Appendix G: Joint Observing Program 2, Active Regions

RESEARCH OBJECTIVES

Study the three dimensional structure of active regions, the horizontal and vertical variation of the temperature, density, velocity, and magnetic field.

Study the short term (minutes to hours) and long term (days) evolution of the chromosphere, transition region, and corona in active regions.

Investigate the relationship between the three dimensional structure of an active region and its evolution as it relates to the production of flares and other transient phenomena.

Obtain information about the structure of the photosphere, chromosphere, transition region, and corona in and above sunspots.

Map the differential velocity fields in the chromospheric, transition, and coronal layers over active regions and other solar features.

OBSERVATIONS

X-ray filtergrams from S054 and S056 and spectroheliograms from S055 and S082A will contain information about the three dimensional structure. In addition, the spectra obtained by S055 and S082B will contain detailed information about the variation of temperature, density, and velocity with height at selected positions. White light pictures of the corona from S052 will provide a detailed description of the density structure of the corona overlying active regions. For evolutionary studies, observations will be obtained at a rate compatible with the time scale of the development of the regions.

OPERATIONAL DESCRIPTION

  1. A. Rapidly developing active region: This program will be initiated when the astronaut or PISobserve a rapidly developing active region. When the decision is made to carry out this observation, BB-5 [building block 5, a set of instructions for setting up the instruments] will immediately be carried out. BB-5, BB-6, and/or BB-10 may be repeated a number of times as determined by the PIS. If the active region is within 45° of the limb, BB-2 should be carried out as often as determined by the PIS. Which building blocks are performed will depend on the rate of development of the active region and/or the flaring rate of the region.
  2. B. Long-term evolution of an active region: The active region to be studied will be selected by the PIS on the ground and pointing information will be telemetered to the astronauts. An active region will be selected that can be studied for a minimum of 10 days and at least one limb passage. The most desirable observation would be from limb to limb.
    1. 1. When the active region is on the disk, it should be observed once per day, performing BB-4 and BB-5 on alternate days. Point ATM at different bright and dark areas of the plage. For the S055 spectra, the pointing should be adjusted so that output of detector no. 3 (grating in optical reference) is maximized for some points and minimized for some points. When the active region is within 45° of the limb BB-2 will be carried out at least once.
    2. 2. When the active region is near the limb passage BB-2 (once) will be carried out, followed by BB-5 (once), BB-6 (3 times), BB-13 (once), BB-14 (once), and BB-2 (once).
  3. C. Structure of active regions: The active region to be studied will be selected by the PIS on the ground. The ATM slit will be pointed at a number of selected positions across the active region, and BB-6, and/or BB-5, and/or BB-4, will be performed, with the number of times in each mode being selected during the mission.
  4. D. Sunspots: An active region containing large sunspots will be selected for study. If the diameter of the umbra is at least 60 arc seconds, the ATM slit will be pointed at two positions in the center of the umbra, and BB-6 plus BB-12 will be carried out (2 pointings). ATM will also be pointed at two positions in the penumbra, and BB-6 plus BB-12 performed at each point. If the diameter of the umbra is significantly less than 60 arc seconds, the above sequences may be performed without S082B.
  5. E. Chromospheric velocities: This program will be implemented in the following manner. An active region or other area of interest will be selected. The ATM slit will be pointed at the area, rolled so that the S055 scan line is east-west, and BB-18 carried out. The ATM will be rolled 90°, so that the S082B slit is parallel to the S055 scan line in BB-18, and positioned along that line to the best position for observing uniform line-of-sight plasma motion. BB-11 will then be performed. S055 and SOS82B will obtain velocity information while S054, S056, and S082B obtain information about the atmospheric structure in the region being observed.