JOP165 High Cadence Active region oscillation: Center to limb variation Short title: High Cadence AR Oscillations Center-Limb Contributors:D. Banerjee - CPA, K.U.Leuven (dipu@wis.kuleuven.ac.be) A. De Groof- CPA, (Anik.DeGroof@wis.kuleuven.ac.be) S. Poedts - CPA, (Stefaan.Poedts@wis.kuleuven.ac.be L. Van Driel-Gesztelyi- CPA&MSSL,UCL,UK (Lidia.vanDriel@obspm.fr) E. O'Shea - IAC, Tenerife (eoshea@ll.iac.es) F. Moreno Insertis - IAC (fmi@ll.iac.es) A. Sainz Dalda- IAC (asainz@themis.iac.es) D. Berghmans- ROB (David.BERGHMANS@oma.be) F. Clette -ROB (Frederic.CLETTE@oma.be) A. Zhukov-ROB (Andrei.Zhukov@oma.be) V. Slemzin - Lebedev Phys. Institute, Russia(slem@sci.lebedev.ru) A. Urnov - Lebedev Phys. Institute, Russia (urnov@sci.lebedev.ru) Participating instruments: CDS, MDI EIT (Shutterles), TRACE and SPIRIT/CORONAS-F (http://www.xras.lebedev.ru/) Version dated:13th March 2003 Scientific Objective: --------------------- The primary objective of this observing program is to search for high frequency active region oscillations in active regions, loop systems and also to follow the active region from one limb to the other to look for variations: the effects of LOS. Interpreting the oscillation in terms of different wave modes and/or plasma motions always depend on the line of sight as we observe in the limb or on the center of the disk. This campaign will address some of these questions. MDI and TRACE photospheric and UV imaging of TRACE and SPIRIT are requested to acquire simultaneous high temporal and spatial coverage along with the spectroscopic data from CDS. EIT will operate in the shutterless mode to achieve high Cadence. Scientific Justification: ------------------------ A previous JOP program (80) has revealed the existence of weak transient disturbances in extended coronal loop systems (Robbrecht et al, 2001). These propagating disturbances (PDs) originate from small scale brightenings at the footpoints of the loops and propagate upward along the loops. In all cases observed, the projected propagation speed is close to, but below the expected sound speed in the loops. This suggest that the PDs could be interpreted as slow mode MHD waves. Such a conclusion is however hampered by the fact that with the JOP80 data we only have the projection of the propagation speeds in the plane of the sky. Since we do not know the 3D configuration of the loops, it was not possible to confirm if the real speed (not projected) indeed matches the sound speed (or tube speed). Therefore, some doubts remained whether the propagating disturbances should be interpreted as slow mode MHD waves or as bulk plasma flows. With the present JOP we propose to follow the same active region as it rotates over the solar disk and the line-of-sight perspective changes from day to day. The target of opportunity that we envision is a relatively large, decaying bipolar active region with an extended loop system. For such an active region we can hope that the overall 3D configuration remains fairly constant on a time-scale of -say- 1 week. On a daily basis we will determine the propagation speed of PDs in the extended loop system. From the daily variation in the projected speeds we will be able to determine the actual speed and check if this is indeed compatible with the slow mode MHD wave hypothesis. Apart from studying the nature of the oscillations we would also like to address the origin of these oscillations. The origin of high-frequency oscillations are believed to have connection with magnetic footpoint motions. In decaying AR the dominant type of footpoint motions is related to the so-called moving magnetic feature (MMF) activity, which have been related to sunspot decay. MMF activity is observed to be related to X-ray transient brightenings (Shimizu, 1994), and surge and X-ray jet activity (Canfield et al, 1996), and even hard X-ray emitting microflares (Nitta, 1997). Recently a relation to the Ellerman bomb phenomenon (H-alpha brightenings) has been proposed (see review by Martinez-Pillet, 2002). All these transient brightenings are due to some reconnection process taking place in different atmospheric layers. Furthermore, MMF activity have been shown to lead to the acceleration of electrons which emit metric radio noise storms due to a large number of low-energy magnetic reconnection processes at the moat boundary (Bentley et al, 2000). We aim to investigate the possible wave-generating processes linked to the long-term sunspot decay, which would be best studied during the disc transit of a simple bipolar AR. Operation: ---------- MDI: Full disk magnetograms ( with 1 min cadence) when the AR is close to limb and High resolution mode when the AR is within the high resolution FOV, sequence- hr_t2_ve_me with tracking (Similar to TRACE FOV). Contact: L. Van Driel-Gesztelyi (Lidia.vanDriel@obspm.fr) ------------------------------------------- Operational Sequence:CDS Active Region Raster Initial Pointing Active region Spectrometer NIS Slit 4 x 240 arcsec Steps 60 (to build up raster of 240"x240") Exposure Time 15s Total Duration ~2000s (aiming for duration of 30 minutes) Line Selection (20 lines) Si XII 520.67 He