Longitudinal Magnetic Field Measurements Research Articles

Integral properties of the magnetic fields of solar active regions under quiet and flare activity conditions

The well-known problem of the correlations between eruptive processes in the chromosphere and corona and peculiarities of the magnetic field structure in solar active regions (ARs) on the photospheric level are discussed in this paper. We study the time variations in the first four moments of distribution (over the field) of four integral parameters of the magnetic field of an AR. We used Huairou (PR China) and Solar Orbit Heliospheric Observatory, Michelson–Doppler Interferometer (SOHO/MDI) measurements of longitudinal magnetic fields for ten ARs. We study the following integral parameters of an AR: total magnetic flux F a, tilting angle A n, complexity parameter H u and relative total magnetic flux imbalance O v. The distributions of these parameters show essential differences between quiet and flare productive ARs. One can observe specific differences in the distributions before and during flares. The four first distribution moments take into account these differences and so they can be good quantitati...

Magnetic Models Can Not Explain The Blazhko Effect in RR Lyrae Stars

AbstractWe report a new series of high-precision Stokes V profiles and longitudinal magnetic field measurements of RR Lyrae, obtained with the MuSiCoS spectropolarimeter over a period of four years. These data provide no evidence whatsoever for a strong magnetic field in the photosphere of RRLyrae, which is consistent with Preston’s (1967) results, but inconsistent with apparent magnetic field detections by Babcock (1958) and Romanov et al. (1987, 1994). Following discussion of these disparate results, we conclude that RR Lyrae is a bona fide non-magnetic star, a conclusion which leads to the general falsification of models of the Blazkho effect requiring strong photospheric magnetic fields.

No evidence of a strong magnetic field in the Blazhko star RR Lyrae

In this paper we report a new series of high-precision (median G) longitudinal magnetic field measurements of RR Lyrae, the brightest Blazhko star, obtained with the MuSiCoS spectropolarimeter over a period of almost 4 years from 1999-2002. These data provide no evidence whatsoever for a strong magnetic field in the photosphere of RR Lyrae, a result consistent with Preston's ([CITE]) results, but inconsistent with apparent magnetic field detections by Babcock ([CITE]) and Romanov et al. ([CITE], [CITE]). Following discussion of these disparate results, we conclude that RR Lyrae is a bona fide non-magnetic star, a conclusion which leads to the general falsification of models of the Blazkho effect requiring strong photospheric magnetic fields. Furthermore, due to the 4 year baseline of our observations, we can also dismiss the hypothesis that RR Lyrae undergoes a 4-year “magnetic cycle”. Therefore the origin of the observed 4–year modulation of RR Lyrae remains unexplained, and we stress the need for additional theoretical efforts to come to a better understanding of this phenomenon.

No magnetic field variations with pulsation phase in the classical Cepheid starη Aquilae

We report new high resolution Stokes V spectropolarimetry and ultra-high precision longitudinal magnetic field measurements of the pulsating classical Cepheid η Aql which fail to corroborate the report by Plachinda ([CITE]) of a ~100 G magnetic field in this star.

Magnetic Power Spectra Derived from Ground and Space Measurements of the Solar Magnetic Fields

We study magnetic power spectra of active and quiet regions by using Big Bear Solar Observatory and SOHO/MDI measurements of longitudinal magnetic fields. The MDI power spectra were corrected with Gaussian Modulation Transfer Function. We obtained reliable magnetic power spectra in the high wave numbers range, up to k=4.6 Mm−1, which corresponds to a spatial scale l=1.4 Mm. We find that the occurrence of the spectral discontinuity at high wave numbers, k≥3 Mm−1, largely depends on the spatial resolution of the data and it appears at progressively higher wave numbers as the resolution of the data improves. The spectral discontinuity in the raw spectra is located at wave numbers about 3 times smaller than wave numbers, corresponding to the resolution of the data, and about 1.5–2.0 times smaller in the case of the noise- and-resolution corrected spectra. The magnetic power spectra for active and quiet regions are different: active-region power spectra are described as ∼k −1.7, while in a quiet region the spectrum behaves as ∼k −1.3. We suggest that the difference can be due to small-scale dynamo action in the quiet-Sun photosphere. Our estimations show that the dynamo can generate more than 6% of the observed magnetic power.

