The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform

S. F. Pimenov - One of the best experts on this subject based on the ideXlab platform.

  • An exact solution of the kompaneets equations for a strong point explosion in a medium with quadratic density decrease
    Radiophysics and Quantum Electronics, 1998
    Co-Authors: V. M. Kontorovich, S. F. Pimenov
    Abstract:

    In the Kompaneets approximation, we study the propagation of a shock front from the explosion point in an inhomogeneous medium with a power-law variation of the density characterized by the exponent n=2, which is important and corresponds to the external parts of the solar and Stellar Coronas. An unexpectedly simple exact solution, which allows us to clarify the structure of the general solution under an arbitrary monotonous law of the density variation, was obtained. The results for the plane case are compared with Korikanskii’s results for a noncentral point explosion in a radially stratified medium. A correspondence between the exact solutions is established in these cases, and a new solution for the noncentral explosion is obtained for the case of a density with a singularity at a finite radius, which decreases quadratically at infinity.

  • Exact Solution of the Kompaneets Equation for Strong Explosion in Medium with Inverse-Square Decreasing Density
    arXiv: Astrophysics, 1998
    Co-Authors: V. M. Kontorovich, S. F. Pimenov
    Abstract:

    In the framework of the Kompaneets approximation the propagation of a shock front (SF) in inhomogeneous medium with the power-law density decrease at the exponent $n=2$ is investigated. For this important case corresponding to outer regions of the solar and Stellar Coronas an unexpectedly simple exact solution clearing a structure of the general solution for an arbitrary monotonic density of medium is found. Our results for plane-layered medium are compared to the Korycansky one for off-centre explosion in radially stratified medium. The relation between the solutions in these media are found and a new exact solution for a noncentral explosion in the case of density singularity on the finite radius is received.

V. M. Kontorovich - One of the best experts on this subject based on the ideXlab platform.

  • An exact solution of the kompaneets equations for a strong point explosion in a medium with quadratic density decrease
    Radiophysics and Quantum Electronics, 1998
    Co-Authors: V. M. Kontorovich, S. F. Pimenov
    Abstract:

    In the Kompaneets approximation, we study the propagation of a shock front from the explosion point in an inhomogeneous medium with a power-law variation of the density characterized by the exponent n=2, which is important and corresponds to the external parts of the solar and Stellar Coronas. An unexpectedly simple exact solution, which allows us to clarify the structure of the general solution under an arbitrary monotonous law of the density variation, was obtained. The results for the plane case are compared with Korikanskii’s results for a noncentral point explosion in a radially stratified medium. A correspondence between the exact solutions is established in these cases, and a new solution for the noncentral explosion is obtained for the case of a density with a singularity at a finite radius, which decreases quadratically at infinity.

  • Exact Solution of the Kompaneets Equation for Strong Explosion in Medium with Inverse-Square Decreasing Density
    arXiv: Astrophysics, 1998
    Co-Authors: V. M. Kontorovich, S. F. Pimenov
    Abstract:

    In the framework of the Kompaneets approximation the propagation of a shock front (SF) in inhomogeneous medium with the power-law density decrease at the exponent $n=2$ is investigated. For this important case corresponding to outer regions of the solar and Stellar Coronas an unexpectedly simple exact solution clearing a structure of the general solution for an arbitrary monotonic density of medium is found. Our results for plane-layered medium are compared to the Korycansky one for off-centre explosion in radially stratified medium. The relation between the solutions in these media are found and a new exact solution for a noncentral explosion in the case of density singularity on the finite radius is received.

Moira Jardine - One of the best experts on this subject based on the ideXlab platform.

  • Topology of Stellar coronae
    Proceedings of the International Astronomical Union, 2006
    Co-Authors: Moira Jardine
    Abstract:

    While the existence of cycles in Stellar chromospheric flux has been known for some time, the nature of the corresponding coronal response has been more elusive. We describe recent results on the relationship between cyclic variations in surface magnetic flux and coronal structure and re-assess the role of prominence observations in understanding the topology of Stellar Coronas. We present a new paradigm for prominence support which allows for extended prominences to co-exist with a compact corona. We discuss briefly the recent results on coronal structure in high- and low-mass stars and their implications for dynamo theory.

M. A. Livshits - One of the best experts on this subject based on the ideXlab platform.

  • The activity of late-type stars: the Sun among stars with cyclic activity
    Astronomy Reports, 2006
    Co-Authors: M. M. Katsova, M. A. Livshits
    Abstract:

    The coronal and chromospheric emission of several hundred late-type stars whose activity was recently detected are analyzed. This confirms the previous conclusion for stars of HK project that there exist three groups of objects: active red M dwarfs, G-K stars with cyclic activity, and stars exhibiting high but irregular activity. The X-ray fluxes, EUV-spectra, and X-ray cycles can be used to study the main property of Stellar Coronas—the gradual increase in the number of high-temperature (T ≥ 10 MK) regions in the transition from the Sun to cyclically active K dwarfs and more rapidly rotating F and G stars with irregular activity. The level of X-ray emission is closely related to the spottedness of the Stellar surface. The correlation between the chromospheric and coronal emission is weak when the cycles are well-defined, but becomes strong when the activity is less regular. Unexpectedly, stars whose chromospheric activity is even lower than that of the Sun are fairly numerous. Common and particular features of solar activity among the activity of other cyclically active stars are discussed. Our analysis suggests a new view of the problem of heating Stellar Coronas: the Coronas of stars with pronounced cycles are probably heated by quasistationary processes in loops, while prolonged nonstationary coronal events are responsible for heating the Coronas of F and G stars with high but irregular activity.

V. A. Kovalev - One of the best experts on this subject based on the ideXlab platform.