,1995). This will allow us to monitor the emerging magnetic flux and the re-organisation of the magnetic field lines together with the chromosperic surge activity. The reconnection could occur at different levels in the atmosphere and lead to energy deposition. The plasma physical conditions where the energy is released are important in the study of energetic phenomena - surges, explosive events, X-ray bright points and jets. The central observational objective is to flesh out the physical parameters of the plasma itself: velocities, temperature structure, densities, magnetic configuration, coronal mass content, etc., all of which are possible in principle with the SOHO instrumentation. The initial most desirable part of the program would consist of getting velocities and temperature distributions from CDS line spectroscopy. Ideally, we would like to combine these observations with measuremnets of the magnetic field and chromospheric emission. References: Brueckner, G.E. and Bartoe, J.-D.F., 1983, Astrophys. J., 272, 329 Dere, K.P., Bartoe, J.-D.F. and Brueckner, G.E., 1989, Sol. Phys., 123, 41 Dere, K.P., Bartoe, J.-D.F. and Breuckner, G.E., 1991, J. Geophys. Res., 96, 9399 Kundu, M.R., Strong, K.T., Pick, M., Harvey, J.W., White, S.M. and Hudson, H.S. 1994, Astrophys. J. Lett., 427, L59 Schmieder, B., Shibata, K., Van Driel-Gesztelyi, L. and Freeland, 1995, Sol. Phys., 156, 245 Shibata et al, 1992, PASJ, 44, L173 Shimojo et al, 1994, Astrophys. J., submitted Strong et al 1992, PASJ, 44, ? Scheme: Based upon our Yohkoh experience, select a likely target. Since the jets recur, often repeatedly over periods of several days, a close watch on concurrent Yohkoh or EIT data will be indispensible. Small fields of view will be satisfactory, because the jet sources are typically compact loop structures. SOHO Observing Sequences ------------------------ Physical parameters of UV and X-ray Jets H.E. Mason, H. Hudson, B. Schmieder, K. Shibata, P.R. Young The instruments on SOHO offer the first opportunity to study jets from the upper chromosphere through to the outer corona with high temporal and spatial resolution. The nature of the UV transition region jets has been extensively studied. The nature of the X-ray jets is well established. The connection between the two has not been established. In addition the SOHO CDS and SUMER instruments offer the possibility to obtain precise measurements of the electron density and temperature structure together with the flow velocities and turbulent broadening. The SOHO instruments could be used to define the physical characteristics of the jets from the upper chromosphere to the outer corona. The pointing for SOHO should be co-ordinated with that of YOHKOH. The approximate parameters of UV and X-ray jets derived from the YOHKOH and HRTS observations are: HRTS YOHKOH Electron temperature = 2 10^4 - 2 10^5 K 3 10^6 K Electron density = 7 10^9 cm^-3 2 10^9 cm^-3 Velocities = 50 - 400 km/s 30 - 300 km/s Spatial extent = 4 10^3 km (5") 3 10^3 km (4") - 1.6 10^4 km (20") - 4 10^5 km (8') The CDS instrument can be used to study the coronal emission - to define the temperature and density values together with changes in spatial distribution. The SUMER instrument could define the transition region parameters and velocity shifts from spectral line profiles. EIT, UVSC, LASCO can be used to study the temporal and spatial variations of the coronal emission. CDS Observing Sequence ---------------------- The CDS observations are designed to determine the temperature structure (from the EM), flows and electron density structure from Ne diagnostic line ratios. These techniques are described in numerous reviews (cf Mason,1994 , Mason and Monsignori Fossi, 1994 - table I). Spectral lines have been chosen from the lists by Dere (1978) for a compact solar flare observed with S082A on Skylab and Thomas and Neupert (1994) for an active region observed with the SERTS instrument. The precise lines used may be adjusted when these diagnostic ratios are explored in the early stages of the CDS science analysis. The NIS stigmatic slit (2" x 240") is chosen to cover a large spatial area [1' x 2'] in a short time [60s]. The short wavelength band from 310-380 covers a sequence of iron lines (Fe X - Fe XVI), which can be used to determine the electron temperature and density structure of the coronal