scholarly journals The connection of fine-structure photospheric features in active regions with magnetic fields

1968 ◽  
Vol 35 ◽  
pp. 201-201
Author(s):  
N. V. Steshenko
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
High Resolution ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Active Regions ◽  
Transverse Magnetic ◽  
List Type ◽  
The Magnetic Field

1.The fine structure of the proton sunspot group of July 4–8, 1966 was studied on the basis of high-resolution heliograms. The comparison of the orientation between penumbral filaments and the transverse magnetic fields (observed by A.B. Severny and T.T. Tsap) shows that the direction of the filaments coincides in general with that of the magnetic field.2.Measurements of the magnetic fields of smallest pores (1·5″-2″) showed that the pores are always connected with strong magnetic field (in average 1400 gauss), which is localized at the same small area as the pore.3.Magnetic fields of faculae are concentrated in small elements with the dimension not exceeding 1·5″-3″. Magnetic-field strength H|| of about 45% of facular granules is within the limits of photographic measuring errors (approximately 25 gauss). For a quarter of all facular granules the strength H|| is from 25–50 gauss; about 30% of facular granules have H|| > 50 gauss, and sometimes there appear faculae with field strength of about 200 gauss. The magnetic-field strength of facular granules, which are found directly above spots, is 10–20 times less than the field strength of spots. This field is 80–210 gauss only.4.All observational data mentioned above show that the appearance of the fine-structure features in active regions is directly connected with the fine structure of magnetic field of different strength and different orientation. The study of high-resolution heliograms gives additional information about the fine structure of the magnetic field.

A Discussion on solar studies with special reference to space observations - The manifold structure of the chromosphere and corona

1971 ◽  
Vol 270 (1202) ◽  
pp. 77-80 ◽  
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
High Resolution ◽  
Field Strength ◽  
Special Reference ◽  
Velocity Fields ◽  
Field Patterns ◽  
Uniform Region ◽  
Determining Factor ◽  
The Magnetic Field

Although the photosphere is a uniform region for scales greater than the granulation, the fact that the magnetic field strength falls off less sharply than the gas pressure leads to strong magnetic influence at greater heights in the solar atmosphere. This magnetic influence leads to non-uniformity and fine structure in the chromosphere and corona. The existence of such structure has been deduced mostly from measurements of photospheric phenomena; in particular, from measurements of photospheric velocity fields (Leighton, Noyes & Simon 1962) and of photospheric magnetic fields (Bumba & Howard 1965). The determining factor would thus appear to be in the photosphere; but visible effects only are produced in the chromosphere and corona. In recent years, high resolution filter photography has enabled us to recognize different regions of the chromosphere, where qualitatively different structure is associated with distinct magnetic field patterns. This progress has been possible because of better Lyot filters, better films and better observing sites; the spectroheliograph has always been limited for high resolution work by the finite slit width and the difficulty of accurate guiding during the long exposures.

A portable apparatus for measuring the magnetic field strength in an electromagnetic wave

1931 ◽  
Vol 27 (3) ◽  
pp. 481-489
Author(s):  
L. G. Vedy ◽  
A. F. Wilkins
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Special Means ◽  
Portable Apparatus ◽  
The Magnetic Field ◽  
Field Strengths

A portable apparatus is described which is capable of measuring directly, by means of a loop aerial, the magnetic field in an electromagnetic wave. Accurate measurements are possible of magnetic fields corresponding to field strengths of 0·2 millivolts per metre. Special means of providing small known calibrating E. M. F. S are described. The apparatus can be used to measure signals over the range 6 microvolts to 300 millivolts. Used in conjunction with a small portable vertical aerial, field strengths down to 2 microvolts per metre can be measured.

scholarly journals Magnetic properties of a long-lived sunspot

2018 ◽  
Vol 620 ◽  
pp. A104 ◽  
Author(s):  
M. Schmassmann ◽  
R. Schlichenmaier ◽  
N. Bello González
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Field Component ◽  
Active Regions ◽  
Magnetic Field Component ◽  
Stable Phase ◽  
Vertical Magnetic Field ◽  
Continuum Intensity ◽  
The Magnetic Field

Context. In a recent statistical study of sunspots in 79 active regions, the vertical magnetic field component Bver averaged along the umbral boundary is found to be independent of sunspot size. The authors of that study conclude that the absolute value of Bver at the umbral boundary is the same for all spots. Aims. We investigate the temporal evolution of Bver averaged along the umbral boundary of one long-lived sunspot during its stable phase. Methods. We analysed data from the HMI instrument on-board SDO. Contours of continuum intensity at Ic = 0.5Iqs, whereby Iqs refers to the average over the quiet sun areas, are used to extract the magnetic field along the umbral boundary. Projection effects due to different formation heights of the Fe I 617.3 nm line and continuum are taken into account. To avoid limb artefacts, the spot is only analysed for heliocentric angles smaller than 60°. Results. During the first disc passage, NOAA AR 11591, Bver remains constant at 1693 G with a root-mean-square deviation of 15 G, whereas the magnetic field strength varies substantially (mean 2171 G, rms of 48 G) and shows a long term variation. Compensating for formation height has little influence on the mean value along each contour, but reduces the variations along the contour when away from disc centre, yielding a better match between the contours of Bver = 1693 G and Ic = 0.5Iqs. Conclusions. During the disc passage of a stable sunspot, its umbral boundary can equivalently be defined by using the continuum intensity Ic or the vertical magnetic field component Bver. Contours of fixed magnetic field strength fail to outline the umbral boundary.

