The long-term optical activity of the propellers AE Aquarii and AR Scorpii

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Vojtěch Šimon
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Optical Activity ◽  
White Dwarf ◽  
Transient Decrease ◽  
Mass Outflow ◽  
Orbital Modulation ◽  
The Magnetic Field

Abstract This analysis of the long-term optical activity of the propellers AE Aqr and AR Sco uses data from the Catalina Real-time Transient Survey, DASCH, and AAVSO. The site and character of the emissions from the phenomena caused by the magnetic field of the white dwarf (WD) vary from system to system. The histogram of intensities of the ensemble of flares of AE Aqr suggests that the long-term activity consists of a large variety of the peak magnitudes of the flares, with the probability of their detection gradually decreasing with increasing intensity. Any increase of activity only leads to an increase of the number of blobs of the transferring matter. We also detected a season with a transient decrease or even a cessation of the mass outflow from the donor to the lobe of the WD. The very strong orbital modulation of AR Sco is most stable in the phases of the extrema of brightness for about a century; its minor changes suggest that the trailing side of the synchrotron-emitting region is more unstable than the leading side.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

scholarly journals Practice and perspectives of using ultrasensitive magnetometers in biomedical research.

2021 ◽  
Author(s):  
Yu.V. Maslennikov ◽  
◽  
◽  
Keyword(s):  
Magnetic Field ◽  
Biomedical Research ◽  
Magnetic Measurements ◽  
Signal To Noise Ratio ◽  
Frequency Range ◽  
Optically Pumped ◽  
Technical Solutions ◽  
Further Development ◽  
The Magnetic Field

There are a large number of sensors for measuring the magnetic field of biological objects. They are characterized by the type of the measured physical parameter (magnetic field strength, magnetic flux, etc.), the level of intrinsic sensitivity, and the frequency range of the recorded signals. The long-term practice of studying biomagnetic signals shows that only SQUID-based magnetometers and optically pumped magnetometers have sensitivity levels sufficient for recording biomagnetic signals with the required signal-to-noise ratio. This chapter reflects the main directions of using such magnetometers and methods of magnetic measurements in biomedical research, gives examples of existing technical solutions, and shows possible ways of their further development.

EFFECT OF ATTENUATED MAGNETIC FIELD ON DEVELOPMENT OF THE LIVER AND SPLEEN IN EMBRYONIC JAPANESE QUAIL

2021 ◽  
Vol 55 (6) ◽  
pp. 50-55
Author(s):  
S.A. Pineguin ◽  
◽  
O.A. Dadasheva ◽  
E.I. Mednikova ◽  
O.A. Grushina ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Japanese Quail ◽  
First Generation ◽  
Space Missions ◽  
The Moon ◽  
Living Organisms ◽  
The Magnetic Field

Expectation of remote space missions and long-term stay and work on the Moon with the magnetic field 1,000 times weaker than on Earth sets the researchers the formidable task to investigate effects of the hypomagnetic environment on living organisms. The paper reports data about the liver and spleen development in Japanese quail embryos of various age exposed in a modeled lunar magnetic field. Retardation of hemopoiesis was observed as in the first generation embryos (F1), so in sequential embryo generations developed in the ordinary magnetic environment (F2).

scholarly journals Correcting the geomagnetic IHV index of the Eskdalemuir observatory

2006 ◽  
Vol 24 (12) ◽  
pp. 3411-3419 ◽  
Author(s):  
D. Martini ◽  
K. Mursula
Keyword(s):  
Magnetic Field ◽  
Data Center ◽  
Early Years ◽  
Correction Factors ◽  
Hourly Data ◽  
The World ◽  
Variability Index ◽  
The Magnetic Field ◽  
Long Term Studies

Abstract. We study here the recently proposed measure of local geomagnetic activity called the IHV (Inter-Hour Variability) index calculated for the Eskdalemuir (ESK) station. It was found earlier that the ESK IHV index depicts an artificial, step-like increase from 1931 to 1932. We show here that this increase is due to the fact that the values of the magnetic field components of the ESK observatory stored at the World Data Center are two-hour running averages of hourly data stored in ESK yearbooks. Two-hour averaging greatly reduces the variability of the data which leads to artificially small values of the IHV index in 1911–1931. We also study the effect of two-hour averaging upon hourly mean and spot values using 1-minute data available for recent years, and calculate the correction factors for the early years, taking into account the weak dependence of correction factors on solar activity. Using these correction factors, we correct the ESK IHV indices in 1912–1931, and revise the estimate of the centennial change based on them. The effect of correction is very significant: the centennial increase in the ESK IHV-raw (IHV-cor) index in 1912–2000 changes from 73.9% (134.4%) before correction to 10.3% (25.3%) thereafter, making the centennial increase at ESK quite similar to other mid-latitude stations. Obviously, earlier long-term studies based on ESK IHV values are affected by the correction and need to be revised. These results also strongly suggest that the ESK yearbook data should be digitized and the hourly ESK data at WDC should be replaced by them.

scholarly journals Noninvasive muscle activity imaging using magnetography

2020 ◽  
Vol 117 (9) ◽  
pp. 4942-4947 ◽  
Author(s):  
Rodolfo R. Llinás ◽  
Mikhail Ustinin ◽  
Stanislav Rykunov ◽  
Kerry D. Walton ◽  
Guilherme M. Rabello ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Contrast Media ◽  
Electrical Activity ◽  
Real Time ◽  
Human Body ◽  
Muscle Activity ◽  
Muscular Activity ◽  
Exponential Increase ◽  
Somatic Musculature ◽  
The Magnetic Field

