Joint Observing Program No. 23 BRIGHT POINTS Authors: A. Fludra (CDS/RAL), W. Curdt (SUMER/Lindau), O. Vilhu (Helsinki), J. Saba (MDI/Lockheed @GSFC), R. Thomas (CDS & SUMER/ GSFC), J. T. Hoeksema (MDI/Stanford), C. J. Wolfson (MDI/Lockheed), B. Schmieder (IAS), and other interested parties Bright points have been studied extensively in X-ray images (e.g. Golub et al. 1977), but have also been observed in EUV wavelengths and, recently, 17 GHz radio emission has been detected from some X-ray bright points (Kundu et al. 1994). BP are small (10-40 arcsec) regions of enhanced emission, located above pairs of opposite polarity magnetic features in the photosphere. They are seen in the quiet corona and coronal holes, with lifetimes ranging between about two hours and two days (Harvey et al. 1994). The number of BPs seems to anti-correlate with the solar activity. BPs fluctuate in intensity and some of them have been observed to flare. Webb et al. (1993) show that at least 72 percent of X-ray BP are associated with Cancelling Magnetic Features (CMF), i.e. pairs of opposite polarity features that converge together and shrink in area. Less than 28 percent of XBPs overlie Ephemeral Active Regions (ER), i.e. small emerging magnetic bipoles which grow and separate in opposite directions. A 'converging flux' model for bright points has been proposed by Priest, Parnell and Martin (1994). The aim of this programme is to study the origin, evolution, variability and characteristics of EUV Bright Points (temperature, density, chemical composition), their association with cancelling magnetic features or emerging ephemeral active regions, relation to X-ray BP and He I 10830 A dark points. It may be possible to resolve spatially the BP site to identify the configuration of magnetic loops inside the BP area and also find out whether BP brightenings can be regarded as small flares. Velocities of surges associated with flaring BPs can be studied. REFERENCES: Golub, L. et al., 1977, Sol. Phys., 53, 111 Habbal S.R.: 1990, in P. Ulmschneider, E.R.Priest, R.Rosner (eds.) 'Mechanisms of Chromospheric and Coronal Heating', Springer Verlag, p. 127. Harvey et al. 1994, ASP Conference Series Vol. 68: Solar Active Region Evolution, ed. K.S. Balasubramaniam and G.W. Simon, p. 377. Kundu, M., Shibasaki, K, Enome, S., and Nitta, N., 1994, ApJ, 431, L155 Priest, E.R., Parnell, C.E., and Martin, S.F., 1994, ApJ, 427, 459 Webb D.F., et al. 1993, Sol. Phys., 144, 15 DATA TO BE USED: - CDS and SUMER image and spectroscopic data as specified below - MDI data: High-resolution magnetograms, dopplergrams, and continuum intensity images. - Cospatial images from EIT, and TRACE when available. Images from Yohkoh SXT to identify X-ray BPs. - Supporting ground-based data (in particular, He I 10830 data) JOP OPTIONS: (1) To observe a full history of a BP (birth -- evolution -- disappearance) a selected area is scanned repeatedly by CDS or SUMER with a possibly high time resolution, until a BP is detected. A flag will be issued when an increase of intensity in one of the lines is detected, and a different study will be executed, e.g. a smaller raster centred on the BP (see option 2 below). SUMER or CDS can be a flag master. With about 100 BP/day on the disk at the present time, on average, about 2 BP should fall within the CDS 4x4 arcmin field of view. Suggested pointing: within the MDI high-resolution area (or any area if simultaneously covered by ground-based magnetographs) (2) To study the temperature, density structure, and dynamics of selected BPs. the instruments can be pointed to the BP found in Option 1 (when the flag is issued). Alternatively, a BP can be selected at EOF from real-time EIT images. Use a small raster centred on the BP and spectral lines covering a wide temperature range. Frequency: TBD Duration: For instruments requiring NRT commanding, 3-day intervals of about 8 hours, if possible, but shorter periods (e.g., one 8-hr interval) also acceptable. When using deferred commanding and a 'BP search study' with a BP flag, CDS study can be run for up to 18 hours per day. Solar conditions: This study should be made on a