Vector magnetic field changes associated with X-class flares

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The extraordinary magnetic variation of the helium-strong star HD 37776 - A quadrupole field configuration

view Abstract Citations (89) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The extraordinary magnetic variation of the helium-strong star HD 37776 : a quadrupole field configuration. Thompson, I. B. ; Landstreet, J. D. Abstract Extensive longitudinal magnetic field measurements of the helium-strong B star HD 37776 have been obtained. It is found that when these data are phased with a period of 1.538 days derived from helium line variations, an extraordinary double-wave magnetic curve results. It is argued that this curve is in fact the real magnetic curve of the star and that HD 37776 is therefore the first known star in which a quadrupole-like field geometry dominates the usual dipole found in other magnetic stars. Publication: The Astrophysical Journal Pub Date: February 1985 DOI: 10.1086/184424 Bibcode: 1985ApJ...289L...9T Keywords: B Stars; Magnetic Field Configurations; Magnetic Stars; Periodic Variations; Quadrupoles; Stellar Magnetic Fields; Helium; Spectral Energy Distribution; Astrophysics full text sources ADS | data products SIMBAD (1)

On the Time Fluctuations of Magnetic Fields

The simultaneous measurements of longitudinal magnetic fields in lines λ5250 and λ6103, the line of sight velocities and intensities in these lines at some fixed point (area 2″.3 × 4″.5) within the moderately strong (∼ 100 G) areas of solar magnetic fields were examined to find the possible fluctuations of m.f. with time. No fluctuations were found which cannot be correlated with the simultaneously measured seeing conditions such as contrast, image excursions and scintillations for characteristic periods less than 5m. The possibility of ∼ 5m oscillations of magnetic fields correlated with the well known sight-line velocity oscillations is pointed out.

Magnetic Fields in Polar Prominences

The results of longitudinal magnetic field measurements in polar prominences (PP), obtained by Rust during 1964–1965 and by the author during 1966, 1969 and 1970, are considered. The magnetic field configuration in PP is similar to that of an arc. In opposite branches of such an arc the magnetic field has different polarities that do not coincide with the magnetic field polarity in current cycle BMR's. The magnetic field value increases as the angle between the line of sight and filament long axis grows. PP's reflect the behaviour of the border line between the magnetic fields of preceding and current cycles.

Magnetic and Doppler oscillations in active regions

With the Capri magnetograph of the Fraunhofer Institute simultaneous measurements of sightline velocities and longitudinal magnetic fields have been carried out, in order to investigate the dependence of the 300-sec oscillation of sightline velocities on the magnetic-field strengths, and the oscillatory behavior of the latter, if there is any.

Pulsed Magnetic Field Studies of the Negative Magnetoresistivities of Dilute Ti-Mn and Cu-Mn Alloys at Low Temperatures

Measurements of the low-temperature negative magnetoresistivities of dilute Ti-Mn and Cu-Mn alloys have been extended to higher magnetic fields by means of pulsed magnetic field techniques. At 4.2\ifmmode^\circ\else\textdegree\fi{}K the observed decreases of resistivity in a transverse magnetic field of 130 kG are approximately 5, 23, and 26% of the zero-field resistivity, respectively, for Ti-0.101 at.% Mn, Ti-1.00 at.% Mn, and Cu-1.00 at.% Mn. Saturation of the negative magnetoresistivity is essentially complete in Ti-0.101 at.% Mn below 100 kG. A trend toward saturation is strongly evident in Ti-1.00 at.% Mn and is less marked in Cu-1.00 at.% Mn. Close agreement between transverse and longitudinal magnetic field measurements is observed in all cases. The Ti-Mn data are in accord with earlier evidence which suggests that in these alloys there exist localized magnetic states which interact with the conduction electrons.