The magnetic sun from different views: A comparison of the mean and background magnetic field observations made in different observatories and in different spectral lines

2000 ◽  
Vol 21 (3-4) ◽  
pp. 209-212 ◽  
Author(s):  
M. L. Demidov
Keyword(s):  
Magnetic Field ◽  
Spectral Lines ◽  
Field Observations ◽  
Background Magnetic Field ◽  
The Mean ◽  
Made In

The Magnetic Sun from Different Views: A Comparison of the Mean and Background Magnetic Field Observations made in Different Observatories and in Different Spectral Lines

2000 ◽  
Vol 179 ◽  
pp. 209-212
Author(s):  
M. L. Demidov
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Solar Observatory ◽  
Spectral Lines ◽  
The Sun ◽  
Background Magnetic Field ◽  
The Mean ◽  
Selection Of ◽  
Made In

AbstractA comparison is made of observational data on the mean magnetic field of the Sun from several observatories (a selection of published information and new measurements). Results of correlation and regression analyses of observations of background magnetic fields at the STOP telescope of the Sayan solar observatory in different spectral lines are also presented. Results obtained furnish an opportunity to obtain more unbiased information about large-scale magnetic fields of the Sun and, in particular, about manifestations of strong (kilogauss) magnetic fields in them.

scholarly journals The anomalous atmospheric structure of the strongly magnetic Ap star HD 166473

2020 ◽  
Vol 499 (2) ◽  
pp. 2734-2743
Author(s):  
S P Järvinen ◽  
S Hubrig ◽  
G Mathys ◽  
V Khalack ◽  
I Ilyin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Rare Earth ◽  
Field Strength ◽  
Longitudinal Magnetic Field ◽  
Chemical Elements ◽  
Field Measurements ◽  
Horizontal Distribution ◽  
Spectral Lines ◽  
Surface Distribution ◽  
The Mean

ABSTRACT High-resolution spectropolarimetric observations of the strongly magnetic, superslowly rotating rapidly oscillating Ap star HD 166473 are used to investigate the implications of the presence of a variable strong magnetic field on the vertical and surface horizontal distribution of various chemical elements. The analysis of the calculated least-squares deconvolution Stokes I and V profiles confirms the previously reported detection of non-uniform horizontal surface distribution of several chemical elements. To test the vertical abundance stratification of iron peak and rare earth elements, magnetic field measurements were carried out using spectral lines of these elements belonging to neutral and ionized stages. We find clear indication of the existence of a relation between the magnetic field strength and its orientation and vertical element stratification: magnetic field values obtained for elements in different stages close to the magnetic equator are rather similar, whereas the dispersion in field strengths is remarkably large in the regions close to magnetic field poles. At the phases of negative and positive extrema the mean longitudinal field strength determined from the analysis of the rare-earth element lines is usually stronger than when using Fe and Cr. The strongest mean longitudinal magnetic field, up to −4160 ± 226 G, is detected using the La ii line list at the negative extremum, followed by the measurements using the Pr iii lines with 〈Bz〉=−3740 ± 343 G and the Ce ii lines with 〈Bz〉 = −3372 ± 247 G. The strongest mean longitudinal magnetic field of positive polarity, up to 3584 ± 354 G is detected using the Pr iii lines, followed by the measurement 〈Bz〉 = 2517 ± 249 G using the Ce ii lines.

Measurement of the growth of a turbulent mercury jet in a coaxial magnetic field

1967 ◽  
Vol 27 (1) ◽  
pp. 81-96 ◽  
Author(s):  
Miklos Sajben ◽  
James A. Fay
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Axial Magnetic Field ◽  
Magnetic Interaction ◽  
Low Frequencies ◽  
Frequency Components ◽  
Profile Changes ◽  
The Mean ◽  
Wire System ◽  
Made In

Using a hot-wire system developed for this purpose, measurements of the velocity were made in a circular liquid-mercury jet issuing into a low-speed secondary flow and subject to a uniform axial magnetic field. The Reynolds number of the jet was about 10,000 while the magnetic interaction parameter varied from zero to slightly over one. The jet was strongly turbulent under all conditions investigated. The radial distribution of the mean and fluctuating component of the meridional velocity was measured at four axial stations located between 2 and 34 diameters from the nozzle exit. The results indicate that the rate of spreading of the jet is decreased, that the shape of the velocity profile changes and that the turbulent intensity decreases with increasing magnetic-field strength. The high-frequency components of the fluctuations in the second flow seem to be damped more strongly than fluctuations at low frequencies, while the reverse is observed within the core of the jet.

