IVM Magnetic Field Observations =============================== This IVM program has two components: the first ("Survey" mode) is used when solar flare activity is low and the second ("Flare" mode) is used when the flare activity is high. We define the level of activity using the flare probabilities in the NOAA/USAF report. A high level means 30% or greater probability of an M class flare. SURVEY MODE. When there is low solar activity, the best use of the IVM is to take several magnetograms per day of all active regions. This gives us a good view of the evolution of the large scale magnetic fields in all regions, which we have never been able to obtain in the pre-IVM days. FLARE MODE. When there is a high level of activity, the best use of the IVM is to observe the magnetic field in the single most active region repeatedly. This allows us to search for rapid changes in the magnetic field associated with solar flares. Low Activity: Repeated Active Region Survey (SURVEY MODE) ========================================================= IVM: DLM03 MCCD: JPW05 Goal: - ----- Document the magnetic structure of all regions on the solar disk for comparison with Yohkoh data. Key Features of the Setup: - -------------------------- - - The IVM is used to repeatedly observe every NOAA-numbered active region each day, as well as any newly emerging regions. - - The MCCD is run on the single most active region, independent of the survey that the IVM is carrying out. Observing Procedures: - --------------------- - - If the center of an active region is greater than 70 degrees from suncenter then we don't observe that region because the data would not be usable. - - We want to see how all active regions evolve over time so our goal is to get at least 3 surveys fairly evenly spaced throughout the observing day. If there is time, more than three surveys would be scientifically useful, but there is no need to run continuously. - - The IVM should be calibrated before starting each survey, but not more than once every two hours: recenter the line, run calrtd (once per day), take flats and darks, run calseq. Since speed is not issue in Survey Mode, we take all the calibrations before starting the observations. This is different from Flare Mode where speed is critical and some calibrations are postponed until the first dataset has been recored. IVM Survey Mode Time line: Start of Day: etalon calrtd dark flat calseq Active Region Survey |---> etalon Repeat | dark Until | flat End | calseq of | Observing | Active Region Survey Day | | Wait | | ------- High Activity: Flare Related Changes in Currents (FLARE MODE) ============================================================= IVM: DLM03 MCCD: JPW05 GOAL: - ----- Discover changes in electric currents during flares. KEY FEATURES OF THE SETUP: - -------------------------- After an initial survey of all NOAA numbered active regions on the disk, the IVM is used to repeatedly observe the magnetic field of the single most active region. This allows the electric current to be measured with relatively high time cadence. We will use these data to search for changes in the electric current which are related to solar flares. The MCCD must be observing the same region as the IVM. OBSERVING PROCEDURES: - --------------------- - - Before beginning the observations of the single most active region, make a single survey of all active regions as in the survey mode. - - After the survey is completed, only the single most active region should be observed, and these observations should continue as long as possible. There is no point in "flare-chasing"; by the time you see a flare in another region, it is too late. - - The spectrum observed by the IVM should be centered on the iron 6301 or 6302 line. Use 256x256 images, binned by 2's. Set the nmags parameter in the IVM program (DLM03) to a number which allows the IVM to run continuously for about 2 hours. This will be about 30 since the magnetograms are obtained about one per four minutes. - - The IVM data should be writted directly to tape. Check the appropriate box on the setup screen. - - After 2 hours of continuous operation the IVM should be stopped to take calibration data. - - The calibrations for "flare mode" are a bit different from "survey mode". First, check the etalon and run calrtd at the beginning of the day, then do the survey, followed by a dark, flat, and calseq. This prioritizes the data correctly, i.e. we can use the survey magnetograms without dark/flat/calseq if we have to, but we have to check the spectrum and run calrtd to make sure nothing weird has happened to the retarders. Following calseq, check and adjust the etalon. Set up and run the rapid-cadence sequence for about two hours. Then take a dark and a flat. Repeat etalon/magnetograms/dark/flat. This gets us four hours of flare-mode data. Now run calseq again. Repeat this sequence until dark. With this scheme we get calseq every four hours, which should be more than enough. IVM Flare Mode Time line: Start of Day: etalon calrtd Active Region Survey dark flat calseq |-----------> |-> etalon | | | | flare-mode (2 hours) Repeat | Repeat | Until | Once | dark End | | flat Of | | | Observing | ------- Day | | calseq | | ---------------------