scholarly journals FIP Effect and FIP-Dependent Bias in the Solar Corona

2004 ◽  
Vol 219 ◽  
pp. 493-497
Author(s):  
B.N. Dwivedi ◽  
A. Mohan ◽  
E. Landi
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Solar Disk ◽  
Field Of View ◽  
Magnetic Structures ◽  
Abundance Anomalies ◽  
Soho Spacecraft

Using EUV spectra of an active region observed off the solar disk by the SOHO/SUMER spectrograph on the SOHO spacecraft, we investigate the dependence of the FIP effect on the height above the photosphere, and its relation to plasma magnetic structures present in the field of view. We also investigate the possibility of the FIP bias in the low-FIP elements to be FIP-dependent, so that different abundance anomalies must be found even within the low-FIP class of elements, which can provide important constraints on the FIP effect models.

scholarly journals Very Large Array (VLA) Observations of Solar Active Regions

1980 ◽  
Vol 86 ◽  
pp. 109-117
Author(s):  
Kenneth R. Lang ◽  
Robert F. Willson
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Circular Polarization ◽  
Zeeman Effect ◽  
Active Regions ◽  
Large Array ◽  
Magnetic Dipoles ◽  
Very Large Array ◽  
Magnetic Structures ◽  
Brightness Temperatures

Very Large Array (VLA) synthesis maps of the total intensity and the circular polarization of three active regions at 6 cm wavelength are presented. The radiation from each active region is dominated by a few intense cores with angular sizes of ~ 0.5′, brightness temperatures of ~ 106 K, and degrees of circular polarization of 30 to 90%. Some of the core sources within a given active region exhibit opposite senses of circular polarization, suggesting the feet of magnetic dipoles, and the high brightness temperatures suggest that these magnetic structures belong to the low solar corona. We also present comparisons between our VLA maps of circular polarization and Zeeman effect magnetograms of the lower lying photosphere. There is an excellent correlation between the magnetic structures inferred by the two methods, indicating that synthesis maps of circular polarization at 6 cm can be used to delineate magnetic structures in the low solar corona.

scholarly journals Looking for the FIP Effect in EUV Spectra

2001 ◽  
Vol 203 ◽  
pp. 356-358
Author(s):  
B. N. Dwivedi ◽  
E. Landi ◽  
A. Mohan
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Extreme Ultraviolet ◽  
Solar Limb ◽  
Magnetic Loop ◽  
Field Of View ◽  
Element Abundances ◽  
Line Intensities ◽  
Height Dependence ◽  
Considerable Detail

We present results from a study of extreme-ultraviolet (EUV) off-limb spectra obtained with the SUMER instrument on the spacecraft SOHO. Using EUV line intensities, we deduce plasma temperatures and densities in the off-limb solar plasma. We make use of this information to study the FIP effect in the solar corona. We have looked for FIP effect in EUV spectra obtained by SUMER in a considerable detail. In particular, we report K/Ar, Si/Ar and S/Ar relative element abundances and investigate the height dependence of the FIP bias in the solar corona. Also, we study the relative Mg/Ne abundance in an active region at the solar limb to investigate the correlation of the FIP bias with magnetic loop structures in the field of view.

scholarly journals Statistical Properties of Magnetic Separators in Model Active Regions

2000 ◽  
Vol 195 ◽  
pp. 443-444
Author(s):  
B. T. Welsch ◽  
D. W. Longcope
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
First Principles ◽  
Magnetic Charge ◽  
Active Regions ◽  
Heating Rates ◽  
X Ray ◽  
Field Lines ◽  
Charge Topology

“Transient brightenings” (or “microflares”) regularly deposit 1027 ergs of energy in the solar corona, and account for perhaps 20% of the active corona's power (Shimizu 1995). We assume these events correspond to episodes of magnetic reconnection along magnetic separators in the solar corona. Using the techniques of magnetic charge topology, we model active region fields as arising from normally distributed collections of “magnetic charges”, point-like sources/sinks of flux (or field lines). Here, we present statistically determined separator (X-ray loop) lengths, derived from first principles. We are in the process of statistical calculations of heating rates due to reconnection events along many separators.

scholarly journals Optical Evidence for Plasma Ejections and Waves in the Solar Corona

1974 ◽  
Vol 57 ◽  
pp. 323-332 ◽  
Author(s):  
A. Bruzek
Keyword(s):  
Solar Corona ◽  
White Light ◽  
Solar Disk ◽  
Dense Plasma ◽  
Radio Bursts ◽  
X Ray ◽  
Imperfect Knowledge ◽  
Optical Evidence ◽  
Made In

Plasma ejections and waves in the solar corona are almost exclusively flare associated phenomena. Ejections of relatively cool and dense plasma are frequently observed in Hα whereas observations in coronal light (visible, EUV- and X-radiation) are still rather scarce. Occurrence of coronal waves is so far best known from their effects on the Hα chromosphere and, of course, from the production of radio bursts. Only in relatively few cases have observations been made in coronal lines and in coronal continuum by ground based as well as by satellite borne equipment. We may expect, however, that the white light coronagraph and the X-ray telescopes on board of the Skylab will detect quite a number of events in front of the solar disk and high in the solar corona and will considerably increase and improve our imperfect knowledge and understanding of coronal ejections and waves as it is presented in this review.

