Self-regulation of solar coronal heating process via the collisionless reconnection condition

I propose a new paradigm for solar coronal heating viewed as a self-regulating process keeping the plasma marginally collisionless. The mechanism is based on the coupling between two effects. First, coronal density controls the plasma collisionality and hence the transition between the slow collisional Sweet-Parker and the fast collisionless reconnection regimes. In turn, coronal energy release leads to chromospheric evaporation, increasing the density and thus inhibiting subsequent reconnection of the newly reconnected loops. As a result, statistically, the density fluctuates around some critical level, comparable to that observed in the corona. In the long run, coronal heating can be represented by repeating cycles of fast reconnection events (nanoflares), evaporation episodes, and long periods of slow magnetic stress buildup and radiative cooling of the coronal plasma.     

Observation of collisionless plasma heating by strong shock waves

The heating of a plasma by collisionless shock waves is investigated by measuring the variation of magnetic field (with magnetic probes), density and electron temperature (from Thomson scattering of laser light) in the shock waves. The compression waves are produced in a tube of 14 cm diameter by the fast rising magnetic field (12 kG in 0.5Μsec) of a theta pinch. For shocks with Mach numbers between 2 and 3 propagating into a hydrogen or deuterium plasma with a localΒ of about 1 (Β=ratio of particle pressure to magnetic pressure) the measured jump in density and magnetic field across the front is 2 to 4, and the electron temperature increases in the front from 3 to 50 eV with a further rise to between 100 and 250 eV in the piston region. Only about 20% of the measured electron heating can be explained by adiabatic heating and resistive heating based on binary collisions, indicating a high turbulent plasma resistance. Both the observed electron heating and the width of the shock front, which is about 0.6 ·c/Ω _p, can be accounted for using an effective collision frequency close to the ion plasma frequencyΩ _p. The ion heating in the almost stationary shock fronts can be inferred indirectly from the steady state conservation relations. For shock waves with Mach numbersM<M _crit it seems to be consistent with an adiabatic heating process, whereas forM>M _crit the calculated ion temperatures exceed those one would except for a merely adiabatic heating.     

Turbulent heating of electrons and ions in a collisionless shock wave

Turbulent heating of a nonisothermal plasma by a collisionless shock wave is analysed in the situation when a small-scale high-frequency instability occurs at the wave front. Effective time of electron and ion heating is estimated.     

Weak compressible magnetohydrodynamic turbulence in the solar corona

This Letter presents a calculation of the power spectra of weakly turbulent Alfvén waves and fast magnetosonic waves ("fast waves") in low- plasmas. It is shown that three-wave interactions transfer energy to high-frequency fast waves and, to a lesser extent, high-frequency Alfvén waves. High-frequency waves produced by MHD turbulence are a promising explanation for the anisotropic heating of minor ions in the solar corona.     

The coronograph-polarimeter: An algorithm for creation of solar corona polarization images

An algorithm for polarization imaging of the white light corona has been devised on the basis of the Stokes vector presentation and the IDL software applied to statistical data. The use of the algorithm for a 24-frame color negative polarization film of the corona of November 3, 1994, digitized in the green light allowed new data to be obtained on the distribution of the polarization degree in the white (summary of the blue and red spectral interval emissions) corona. On the average, the monotonic increase in the polarization degree, which is characteristic for the van de Hülst model, was not found over the range (1.2–2.0)R in heliolatitudes ±45°.The polarization degree was virtually constant in the region (1.2–1.4)R .The apparent plateau in the polarization degree distribution is obviously due to the deviation of the model with local spherical symmetry from the actual 3D structure of the inner corona.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1298–1305, October, 1996.     

A peculiarity of silver-based corona wire heating on ozone generation

The effect of corona wire temperature on the ozone generation in the positive dc corona electrostatic precipitator is studied experimentally. The external heating of the corona wire can suppress the ozone generation. In this study, nichrome and two kinds of silver-based wires 0.1 mm diameter were tested as discharges electrodes. The nichrome corona wire heating shows a well-known monotonic decreasing the rate of ozone production. In the case of the tested silver-based wires the rate of ozone production decreases nonlinearly and passes through a local minimum in the range from 35 to 55 °C with increasing the wire temperature. At the wire temperature about 46 °C ozone generation by positive dc corona discharge is decreased by 53% with Ag:Mn = 0.85:0.15 wire and by 25% with Ag:Ni = 0.7:0.3 wire as compared to the same wire at 26 °C. Under these conditions the corona wire heating increases slightly the corona current and speed of airflow.     

Photometry of the solar corona of March 7, 1970

Isophotes obtained by equidensitometry techniques from four exposures of the March 7, 1970 corona are used for derivation of intensity distributions along the equator, poles, streamers and dark ‘gaps’ in the visible corona. The distributions differ from the van de Hulst curves for a maximum corona. The Kodaikanal measures agree well with the NRL measures of the outer corona made from a rocket coronagraph and together provide data from 1·2R_⊙ to 8·0R_⊙ along the solar equator. Radial intensity gradients for different position angles and the Ludendorff parameters obtained, characterize this corona as typical of the solar maximum.     

Measuring magnetic fields in the solar corona by radio emissions

Some ways of identifying magnetic fields in the solar corona using the observed properties of solar radio emissions are discussed. Examples are given for measuring the magnetic field in the active region atmosphere (in the chromosphere-corona transition region) based on spectral observations of microwave radiation from local sources associated with sunspots. Ways of determining the magnetic field in hot coronal loops in the case of recording cyclotron lines in solar microwave radiation are considered. It is shown that polarization of the second harmonic in Type III bursts testifies to a magnetic field on the track of electrons accelerated in the flare region and moving outward.Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 7, pp. 821–835, July, 1994.     

