Solar Corona

Hypersphere World-Universe Model (WUM) envisions Matter carried from Universe into World from fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is byproduct of Dark Matter (DM) annihilation. WUM introduces Dark Epoch (spanning from Beginning of World for 0.4 billion years) when only DMPs existed, and Luminous Epoch (ever since for 13.8 billion years). Big Bang discussed in standard cos-mological model is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning DM Supercluster's Cores and annihilation of DMPs. WUM solves a number of physical problems in contemporary Cosmology and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems-how do they obtain it; Fermi Bubbles-two large structures in gamma-rays and X-rays above and below Ga-lactic center; Mysterious Star KIC 8462852 with irregular dimmings; Coronal Heating problem in solar physics-temperature of Sun's corona exceeding that of photo-sphere by millions of degrees; Cores of Sun and Earth rotating faster than their surfaces ; Diversity of Gravitationally-Rounded Objects in Solar system and their Internal Heat; Lightning Initiation problem-electric fields observed inside thunderstorms are not sufficient to initiate sparks; Terrestrial Gamma-Ray Flashes-bursts of high energy X-rays and gamma rays emanating from Earth. Model makes predictions pertaining to Masses of DMPs, proposes New Types of their Interactions. WUM reveals Inter -Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.

The SOHO mission has achieved important results in the physics of solar wind and coronal mass ejection acceleration, but most of the processes that drive this acceleration have not yet been explained. The Advanced Spectroscopic and Coronagraphic Explorer (ASCE) mission will carry on-board spectroscopic and polarimetric instrumentation of new generation that is designed to address the fundamental questions on this processes. Following a brief description of ASCE scientific objectives and instrumentation, the EUV polarimetric channel is described. The EUV Polarimeter (EUVP) is designed to measure for the first time the magnetic field vector in the extended corona through the Hanle effect, and the anisotropy of the ion velocity. The EUVP represents the contribution of the Italian solar physics community to the ASCE mission.

We study the propagation and dissipation of Alfvén gravity waves in the solar corona, considering viscosity as a damping mechanism, and derive a general dispersion relation for Alfvén gravity waves under WKB and Boussinesq approximation. We find that in the presence of viscosity, the wave normal surfaces do not differ significantly from the results obtained in an ideal MHD. From dissipation point of view, we find that for the wave frequency less than the Brunt-Väisälä frequency (i.e., ω¯<1) there are two types of damping, one is strong damping when LD ˜ λ and the other is weak damping when LD ≫ λ. For the wave frequencies greater than the Brunt-Väisälä frequency (i.e., ω¯>1), however, we get only weak damped oscillations. Thus, Brunt-Väisälä frequency separates regimes of wave frequency in which damping is weak or strong.

We have analysed, for the first time, the high resolution X-ray images of the solar corona, obtained by the Yohkoh Mission, as non-linear extended systems. To quantify the spatio-temporal complexity in this extended system, we use an asymmetric spatial fragmentation parameter computed from a matrix representing an image. Choosing different spatial scales on the same image, wave numbers are computed from the intensity contours and this yields a fragmentation spectrum. This spectrum is used to analyze the images of a complex transient event obtained by the Soft X-ray Telescope board the Yohkoh satellite. The dynamics of the fine structures of the contours suggests the origin of the observed fragmentation to be localized weak turbulence process occuring in an evolving coronal active region.

This paper discusses the scattering in the solar corona of the radiation emitted by the solar disk. We obtain expressions for the emissivity which permit to deduce the spectral characteristics of the scattered radiation. With these expressions, assuming a Maxwellian distribution for the velocities of the scattering ions and a simple spectral shape of the exciting radiation, we produce approximate analytic formulae which show some interesting properties of the scattered radiation that do not clearly emerge from the exact expressions. Among them, the expression for the Doppler shift of the radiatively excited component of a line, and that for its width. We also examine the case of bi-Maxwellian velocity distributions and the scattering by the free electrons.

The 2-D continuous wavelet transform has been applied to a number of problems in astrophysics. We survey quickly some of these, then focus on two new applications. The first one is the automatic detection and analysis of special objects from the solar corona in the data taken by the EIT instrument aboard the SoHO satellite. The second problem is the detection of gamma sources in the Universe, the difficulty lying in the discrimination of faint sources against a highly nonuniform background and the large number of sources (to be) ...

There is abundant observational evidence that the energization of plasma particles in space is correlated with an enhanced activity of large-scale MHD waves. Since these waves cannot interact with particles, we need to find ways for these MHD waves to transport energy in the dissipation range formed by small-scale or high-frequency waves, which are able to interact with particles. In this paper we consider the dissipation range formed by the kinetic Alfvén waves (KAWs) which are very short- wavelengths across the magnetic field irrespectively of their frequency. We study a nonlocal nonlinear mechanism for the excitation of KAWs by MHD waves via resonant decay AW(FW)→KAW1+KAW2, where the MHD wave can be either an Alfvén wave (AW), or a fast magneto-acoustic wave (FW). The resonant decay thus provides a non-local energy transport from large scales directly in the dissipation range. The decay is efficient at low amplitudes of the magnetic field in the MHD waves, B/B0~10-2. In turn, KAWs are very efficient in the energy exchange with plasma particles, providing plasma heating and acceleration in a variety of space plasmas. An anisotropic energy deposition in the field-aligned degree of freedom for the electrons, and in the cross-field degrees of freedom for the ions, is typical for KAWs. A few relevant examples are discussed concerning nonlinear excitation of KAWs by the MHD wave flux and consequent plasma energization in the solar corona and terrestrial magnetosphere.

The set of equations for magnetohydrodynamic (MHD) waves in a shear flow is consecutively derived. The proposed scenario involves the presence of a self-sustained turbulence and magnetic field. In the framework of Langevin--Burgers approach the influence of the turbulence is described by an additional external random force in the MHD system. Kinetic equation for the spectral density of the slow magnetosonic (Alfvenic) mode is derived in the short wavelength (WKB) approximation. The results show a pressing need for conduction of numerical Monte Carlo (MC) simulations with a random driver to take into account the influence of the long wavelength modes and to give a more precise analytical assessment of the short ones. Realistic MC calculations for the heating rate and shear stress tensor should give an answer to the perplexing problem for the missing viscosity in accretion disks and reveal why the quasars are the most powerful sources of light in the universe. The planned MC calculati...