Magnetic Field/Electric Field Instruments
VECTOR MAGNETOGRAPHS
The MSFC magnetograph was developed in the early 1970s and has been operating as a vector system since 1976 in support of NASA space missions (Solar Maximum Mission and Spacelab), rocket and balloon experiments, and joint ground-based observations. The magnetograph consists of a symmetric 30-cm Cassegrain system which has a field of view of 6 x 6 arc-min giving an effective pixel size of 2.8 x 2.8 arc- sec in the 2 x 2 pixel-binning mode of the CCD camera. The absorption line Fe I 5250.2 is selected by a Zeiss birefringent filter (FWHM = 0.125A). The polarimeter consists of quarter-wave plates, a KD*P electro-optical modulator, and an analyzer provided by the sheet polarizers in the Zeiss filter. The resulting magnetic field sensitivities are 5 and 125 G in the line-of-sight and transverse components, respectively, with a temporal cadence of 5 min. The Zeiss filter can be tuned +/- 8 Angstroms about the Fe I 5250.2 line. This allows the three Fe I lines at 5247.0, 5250.2, and 5250.6 to be selected for performing flux tube analyses. Information on the method of calibration used for the interpretation of MSFC vector magnetograph data can be found in NASA TM-4048, 'The SAMEX Vector Magnetograph - A Design Study for a Space- Based Solar Vector Magnetograph' (M. J.Hagyard, G. A. Gary, and E. A. West, 1988). The capabilities of the MSFC vector magnetograph were extended in September 1989 by the addition of a coaligned H-alpha telescope with a CCD camera. This telescope was the engineering-backup model of the Skylab ATM H-alpha 1 telescope. The system is a 17-cm Cassegrain which feeds a Fabry-Perot filter with a 0.7 A bandpass. The H-alpha system provides video images of chromosphe- ric activity that are cospatial and cotemporal with the vector magnetograms. Research programs carried out with the coaligned instruments include studies of magnetic morphology, evaluation of magnetic shear at flare sites, calculation of vertical electric currents, analysis of magnetic field submergence/emergence, studies of magnetic canopies, evaluation of magnetic energy, coronal field extrapolations, Stokes profile analysis, and the study of magneto-optical effects. Because the MSFC magnetograph is a dedicated system, the MSFC team can observe each day that weather permits. The observational data are reported in: 'The MSFC Solar Observatory Report,' (published twice a year and distributed to the solar community). For further information on the MSFC Solar Vector Magnetograph, link to the web at "http://science.msfc.nasa.gov/ssl/pad/solar/magmore.htm"