scholarly journals The influence of convective blueshift on radial velocities of F, G, and K stars

2018 ◽  
Vol 610 ◽  
pp. A52 ◽  
Author(s):  
F. F. Bauer ◽  
A. Reiners ◽  
B. Beeck ◽  
S. V. Jeffers
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Active Regions ◽  
Stellar Surface ◽  
Mhd Simulations ◽  
Convective Motions ◽  
The Impact ◽  
The Magnetic Field ◽  
Spot Temperature

Context.Apparent radial velocity (RV) signals induced by stellar surface features such as spots and plages can result in a false planet detection or hide the presence of an orbiting planet. Our ability to detect rocky exoplanets is currently limited by our understanding of such stellar signals.Aims.We model RV variations caused by active regions on the stellar surface of typical exoplanet-hosting stars of spectral type F, G, and K. We aim to understand how the stellar magnetic field strength, convective blueshift, and spot temperatures can influence RV signals caused by active regions.Methods.We use magneto-hydrodynamic (MHD) simulations for stars with spectral types F3V, a G2V, and a K5V. We quantify the impact of the magnetic field strength inside active regions on the RV measurement using the magnetic and non-magnetic FeI lines at 6165 Å and 6173 Å. We also quantify the impact of spot temperature and convective blueshift on the measured RV values.Results.Increasing the magnetic field strength increases the efficiency to suppress convection in active regions which results in an asymmetry between red- and blueshifted parts of the RV curves. A stronger suppression of convection also leads to an observed increase in RV amplitude for stronger magnetic fields. The MHD simulations predict convective motions to be faster in hotter stars. The suppression of faster convection leads to a stronger RV amplitude increase in hotter stars when the magnetic field is increased. While suppression of convection increases the asymmetry in RV curves,c a decreasing spot temperature counteracts this effect. When using observed temperatures for dark spots in our simulations we find that convective blueshift effects are negligible.

scholarly journals Effect of transverse magnetic fields on high-harmonic generation in intense laser–solid interaction

2016 ◽  
Vol 34 (3) ◽  
pp. 545-551
Author(s):  
J. Mu ◽  
F.-Y. Li ◽  
Z.-M. Sheng ◽  
J. Zhang
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
High Harmonic ◽  
High Harmonic Generation ◽  
Transverse Magnetic ◽  
Intense Laser ◽  
The Magnetic Field

AbstractThe effect of transverse magnetic fields on surface high-harmonic generation in intense laser–solid interactions is investigated. It is shown that the longitudinal motion of electrons can be coupled with the transverse motion via the magnetic fields, which lead to even-order harmonics under normal laser incidence. The dependence of the coupling efficiency and hence even harmonic generation with preplasma scale length and magnetic field strength are presented based upon particle-in-cell simulations. When the magnetic field is parallel to the laser electric field, the spectral intensity of the second harmonic is proportional to the magnetic field strength in a wide range up to 160 MG, while the situation with the magnetic field perpendicular to the laser electric field is more complicated. The second harmonic generation due to the magnetic field also tends to increase with the plasma density scale lengths, which is different from the high-harmonic generation by the oscillating mirror mechanism. With the increase of the laser spot size from a laser wavelength λL, both the magnetic field-induced harmonics and oscillating mirror high harmonics tend to increase first and then become saturated after 3λL. The magnetic field-induced second harmonic may be used to evaluate large self-generated magnetic fields developed near the critical density region and the preplasma conditions.

scholarly journals On the magnetic-field configuration in sunspots

1968 ◽  
Vol 35 ◽  
pp. 202-210
Author(s):  
O. Kjeldseth Moe
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Solar Disk ◽  
Field Configuration ◽  
Solar Observatory ◽  
Line Profiles ◽  
Magnetic Field Configuration ◽  
The Magnetic Field

During 1963–67 observations of the magnetic fields in sunspots have been obtained at the Oslo Solar Observatory. For the largest spots the detailed distribution of the magnetic-field strength is found. Based on calculations of line profiles made by the author (Kjeldseth Moe, 1967) also the direction of the magnetic field is derived. Observations of the magnetic field of the same spot at several positions on the solar disk give further information regarding the magnetic-field configuration. Our results are in fair agreement with those of Bumba (1962).

scholarly journals PENGARUH MEDAN MAGNET TERHADAP DIAMETER PERKECAMBAHAN KACANG HIJAU

2020 ◽  
Vol 5 (1) ◽  
pp. 66-70
Author(s):  
Aditya Vethra Prasetyo
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Green Bean ◽  
Green Beans ◽  
Bean Sprout ◽  
Randomized Design ◽  
Completely Randomized Design ◽  
The Magnetic Field