large sample of potential BP targets, in quiet Sun and coronal hole regions, during various levels of activity, to see if overall solar conditions affect the results; study of BPs near active regions is also desirable. CONTRIBUTIONS FROM PARTICIPATING INSTRUMENTS: *** CDS Operations: *** Search Phase: Spectrometer: Normal Incidence Slit: 2 x 240 arcsec Raster Area: 240 x 240 arcsecond Step (DX) 2 arcsec Raster Locations: 120 x 1 Exposure Time: 2 s Duration of raster: 240 sec Number of rasters: repeat until a BP found Total duration: up to 18 hours Line selection: Brightest lines: O V 629.73 (2.0e5 K), Mg IX 368.06 (1.0e6 K), Fe XVI 335.40 (2.5e6 K), He I 584.33 (2.0e4 K) Bins Across Line: 15 Flags: CDS as a flag Master Study Phase: The CDS study BRPNT (Blue Book) described below focuses on individual bright points to observe their origin and evolution, provide density and temperature diagnostics, and trace variability of their EUV emission. Sequence: NIS, GIS, NIS. This could be repeated several times, throughout the BP's life (up to 10-12 hours). Spectrometer: Normal Incidence Slit: 2 x 240 arcsec Raster Area: 60 x 60 arcsecond Step (DX, DY) 2 arcsec, 0 arcsec Raster Locations: 30 x 1 Exposure Time: 10 s Duration of raster: 385 sec Number of rasters: 10 Total duration: 64.2 minutes Line selection: Bright Point Selection 1 (16 lines) Bins Across Line: 15 Telemetry/Compression: truncate to 12 bits 8.3 s/exposure = 16 lines x15 bins x60 pixels x12 bits /10 kbits/s Pointing: to a bright point. Location must be known from EIT or Yohkh images Flags: Will be run in response to interinstrument or internal flag Solar Feature Tracking: Yes Product: 60 x 60 arcmin image in 16 lines. The raster area can be made larger if the number of lines are reduced or longer exposure time is used. Spectrometer: Grazing Incidence Slit: 4 x 4 arcsec Raster Area: 40 x 40 arcmin Step (DX, DY) 4 arcsec, 4 arcsec Raster Locations: 10 x 10 Exposure Time: 15 s Duration of raster: 1525 sec Number of rasters: 1 Total duration: 25.4 min Line selection: full GIS output Bins Across Line: N/A Telemetry/Compression: straight copy 13 s/exposure Pointing: to a bright point - the same location as NIS from NIS, EIT or Yohkoh image Flags: Will be run in response to interinstrument or internal flag Solar Feature Tracking: Yes Product: A 40 x 40 arcsec image of a bright point, full GIS output. Practice will show whether 2x2 slit is preferable in order to obtain finer spatial details even at the expense of increasing the duration of the raster. For a small BP, if the pointing accuracy is good, the area of the raster can be reduced to 20x20 arcseconds. *** SUMER Operations: *** First, a multiple spectroheliogramme of 300 x 120 arcsec field with moment calculation and solar rotation compensation is made, using the slit No. 2 (1 x 300 arcsec). The scan is repeated 10 times using the wavelength set No. 1 (scan Pos. 1) and no data are accumulated in the memory. If a dynamical event is diagnosed (the average line intensity is greater or equal to 5 times that of the background), the scan position is marked. Normally, several BP's should exist in a field of size 300 x 120 arcsec. The position can be later compared with simultaneous magnetic field and X-ray maps. Next, the programme switches into static mode, the new pointing position is taken and 10 scans are performed around this new position. The scan is repeated with all line sets. 25 wavelength pixels around line centers at 10 x 10 spatial pixels are stored. Hence, 11 lines x 25 wavelength pixels x 10 x 10 spatial pixels = 25.000 numbers (0.03 MB) are transmitted. The scan is repeated 130 times. If a dynamical event is diagnosed in the EOF, a flag and the scan position have to be commanded. Following this, the programme switches to a small scan mode, i.e., the new pointing position is taken and only 24 x 0.76 arcsec steps will be scanned. Spectra will be transmitted in format F30 (11 x 0.5 s) and the integration time is 1 s. The small scan mode takes 60 minutes and requires 4 MByte of memory. Parameter List for SUMER Study: STUDY_8_1_2_28 Item # 0 ------------------------------------------------- You have selected (Irrelevant points are not listed.): 1. Interruption or flag mode: Interruption by ground command. 