Energy equilibrium in a coronal magnetic loop

1993 ◽  
Vol 207 (1) ◽  
pp. 55-82 ◽  
Author(s):  
Suresh Chandra ◽  
Lalan Prasad
Keyword(s):  
Magnetic Loop ◽  
Coronal Magnetic Loop ◽  
Energy Equilibrium

scholarly journals Source Structure in Metre-Wave Type V Solar Bursts

1974 ◽  
Vol 57 ◽  
pp. 235-238
Author(s):  
N. R. Labrum ◽  
R. A. Duncan
Keyword(s):  
Second Harmonic ◽  
Magnetic Loop ◽  
Plasma Waves ◽  
Trapping Region ◽  
Type Iii ◽  
Coronal Magnetic Loop ◽  
Field Lines ◽  
Set Up ◽  
Type V ◽  
Open Magnetic Field

(Astrophys. Letters). The type V burst has been defined as a wideband continuum which sometimes appears for a minute or so following a type III burst (Wild et al., 1959b). It is now generally accepted that type III bursts arise from plasma waves set up by electrons escaping with velocity ~c/3 along open magnetic field lines (Wild et al., 1959a; Stewart, 1965); the most widely accepted explanation of type V continua is that they arise from plasma waves set up by electrons of similar velocity which have become trapped in a coronal magnetic loop (Weiss and Stewart, 1975). On this hypothesis the plasma waves are set up by two opposing electron streams in the trapping region, and from this consideration Zheleznyakov and Zaitsev (1968) have concluded that type V emission should be predominantly at the second harmonic of the local plasma frequency. In this paper we describe and discuss some two-dimensional observations of source positions of type III–V events which were obtained at 80 MHz on the Culgoora radioheliograph.

Helicity injection and relaxation in a solar-coronal magnetic loop with a free surface

1988 ◽  
Vol 40 (2) ◽  
pp. 263-280 ◽  
Author(s):  
P. K. Browning
Keyword(s):  
Multiple Equilibria ◽  
Energy State ◽  
Minimum Energy ◽  
Magnetic Loop ◽  
External Pressure ◽  
Magnetic Flux Tube ◽  
Helicity Injection ◽  
Taylor’S Hypothesis ◽  
Coronal Magnetic Loop ◽  
Solar Coronal

A solar-coronal magnetic loop is rooted in the photosphere, where motions shuffle the footpoints of the field, generating currents in the corona. The dissipation of these currents provides a possible mechanism for heating the solar corona. A theory is described based on a generalization of Taylor's hypothesis, predicting that as the loop is twisted up, it relaxes towards a minimum-energy state V × B = μB. The footpoint motions inject helicity as well as energy, and the evolution is determined through a helicity-injection equation. The loop is modelled as a straight magnetic-flux tube, with twisting motions at the ends, confined by a constant external pressure at the curved surface, which is a free boundary. The problem of the loop evolution in response to given footpoint motions is solved, and an interesting example of multiple equilibria arises. The heating rate is calculated for an almost-potential loop. The model may also be regarded as representing a laboratory experiment: in particular, a simple idealization of a spheromak, with the footpoint motions replaced by an applied voltage.

scholarly journals EUVE and VLA Observations of the Eclipsing Pre-Cataclysmic Variable V471 Tauri

1996 ◽  
Vol 152 ◽  
pp. 349-354
Author(s):  
S.L. Cully ◽  
J. Dupuis ◽  
T. Rodriguez-Bell ◽  
G. Basri ◽  
O.H.W. Siegmund ◽  
...  
Keyword(s):  
White Dwarf ◽  
Extreme Ultraviolet ◽  
Magnetic Loop ◽  
Pure Hydrogen ◽  
Very Large Array ◽  
Hyades Cluster ◽  
Hydrogen Column Density ◽  
Orbital Phase ◽  
Coronal Magnetic Loop ◽  
Euv Spectrum

We present observations of the eclipsing binary V471 Tauri by the Extreme Ultraviolet Explorer (EUVE) and the Very Large Array (VLA). The EUV spectrum is dominated by the continuum of the hot white dwarf and the time-averaged spectrum is fitted by a 33.1 ± 0.5 × 103 K pure hydrogen white dwarf atmosphere assuming log g = 8.5. An ISM hydrogen column density of 1.5 ± 0.4 × 1018 cm−2 is required to explain the attenuation of the white dwarf spectrum thus setting the HI column in the line of sight of the Hyades cluster. The He II λ304 Å line is in emission and varies over the orbital period of V471 Tauri following a sinusoidal modulation with the maximum reached when the K star is at inferior conjunction. Transient dips are detected at orbital phase −0.12 in the SW and MW spectrometers integrated lightcurves but are notably absent in the LW lightcurve indicating the occulting material is ionized. The VLA observation suggest the presence of a K star coronal magnetic loop between the two stars reconnecting with the white dwarf magnetic field. Such a structure could be the occulting source needed to explain the dips seen in the lightcurves of V471 Tauri in the EUV.

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