scholarly journals The Relationship Between Solar Coronal X-Ray Brightness and Active Region Magnetic Fields: A Study Using High-Resolution Hinode Observations

Solar Physics ◽  
2015 ◽  
Vol 290 (3) ◽  
pp. 771-785 ◽  
Author(s):  
Soumitra Hazra ◽  
Dibyendu Nandy ◽  
B. Ravindra
Keyword(s):  
High Resolution ◽  
Active Region ◽  
Magnetic Fields ◽  
X Ray ◽  
The Relationship ◽  
Solar Coronal

Practical High Resolution Microscopy

1968 ◽  
Vol 26 ◽  
pp. 302-303
Author(s):  
P. A. Marsh ◽  
T. Mullens ◽  
D. Price
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Resolving Power ◽  
Careful Attention ◽  
Electron Microscopes ◽  
The Relationship ◽  
High Resolution Microscopy ◽  
New Facilities

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion nebula cluster

2010 ◽  
Vol 6 (S272) ◽  
pp. 208-209 ◽  
Author(s):  
Véronique Petit ◽  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
Laurent Drissen ◽  
Thierry Montmerle ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Theoretical Models ◽  
Magnetic Star ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
The Impact ◽  
The Relationship

AbstractIn some massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind. Although theoretical models and MHD simulations are able to illustrate the dynamics of such a magnetized wind, the impact of this wind-field interaction on the observable properties of a magnetic star - X-ray emission, photometric and spectral variability - is still unclear. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars, by providing empirical observations and confronting theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion Nebula Cluster

2008 ◽  
Vol 4 (S259) ◽  
pp. 449-452 ◽  
Author(s):  
Véronique Petit ◽  
G. A. Wade ◽  
L. Drissen ◽  
T. Montmerle ◽  
E. Alecian
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Magnetic Confinement ◽  
Stellar Winds ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
Complex Processes ◽  
The Relationship

AbstractIn massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind, resulting in X-ray emission that is harder, more variable and more efficient than that produced by instability-generated shocks in non-magnetic winds. Although magnetic confinement of stellar winds has been shown to strongly modify the mass-loss and X-ray characteristics of massive OB stars, we lack a detailed understanding of the complex processes responsible. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars. In conjunction with a Chandra survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

Time-Dependent Magneto-Convection with Hexagonal Planform

1982 ◽  
Vol 4 (4) ◽  
pp. 373-376 ◽  
Author(s):  
J.M. Lopez ◽  
J.O. Murphy
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Time Dependent ◽  
Convection Cell ◽  
Small Scale ◽  
Solar Photosphere ◽  
X Ray ◽  
Bright Spots

High-resolution observations indicate that very strong, small scale magnetic fields in the solar photosphere are concentrated into ropes which emerge through it. The scale of these ropes is only a few hundred kilometres across (Stenflo 1976) and their strength is estimated to vary between 1,000 and 2,000 G (Harvey 1977). These features are closely related to photospheric granular convection. The flux is observed as X-ray bright spots and sheet-like crinkles in the dark intergranular lanes, and is buffeted and shifted about by the granules (Dunn and Zirker 1973). Further, the crinkles can be resolved into separate features which outline small micropores as though a flux sheet at the end of a convection cell has separated into several isolated tubes (Galloway and Weiss 1981).

scholarly journals High-resolution imaging and near-infrared spectroscopy of penumbral decay

2018 ◽  
Vol 614 ◽  
pp. A2 ◽  
Author(s):  
M. Verma ◽  
C. Denker ◽  
H. Balthasar ◽  
C. Kuckein ◽  
R. Rezaei ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Active Region ◽  
Magnetic Fields ◽  
Near Infrared ◽  
Imaging Spectroscopy ◽  
Imaging Data ◽  
Horizontal Magnetic Field ◽  
Flux System ◽  
Resolution Imaging

