scholarly journals Solar Mass Ejections and Coronal Holes

1996 ◽  
Vol 154 ◽  
pp. 105-112
Author(s):  
Arvind Bhatnagar
Keyword(s):  
Coronal Hole ◽  
Large Scale ◽  
Neutral Line ◽  
Coronal Holes ◽  
Field Configuration ◽  
Solar Mass ◽  
X Ray ◽  
Filament Eruption ◽  
Open Magnetic Field ◽  
Interplanetary Scintillations

AbstractIn this paper we present observations of two types of solar mass ejections, which seem to be associated with the location of coronal holes. In the first type, a filament eruption was observed near a coronal hole, which gave rise to a strong interplanetary scintillations, as detected by IPS observations. In the second type, several large scale soft X-ray ‘blow-outs’ were observed in the YOHKOH SXT X-ray movies, in all the cases they erupted from or near the boundary of coronal holes and over the magnetic neutral line. It is proposed that the open magnetic field configuration of the coronal hole provides, the necessary field structure for reconnection to take place, which in turn is responsible for filament eruption, from relatively lower heights. While, in the case of X-ray ‘blow-outs’, the reconnection takes place at a greater height, resulting in high temperature soft X-ray emission visible as X-ray ‘blow-outs’.

scholarly journals Variations of the Coronal Radiation in X-ray Related to Coronal Holes, Active Region Loop Systems, Bright Points

1994 ◽  
Vol 143 ◽  
pp. 159-171
Author(s):  
Ester Antonucci
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Large Scale ◽  
Coronal Holes ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Small Scale ◽  
X Ray ◽  
Coronal Structures

The coronal features observed in X-ray emission, varying from the small-scale, short-lived bright points to the large-scale, long-lived coronal holes, are closely associated with the coronal magnetic field and its topology, and their variability depends strongly on the solar cycle. Here we discuss the spatial distribution of the coronal structures, the frequency distribution of the brightness variations in active regions, and the role of magnetic reconnection in determining the variability of the coronal features, on the basis of the new observations of the soft X-ray emission recently obtained with the Yohkoh satellite and the NIXT experiment.

scholarly journals The contribution of X-ray polar blowout jets to the solar wind mass and energy

2013 ◽  
Vol 8 (S300) ◽  
pp. 239-242 ◽  
Author(s):  
Giannina Poletto ◽  
Alphonse C. Sterling ◽  
Stefano Pucci ◽  
Marco Romoli
Keyword(s):  
Solar Wind ◽  
Kinetic Energy ◽  
Energy Budget ◽  
Coronal Mass Ejections ◽  
Mass Flux ◽  
Large Scale ◽  
Coronal Holes ◽  
Magnetic Loop ◽  
Small Scale ◽  
X Ray

AbstractBlowout jets constitute about 50% of the total number of X-ray jets observed in polar coronal holes. In these events, the base magnetic loop is supposed to blow open in what is a scaled-down representation of two-ribbon flares that accompany major coronal mass ejections (CMEs): indeed, miniature CMEs resulting from blowout jets have been observed. This raises the question of the possible contribution of this class of events to the solar wind mass and energy flux. Here we make a first crude evaluation of the mass contributed to the wind and of the energy budget of the jets and related miniature CMEs, under the assumption that small-scale events behave as their large-scale analogs. This hypothesis allows us to adopt the same relationship between jets and miniature-CME parameters that have been shown to hold in the larger-scale events, thus inferring the values of the mass and kinetic energy of the miniature CMEs, currently not available from observations. We conclude our work estimating the mass flux and the energy budget of a blowout jet, and giving a crude evaluation of the role possibly played by these events in supplying the mass and energy that feeds the solar wind.

scholarly journals Coronal Structure and Solar Wind

1980 ◽  
Vol 91 ◽  
pp. 73-78
Author(s):  
J. N. Tandon
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Coronal Holes ◽  
Solar Magnetic Fields ◽  
Coronal Structure ◽  
Active Centers ◽  
Hydromagnetic Wave ◽  
Field Lines ◽  
Open Magnetic Field ◽  
Coronal Structures

Recent observations of large scale coronal structures and solar wind have been studied. The intercorrelation of the two have been qualitatively explained through the focussing of solar-ion streams taking account of the local and general solar magnetic fields. This explains the association of coronal holes with weak, diverging open magnetic field lines and envisages the transfer of hydromagnetic wave energy from nearby active centers to account for the enhanced outflow of solar wind associated with coronal holes.

scholarly journals Eruptions from coronal hole bright points: Observations and non-potential modelling

2020 ◽  
Vol 643 ◽  
pp. A19
Author(s):  
Maria S. Madjarska ◽  
Klaus Galsgaard ◽  
Duncan H. Mackay ◽  
Kostadinka Koleva ◽  
Momchil Dechev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Coronal Hole ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Free Field ◽  
Flux Rope ◽  
Small Scale ◽  
X Ray ◽  
Lift Off