I 584.33 O III 599.59 Fe XVI 360.76 Mg X 624.94 O V 629.505 pixel posn. 1008 Spectral window width 30 pixels Binning If necessary binning by 2 along the slit to achieve study duration of 30 minutes ----------------------------------------------------------------- Temporal series observations of active regions (Modification of OS_AR sequence) Initial Pointing Active Regions Spectrometer NIS Slit 4 x 240 arcsec Raster Locations 1 (no rotation compensation) Exposure Time 15 sec Number of Repeats/Rasters 85 Total Duration 1785s (cadence of ~21s) aiming for 30 minutes duration Line Selection Fe XVI 360 Si XII 520 O III 599 O V 629 pixel posn. 1008 He I 584 Mg X 624 No. of spectral bins across line 30 Contact: D. Banerjee (dipu@wis.kuleuven.ac.be) ----------------------------------------------------------------------------- TRACE: TRACE will run a high cadence sequence of the active region chosen by CDS. As a minimum, each TRACE run should envelop every CDS and EIT run. A few additional images (white light, 195, 284, 1600) in the beginning and end of a TRACE run should be included for context and comparison with EIT and SPIRIT. FOV: full FOV Channel: 17.1 nm channel + a cycle of context images (white light, 195, 284, 1600) in the beginning and end of a sequence Cadence: 60 sec cadence Exposure time : Slightly enhanced exposure times (>20 sec) are considered to enhance the signal-to-noise ratio of weak disturbances (about 10% in intensity) in extended loop systems (TBD in agreement with TRACE planner). Sequence: to be run at least during every CDS and EIT observations of this JOP, every TRACE sequence should last at least 3 hours. Pointing: to be taken from the CDS observations Contact: David Berghmans ----------------------------------------------------------------------------- EIT: This job will be executed preferentially while EIT can execute a shutterless mode run of its High cadence synoptic program (see http://sol.oma.be/High-cadence/ for all details). Such an opportunity exists typically every 3 months, and is planned in agreement with the DSN contact and the LASCO/EIT operators team). An EIT shutterless mode run lasts 2 hours and is typically scheduled late in the UT day to allow for operator presence during US East-Coast office hours. The EIT High cadence synoptic program will be exceptionally modified in the sense that we will make 2 shutterless mode runs roughly 1 week apart (min 3 days, max 13 days). The FOV of the first run would be the NE or the SE quadrant (TBD as target of opportunity). The FOV of the second run would be the corresponding quadrant at the western side. EIT will operate in the 19.5 nm bandpass Contact: David Berghmans, Kevin Schenk --------------------------------------------------------- SPIRIT (onboard CORONAS-F satellite): SPIRIT will run a high cadence sequence of the selected active region (target selection by EIT or TRACE) in the center of 15'x15' window. The Ritchey-Chretien telescope (171, 195, 284, 304 A) can be used as well as the Herschel telescope (175, 304 A). Several full disk images will be made (in 171, 175, 195, 284, 304 A bands) for context and comparison with TRACE and EIT. Total duration of the run is 2100 s, one run a day. Possible modes of observation: 1) Herschel telescope - synchronous pairs of images, 175/304 A, exposure time 2,2 s, cadence 30 s. 2) Herschel telescope - images in 175 A band, exposure time 2,2 s, cadence 10 s. 3) Ritchey-Chretien telescope - images in one of 4 bands, exposure time 9 s, cadence 12 s. First mode was used during High cadence campaigns #8 and 9. Second mode probably will be used in the High cadence campaign #10. The first mode seems to be the preferred one, as the fine structure dynamics is better observed with higher signal-to-noise ratio. The Herschel telescope gives 10 times higher efficiency than the Ritchey-Chretien telescope. Selection of the time and target for the SPIRIT must be done at least two days before observation for a period up to 3 days. Contact: Andrei Zhukov, Vladimir Slemzin, Alexander Urnov. --------------------------------------- Targets: Relatively large, decaying active region with an extended loop system as it appears in the west limb and then follow it everyday until it disappears from the east limb. ------------------------------------------------------------------ Proposed observation dates: During next shutterless campaign. Tentatively first week of June. We follow the same active region from one limb to other for 10 days or so, (3-4 hrs each day), within this 10 days there will be two sutterless campaigns. ------------------------------------------------------------------ References: Bentley R.D., Klein K.-L., van Driel-Gesztelyi L., Demoulin P., Trottet G., Tassetto P., Marty G.: 2000, Solar Phys. 193, 227. Canfield, R.C., Reardon, K.P., Leka, K.D., Shibata, K., Yokoyama, T., & Shimojo, M. 1996, ApJ, 464, 1016 Martinez Pillet, V., 2002, Astron. Nachr. 323, 342 Nitta, N. 1997, ApJ, 491, 402 Robbrecht, E., et al, 2001, A&A, 370, 591 Shimizu, T. 1994, in T. Sakurai, T. Hirayama \& G. Ai (eds.) Proc. of the 2nd Japan-China Seminar on Solar Phys., Nat. Astron. Obs. of Japan, 193