Aims. Combining high-resolution spectropolarimetric and imaging data is key to understanding the decay process of sunspots as it allows us to scrutinize the velocity and magnetic fields of sunspots and their surroundings. Methods. Active region NOAA 12597 was observed on 2016 September 24 with the 1.5-meter GREGOR solar telescope using high-spatial-resolution imaging as well as imaging spectroscopy and near-infrared (NIR) spectropolarimetry. Horizontal proper motions were estimated with local correlation tracking, whereas line-of-sight (LOS) velocities were computed with spectral line fitting methods. The magnetic field properties were inferred with the “Stokes Inversions based on Response functions” (SIR) code for the Si I and Ca I NIR lines. Results. At the time of the GREGOR observations, the leading sunspot had two light bridges indicating the onset of its decay. One of the light bridges disappeared, and an elongated, dark umbral core at its edge appeared in a decaying penumbral sector facing the newly emerging flux. The flow and magnetic field properties of this penumbral sector exhibited weak Evershed flow, moat flow, and horizontal magnetic field. The penumbral gap adjacent to the elongated umbral core and the penumbra in that penumbral sector displayed LOS velocities similar to granulation. The separating polarities of a new flux system interacted with the leading and central part of the already established active region. As a consequence, the leading spot rotated 55° clockwise over 12 h. Conclusions. In the high-resolution observations of a decaying sunspot, the penumbral filaments facing the flux emergence site contained a darkened area resembling an umbral core filled with umbral dots. This umbral core had velocity and magnetic field properties similar to the sunspot umbra. This implies that the horizontal magnetic fields in the decaying penumbra became vertical as observed in flare-induced rapid penumbral decay, but on a very different time-scale.

scholarly journals Twist and writhe of δ active region magnetic fields

2005 ◽  
Vol 13 ◽  
pp. 120-121
Author(s):  
Lirong Tian ◽  
Jing Yang
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Flux Tube ◽  
Tilt Angle ◽  
Magnetic Configuration ◽  
Major Flare ◽  
Field Lines ◽  
The Relationship ◽  
Best Fit

Twist is a parameter to measure turning of the field lines around axis of the flux tube. Observations show that each active region (AR) has a pronounced overall twist, following hemispheric helicity rule (Pevtsov et al. 1995; Bao & Zhang 1998). αbest, best-fit single value for a whole AR, is used to characterize the overall twist. Writhe is a measure of the spatial turning of the axis of the flux tube. It is described by systematic tilt angle of an AR, an angle of joined line of opposite main polarities with respect to the equator. Observations show that most ARs follow Joy’s Law. The relationship between the twist and writhe is important to studying origin of the twist and solar activities. Canfield & Pevtsov (1998) found the same handedness of the twist as that of writhe, using 99 ARs observed at MSO. However, Tian et al. (2001) found opposite handedness of them for 286 ARs taken at HSOS, among which only 19% have δ magnetic configuration. López Fuentes et al. (2003) also obtained opposite handedness for 22 ARs measured again at MSO, among which 41% have δ magnetic class. Most recently, Tian & Liu (2003) found that the twist and the writhe have same handedness for major flare-producing ARs.

scholarly journals Recent High Resolution X-Ray Spectra of the Sun

1972 ◽  
Vol 14 ◽  
pp. 740-741
Author(s):  
J. H. Parkinson ◽  
K. Evans ◽  
K. A. Pounds
Keyword(s):  
High Resolution ◽  
Active Region ◽  
Wavelength Range ◽  
South Australia ◽  
Active Regions ◽  
Effective Area ◽  
Field Of View ◽  
The Sun ◽  
X Ray

New results are presented from high resolution Bragg crystal spectrometers flown in late 1970 on two Skylark rockets. The first instrument, launched on 24 November 1970 at 22 13 UT from Woomera, South Australia, contained two crystal spectrometers, each with an effective area of 50 cm2 and field collimation to 3’ FWHM. This instrument obtained the X-ray spectrum of the quiet corona in the wavelength range 5–14 Å. The second instrument was launched on 6 December 1970 at 11 13 UT from Sardinia, Italy, and contained four crystals of 6 cm2, each collimated to 4’ FWHM. This instrument was pointed at a non-flaring active region near N20 W40(McMath region 11060), and obtained an X-ray spectrum between 5 and 23 Å. This first use of a collimator to limit the field of view has considerably increased the spectral clarity compared with earlier observations by excluding the contributions of other active regions.

scholarly journals Electrodynamic Coupling in Magnetically Confined Stellar X-Ray Loops

1983 ◽  
Vol 102 ◽  
pp. 391-396
Author(s):  
James A. Ionson
Keyword(s):  
High Resolution ◽  
Closed Loop ◽  
Important Lesson ◽  
X Ray ◽  
Spatially Resolved ◽  
Magnetically Confined ◽  
Radiative Output ◽  
Solar Coronal

The solar-coronal complex is the only astrophysical system whose X-ray structure has to some degree been spatially resolved. The most important lesson that we have learned from these relatively high-resolution observations is that the corona is highly structured, comprising a variety of closed, loop-like regions of enhanced radiative output. Furthermore, coronal radiation loops are now known to be spatially coincident with magnetic loops which confine the radiating plasma.

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