A spectroscopic paradigm has been developed that allows the magnetic field emissions generated by the electrical activity in the human body to be imaged in real time. The growing significance of imaging modalities in biology is evident by the almost exponential increase of their use in research, from the molecular to the ecological level. The method of analysis described here allows totally noninvasive imaging of muscular activity (heart, somatic musculature). Such imaging can be obtained without additional methodological steps such as the use of contrast media.

scholarly journals The Chandrasekhar Mass of A Gravitating Electron Crystal

1994 ◽  
Vol 147 ◽  
pp. 565-570
Author(s):  
D. Engelhardt ◽  
I. Bues
Keyword(s):  
Magnetic Field ◽  
Density Matrix ◽  
White Dwarf ◽  
Matrix Formalism ◽  
Plasma Zone ◽  
Isothermal Model ◽  
Fermi Function ◽  
Density Matrix Formalism ◽  
The Magnetic Field ◽  
Electron Crystal

AbstractThe internal structure of a white dwarf may be changed by a strong magnetic field. A local model of the electrons is constructed within a thermal density matrix formalism, essentially a Heisenberg magnetism model. This results in a matrix Fermi function which is used to construct an isothermal model of the electron crystal. The central density of the crystal is 108kg/m3 independent of the magnetic field within the plasma and therefore lower than the relativistic density, whereas this density is constant until the Fermi momentum x f = 0.3 * me * c. Chandrasekhar masses up to 1.44 * 1.4M0 are possible for polarizations of the plasma zone lower than 0.5, if the temperature is close to the Curie point, whereas the crystal itself destabilizes the white dwarf dependent on temperature.

scholarly journals Nova GK Persei – A Miniature Supernova Remnant?

1988 ◽  
Vol 101 ◽  
pp. 47-50
Author(s):  
E.R. Seaquist ◽  
D.A. Frail ◽  
M.F. Bode ◽  
J.A. Roberts ◽  
D.C.B. Whittet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Strong Evidence ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Optical Images ◽  
Ambient Gas ◽  
The Magnetic Field

AbstractWe present radio and optical images of the shell-like remnant of the 1901 outburst of Nova GK Persei. The behaviour of this object is remarkably similar to supernova remnants. The synchrotron radiation-emitting shell is polarized with the magnetic field oriented radially, as in young SNR’s. This similarity plus extensive data we have acquired on the expansion and the interstellar environment of GK Per indicate that the nova shell is colliding with ambient gas whose density is substantially higher than the ISM.Furthermore, there is strong evidence that the ambient gas is circumstellar rather than interstellar, and that this material is the shell of an ancient planetary nebula associated with the white dwarf companion of GK Per.

The long-term behavior of the magnetic field of beta CrB.

1973 ◽  
Vol 186 ◽  
pp. 211 ◽  
Author(s):  
E. F. Borra ◽  
M. M. Dworetsky
Keyword(s):  
Magnetic Field ◽  
Long Term Behavior ◽  
The Magnetic Field

scholarly journals A short and sudden increase of the magnetic field strength and the accompanying spectral variability in the O9.7 V star HD 54879

2019 ◽  
Vol 484 (4) ◽  
pp. 4495-4506 ◽  
Author(s):  
S Hubrig ◽  
M Küker ◽  
S P Järvinen ◽  
A F Kholtygin ◽  
M Schöller ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Longitudinal Magnetic Field ◽  
Sudden Increase ◽  
Spectral Variability ◽  
Dipole Strength ◽  
Large Program ◽  
Short And Long Term ◽  
The Magnetic Field

Abstract Only 11 O-type stars have been confirmed to possess large-scale organized magnetic fields. The presence of a −600 G longitudinal magnetic field in the O9.7 V star HD 54879 with a lower limit of the dipole strength of ∼2 kG was discovered a few years ago in the framework of the ESO large program ‘B-fields in OB stars’. Our FORS 2 spectropolarimetric observations from 2017 October 4 to 2018 February 21 reveal the presence of short- and long-term spectral variability and a gradual magnetic field decrease from about −300 G down to about −90 G. Different scenarios are discussed in an attempt to interpret our observations. Our FORS 2 radial velocity measurements indicate that HD 54879 is a member of a long-period binary.

scholarly journals A new weak-field magnetic DA white dwarf in the local 20 pc volume

2019 ◽  
Vol 628 ◽  
pp. A1 ◽  
Author(s):  
J. D. Landstreet ◽  
S. Bagnulo
Keyword(s):  
Magnetic Field ◽  
White Dwarf ◽  
Field Component ◽  
Main Sequence ◽  
Mean Field ◽  
Weak Field ◽  
Line Of Sight ◽  
Limited Sample ◽  
Field Decay ◽  
The Magnetic Field

We report the discovery of a new magnetic DA white dwarf (WD), WD 0011 − 721, which is located within the very important 20 pc volume-limited sample of the closest WDs to the Sun. This star has a mean field modulus ⟨|B|⟩ of 343 kG, and from the polarisation signal we deduce a line-of-sight field component of 75 kG. The magnetic field is sufficiently weak to have escaped detection in classification spectra. We then present a preliminary exploration of the data concerning the frequency of such fields among WDs with hydrogen-rich atmospheres (DA stars). We find that 20 ± 5% of the DA WDs in this volume have magnetic fields, mostly weaker than 1 MG. Unlike the slow field decay found among the magnetic Bp stars of the upper main sequence, the WDs in this sample show no evidence of magnetic field or flux changes over several Gyr.

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