scholarly journals Diamagnetic Abundance Differentiation in the Solar System

1992 ◽  
Vol 150 ◽  
pp. 425-426
Author(s):  
Raphael Steinitz ◽  
Estelle Kunoff
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Solar Corona ◽  
Ionization Potential ◽  
Chemical Abundances ◽  
Magnetic Structures ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
First Ionization Potential

Chemical abundances in the solar corona or solar wind compared to those in the photosphere differentiate according to first ionization potential (FIP). We suggest that the effect is the result of diamagnetic diffusion pumps operating in the presence of gravitation and diverging magnetic structures. We then comment briefly on implications concerning abundances in the solar system and chemically peculiar stars.

High resolution multi-viewpoint observations of CME kinematics and dynamics

2020 ◽  
Author(s):  
Niclas Mrotzek ◽  
Volker Bothmer
Keyword(s):  
Extreme Ultraviolet ◽  
Spatial Scales ◽  
Systematic Investigation ◽  
3D Modelling ◽  
Field Of View ◽  
Magnetic Structures ◽  
Weather Forecasts ◽  
Modelling Method ◽  
Temporal And Spatial ◽  
Ambient Solar Wind

<p>Coronal mass ejections (CMEs) are impulsive outbursts of coronal plasma bound in magnetic structures. Their initiation and evolution into the heliosphere covers several orders of magnitude of temporal and spatial scales that can be observed with space-borne extreme ultraviolet imagers, coronagraphs and heliospheric imagers. In this work we present a systematic investigation of the early dynamics of CMEs including their kinematics, orientation and geometrical evolution. For this purpose, a dedicated set of 21 Earth-directed CMEs between July 2011 and November 2012 was selected and analyzed. The CME parametrization is obtained by applying a 3D modelling method, the Graduated Cylindrical Shell (GCS) model, to simultaneous multi-viewpoint observations taken with the SECCHI instrument suite onboard the twin STEREO spacecraft and with the LASCO coronagraphs onboard the SOHO satellite. By using these instruments, the CME dynamics including the kinematics and geometry, are covered in high detail over a wide spatial range. For the majority of events it started in the field of view of EUVI below 2 solar radii and extended into the field of view of HI1 up to 100 solar radii. The results reveal interactions of the CMEs with the ambient solar wind. CME deflections of up to 31° in longitude and 18° in latitude were measured within the first 30 solar radii. Furthermore, evidence of CME oscillations with periods between 29 and 93 minutes were found. The analysis provides important implications for more reliable space weather forecasts and further analysis through the new observations from Parker Solar Probe and Solar Orbiter.</p><p> </p>

Equivalent Path and Absorption for Electromagnetic Radiation in the Solar Corona

1950 ◽  
Vol 3 (3) ◽  
pp. 376 ◽  
Author(s):  
JC Jaeger ◽  
KC Westfold
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Electromagnetic Radiation ◽  
Spherical Symmetry ◽  
Solar Disk ◽  
Frequency Range ◽  
Echo Signal

Calculations of the trajectories, equivalent path, and absorption of rays, in the frequency range 20-100 Mc/s., in the solar corona have been made, neglecting possible magnetic fields and assuming spherical symmetry. Interpreting the double-humped burst of solar noise as the superposition of a direct and an echo signal, inferences are made as to the height in the corona and location on the solar disk of its source.

Multiple moving magnetic structures in the solar corona

Solar Physics ◽  
1990 ◽  
Vol 128 (2) ◽  
pp. 377-397 ◽  
Author(s):  
N. Gopalswamy ◽  
M. R. Kundu
Keyword(s):  
Solar Corona ◽  
Magnetic Structures

scholarly journals Coronal global EIT waves as tools for multiple diagnostics

2007 ◽  
Vol 3 (S247) ◽  
pp. 243-250
Author(s):  
I. Ballai ◽  
M. Douglas
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Solar Disk ◽  
Coronal Loop ◽  
Large Scale ◽  
Theoretical Models ◽  
Coronal Loops ◽  
Quiet Sun ◽  
Propagating Waves ◽  
Global Magnetic Field

AbstractObservations in EUV lines of the solar corona revealed large scale propagating waves generated by eruptive events able to travel across the solar disk for large distances. In the low corona, CMEs are known to generate, e.g. EIT waves which can be used to sample the coronal local and global magnetic field. This contribution presents theoretical models for finding values of magnetic field in the quiet Sun and coronal loops based on the interaction of global waves and local coronal loops as well as results on the generation and propagation of EIT waves. The physical connection between local and global solar coronal events (e.g. flares, EIT waves and coronal loop oscillations) will also be explored.

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