Current driven low-frequency electrostatic waves in the solar corona: Linear theory and nonlinear saturation

2007 ◽  
Vol 14 (11) ◽  
pp. 112903 ◽  
Author(s):  
Kuang Wu Lee ◽  
Jörg Büchner ◽  
Nina Elkina
Keyword(s):  
Solar Corona ◽  
Linear Theory ◽  
Low Frequency ◽  
Nonlinear Saturation ◽  
Electrostatic Waves

Low-frequency heating of doublets

1981 ◽  
Vol 25 (1) ◽  
pp. 133-143 ◽  
Author(s):  
T. H. Jensen ◽  
F. W. McClain ◽  
H. Grad
Keyword(s):  
Physical Model ◽  
Linear Theory ◽  
Low Frequency ◽  
Plasma Temperature ◽  
Auxiliary Heating ◽  
Power Sources ◽  
Axisymmetric Mode ◽  
Low Frequency Power ◽  
Frequency Power ◽  
Frequency Heating

Heating of a doublet plasma by driving an axisymmetric mode at low frequency may be an attractive means for auxiliary heating. The attractiveness of the method stems from (1) the low technology required for low-frequency power sources, (2) the fact that the field-shaping coils required for doublets may also be used as the antennae for transmitting the power, (3) the possibility of transmitting the power through a resistive vacuum wall, (4) the insensitivity to the plasma temperature and density and (5) the relative simplicity of the physical model. The utility of the concept depends on the existence of a special axisymmetric eigenmode in the resistive M.HD approximation which is used. This mode has nodes through the elliptic axes of the doublet equilibrium and an antinode at the hyperbolic axis. It is remarkable that the dissipation per cycle of this mode remains large at low plasma resistivity. This paper describes a linear theory for such heating.

scholarly journals LOFAR observations of the quiet solar corona

2018 ◽  
Vol 614 ◽  
pp. A54 ◽  
Author(s):  
C. Vocks ◽  
G. Mann ◽  
F. Breitling ◽  
M. M. Bisi ◽  
B. Dąbrowski ◽  
...  
Keyword(s):  
Radio Emission ◽  
Solar Corona ◽  
Density Profile ◽  
Extreme Ultraviolet ◽  
Low Frequency ◽  
Scale Height ◽  
Solar Radio Emission ◽  
Radial Magnetic Field ◽  
Brightness Temperatures ◽  
Hydrostatic Model

Context. The quiet solar corona emits meter-wave thermal bremsstrahlung. Coronal radio emission can only propagate above that radius, Rω, where the local plasma frequency equals the observing frequency. The radio interferometer LOw Frequency ARray (LOFAR) observes in its low band (10–90 MHz) solar radio emission originating from the middle and upper corona. Aims. We present the first solar aperture synthesis imaging observations in the low band of LOFAR in 12 frequencies each separated by 5 MHz. From each of these radio maps we infer Rω, and a scale height temperature, T. These results can be combined into coronal density and temperature profiles. Methods. We derived radial intensity profiles from the radio images. We focus on polar directions with simpler, radial magnetic field structure. Intensity profiles were modeled by ray-tracing simulations, following wave paths through the refractive solar corona, and including free-free emission and absorption. We fitted model profiles to observations with Rω and T as fitting parameters. Results. In the low corona, Rω < 1.5 solar radii, we find high scale height temperatures up to 2.2 × 106 K, much more than the brightness temperatures usually found there. But if all Rω values are combined into a density profile, this profile can be fitted by a hydrostatic model with the same temperature, thereby confirming this with two independent methods. The density profile deviates from the hydrostatic model above 1.5 solar radii, indicating the transition into the solar wind. Conclusions. These results demonstrate what information can be gleaned from solar low-frequency radio images. The scale height temperatures we find are not only higher than brightness temperatures, but also than temperatures derived from coronograph or extreme ultraviolet (EUV) data. Future observations will provide continuous frequency coverage. This continuous coverage eliminates the need for local hydrostatic density models in the data analysis and enables the analysis of more complex coronal structures such as those with closed magnetic fields.

scholarly journals The Origin of Switchbacks in the Solar Corona: Linear Theory

2020 ◽  
Vol 903 (1) ◽  
pp. 1
Author(s):  
G. P. Zank ◽  
M. Nakanotani ◽  
L.-L. Zhao ◽  
L. Adhikari ◽  
J. Kasper
Keyword(s):  
Solar Corona ◽  
Linear Theory

scholarly journals The Low-Frequency Solar Corona in Circular Polarization

Solar Physics ◽  
2019 ◽  
Vol 294 (8) ◽  
Author(s):  
Patrick I. McCauley ◽  
Iver H. Cairns ◽  
Stephen M. White ◽  
Surajit Mondal ◽  
Emil Lenc ◽  
...  
Keyword(s):  
Solar Corona ◽  
Circular Polarization ◽  
Low Frequency

E×B guiding-centre motion in three electrostatic waves: statistics of separatrix crossings

1998 ◽  
Vol 59 (4) ◽  
pp. 761-772
Author(s):  
B. WEYSSOW
Keyword(s):  
Phase Space ◽  
Low Frequency ◽  
Integration Scheme ◽  
Symplectic Integrator ◽  
Third Order ◽  
Special Configuration ◽  
Electrostatic Waves ◽  
Hamiltonian Theory ◽  
Numerical Integration Methods ◽  
Adiabatic Motion

E×B guiding-centre (GC) motion in a special configuration of three low-frequency electrostatic waves can be considered as a paradigmatic Hamiltonian system for studying adiabatic motion and separatrix crossings. A peculiarity of this system is that a single initial condition gives rise to two stroboscopic phase-space trajectories. According to the classical Hamiltonian theory, the proportion of points on the stroboscopic trajectories is a function of the time evolution of the surfaces enclosed by the separatrices in the phase space. This behaviour is qualitatively observed in test-particle numerical experiments. The ability of numerical integration methods like the ‘classical’ fourth-order Runge–Kutta integration scheme or a third-order symplectic integrator to reproduce the statistics is analysed.

A Low-Frequency Radio Spectropolarimeter for Observations of the Solar Corona

Solar Physics ◽  
2015 ◽  
Vol 290 (9) ◽  
pp. 2409-2422 ◽  
Author(s):  
P. Kishore ◽  
R. Ramesh ◽  
C. Kathiravan ◽  
M. Rajalingam
Keyword(s):  
Solar Corona ◽  
Low Frequency
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