Electron density of the magnesium XII doublet in the solar corona by use of a collision excitation model

For accurate spectroscopic diagnostics in the solar corona, the principle of spectral diagnostics of electron density is discussed by collision excitation model. Variation in electron density in the solar corona is calculated by this method using the observed signal ratio of spectral lines produced by the magnesium XII ion in the solar corona. Results show that with increasing signal ratio, the electron density will decrease; furthermore, the electron density is on the order of 10¹⁰?cm^?3, which is a reasonable value in the solar corona. Finally, variation in temperature with different signal ratio is discussed. This investigation will be significant for solar plasma diagnostics and study on the solar coronal.     

Bianchi type I anisotropic cosmological model with a collisionless gas

The self-consistent system of Einstein-Vlasov equations is investigated in a class of homogeneous spaces. The Bianchi Type I anisotropic cosmological model with orthogonal Killing vectors is considered in detail. It is shown that the energymomentum tensor of a collisionless gas is spatially anisotropic. Exact solutions of the Einstein-Vlasov equations are found in the case of strong anisotropy. The behavior of small perturbations is investigated for a mixture of an ideal fluid and a collisionless gas as well as for a nonrelativistic collisionless gas.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 3–8, May, 1981.     

Coexistence of self-organized criticality and intermittent turbulence in the solar corona

An extended data set of extreme ultraviolet images of the solar corona provided by the SOHO spacecraft is analyzed using statistical methods common to studies of self-organized criticality (SOC) and intermittent turbulence (IT). The data exhibit simultaneous hallmarks of both regimes: namely, power-law avalanche statistics as well as multiscaling of structure functions for spatial activity. This implies that both SOC and IT may be manifestations of a single complex dynamical process entangling avalanches of magnetic energy dissipation with turbulent particle flows.     

Parameter space for collisionless RF sheaths

As plasma processing reactors approach higher density, the sheath models which neglect the radio frequency (RF) response of the ions become invalid. This work show that the nature of the collisionless RE ion sheath can be described in a number of different regimes of parameter space. These regimes can all be visualized on a single two-dimensional (2-D) plot where the horizontal axis is the ion plasma frequency divided by the frequency, and the vertical axis is the electron oscillating velocity divided by the ion sound speed     

Performance optimization of solar chimney power plant using electric/corona wind

The effect of the corona wind on the natural convection at absorber of a solar chimney power plant pilot was investigated experimentally. The aim of the study is to improve the efficiency of SCPP through enhanced the heat transfer coefficient of absorber with corona wind. The results show that corona wind enhanced the absorber convective heat transfer coefficient leading to increment in air the velocity and the output power of the SCPP. The amount of heat transfer of pilot increased more than 14.5% when applying voltage of 15 KV and the speed in chimney experienced about 72% amelioration.     

Toward a theory of the double plasma resonance in the solar corona

Specific features of the double plasma resonance effect in a magnetized plasma of the solar corona are discussed. The effect consists in enhanced generation of plasma waves in the regions where the upper hybrid frequency coincides with electron gyrofrequency harmonics. It is widely used for interpretation of a fine structure in solar radio emission spectrum in the form of parallel drifting quasi-harmonic stripes of enhanced radiation intensity (zebra pattern). It is shown that the plasma-wave growth rate increases due to both dispersion properties of plasma waves, which are determined by the equilibrium plasma component, and electrons which are non-equilibrium with respect to the velocities transverse to the magnetic field. Special attention is given to an incorrect consideration of the double plasma resonance effect in some papers. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 2, pp. 95–108, February 2009.     

无碰撞电流片低频电磁模不稳定性：MHD模型

利用含无电阻广义Ohm定律的可压缩磁流体力学(MHD)理论，研究了在具有剪切磁场的无碰撞电流片中低频电磁模不稳定性，假定等离子体压力各向同性，推导出了三维扰动传播波模的色散关系.色散关系的数值求解集中在电流片中间平面(z=0)和半厚度边缘(z=1)上，并分别考虑了二维传播和三维传播，以及不同的离子惯性长度情况.主要结果如下：1)对 于二维扰动传播(k_z=0)的波，在z=0平面上，Alfven波增长率最大，不稳定的波 频率 和波数范围也更宽.离中间平面越远，增长率越小，波数区域越小.同时，随着离子惯性长度 的增大，Alfven波不稳定性的增长率变大.2)对于三维扰动传播(k_z≠0)的波， 哨声是 不稳定的.在电流片中间平面上，哨声有明显的增长率；而在离子惯性区外边，哨声的增长 率还变大.3)在电流片中间(z=0)平面上，低频波主要是电流不稳定性激发的.在离中间 平面较远处，电流、密度和压力的梯度不稳定性变得更重要. 关键词： 无碰撞电流片 磁流体力学 色散关系 不稳定性     

Generation of plasma waves by electron streams in a nonuniform solar corona

The one-dimensional process of propagation of a spatially bounded electron stream in the solar corona is simulated. It is shown that the background plasma inhomogeneity has a significant influence on the stream propagation and plasma-wave generation. The results are qualitatively interpreted in application to type III solar radio bursts, and model dynamic spectra of such bursts are constructed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 9, pp. 731–743, September 2006.     

Diagnostics of the solar corona structure by the refraction effects on radio emission

The solar disc radio brightness distribution observed at RATAN-600 can be interpreted as the angular directivity of the disk center emission at viewing anglesΘ=arcsin(R/R₀) over an angular range of R<0.9R ₀ at several wavelengths in the 2.0–32 cm region. These spectra can be treated as an emission enhancement due to refraction effects in free-free corona emission. The model simulations show good agreement with the observations and lead to estimation of the electron density N_e=1·10 ⁹ cm^?3 and emission measureEM=6·10 ²⁶ cm^?5 for the quiet Sun.