E. A. Rudenchik

Fractal properties of solar magnetic fields

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution of active and quiet regions considered as global structures. To study the spatial structure of sunspots, we use a well-known method of determining the fractal dimension based on an analysis of the perimeter—area relation. To analyze the fractal properties of the spatial magnetic field distribution over the solar surface, we use a technique developed by Higuchi. We have revealed the existence of three families of self-similar contours corresponding to the sunspot umbra, penumbra, and adjacent photosphere. The fractal coefficient has maxima near the umbra—penumbra and penumbra—photosphere boundaries. The fractal dependences of the longitudinal and transverse magnetic field distributions are similar, but the fractal numbers themselves for the transverse fields are larger than those for the longitudinal fields approximately by a factor of 1.5. The fractal numbers decrease with increasing mean magnetic field strength, implying that the magnetic field distribution is more regular in active regions.

Method for absolute calibration of reference plates for interferometric inspection of surfaces

A method for absolute calibration of reference plates of interferometers for measuring surface profiles of optical elements is described. It is based on the solution of the inverse problem of reconstruction of a surface profile from the data of relative measurements of three plates by way of minimizing the goal function. The method takes into account the gravitational sagging of the reference plate and allows one to obtain its profile with an accuracy of ∼λ/1000 for λ=6328 Å. The calibration algorithm as well as theoretical calculations and experimental results are presented.

A new controlling system for the solar tower telescope of IZMIRAN: I. Guide

A new guiding system for the solar tower telescope is described. Two mutually perpendicular CCD arrays are used as photodetectors. The guide provides a positional error of no larger than 0.2″ in a frequency band of 0–10 Hz. The software allows for referring the spectrograph slit position to solar coordinate systems and provides for various guide operation modes.

Second version of the IZMIRAN solar spectromagnetograph. Part I. Instrument design

The second version of the IZMIRAN solar spectromagnetograph (SM), which is designed for measuring the full vector of the magnetic field and the line-of-sight velocities in the solar photosphere, is described. In contrast to the conventional schemes, the described SM uses the parallel analysis of the spectrum and polarization of optical radiation. The latter could be performed thanks to the method of precise calibration of circuits with multielement photodetectors. The new scheme of the SM allows measurements of the Stokes parameters for two magnetically active lines with an accuracy limited by only the quantum noise of photodetectors.

Second version of the IZMIRAN solar spectromagnetograph. Part II. Algorithms for preliminary data processing

A system of experiments and an algorithm for data processing that allow elimination of systematic errors, which are caused by instrument effects of the spectromagnetograph, are described. It is shown that the residual systematic error in measuring the Stokes parameters is approximately three times lower than the statistical errors related to quantum noise of receivers.

A Solar Spectromagnetograph

A new solar spectromagnetograph for measuring the full magnetic-field vector and line-of-sight velocities is described. A new version of a polarization analyzer ensuring parallel measurements of six polarization components of spectral lines is considered. The spectromagnetograph allows the use of any algorithms for obtaining the magnetic fields vector, in particular, the Babcock algorithm and the Fourier transform technique. The sensitivity of the instrument for the longitudinal and transverse magnetic field is ∼ 3–5 and ∼ 20–30 G, respectively, and ∼10 m/s for the line-of-sight velocities.

A new controlling system for the solar tower telescope of IZMIRAN: II. A solar image motion compensator

A solar image motion compensator for the solar tower telescope is described. Two mutually perpendicular CCD linear arrays are used as photodetectors. An algorithm for forecasting the system behavior is used for generation of correction signals. Analyzing the solar image motion data obtained using the compensator and without it has shown that, thanks to its use, the total image motion value decreases to 0.5″–0.6″ in a frequency band of 0–100 Hz, being close to the amplitude of noncorrelated image motion component. The compensator operates equally effectively in both the pointing and scanning modes.