Context. We report on the third part of a series of studies on eruptions associated with small-scale loop complexes named coronal bright points (CBPs). Aims. A single case study of a CBP in an equatorial coronal hole with an exceptionally large size is investigated to expand on our understanding of the formation of mini-filaments, their destabilisation, and the origin of the eruption triggering the formation of jet-like features recorded in extreme ultraviolet (EUV) and X-ray emission. We aim to explore the nature of the so-called micro-flares in CBPs associated with jets in coronal holes and mini coronal mass ejections in the quiet Sun. Methods. Co-observations from the Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory as well as GONG Hα images are used together with a non-linear force free field (NLFFF) relaxation approach, where the latter is based on a time series of HMI line-of-sight magnetograms. Results. A mini-filament (MF) that formed beneath the CBP arcade about 3−4 h before the eruption is seen in the Hα and EUV AIA images to lift up and erupt triggering the formation of an X-ray jet. No significant photospheric magnetic flux concentration displacement (convergence) is observed and neither is magnetic flux cancellation between the two main magnetic polarities forming the CBP in the time period leading to MF lift-off. The CBP micro-flare is associated with three flare kernels that formed shortly after the MF lift-off. No observational signature is found for magnetic reconnection beneath the erupting MF. The applied NLFFF modelling successfully reproduces both the CBP loop complex as well as the magnetic flux rope that hosts the MF during the build-up to the eruption. Conclusions. The applied NLFFF modelling is able to clearly show that an initial potential field can be evolved into a non-potential magnetic field configuration that contains free magnetic energy in the region that observationally hosts the eruption. The comparison of the magnetic field structure shows that the magnetic NLFFF model contains many of the features that can explain the different observational signatures found in the evolution and eruption of the CBP. In the future, it may eventually indicate the location of destabilisation that results in the eruptions of flux ropes.

Mass and Energy Flow in the Solar Atmosphere Implications of Skylab Observations

1977 ◽  
Vol 36 ◽  
pp. 263-315
Author(s):  
George L. Wlthbroe
Keyword(s):  
Solar Atmosphere ◽  
Energy Flow ◽  
Large Scale ◽  
Strong Field ◽  
Coronal Holes ◽  
Active Regions ◽  
Weak Field ◽  
X Ray ◽  
The North ◽  
East Limb

The Skylab experiments acquired a wealth of observations applicable to investigating problems associated with the mass and energy flow in the solar atmosphere. In this review we discuss some of the observations of quiet regions, coronal holes and active regions and Illustrate the fundamental role that magnetic fields play in defining the structure and the mass and energy flow in these regions. Figure 1 (Altschuler et al., 1976) illustrates three major classes of structure: (1) strong field, magnetically closed areas typified by active regions, (2) weak field, open regions which, according to present evidence, appear to be associated primarily with coronal holes, and (3) weak field regions which appear to be magnetically closed on a large scale and appear to be associated primarily with normal quiet areas. Some of these latter structures can be seen in the X-ray photograph presented in Figure 2 (Vaiana et al., 1973a). Also evident in this figure are large coronal holes near the east limb at the north pole.

scholarly journals Implications of NRL/ATM Solar Flare Observations on Flare Theories

1975 ◽  
Vol 68 ◽  
pp. 423-424
Author(s):  
C. C. Cheng ◽  
D. S. Spicer
Keyword(s):  
Magnetic Field ◽  
Neutral Line ◽  
Three Dimensional ◽  
Spatial Relationship ◽  
Wavelength Region ◽  
Field Configuration ◽  
Spatial Distributions ◽  
X Ray ◽  
Cool Plasma ◽  
The Many

SummaryDuring the Skylab mission, many solar flares were observed with the NRL XUV spectroheliogram in the wavelength region from 150 to 650 Å. Because of its high spatial resolution (∼2″) the three-dimensional structures of the flare emission regions characterized by temperatures from 104 K to 20 × 106 K can be resolved. Thus the spatial relationship between the relatively cool plasma and the hot plasma components of a flare, and the associated magnetic field structure can be inferred. For example, the Fe XXIV plasma (T≃20 × 106 K) observed near the soft X-ray maximum during the 2B (M2) disk flare of 1973, July 15 is elongated perpendicular to the neutral line shown on the photospheric magnetogram, while lines of lower ionization temperatures such as He II–Fe XVI show the familiar double ribbon structures on either side of the neutral line (Widing and Cheng, 1974). The disk flare of 1973, September 5 shows the same spatial structures. The flare was observed at 1831 UT at the X-ray maximum, and shows that the hot Fe XXIV cloud is located spatially between the ribbons of the He II, Fe XIV–Fe XVI emissions. As the flare cools at 1837 UT, the Fe XXIV cloud disappears while the gap is filled with emissions from ions of lower ionization potentials, and exhibit loop structure. Many other flares also show similar spatial distributions in the XUV emissions. The linear dimensions of the Fe XXIV plasmas as measured from the photospheric plates range from 7000 km to 14000 km, and the heights of associated loops range from 10000 to 30000 km. From the spatial distributions of the XUV emissions of the many flares, and the comparisons with the magnetograms, we concluded that the magnetic field configuration for the flares we observed are simple bipolar magnetic flux loops with the hot flare plasma located near the top and the cool plasma component on the footprints of the loop.

