The Zeeman effect in astrophysical water masers and the observation of strong magnetic fields in regions of star formation

In several previous communications the author has described a method by which magnetic fields up to 300,000 gauss could be obtained for a duration of time of the order of 1/100 of a second. It was shown that these magnetic fields, in spite of the shortness of their duration, can be applied to the study of different phenomena such as the change of resistance, the Zeeman effect, and others. The present paper describes a number of investigations which have been made on different substances, extending the application of intense magnetic fields to the study of magnetic susceptibility and magnetostriction. The interest in measuring the susceptibility of different substances in strong magnetic fields lies mainly in seeing whether the linear law of magnetisation for ordinary para- and diamagnetic substances holds for higher fields, and also in the investigation of the saturation of paramagnetic bodies at low temperatures, with a view to determining the elementary magnetic moments. In the present communication a method of measuring the magnetic susceptibility is described and experimental results are given which verify the linear law of magnetisation for several paramagnetic and diamagnetic substances. The saturation of iron and nickel in strong fields is also studied. As will be seen later, the possibility of making these measurements in such a small fraction of time results from the increased magnitude of the phenomenon itself. The most direct method for measuring the magnetic susceptibility is to record the force on a magnetised body in an inhomogeneous magnetic field. In the usual experiments at room temperature this force is only a few hundred dynes, but when fields reach the magnitude of 300 kilogauss the force becomes several grams, and is then sufficiently large to be measured with fair accuracy even in short times of the order of 1/100 of a second. In this paper a special type of balance will be described by which these measurements are made possible.

Download Full-text

The Zeeman Effect in Strong Magnetic Fields

Nature ◽

10.1038/114273b0 ◽

1924 ◽

Vol 114 (2860) ◽

pp. 273-273 ◽

Cited By ~ 2

Author(s):

P. KAPITZA ◽

H. W. B. SKINNER

Keyword(s):

Magnetic Fields ◽

Zeeman Effect ◽

Strong Magnetic Fields

Download Full-text

Magnetic fields in the non-masing ISM

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307012550 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 47-54

Author(s):

Richard M. Crutcher

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Magnetic Fields ◽

Field Strength ◽

Magnetic Field Strength ◽

Linear Polarization ◽

Formation Process ◽

Molecular Clouds ◽

Zeeman Effect ◽

Flux Ratio

AbstractObservations of the Zeeman effect in OH and H2O masers provide valuable information about magnetic field strength and direction, but only for the very high density gas in which such masers are found. In order to understand the role of magnetic fields in the evolution of the interstellar medium and in the star formation process, it is essential to consider the maser results in the broader context of magnetic fields in lower density gas. This contribution will (very briefly) summarize the state of observational knowledge of magnetic fields in the non-masing gas. Magnetic fields in H I and molecular clouds may be observed via the Zeeman effect, linear polarization of dust emission, and linear polarization of spectral-line emission. Useful parameters that can be inferred from observations are the mass-to-flux ratio and the scaling of field strength with density. The former tells us whether magnetic fields exert sufficient pressure to provide support against gravitational contraction; the latter tells whether or not magnetic fields are sufficiently strong to determine the nature (spherical or disk geometry) of the contraction. Existing observations will be reviewed. Results are that the strength of interstellar magnetic fields remains roughly invariant at 5-10 microgauss between densities of 0.1 cm−3 < n(H) < 1,000 cm−3 but increases proportional to approximately the square root of density at higher densities. Moreover, the mass-to-flux ratio is significantly subcritical (strong magnetic support with respect to gravity) in diffuse H I clouds that are not self-gravitating, but becomes approximately critical in high-density molecular cloud cores. This suggests that MCs and GMCs form primarily by accumulation of matter along magnetic field lines, a process that will increase density but not magnetic field strength. How clumps in GMCs evolve will then depend crucially on the mass-to-flux ratio in each clump. Present data suggest that magnetic fields play a very significant role in the evolution of molecular clouds and in the star formation process.