scholarly journals Revisiting the magnetization of comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A46 ◽  
Author(s):  
P. Heinisch ◽  
H.-U. Auster ◽  
I. Richter ◽  
K. H. Glassmeier
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Field Observations ◽  
Upper Limit ◽  
Background Magnetic Field ◽  
Surface Magnetization ◽  
Cometary Material ◽  
History Of ◽  
Comet 67P ◽  
The Magnetic Field

Context. The landing of the Philae probe as part of the ESA Rosetta mission made it possible to study the magnetization of comet 67P/Churyumov-Gerasimenko (67P) by combining observations from the lander and orbiter. In this work, we revisit the magnetic properties with information gained during the progression of the mission for a comprehensive understanding of the circumstances of Philae’s descent and landing. Aims. The aim is to derive a limit for any possible magnetization of the cometary material on the surface of 67P. To achieve this, the surface contacts of Philae were analyzed. Combined with a more detailed understanding of the background magnetic field, this allows us to interpret the underlying magnetic measurements in detail. Methods. We combined magnetic field observations from the ROMAP magnetometer on board Philae with observations from the RPC-MAG instrument on board the Rosetta orbiter. To facilitate this, a correlation analysis was used to correct phase shifts between the observed signals. Additionally, in-flight calibration of the ROMAP offsets was performed using information about the dynamics of Philae during flight. These corrections made it possible to use the orbiter measurements as reference for the comet-based Philae observations. We assumed a simple dipole model and used the magnetic field observations to derive an upper limit for the magnetization of the cometary material. Results. An upper limit of 0.9 nT for the observed magnetic field on the surface of 67P was derived for any contribution from surface magnetization. For homogeneously magnetized pebbles with a size of typical aggregates in the range of ~5 cm, this translates into an upper limit of ~5 × 10−5 Am2 kg−1 for the specific magnetic moment. Depending on the exact history of formation, this results in an upper limit of 4 μT for the magnitude of the magnetic field in the solar nebula during the formation of comet 67P.

scholarly journals How reliable are observations of solar magnetic fields? Comparison of full-disk measurements in different spectral lines and calibration issues of space missions SOHO, Hinode, and SDO

2010 ◽  
Vol 6 (S273) ◽  
pp. 374-378
Author(s):  
Mikhail Demidov
Keyword(s):  
Magnetic Field ◽  
Solar Physics ◽  
Space Missions ◽  
Spectral Lines ◽  
Data Sets ◽  
Solar Magnetic Fields ◽  
Space Observatories ◽  
The Difference ◽  
Made In ◽  
Full Disk

AbstractAn urgent problem in modern solar physics, which is not completely solved up to now, is to obtain realistic magnetic field strength values from parameters measured magnetographs or Stokes-meter instruments. One of the important tools on this way is a comparison of observations made in different spectral lines with the same or with the different telescopes. This issue is an actual task in the analysis of the new data sets provided by the space missions SOHO and Hinode, which measurements are available for several years already, and SDO, which data appeared recently. The main aim of this study is a cross-comparison of magnetic field observations made in different spectral lines used on the above mentioned space observatories: Ni i λ676.77 nm (SOHO/MDI), Fe i λ630.152 nm and Fe i λ630.25 nm (Hinode/SP), and Fe i λ617.33 nm (SDO/HMI). Full-disk high-precision Stokes-meter measurements with the STOP telescope at the Sayan observatory in these lines are used basically, as well as some observations in other spectral lines having a great diagnostic impact, such as Fe i λ525.02 nm, Fe i λ523.29 nm and Fe i λ532.42 nm. The difference between one-instrument (STOP) simultaneous or quasi-simultaneous observations in different spectral lines do not exceed the factor of 2-3 depending on the combination of spectral lines and the position on the solar disk. This is significantly less than in some other studies devoted to cross-comparison of different data sets. Importance and consequences of the obtained results are discussed.

scholarly journals On ion gyro-harmonic structuring in the stimulated electromagnetic emission spectrum during second electron gyro-harmonic heating

2012 ◽  
Vol 30 (11) ◽  
pp. 1587-1594 ◽  
Author(s):  
A. Samimi ◽  
W. A. Scales ◽  
P. A. Bernhardt ◽  
S. J. Briczinski ◽  
C. A. Selcher ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Electromagnetic Emission ◽  
Spectral Lines ◽  
Critical Parameters ◽  
Pump Field ◽  
Pump Frequency ◽  
Ionospheric Heating ◽  
Background Magnetic Field ◽  
Stimulated Electromagnetic Emission