2. Slit 2 with 1*300 arcsec^2. 3. Point to QUIET SUN, CORONAL HOLE SOHO roll angle: 0.000000 deg 4. Solar rotation: Standard compensation. 5. Binning (spectral) = 1 (spatial) = 1 6. Compression: 11. Gauss_b2 (0.96 s). 7. Reference pixel 1: 140 on detector A Flat-field correction: ON Ion(s) in band 1: C I .... 1253.47 Angstroem N V .... 1242.80 Angstroem MG X .... 624.943 Angstroem FE XII .... 1242.01 Angstroem N V .... 1238.82 Angstroem O V .... 1218.41 Angstroem Spectral window(s) (pixel): 50 8. Image format: Format #41 (2*360, I2); 6 time(s) 9. Spectrohelio mode: Spectrohelio 3 Scans back and forth. Integration time: 6.00000 s Step size: 0.760000 arcsec or 2 units. Step number: 150 Step mode: Normal steps Repetition number: 10 Staggering: 1 17. Your selection requires a telemetry rate of: 11.5200 kbit/s Bitrate: 10.0000 kbit/s This item will run for approximately: 154.721 minutes and will cover a solar area defined by 300 px time(s) 114.000 arcsec^2 Note that the memory monitoring and the run times are not very accurate. The run times just give the total exposure times with a margin of 1%. More detailed information can be provided by the SUMER Simulator. All items up to now will run for approximately: 154.721 minutes You will use for this item: 1.88632 MB out of which 0.000000 MB are for uncompressed images. You will have used in total: 1.88632 MB out of which 0.000000 MB are for uncompressed images. Parameter List for SUMER Study: STUDY_8_1_2_28 Item # 1 ------------------------------------------------- You have selected (Irrelevant points are not listed.): 1. Interruption or flag mode: Interruption by ground command. 2. Slit 2 with 1*300 arcsec^2. 3. Point to QUIET SUN, CORONAL HOLE SOHO roll angle: 0.000000 deg 4. Solar rotation: Standard compensation. 5. Binning (spectral) = 1 (spatial) = 1 6. Compression: 5. Quasilog_min_max (0.92 s). 7. Reference pixel 1: 140 on detector A Flat-field correction: OFF Ion(s) in band 1: C I .... 1253.47 Angstroem N V .... 1242.80 Angstroem MG X .... 624.943 Angstroem FE XII .... 1242.01 Angstroem N V .... 1238.82 Angstroem O V .... 1218.41 Angstroem Spectral window(s) (pixel): 25 8. Image format: Format #30 (25*24, B1); 6 time(s) 9. Spectrohelio mode: Spectrohelio 3 Scans back and forth. Integration time: 4.00000 s Step size: 0.760000 arcsec or 2 units. Step number: 150 Step mode: Normal steps Repetition number: 10 Staggering: 1 17. Your selection requires a telemetry rate of: 7.20000 kbit/s Bitrate: 10.0000 kbit/s This item will run for approximately: 103.885 minutes and will cover a solar area defined by 24 px time(s) 114.000 arcsec^2 Note that the memory monitoring and the run times are not very accurate. The run times just give the total exposure times with a margin of 1%. More detailed information can be provided by the SUMER Simulator. All items up to now will run for approximately: 258.606 minutes You will use for this item: 0.000000 MB out of which 0.000000 MB are for uncompressed images. You will have used in total: 0.000000 MB out of which 0.000000 MB are for uncompressed images. Parameter List for SUMER Study: STUDY_8_1_2_28 Item # 2 ------------------------------------------------- You have selected (Irrelevant points are not listed.): 1. Interruption or flag mode: No interruption. 2. Slit 4 (centred) with 1*120 arcsec^2. 3. Point to BRIGHT POINT SOHO roll angle: 0.000000 deg 4. Solar rotation: Standard compensation. 5. Binning (spectral) = 1 (spatial) = 1 6. Compression: 5. Quasilog_min_max (0.92 s). 7. Reference pixel 1: 433 on detector A Flat-field correction: OFF Ion(s) in band 1: C III .... 