Abstrak Penelitian yang dilakukan berjudul “Pengaruh Medan Magnet  Terhadap Diameter Perkecambahan Kacang Hijau”. Penelitian ini bertujuan untuk mengetahui pengaruh medan magnet terhadap diameter perkecambahan kacang hijau. Penelitian ini disusun dalam Rancangan Acak Lengkap (RAL) dengan satu faktor, yaitu kuat medan magnet dalam waktu yang sama yang terdiri dari kontrol (0 mT), 5,3 mT, 10,7 mT, 16,1 mT, 21,5 mT. Parameter yang diukur adalah diameter batang kecambah kacang hijau. Data dianalisis ragam dilanjutkan dengan uji DMRT pada taraf α = 5%. Hasil penelitian menunjukkan bahwa pemaparan medan magnet  mempengaruhi diameter batang kecambah kacang hijau. Perlakuan yang menyebabkan perkembangan diameter batang terbesar adalah 21,5 mT. Kata kunci: kacang hijau, medan magnet, diameter Abstract The study was conducted entitled "The Effect of Magnetic Fields on the Diameter of Green Bean Germination". This study aims to determine the effect of the magnetic field on the diameter of green bean germination. This research was arranged in a Completely Randomized Design (CRD) with one factor, namely magnetic field strength at the same time consisting of controls (0 mT), 5.3 mT, 10.7 mT, 16.1 mT, 21.5 mT . The parameter measured is the diameter of the green bean sprout stem. Data were analyzed by continued variance with DMRT test at α = 5%. The results showed that exposure to the magnetic field affected the diameter of the green bean sprout stem. The treatment that caused the largest stem diameter development was 21.5 mT. Keywords: green beans, magnetic field, diameter

scholarly journals Solar Coronal Magnetic Fields

1993 ◽  
Vol 157 ◽  
pp. 59-61
Author(s):  
J. Hildebrandt ◽  
B. Kliem ◽  
A. Krüger
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
Small Scale ◽  
List Type ◽  
Standard Distribution ◽  
Limb Flare ◽  
Complex Picture ◽  
The Magnetic Field

A short compilation of various radio methods of the determination of magnetic fields in the solar corona is given which, completed by observations in other spectral ranges (e.g. the optical and X-ray ranges), results in a complex picture of the magnetic field. Some topics of interest are the following: (1)Comparison with a standard reference magnetic field in the solar corona,(2)Possible evidence of substantial small-scale fluctuations of the magnetic field (e.g. in active regions),(3)Indication of magnetic fields substantially in excess of the standard distribution (e.g. in limb flare events).

scholarly journals Eindimensionale Plasmaströmung in gekreuzten elektrischen und magnetischen Feldern

1965 ◽  
Vol 20 (8) ◽  
pp. 1019-1026 ◽  
Author(s):  
E. Rebhan
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Shock Front ◽  
Magnetic Field Strength ◽  
Plasma Flow ◽  
One Dimensional ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field ◽  
Steady Shock

An investigation was made of a steady, one-dimensional plasma flow in crossed electric and magnetic fields. The interaction between the flow and the fields causes various flow types. In general, the flow is either supersonic or subsonic in the entire channel. Under certain circumstances, however, a transsonic flow may develop. Finally, flows exist with a steady shock front, the position and strength of which depend on the magnetic field strength and the pressure at the end of the tube.

Analysis of the He i chromosphere in relation to the magnetic field activity over solar cycle time periods

2020 ◽  
Vol 497 (1) ◽  
pp. 969-975
Author(s):  
K J Li ◽  
W Feng
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Active Regions ◽  
Solar Observatory ◽  
Small Scale ◽  
Large Magnetic Field ◽  
National Solar Observatory ◽  
Magnetic Elements ◽  
The Magnetic Field

ABSTRACT Solar synoptic maps of both He i 10 830 Å intensity and the magnetic field, which are observed by the Vacuum Telescope at National Solar Observatory/Kitt Peak from 2005 July to 2013 March are utilized to study relationship of He i intensity of the weakly magnetized chromosphere with the respective magnetic field strength. Strong absorption in He i intensity presents the butterfly-pattern latitude migration zone as active regions do, indicating that strong magnetic field corresponds to high-temperature structures of the active chromosphere. For He i intensity and magnetic field strength, their distribution at the time-latitude coordinate and their time series at each of the 180 measurement latitude are found to be significantly negatively correlated with each other in most cases. When a solar hemisphere is divided into three latitude bands: low, middle, and high latitude bands, and even after large magnetic field values not taken into account, they are still negatively correlated in most cases, and further when large magnetic field values are subtracted He i intensity varies more sensitively with magnetic field strength than the corresponding cases when large magnetic field values are not subtracted. He i intensity in the quiet chromosphere thus mainly presents a negative correlation with the magnetic field, and the heating of the quiet chromosphere is inferred to be caused mainly by small-scale magnetic elements.

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