Abstract. Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on occasion, a broadband downshifted emission is observed simultaneously with these spectral lines. Parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and low-frequency ion Bernstein (IB) and oblique ion acoustic (IA) modes is considered responsible for generation of these spectral features. Guided by predictions of an analytical model, a two-dimensional particle-in-cell (PIC) computational model is employed to study the nonlinear processes during such heating experiments. The critical parameters that affect the spectrum, such as whether discrete gyro-harmonic on broadband structures is observed, include angle of the pump field relative to the background magnetic field, pump field strength, and proximity of the pump frequency to the gyro-harmonic. Significant electron heating along the magnetic field is observed in the parameter regimes considered.

scholarly journals The Magnetic and Velocity Fields and Brightness in the Solar Atmosphere

1971 ◽  
Vol 43 ◽  
pp. 274-278 ◽  
Author(s):  
S. I. Gopasyuk ◽  
T. T. Tsap
Keyword(s):  
Active Regions ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Line Of Sight ◽  
Solar Photosphere ◽  
Zero Line ◽  
Isotropic Distribution ◽  
The Mean ◽  
Different Levels ◽  
Made In

Simultaneous observations of the magnetic fields, the line-of-sight velocities and brightness were made in active and quiet regions with the Crimean double-magnetograph in the following lines: Hα, K3 Ca II, Hβ, Hγ, Hδ, MgI λ 5184 Å, CaI λ 4227 Å, D1 NaI, BaII λ 4554 Å, CaI λ 6103 Å, FeI λ 5250 Å.It is shown, that in the active regions the horizontal velocity is larger than the vertical one.The mean velocities in the quiet solar photosphere have an isotropic distribution (Gopasyuk and Kalman, 1971).The mean vertical velocities increase exponentially with height in active and quiet regions.The correlation between velocities at different levels in active and quiet regions decreases with the distance between the levels of the formation of spectral lines, and it disappears for the velocities recorded in λ 6103 Å and Hβ, for λ 5184 and Hα lines in active regions and for the velocities recorded in λ 5250 Å and Hα lines in quiet regions.The position of the maximal field strength within a magnetic hill coincides statistically with the zero line of the line-of-sight velocities for active as well as for quiet regions.

scholarly journals Long-Term Coherent Periodicities in the Mean Magnetic Field of the Sun

1983 ◽  
Vol 102 ◽  
pp. 23-27
Author(s):  
V.A. Kotov ◽  
L.S. Levitsky
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Field Measurements ◽  
Magnetic Star ◽  
Time Interval ◽  
The Sun ◽  
Total N ◽  
The Mean ◽  
Made In

To investigate periodic variations of the magnetic field of the Sun as a star (SMMF; see Severny, 1969) we have used the mean field measurements made in Crimea, Mt. Wilson, and Stanford observatories; in total N = 5783 daily values were available for the time interval 1968–1981. In essence, these data offer a unique possibility to study the Sun as a variable magnetic star (Scherrer et al., 1977).

Germination and initial growth of triticale seeds under stationary magnetic fields

2014 ◽  
Vol 2 (2) ◽  
pp. 72-79 ◽  
Author(s):  
Mercedes Florez ◽  
Elvira Martinez ◽  
Victoria Carbonell
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Seed Vigor ◽  
Initial Growth ◽  
Practical Application ◽  
Biochemical Processes ◽  
Mean Germination Time ◽  
Nutrition Value ◽  
The Mean ◽  
Growth Of Seedlings

The main objective of this study is to determine the effects of 125 mT and 250mT magnetic treatment on the germination and initial growth of triticale seeds. This objective has a practical application in agriculture science: early growth of triticale. An increase in the percentage and rate of germination of seeds and a stimulation of growth of seedlings as positive response to magnetic field treatment in rice, wheat, maize and barley seeds have been found in previous studies. Germination tests were carried out under laboratory conditions by exposing triticale seeds to magnetic field for different times. The effect was studied by exposure of seeds prior sowing. The mean germination time were reduced for all the magnetic treatments applied. Most significant differences were obtained for time of exposure of 1 and 24 hours and maximum reductions was 12%. Furthermore, seedlings from magnetically treated seeds grew taller than control. The longest mean total length was obtained from seedlings exposed to 125 and 250 mT for 24 hours. External magnetic fields are assumed to enhance seed vigor by influencing the biochemical processes by stimulating activity of proteins and enzymes. Numerous studies suggested that magnetic field increases ions uptake and consequently improves nutrition value.

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