1175.71 Angstroem Spectral window(s) (pixel): 25 8. Image format: Format #30 (25*24, B1); 1 time(s) 9. Spectrohelio mode: Spectrohelio 3 Scans back and forth. Integration time: 0.500000 s Step size: 0.760000 arcsec or 2 units. Step number: 15 Step mode: Normal steps Repetition number: 10 Staggering: 1 17. Your selection requires a telemetry rate of: 9.60000 kbit/s Bitrate: 10.0000 kbit/s This item will run for approximately: 1.58099 minutes and will cover a solar area defined by 24 px time(s) 11.4000 arcsec^2 Note that the memory monitoring and the run times are not very accurate. The run times just give the total exposure times with a margin of 1%. More detailed information can be provided by the SUMER Simulator. All items up to now will run for approximately: 260.187 minutes You will use for this item: 0.000000 MB out of which 0.000000 MB are for uncompressed images. You will have used in total: 0.000000 MB out of which 0.000000 MB are for uncompressed images. Parameter List for SUMER Study: STUDY_8_1_2_28 Item # 3 ------------------------------------------------- You have selected (Irrelevant points are not listed.): 1. Interruption or flag mode: No interruption. 2. Slit 4 (centred) with 1*120 arcsec^2. 3. Point to SAME SOHO roll angle: 0.000000 deg 4. Solar rotation: Standard compensation. 5. Binning (spectral) = 1 (spatial) = 1 6. Compression: 5. Quasilog_min_max (0.92 s). 7. Reference pixel 1: 515 on detector A Flat-field correction: OFF Ion(s) in band 1: C III .... 977.020 Angstroem Spectral window(s) (pixel): 25 8. Image format: Format #30 (25*24, B1); 1 time(s) 9. Spectrohelio mode: Spectrohelio 3 Scans back and forth. Integration time: 0.500000 s Step size: 0.760000 arcsec or 2 units. Step number: 15 Step mode: Normal steps Repetition number: 10 Staggering: 1 17. Your selection requires a telemetry rate of: 9.60000 kbit/s Bitrate: 10.0000 kbit/s This item will run for approximately: 1.58099 minutes and will cover a solar area defined by 24 px time(s) 11.4000 arcsec^2 Note that the memory monitoring and the run times are not very accurate. The run times just give the total exposure times with a margin of 1%. More detailed information can be provided by the SUMER Simulator. All items up to now will run for approximately: 261.768 minutes You will use for this item: 0.000000 MB out of which 0.000000 MB are for uncompressed images. You will have used in total: 0.000000 MB out of which 0.000000 MB are for uncompressed images. Parameter List for SUMER Study: STUDY_8_1_2_28 Item # 4 ------------------------------------------------- You have selected (Irrelevant points are not listed.): 1. Interruption or flag mode: No interruption. 2. Slit 4 (centred) with 1*120 arcsec^2. 3. Point to SAME SOHO roll angle: 0.000000 deg 4. Solar rotation: Standard compensation. 5. Binning (spectral) = 1 (spatial) = 1 6. Compression: 5. Quasilog_min_max (0.92 s). 7. Reference pixel 1: 750 on detector A Flat-field correction: OFF Ion(s) in band 1: S III .... 1533.43 Angstroem C IV .... 1550.77 Angstroem C I .... 1542.18 Angstroem Spectral window(s) (pixel): 25 8. Image format: Format #30 (25*24, B1); 3 time(s) 9. Spectrohelio mode: Spectrohelio 3 Scans back and forth. Integration time: 1.50000 s Step size: 0.760000 arcsec or 2 units. Step number: 15 Step mode: Normal steps Repetition number: 10 Staggering: 1 17. Your selection requires a telemetry rate of: 9.60000 kbit/s Bitrate: 10.0000 kbit/s This item will run for approximately: 4.27432 minutes and will cover a solar area defined by 24 px time(s) 11.4000 arcsec^2 Note that the memory monitoring and the run times are not very accurate. The run times just give the total exposure times with a margin of 1%. More detailed information can be provided by the SUMER Simulator. All items up to now will run for approximately: 266.042 minutes You will use for this item: 0.000000 MB out of which 0.000000 MB are for uncompressed images. You will have used in total: 0.000000 MB out of which 0.000000 MB are for uncompressed images. *** MDI Operations: *** MDI data from program PLAGE, giving (full-resolution) HR magnetogram + Dopplergram + intensity image every minute for Phase 1. Data should be simultaneous with coronal data due to ephemeral nature of BPs. Higher-cadence (full-resolution) data for smaller field of view is desirable for the Study Phase, Type of Analysis: - Level-1 calibration of high-resolution Dopplergrams, magnetograms, and contiuum images. - extrapolations of HR magnetograms into the corona. - Coregistration of MDI data with data from other instruments.