Solar Magnetic Field Measurements Research Articles

Progress in the Measurement of Solar Magnetic Fields

AbstractThe historical development of optical instruments for solar physics is outlined, from white light to unpolarized and polarized monochromatic light, to Stokes profiles and simultaneous fields of view, from points to lines, plane to cube. An evolutionary series and classificaton of instruments for the solar magnetic field is described. As a next step the 2-D real time polarizing spectrograph has been proposed. The planned instruments in China for measurements of solar magnetic and velocity fields are briefly introduced.

Magnetic field measurements on the sun and implications for stellar magnetic field observations

Results of solar magnetic field measurements in plages, sunspot umbrae, and sunspot penumbrae using high spectral resolution, unpolarized infrared H band spectral data are presented. A Fourier deconvolution analysis scheme similar to that utilized for stellar magnetic field measurements is adopted. As an example, a field strength of 3240 + or - 450 G is determined in a sunspot umbra combined with a value of 2000 + or - 180 G in the associated penumbra. These values are compared with a direct measurement of the spot umbra and penumbra field strengths based on the observed separation of the Zeeman components of the magnetically sensitive lines. Possible origins for the discrepancy between the results inferred by these two different techniques are discussed. The Fourier analysis results confirm the widespread occurrence of kilogauss level fields in the solar photosphere. The implications of the solar results for stellar magnetic field measurements are considered. 45 references.

Large-Scale Solar Magnetic Fields

Measurement of solar magnetic fields is reviewed. Topics covered include: large-scale magnetic surface features; the solar activity cycle and the large-scale patterns; and magnetic fields in the corona. (GHT)

New Levels and Classifications in Fe I

New 5p levels in Fe I have been found from combinations with 5s and 6s between 1.3 μm and 2.5 μm. 55 previously observed lines have been identified in this way, among them the strongest Fe I lines in the investigated region. All 3d64s(6D)5p levels are now well established. 7 previously known but unclassified levels and 9 new levels have tentatively been assigned to 3d7(4F)5p. The term designations are based on a parametric fit of the (d+s)7p energy matrix and on the observed intensities of the combinations with 5s.Arguments are given for changing the J-values of the AEL levels X2 and X3 and the subsequent identification of these levels with 3d8 3P1 and 3P2 respectively.The line at 15 648 Å, which has been suggested for measurement of solar magnetic fields, is now classified as 5s 7D1-5p 7D1 and its effective-g value can be calculated.

Measurements of solar magnetic fields by Fourier transform techniques

Fourier techniques have been exhaustively calibrated using Unno's (1956) results for the absorption profile of a simple Zeeman triplet. If a simple transformation is applied to the normalized line depths, then magnetic-field strengths and inclination angles can be measured very accurately from noisy saturated line profiles. Systematic errors caused by saturation effects can be estimated and reduced by varying one parameter. When a significant fraction of the line profile is unsplit and unpolarized, large errors may be made in measurements of low fields, unless the line is sufficiently weak. For a weak line, a vertical field of 1600 gauss can be measured to 10% accuracy even when 70% of the line profile is stray light. These stray-light errors are troublesome in measuring fields of gaps and pores but not sunspots. Numerical results of the error analysis are presented graphically.

Measurements of solar magnetic fields by Fourier transform techniques

Measurements of solar magnetic fields by Fourier transform techniques

Real Time Digital Subtraction and Enhancement of Video Pictures

Digitization and calculation on video pictures were accomplished in real time. Video pictures were subtracted and added in order to achieve an enhanced difference picture. The number n of video frames varied from 2 to 2048. Enhancement of signal-to-noise (S/N) ratio went nearly as VII, and S/N ratios of 1700:1 were obtained in about 1 min. A new design is presented to raise the digitizing rate from the present 180 kHz to 2.4 MHz in order to improve resolution. The application is to the measurement of solar magnetic fields, which are proportional to small differences between solar pictures of opposite polarization. A sensitivity increase of NTri and real time display will provide a possible solar flare warning system. Other applications are mentioned.

Spectroscopic measurements of magnetic fields on the sun

The various methods employed for the measurement of solar magnetic fields, on the basis of the Zeeman effect in the Fraunhofer spectrum, are described. The optical arrangements are discussed and illustrated. A short examination is made of the results obtained for the field strength in sunspots, and of the problem of the general magnetic field of the Sun.

Photoelectric Measurements of Solar Magnetic Fields.

Photoelectric Measurements of Solar Magnetic Fields.