A Discussion on the physics of the solar atmosphere - The x-ray corona from Skylab

1976 ◽  
Vol 281 (1304) ◽  
pp. 365-374 ◽  
Keyword(s):  
Large Scale ◽  
Dense Plasma ◽  
Coronal Holes ◽  
Active Regions ◽  
Coronal Loops ◽  
Closed Loops ◽  
X Ray ◽  
Physical Conditions ◽  
Wide Range ◽  
The Magnetic Field

An overview of the images obtained with the A.S. & E. X-ray telescope on Skylab shows the low corona to be highly structured. The plasma is distributed in closed loops shaped by the magnetic field with sizes ranging from the smallest resolvable structures of a few thousand kilometres to loops that reach halfway across the solar disk. Relatively high-temperature and dense plasma loops overlay active regions; large-scale interconnections link active regions to their surrounding fields and in some cases to other active regions. The large-scale loops, which cover most of the Sun outside of active regions, appear to be related to old active regions whose magnetic fields have spread out over the course of several solar rotations. Often at the poles and occasionally on the disk, large regions display radial field configurations (coronal holes) from which the plasma preferentially escapes into high-velocity solar wind streams. A comprehensive view of the structure and evolution of the X-ray corona is given in terms of the physical conditions existing in the various coronal loops, and the importance of active regions is emphasized by examining their structure and time development over a wide range of scales.

scholarly journals Statistical Approach on Differential Emission Measure of Coronal Holes using the CATCH Catalog

Solar Physics ◽  
2021 ◽  
Vol 296 (1) ◽  
Author(s):  
Stephan G. Heinemann ◽  
Jonas Saqri ◽  
Astrid M. Veronig ◽  
Stefan J. Hofmeister ◽  
Manuela Temmer
Keyword(s):  
Solar Cycle ◽  
Coronal Hole ◽  
Electron Density ◽  
Large Scale ◽  
Scattered Light ◽  
Coronal Holes ◽  
Emission Measure ◽  
Solar Dynamics Observatory ◽  
Differential Emission Measure ◽  
Plasma Properties

AbstractCoronal holes are large-scale structures in the solar atmosphere that feature a reduced temperature and density in comparison to the surrounding quiet Sun and are usually associated with open magnetic fields. We perform a differential emission measure analysis on the 707 non-polar coronal holes in the Collection of Analysis Tools for Coronal Holes (CATCH) catalog to derive and statistically analyze their plasma properties (i.e. temperature, electron density, and emission measure). We use intensity filtergrams of the six coronal EUV filters from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, which cover a temperature range from $\approx10^{5.5}$ ≈ 10 5.5 to $10^{7.5}~\mbox{K}$ 10 7.5 K . Correcting the data for stray and scattered light, we find that all coronal holes have very similar plasma properties with an average temperature of $0.94 \pm0.18~\mbox{MK}$ 0.94 ± 0.18 MK , a mean electron density of $(2.4 \pm0.7) \times10^{8}~\mbox{cm}^{-3}$ ( 2.4 ± 0.7 ) × 10 8 cm − 3 , and a mean emission measure of $(2.8 \pm1.6) \times10^{26}~\mbox{cm}^{-5}$ ( 2.8 ± 1.6 ) × 10 26 cm − 5 . The temperature distribution within the coronal holes was found to be largely uniform, whereas the electron density shows a 30 to 40% linear decrease from the boundary towards the inside of the coronal hole. At distances greater than 20″ ($\approx15~\mbox{Mm}$ ≈ 15 Mm ) from the nearest coronal hole boundary, the density also becomes statistically uniform. The coronal hole temperature may show a weak solar-cycle dependency, but no statistically significant correlation of plasma properties with solar-cycle variations could be determined throughout the observed period between 2010 and 2019.

On the Location of Quiescent Prominences with Respect to Coronal Holes

1979 ◽  
Vol 44 ◽  
pp. 209-213
Author(s):  
B. Rompolt
Keyword(s):  
Coronal Hole ◽  
Average Distance ◽  
Coronal Holes

The aim of this contribution is to turn attention to a peculiarity of location of the filaments (quiescent prominences) with respect to the boundaries of the coronal holes. It is generally known that quiescent prominences are located at some distance from the boundary of coronal holes. My intention was to check whether the average distance between the nearest border of a coronal hole and the prominence is comparable to the average horizontal extension of a helmet structure overlying the prominence. As well as, whether this average distance depends upon the orientation of the long axis of the prominence with respect to the nearest boundary of the coronal hole.

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