WSO Mean Field Observations

Mean field observations of the Sun are made at WSO each clear day. Each observation takes a little less than half an hour. Each regular observation consists of six integrations of 180 seconds. The observation is highly accurate and carefully calibrated for systematic effects by observing multiple spectral lines in different instrument configurations.

Each raw observation file is transferred to campus. The program Wdomf reads the raw observation files and collects the relevant information, storing the results sequentially in /wso/scans/mf/rawmf.ds. Every MF with sufficient data is stored in rawmf.ds See WsoMfDataset for a listing.

The number of observations as of 29 August 2019 was more than 92000. The rawmf.ds data series has been divided into files that contain 8000 measurements each.

Each month the raw mean field observations are manually inspected for quality. Obviously incorrect values are marked and the good ones are copied over into the final data series in /wso/scans/mf/mf.ds. As of 7 July 2019 there had been more than 87700 good mean field observations since 16 May 1975.

The daily measurements are averaged to provide a single daily value kept in /wso/scans/mf/mf. That data set give the mean field, estimated uncertainty, and the number of individual observations contributing to the value.

The daily values can be found at WSO Mean Field.

Programs and Files

• ~wso/src/reductions/ -- directory with source code for most analysis programs

  • Wdomf.c -- source for program that interprets WSO MF raw observation files

  • MF.monthly -- script to perform monthly data evaluation

    • tellmf.c -- generates list of recent mean field measurements for evaluation

    • addmf.c -- copies good MFs from rawmf.ds to mf.ds

    • update.c -- computes daily average mean field in mf

    • mftable.c -- prints annual table of daily mf data

• ~wso/src/ds/progs/rotplot.c -- makes Bartels plot of daily mean field

Data sets

• /wso/scans/mf/ -- directory for the MF data series

• ~wso/data/scans/mf/ -- the above is actually a link to this directory

  • /wso/scans/mf/mf -- daily magnetogram series dataset

  • /wso/scans/mf/mf.ds -- dataset with all of the good mean field measurements

  • /wso/scans/mf/rawmf.ds -- dataset with recent mean field measurements

  • /wso/scans/mf/rawmf.00001-08000 -- dataset with first 8000 mean field measurements

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