plasma. In addition, some diagnostic line ratios from cooler ions (Mg, Si) formed in the canopy region can also be observed. It may be possible to observe some transition region ions in this wavelength band aswell. References: Dere, K.P. 1978, Astrophys. J., 221, 1062 Mason, H.E. 1994, Space Sci. Rev., 70, 111 Mason, H.E. and Monsignori Fossi, B.C. 1994, Astron. Astrophs. Rev., 6, 123 Thomas, R.J. and Neupert, W.M. 1994, Astrophys. J. Suppl. Ser., 91, 461 SPECTROMETER: NIS SLIT: 2" x 240" RASTER AREA: 120" x 240" STEP: 2" RASTER LOCATIONS: 60 x 1 EXPOSURE TIME: 1s DURATION OF RASTER: 60s NUMBER OF RASTERS: 30 LINES STUDIED: Mg VI (4 10^5) 349.16* Mg VII (6 10^5) 367.68* Mg VIII (8 10^5) 315.02* Si VIII (8 10^5) 319.83* Mg IX (1.0 10^6) 368.06* Si IX (1.0 10^6) 349.87, 341.97* (Ne) 345.13, 341.97 (Ne) Fe X (1.0 10^6) 345.74* Si X (1.2 10^6) 356.03, 347.41* (Ne) Fe XI (1.3 10^6) 352.67* Fe XII (1.5 10^6) 338.27, 364.47* (Ne) Fe XIII (1.5 10^6) 320.80, 348.18* (Ne) 318.12, 348.18 (Ne) Fe XIV (1.9 10^6) 353.83, 334.17* (Ne) Fe XV (2.0 10^6) 321.79, 327.03* (Ne) Fe XVI (2.5 10^6) 360.75* Ni XVIII(3.1 10^6) 320.56* Ca XVII (5.0 10^6) 371.03* Ca XVIII(6.3 10^6) 344.77* Fe XXI (10^7) 338.06* Temperature of peak abundance indicated in parenthesis * indicates useful for EM and velocity studies Ne indicates electron density diagnostic ratio SUMER Observing sequence ------------------------ The objective of the SUMER observing sequence should be to study the transition region counterpart of the X-ray jets. To see if the jets observed in the UV by HRTS are connected with those seen by YOHKOH. The HRTS jets were observed in the C IV (10^5K) line emission, however this line may be too strong for observing energetic events with SUMER. All the jets were also seen by HRTS in Si IV (6 10^4K). The Si IV line at 1402.8A is a strong allowed transition and is ideal for line profile studies. Also in the same wavelength region are the electron density diagnostic ratios of O IV (1.7 10^5K). These were studied with Skylab S082B and HRTS (Dere et al, 1982). Hayes and Shine (1987) carried out a detailed study of the O IV diagnostic ratios for bursts observed in active regions with the Solar Maximum Mission's (SMM's) Ultra-violet Spectrometer and Polarimeter. These bursts were not the same as the high velocity jets seem by HRTS, but interestingly Hayes and Shine did find that the larger UV bursts were associated with small soft X-ray events observed by SMM's XRP. The electron densities derived by Hayes and Shine were greater than 10^10 cm^-3. A recent study of the O IV diagnostic line ratios has been carried out by Cook et al (1995) using new atomic data. They find the O IV intensity ratio I(1407A)/I(1401A) to be a useful electron density diagnostic above 3 10^9 cm^-3. The ratios I(1407A)/I(1404A) has problems with an unresolved S IV blend. A SUMER POP (8.1.2.12) has been written to study the O IV, Si IV and S IV lines at around 1400A. This may be a useful observing sequence to study these jets. However, it may need some further refinement, subject to actual counts observed for these lines. We have used the count rates estimated in the SUMER red book (edited by Klaus Wilhelm) which are for the quiet Sun and active regions. It should be noted that the SiIV intensities for bursts published by Hayes and Shine (1987) ranged from 20,000 to 120,000 erg/cm^2/sec/st over a 30 min interval. The dwell time for these weak lines is quite long and the SUMER team have suggested ways to speed up the spatial scans. The stronger C IV lines could be used if the SiIV and O IV lines are too weak. References: Cook, J.W., Keenan, F.P., Dufton, P.L., Kingston, A.E., Pradhan, A.K. Zhang, H.L., Doyle, J.G. and Hayes, M.A. 1995, Astrophys. J., in press Dere, K.P., Bartoe, J.-D.F. and Breuckner, G.E. 1982, Astrophys. J., 259, 366 Hayes, M. and Shine, R.A. 1987, Astrophys. J., 312, 943 SUMER POP : Density Diagnostics with O IV, Si IV, S IV lines CONTRIBUTOR: Helen E. Mason Initial Pointing As YOHKOH Slit 1" x 120" Scan Area 30" x 120" Step Size 0.75" Number of Scan Locations 40 Dwell Time 20s Duration of Scan 13.5min Number of Scans 4 Number of Scan mirror settings 1 Repointing none Total Duration 54 mins Line Selection O IV 1397.20A S IV 1398.13A O IV 1399.77A O IV 1401.16A Si IV 1402.77A O IV + S IV 1404.8A S IV 1406.0A O IV 1407.38A Bins across the line 20