Download Full-text

Magnetic Fields in Molecular Clouds—Observation and Interpretation

Galaxies ◽

10.3390/galaxies9020041 ◽

2021 ◽

Vol 9 (2) ◽

pp. 41

Author(s):

Hua-Bai Li

Keyword(s):

Star Formation ◽

Magnetic Fields ◽

Molecular Clouds ◽

Zeeman Effect ◽

Ambipolar Diffusion ◽

Grain Alignment ◽

The Past ◽

Turbulence Velocity ◽

Cloud Cores ◽

Dust Grain

The Zeeman effect and dust grain alignment are two major methods for probing magnetic fields (B-fields) in molecular clouds, largely motivated by the study of star formation, as the B-field may regulate gravitational contraction and channel turbulence velocity. This review summarizes our observations of B-fields over the past decade, along with our interpretation. Galactic B-fields anchor molecular clouds down to cloud cores with scales around 0.1 pc and densities of 104–5 H2/cc. Within the cores, turbulence can be slightly super-Alfvénic, while the bulk volumes of parental clouds are sub-Alfvénic. The consequences of these largely ordered cloud B-fields on fragmentation and star formation are observed. The above paradigm is very different from the generally accepted theory during the first decade of the century, when cloud turbulence was assumed to be highly super-Alfvénic. Thus, turbulence anisotropy and turbulence-induced ambipolar diffusion are also revisited.

Download Full-text

Hochtemperatur-Mikrowellenspektrometer für Zeeman-Effekt-Messungen an diamagnetischen Molekeln

Zeitschrift für Naturforschung A ◽

10.1515/zna-1973-3-420 ◽

1973 ◽

Vol 28 (3-4) ◽

pp. 458-463

Author(s):

R. Honerjäger ◽

R. Tischer

Keyword(s):

Magnetic Susceptibility ◽

High Temperature ◽

Magnetic Fields ◽

Zeeman Effect ◽

Absorption Cell ◽

Vibrational States ◽

Magnetic Susceptibility Anisotropy ◽

Strong Magnetic Fields ◽

Upper Limit ◽

Microwave Spectrometer

AbstractA high-temperature microwave spectrometer has been developed for Zeeman effect measurements in strong magnetic fields up to 50 kG. The absorption cell is placed in a superconducting solenoid and can be heated as high as 1200 °C. The gJ-factor and the magnetic susceptibility anisotropy of TIF, CsF and CsCl, the gJ-factor of CsBr, and an upper limit for the value of the gJ-factor of CsI have been measured. The molecules CsF and CsCl were also studied in higher vibrational states.

Download Full-text

The Zeeman and Paschen-Back effects in strong magnetic fields

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.1938.0114 ◽

1938 ◽

Vol 167 (928) ◽

pp. 1-15 ◽

Cited By ~ 13

Author(s):

Piotr Leonidovich Kapitza ◽

P. G. Strelkov ◽

E. Laurman

Keyword(s):

Magnetic Fields ◽

Experimental Error ◽

Applied Field ◽

Zeeman Effect ◽

Spectral Lines ◽

Strong Magnetic Fields ◽

Current Impulse ◽

Accumulator Battery ◽

Small Capacity ◽

The Magnetic Field

The Zeeman effect in strong magnetic fields was first studied by Kapitza and Skinner (1925), the fields being obtained by a method developed by one of us (Kapitza 1924), in which an accumulator battery of small capacity was discharged through a coil. In this way it was possible to obtain magnetic fields up to 140,000 gauss during a time of 1/100 sec. It turned out that in such fields the majority of the spectral lines which were studied, split up (within the limits of experimental error) proportionally to the applied field, in accordance with the theory which had previously been verified only in weaker magnetic fields. An exception, however, was the zinc line at 4680 A, which gave a splitting about 10% greater than that predicted by the theory, this discrepancy being outside the limits of experimental error. Since then the method of producing strong magnetic fields has been considerably developed (Kapitza 1927); instead of the discharge of an accumulator the powerful current impulse from a short-circuited generator has been used, which has made possible the production of fields more than twice as great as those formerly obtained, and moreover, in considerably larger volumes. A the same time the technique of measuring the magnetic field has also been improved. Using these improvements we have made a new investigation of the Zeeman effect in fields up to 320,000 gauss, in which we have been able to increase considerably the accuracy of the measurements, and to explain the cause of the discrepancies previously found. We have also been able to investigate the Paschen-Back effect and to verify the theory of this effect.

