On the magnetic fields and motions in sunspots at different atmospheric levels

Three dimensional vector magnetic field structure throughout the chromosphere above an active region is deduced by combining high resolution Hc~ filtergrams with a simultaneous digital magnetogram. An analog model of the field is made with 400 metal wires representing fieldlines which are assumed to outline the Hc~ structure. The height extent of the field is determined from vertical field gradient observations around sunspots, from observed fibril heights and from an assumption that the sources of the field should be largely local. After digitization the magnetic field H matrix is retrieved. Electric current densities j are computed from j curl H. The currents (typically I0 mA m -a) flow in patterns not similar to observed features and not parallel to magnetic fields. Lorentz forces are computed from F--j •The force structures correspond to observed solar features and a series of observed dynamics may be expected: downward motion in bipolar areas in lower chromosphere, an outflow of the outer chromosphere into the corona with radially outward flow above bipolar plage regions (where coronal streamers are observed) and motions of arch filament systems. Observed current structure and magnitude agree well with previous vector magnetograph observations but disagree with theoretical current-free or force-free concepts. A dynamic chromosphere with electromagnetic forces in action is thus inferred from observations.

Section: Height Extent Of the Fieldmentioning

confidence: 94%

Magnetic field and electric current structure in the chromosphere

Dravins

1974

“…These were taken in three successive series simultaneously in Ha and Fe I A6302.499 A by scanning with polarizing optics (Abdussamatov, 1970) when the sunspot was closely on the central meridian. The isothermic four-camera spectrograph attached to the Pulkovo horizontal telescope was used, the dispersion equalled 3.7 mm ~-1 at Ha and the diameter of the solar image 162 mm.…”

Section: Observationsmentioning

confidence: 99%

“…The isothermic four-camera spectrograph attached to the Pulkovo horizontal telescope was used, the dispersion equalled 3.7 mm ~-1 at Ha and the diameter of the solar image 162 mm. The method of observation and reduction has been described in detail in Abdussamatov (1970Abdussamatov ( , 1971. The method of scanning sunspots simultaneously in two spectral lines practically provides for a simultaneous investigation of the spatial (three-dimensional) structure of mass motion in large areas of sunspot groups.…”

Section: Observationsmentioning

confidence: 99%

“…Particularly large complex sunspots require further investigation. It is known that the Evershed flow occurs mainly in dark filaments (Beckers and Schr6ter, 1968b;Abdussamatov and Krat, 1970;Harvey, 1971). Penumbral filaments are nearly horizontal and according to Beckers and Schr6ter (1969) the bright and dark filaments show slightly different inclinations.…”

Section: Introductionmentioning

confidence: 99%

“…The inclination of the Evershed velocity with respect to the solar surface does not exceed 15-30 ~ (e.g. Abdussamatov, 1970;Mamadazimov, 1970).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On mass flow in a complex sunspot

Abdussamatov

1980

Self Cite

Vertical gradients of the magnetic fields in active regions

Gopasyuk

Тарасова

et al. 1996

In this paper, we describe the results of an investigation of magnetic field structures in two active regions. The photospheric magnetic fields were measured simultaneously in all three components with the Crimean vector magnetograph in the Fc 15250 line. In our analysis, we compare the observed magnetic field with the potential field. The potential field vector was calculated according to the potential-field theory, and the Hz component was taken as a boundary condition. From these data vertical gradients are calculated from the condition div H = 0. Averaged gradients of both fields increase with the H~ field intensity and within the error limits they do not differ from one another for field strengths up to ~ 1200 G. For larger 1-1~ the potential field gradients become higher than those of the observed field. In large spots, observed field gradients are about two times less than those of the potential field. It is shown that this difference is connected with the observed field twisting.