SOHO/TRACE/Kanzelhoehe Joint Observing Programme 144 ---------------------------------------------------- Title ----- Sources of coronal oscillations Instruments ----------- Kanzelhoehe Solar Observatory, Austria TRACE CDS MDI Authors ------- Jack Ireland (Ast. Obs. of Capodimonte, Naples, Italy) Robert Walsh (UCLAN) Ineke De Moortel (St. Andrews) Pier Francesco Moretti (Ast. Obs. of Capodimonte, Naples, Italy) Contacts (instruments) ---------------------- Pier Francesco Moretti (Kanzelhoehe) Karel Schrijver (TRACE) Andrzej Fludra (CDS) Sarah Gregory (MDI) E-mail Addresses ---------------- Jack Ireland wafels@hotmail.com Robert Walsh rwwalsh@uclan.ac.uk Ineke De Moortel ineke@mcs.st-and.ac.uk Pier Francisco Moretti moretti@na.astro.it Karel Schrijver trace_planner@cheyenne.nascom.nasa.gov Andrzej Fludra fludra@cdso8.nascom.nasa.gov Sarah Gregory mdiops@mdisas.nascom.nasa.gov Progress -------- First Draft April 2001 Objective --------- Our aim is to investigate the time variability of the photospheric magnetic field for events which may act as sources of co-temporally observed oscillations in the solar atmosphere, particularly the corona. Conditions Necessary to Run --------------------------- Occurrence of a suitably well defined coronal loop system on the disk and involvement of at minimum Kanzelhoehe Solar Observatory and TRACE. Scientific Case --------------- Recent observations of oscillations has prompted much speculation as to the nature of the coronal plasma and the oscillations that are supported by it. The results of De Moortel et al, 2000, Robbrecht et al 1999 and Aschwanden et al, 1999 suggest the presence of slow magneto-acoustic waves propagating outwards on (quasi-) open field structures in active regions with periods in the range 200-400 seconds. The mechanism generating these waves - one of the few examples of waves observed in the solar corona - is as yet unknown, as are the details of their propagation in the solar atmosphere. A more complete determination of the source and properties (De Moortel and Hood, 2000) of these waves will allow us to discriminate between wave heating theories. Further, Nakariakov et al, 1999 infer a value of the Lundquist number some six orders of magnitude less than that expected from theory. This value is calculated using scaling laws derived from MHD wave dissipation calculations in conjunction with TRACE observations of a single transversly oscillating and decaying loop. The authors suggest that an incident impulse from a nearby flare causes the loop they analysed to oscillate. This begs the question, however, of why only one loop oscillates in response to the impulse and not more. Schrijver and Brown, 2000, alternately suggest that it is the behaviour of photospheric magnetic flux elements relevant to this loop only that are responsible for the decaying oscillation, doing away with the need to lower the Lundquist number so drastically. A knowledge of the dynamic behaviour of the photospheric magnetic field, coupled with a determination the response of the overlying solar atmosphere, is of crucial importance in both these cases. This Joint Observing Programme between TRACE (high cadence images of the solar atmosphere), SOHO (spectroscopic/magnetogram data) and Kanzelhoehe Observatory (high cadence magnetograms) seeks to investigate, through a selection of differing observing sequences over a range of timescales, the sources of these oscillations. Pointing and Target Selection ----------------------------- Given that magnetograms are of prime importance in this JOP, strong preference will be given to active regions on the disk. In addition those active regions that are either at or close to disk centre (1-2 days either side) are preferred in order to optimise magnetic data. Active regions just past disk-centre will minimise the line-of-sight effects in the solar atmospheric plasma. Times are constrained to sunlight at Kanzelhoehe Solar Observatory in Austria. Note that these times will vary depending on the time of year the JOP is run (approximate times, 8-20 UT: exact times depend on time of year ). Note that the both sets of magnetogram data - those from the Kanzelhoehe Solar Observatory and SOHO-MDI - are important for cross comparison. MDI's superior spatial resolution and location in space will contribute in assessing atmospheric efforts at Kanzelhoehe. Equally, the superior cadence available at Kanzelhoehe will access time-scales below those of SOHO-MDI. If MDI is unable to support high cadence images the JOP should still be carried out as information on atmospheric effects can also be derived from Kanzelhoehe intensitygrams. The active region loop structure should be well defined in EIT, and where available, TRACE and Yohkoh-SXT. Although EIT and Yohkoh-SXT are not formally part of this JOP, data from these instruments is also useful in target selection. There are two types of target, designated Type I and Type II. The precise pointing requirements should be discussed in detail with the JOP authors (and the CDS Deputy PI where applicable). Type I: The first is of the type chosen for the March 1999 JOP 83 83, i.e., bright active regions that are relatively static and quiescent. These seem to be the best locations for observing the coronal oscillations seen by De Moortel et al, 2000. The instruments involved for this choice of region are defined in `Operating Instructions' under Type I. Type II: With these targets we intend to observe transverse loop oscillations, as reported by Nakariakov et al, 1999. Therefore, the preferred target are active regions that have a high probability of flaring (preferably high M- or