Download Full-text

Polarized Radiation from White Dwarfs and Atoms in Strong Magnetic Fields

Symposium - International Astronomical Union ◽

10.1017/s0074180900100087 ◽

1974 ◽

Vol 53 ◽

pp. 287-300

Author(s):

R. F. O'Connell

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Cross Section ◽

White Dwarfs ◽

Zeeman Effect ◽

Initial Response ◽

Model Atmosphere ◽

Radiation Absorption ◽

Strong Magnetic Fields ◽

Polarized Radiation

We present the recent results of our continuing program of investigation of the behavior of matter in strong to super-strong magnetic fields (B ∼ 106−1012 G). This work was motivated by the discovery of strong magnetic fields (B ∼ 107 G) in some white dwarfs and the likely existence of super-strong fields (B ∼ 1012 G) in pulsars. Magnetic white dwarfs were discovered from observations of the continuous spectrum and one of the most intriguing challenges for the theorist is to provide an explanation for the observed wavelength dependence of the fractional circularly and linearly polarized radiation. Our initial response to this question was the determination of an exact solution of Kemp's harmonic oscillator model. These results are used as input to the ATLAS model atmosphere program and then comparison is made with observations. The disparities still existing between theory and observation convince us of the necessity for developing a new model of the continuum radiation, two likely possibilities being photoionization and free-free absorption. This leads us to present a general formulation of radiation absorption and emission processes in a magnetic field. Next we calculate the cross section for the photoionization, correct to first order in B. For the purpose of obtaining exact results for this cross section, the effect of a magnetic field on the energy spectrum and wave functions of hydrogen, helium, etc. must be obtained. The results for hydrogen are presented here. They will be useful also in determining accurate values for the displacements due to the quadratic Zeeman effect in the line spectra of DA stars, particularly for the higher excited states.

Download Full-text

Hot-star wind models with magnetically split line blanketing

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834097 ◽

2018 ◽

Vol 620 ◽

pp. A176 ◽

Cited By ~ 1

Author(s):

J. Krtička

Keyword(s):

Magnetic Fields ◽

Zeeman Effect ◽

Zeeman Splitting ◽

Magnetic Line ◽

Hot Stars ◽

Strong Magnetic Fields ◽

Flux Variability ◽

Line Splitting ◽

Line Force ◽

The Magnetic Field

Fraction of hot stars posses strong magnetic fields that channel their radiatively driven outflows. We study the influence of line splitting in the magnetic field (Zeeman effect) on the wind properties. We use our own global wind code with radiative transfer in the comoving frame to understand the influence of the Zeeman splitting on the line force. We show that the Zeeman splitting has a negligible influence on the line force for magnetic fields that are weaker than about 100 kG. This means that the wind mass-loss rates and terminal velocities are not affected by the magnetic line splitting for magnetic fields as are typically found on the surface of nondegenerate stars. Neither have we found any strong flux variability that would be due to the magnetically split line blanketing.

Download Full-text

THE ZEEMAN EFFECT IN STRONG MAGNETIC FIELDS (A)

Collected Papers of P.L. Kapitza ◽

10.1016/b978-0-08-010744-8.50018-x ◽

1964 ◽

pp. 112-113

Keyword(s):

Magnetic Fields ◽

Zeeman Effect ◽

Strong Magnetic Fields

Download Full-text

Over-tension in a Condenser Battery during a sudden discharge

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100012226 ◽

1926 ◽

Vol 23 (2) ◽

pp. 144-149

Author(s):

P. Kapitza

Keyword(s):

Magnetic Fields ◽

Main Part ◽

Zeeman Effect ◽

Strong Magnetic Fields ◽

Maximum Tension ◽

Spark Gap ◽

Over The Top ◽

Intense Source

In the recent experiments on the Zeeman effect in strong magnetic fields made by Mr H. W. B. Skinner and myself for obtaining an intense source of light for a small fraction of a second, we have been discharging a condenser battery consisting of 32 Leyden jars connected in parallel with a capacity of one-tenth of a microfarad. The discharge was made through a small spark gap by means of an oil immersed switch (the details of this arrangement are to be found in the above-mentioned paper). When the discharge was produced a curious phenomenon was sometimes observed. After the battery had been charged to its maximum tension, and the switch had been put into operation, only a small spark occurred in the spark gap, and the main part of the discharge went over the top of the insulators of one of the Leyden jars.

Download Full-text