Science JOPs: JOP 031
Title: SOLAR WIND ABOVE STREAMERS
Lead Person: Ester Antonucci
Authors: E. Antonucci and J. Kohl (UVCS), A. Fludra (CDS), T. Hoeksema (MDI), P. Lemaire (SUMER), R. Howard (LASCO)
SOHO Instruments involved: UVCS, SUMER, CDS, LASCO, EIT, MDI
Collaborating GBO: Possible collaborations: white light coronagraphs (polarization), radio observatories
Last update: May 1996
First proposed: SPWG January 1995
SOLAR WIND ABOVE STREAMERS (JOP 031)
To identify and characterize the coronal sources of the solar wind: Streamers contribution
The primary scientific goals of the observing program are the following:
(See JOP 006)
This observing program is dedicated to streamers. The characterization of the base of the streamer requires disk observations during a few days before the streamer appears at the limb.
This program is limited to:
Pointing and Target Selection
It is desirable to begin to observe the target region (streamer) in the inner corona, during a period of 2/3 days before arrival at the limb, in order to fully characterize the solar wind source. The coronagraphs shall start the joint observation when the target is approaching the west limb, continuing for the period of visibility at the west limb.
The UVCS observations consists of a mirror scan.
Channel I: Ly , Fe XII 1242, N V 1239, S X
1196 (S X 1213) profiles
Channel II: O VI 1032, O VI 1037, Mg X 610, Ly 1026, Si XII 499, Si XII 521, Ly profiles
Channel III: VL polarized 4500--6000 Å.
To determine electron density, proton/ion kinetic temperature, outflow velocity.
Observing Sequence JOP-31
N--Predicted Counts )
CDS can provide information about the temperature and density of a streamer, its stability, and detect its long term evolution. A comprehensive line list is possible thanks to a long exposure time.
Spectrometer: Normal Incidence Slit: 4 x 240 arcsec Raster Area: 4 x 4 arcminute Step (DX, DY) 4 arcsec, 0 arcsec Raster Locations: 60 x 1 = 120
Exposure Time: 250 s
Duration of raster: 255 minutes Number of rasters: 1 Total duration: 4 hours 15 minutes (incl. overheads)
Line selection: 14 lines as for the Coronal Hole: Fe VIII (370.43), Fe X (365.57), Fe XI (356.54), Fe XII (364.47), Fe XII (338.17), Fe XIII (348.18), Fe XIV (334.17), Fe XVI (335.40), Si IX (349.87), Si IX (341.95), Mg IX (368.06), Mg X (624.94)
plus O III (599.59), O IV (554.52), O V (629.73), Ne VI (562.83), Mg VIII (315.02)
Bins Across Line: 21
Telemetry/Compression: truncate to 12 bits 58 s/exposure = 18 lines x21 bins x120 pixels x12 bits /10 kbits/s
Pointing: to a streamer - field of view including cusp
Flags: Will not be run in response to inter-instrument flag and will not be run with CDS as flag Master
Solar Feature Tracking: Not required
Two different scans will be done: one for disc observation, and another for off-limb observations:
on disc identical to JOP 014,
off-limb identical to JOP 014 excepted that the raster may be extended to 8' x 5' and then offset (in solar Y axis) by 5' for a new scan (if needed by the size of the streamer).
As in JOP 006.
The LASCO primary observables for coronal hole structures will be to determine electron densities, kinetic temperatures, velocities associated with the hole, structures within the hole and structures at the boundaries of the hole. The observations are from the C1 telescope. The C2 observations to obtain electron densities will be taken as part of the normal LASCO synoptic program.
Telescope: C1 Passbands: Fe X and Fe XIV FOV: 512 x 256 pixels ( 48 x 24 arc min) Wavelengths: 6 + 1 off band Resolution: Full spatial resolution Compression: Rice (lossless) TM Downlink: 21 minutes Cycle Repeat: Once at beginning, middle and end of period
A cycle will require several repeated exposures at each wavelength step with on-board summing to be able to obtain a total exposure time at each wavelength step of about 5 minutes.