X-class events, as predicted by NOAA). The instruments involved and the relevant studies are described in `Operating Instructions' under Type II. Please note that the express permission of the CDS Deputy PI (at time of writing, Andrzej Fludra, email fludra@cdso8.nascom.nasa.gov) should be given in order to use CDS on such a target. In particular, the study and exact pointing in the active region should be discussed in detail with the CDS Operations Scientist and the CDS Deputy PI in order to best protect the instrument from exposure to potentially damaging photon fluxes. Operating Details ----------------- Type I ------ (i) Kanzelhoehe High cadence (10-20 seconds) simultaneous Dopplergrams, longitudinal magnetograms and intensity images (all at 4.3 arcsec/pixel) during daylight hours in Austria (+1hr GMT). (approximately 8-20 UT) (ii) MDI Minimum requirement is one minute cadence magnetograms which cover the target active region, at least for the times TRACE is running at its highest cadence *AND* when Kanzelhoehe is observing. If the target active region is in the MDI high res FOV then high res magnetograms are preferred to full disk if at all possible, particularly during the TRACE high-cadence/Kanzelhoehe observing times. (iii) TRACE One of these 3 programs to be chosen at the time of observation 1 : High cadence EUV (195, 171,284) and Ly alpha exposures with intermittent CIV for transition region monitoring. Area : 1024 x 1024 at 0.5'' Cadence : approx. 30s-60s 2 : Higher cadence EUV Observations in two wavelengths (195, 171) alternatively to observe oscillations at two coronal temperarures. Area : 512 x 512 at 1.0'' Cadence : approx 10-15 s with 3-5 compression. 3 : Rapid imaging of part of loop structure with one line (brightest of 195 or 171) producing fastest cadence possible with TRACE for oscillation analysis Area : 512 x 512 at 1.0'' Cadence : 9 s for approx. 25 minute period NOTE: This type of observation has been run at least twice before for the authors, once by Karel Schrijver for the JOP 083 observations in April 2000, and previous to that by Ted Tarbell in April 1999. The notes below outline some aspects of Ted Tarbell's implementation. Please also check with trace_planner@cheyenne.nascom.nasa.gov for more up to date information. In brief, Ted Tarbell put together some experimental runs using 2x2 binning of the CCD which would only run during the radiation-free portions of the TRACE orbit ie for about 25 minutes at a time. In that way, the radiation testing was skipped and AEC was trusted to keep us at good exposures and avoids using too much mass memory. Ted calculated the .utim files for the 4 wavelength combinations for the specific day of observations, computed the HLZ's and checked the mass memory with the timeline program. However, this means that you are relying on AEC (not safeframe) for lumogen protection and thus probably should not be pointed at a very hot active region. (iv) CDS These studies to be chosen at the discretion of the JOP leaders. 1 : Run LARGEBP2 once followed by a series of LOOPS_5 and a final EJECT_V3. Total duration should be several hours - the longer the better. 2 : Run EJECT_V3 once followed by a series of LOOPS_5 and a final EJECT_V3. Total duration should be several hours - the longer the better. CDS rasters LARGEBP2 (CDS Study 10, Variations 25 or 26) NIS, 2x240 slit, 240x240 area, 120 locations Exposure 45s (Var 25) or 20s (Var 26 - if very bright!) Duration 6949s (Var 25) or 6579s (Var 26). Lines: He I 584, O III 599, O V 629, Ca X 557, Mg IX 368, Mg X 625, Si X 346, 356, Fe XII 364, Fe XIII 348, Fe XIV 333, Fe XVI 360, Si XII 520, backgrnd 355, 335. EJECT_V3 (CDS Study 11, Variation 18) NIS, 4x240 slit, 240x240 area, 60 locations, Exposure 10s, Duration 991s. Lines: He I 584, O V 629, Si X 347, 356, Mg IX 368, Fe XVI 360. LOOPS_5 (CDS Study 123, Variation 1) NIS, 4x240 slit, 4x120 area, 1 location Exposure 10s - 50 rasters. Duration 707s. Lines: He I 584, O V 639, Mg IX 368, Fe XVI 360. Type II ------- (i) Kanzelhoehe same as Type I (ii) MDI same as Type I (ii) TRACE same as Type I (iv) CDS To be used with very bright active regions that have a strong chance of flaring. Consult with the CDS Deputy PI on precise pointings. 1 : Run EJECT_V3 once followed by a series of LOOPS_5N and a final EJECT_V3. Total duration should be several hours - the longer the better. 2 : Run LARGEBP2/v28 once, followed by a series of LOOPS_5N and a final EJECT_V3. Total duration should be several hours - the longer the better. CDS Rasters LARGEBP2 (CDS Study 10, Variation 28) NIS, 2x240 slit, 240x240 area, 120 locations Exposure 20s, Duration approx 3000s. Lines: Si XII 520.67, Fe XIV 333.78, Ca X 557.74, WW 335.18, Si X 346.76, Fe XII 348.18, He I 584.42, Fe XIV 353.63, WW 355.04, Si X 356.44, O III 599.66, Fe XVI 360.79, Fe XII 364.47, Mg IX 368.06, Mg X 624.94, O V 629.75. EJECT_V3 (CDS Study 11, Variation 18) NIS, 4x240 slit, 240x240 area, 60 locations, Exposure 10s, Duration 991s. Lines: He I 584, O V 629, Si X 347, 356, Mg IX 368, Fe XVI 360. LOOPS_5N (CDS Study 230, Variation 1) NIS, 2x240 slit, 4x120 area, 1 location Exposure 10s - 50 rasters. Duration 707s. Lines: He I 584, O V 639, WW 558.30, Mg IX 368. REFERENCES Aschwanden, M., Fletcher, L., Schrijver, C. J., Alexander, D., ApJ., 520, 880, 1999. De Moortel, I., Hood, A. W., A & A, 363, 269, 2000. De Moortel, I., Ireland, J. & Walsh, R.W., A & A, 355, L23, 2000. Nakariakov, V. M., Ofman, L., DeLuca, E. E., Roberts, B., Davila, J. M., Science, 285, 862, 1999. Robbrecht, E., Berghmans, D., & Poedts, S., ESA-SP 446, 575, 1999. Schrijver, C.J., Brown, D. S., ApJ., L69, 537, 2000.