共查询到20条相似文献,搜索用时 515 毫秒
1.
The aim of this paper is to determine the flux emergence rate due to small-scale magnetic features in the quiet Sun using
high-resolution Hinode SOT NFI data. Small-scale magnetic features are identified in the data using two different feature identification methods
(clumping and downhill); then three methods are applied to detect flux emergence events. The distribution of the intranetwork
peak emerged fluxes is determined. When combined with previous emergence results, from ephemeral regions to sunspots, the
distribution of all fluxes are found to follow a power-law distribution which spans nearly seven orders of magnitude in flux
(1016 – 1023 Mx) and 18 orders of magnitude in frequency. The power-law fit to all these data is of the form
\fracdNdY = \fracn0Y0\fracYY0-2.7,\frac{\mathrm{d}N}{\mathrm{d}\Psi} = \frac{n_0}{\Psi_0}\frac{\Psi}{\Psi _0}^{-2.7}, 相似文献
2.
The \(^{13}\mathrm{C}(p,\gamma )^{14}\mathrm{N}\) reaction is one of the important reactions in the CNO cycle, which is a key process in nucleosynthesis. We first calculated wave functions for the bound state of \(^{14}\mathrm{N}\) with Faddeev’s method. In this method, the considered reaction components are \(^{12}\mathrm{C}+n+p\). Then, by using direct capture cross section and Breit–Wigner formulae, the non-resonant and resonant cross sections were calculated, respectively. In the next step, we calculated the total S-factor and compared it with experimental data, which showed good agreement between them. Next, we extrapolated the S-factor for the transition to the ground state at zero energy and obtained \(S(0)=5.8 \pm 0.7~(\mbox{keV}\,\mbox{b})\) and then calculate reaction rate. These ones are in agreement with previous reported results. 相似文献
3.
Bakhadir Fayzullaevich Irgaziev Jameel-Un Nabi Abdul Kabir 《Astrophysics and Space Science》2018,363(7):148
Within the framework of potential cluster model, astrophysical S-factor of radiative capture reaction \(^{12}\mathrm{C} (\mathrm{p},\gamma)^{13}\mathrm{N}\) has been calculated in the two body cluster model for the energy range 0–1 MeV. The nuclear interaction in the initial and final states is described by the Woods–Saxon potential. The calculated astrophysical S-factor and rates are compared with known experimental results. 相似文献
4.
G. Ter-Kazarian 《Astrophysics and Space Science》2014,349(2):919-938
We compute the ultra-high energy (UHE) neutrino fluxes from plausible accreting supermassive black holes closely linking to the 377 active galactic nuclei (AGNs). They have well-determined black hole masses collected from the literature. The neutrinos are produced via simple or modified URCA processes, even after the neutrino trapping, in superdense proto-matter medium. The resulting fluxes are ranging from: (1) (quark reactions)— $J^{q}_{\nu\varepsilon}/(\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1})\simeq8.29\times 10^{-16}$ to 3.18×10?4, with the average $\overline{J}^{q}_{\nu\varepsilon}\simeq5.53\times 10^{-10}\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$ , where ε d ~10?12 is the opening parameter; (2) (pionic reactions)— $J^{\pi}_{\nu\varepsilon} \simeq0.112J^{q}_{\nu\varepsilon}$ , with the average $J^{\pi}_{\nu\varepsilon} \simeq3.66\times 10^{-11}\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$ ; and (3) (modified URCA processes)— $J^{URCA}_{\nu\varepsilon}\simeq7.39\times10^{-11} J^{q}_{\nu\varepsilon}$ , with the average $\overline{J}^{URCA}_{\nu\varepsilon} \simeq2.41\times10^{-20} \varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$ . We conclude that the AGNs are favored as promising pure neutrino sources, because the computed neutrino fluxes are highly beamed along the plane of accretion disk, peaked at high energies and collimated in smaller opening angle θ~ε d . 相似文献
5.
Clovis Jacinto de Matos 《Astrophysics and Space Science》2012,337(1):353-354
The phenomenological nature of a new gravitational type interaction between two different bodies derived from Verlinde’s entropic
approach to gravitation in combination with Sorkin’s definition of Universe’s quantum information content, is investigated.
Assuming that the energy stored in this entropic gravitational field is dissipated under the form of gravitational waves and
that the Heisenberg principle holds for this system, one calculates a possible value for an absolute minimum time scale in
nature
t = \frac1516 \fracL1/2(h/2p) Gc4 ~ 9.27×10-105\tau=\frac{15}{16} \frac{\Lambda^{1/2}\hbar G}{c^{4}}\sim9.27\times10^{-105} seconds, which is much smaller than the Planck time t
P
=(ħG/c
5)1/2∼5.38×10−44 seconds. This appears together with an absolute possible maximum value for Newtonian gravitational forces generated by matter
Fg=\frac3230\fracc7L (h/2p) G2 ~ 3.84×10165F_{g}=\frac{32}{30}\frac{c^{7}}{\Lambda \hbar G^{2}}\sim 3.84\times 10^{165} Newtons, which is much higher than the gravitational field between two Planck masses separated by the Planck length F
gP
=c
4/G∼1.21×1044 Newtons. 相似文献
6.
W. B. Song 《Solar physics》2010,261(2):311-320
Referring to the aerodynamic drag force, we present an analytical model to predict the arrival time of coronal mass ejections
(CMEs). All related calculations are based on the expression for the deceleration of fast CMEs in the interplanetary medium
(ICMEs),
[(v)\dot]=-\frac115 700(v-VSW)2\dot{v}=-\frac{1}{15\,700}(v-V_{\mathrm{SW}})^{2}
, where V
SW is the solar wind speed. The results can reproduce well the observations of three typical parameters: the initial speed of
the CME, the speed of the ICME at 1 AU and the transit time. Our simple model reveals that the drag acceleration should be
really the essential feature of the interplanetary motion of CMEs, as suggested by Vršnak and Gopalswamy (J. Geophys. Res.
107, 1019, 2002). 相似文献
7.
Spectroheliograms obtained in extreme ultraviolet (EUV) lines and the Lyman continuum are used to determine the rotation rate of the solar chromosphere, transition region, and corona. A cross-correlation analysis of the observations indicates the presence of differential rotation through the chromosphere and transition region. The rotation rate does not vary with height. The average sidereal rotation rate is given by (deg day–1) = 13.46 - 2.99 sin2
B where B is the solar latitude. This rate agrees with spectroscopic determinations of the photospheric rotation rate, but is slower by 1 deg day–1) = 13.46 - 2.99 sin2 than rates determined from the apparent motion of photospheric magnetic fields and from the brightest points of active regions observed in the EUV. The corona does not clearly show differential rotation as do the chromosphere and transition region. 相似文献
8.
Venugopal Chandu E. Savithri Devi R. Jayapal George Samuel S. Antony G. Renuka 《Astrophysics and Space Science》2012,339(1):157-164
Kinetic Alfven waves are important in a wide variety of areas like astrophysical, space and laboratory plasmas. In cometary
environments, waves in the hydromagnetic range of frequencies are excited predominantly by heavy ions. We, therefore, study
the stability of the kinetic Alfven wave in a plasma of hydrogen ions, positively and negatively charged oxygen ions and electrons.
Each species was modeled by drifting ring distributions in the direction parallel to the magnetic field; in the perpendicular
direction the distribution was simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian
distributions with different temperatures. We find that for frequencies w* < wcH +\omega^{*} < \omega_{c\mathrm{H}^{ +}} (ω
∗ and wcH +\omega_{c\mathrm{H}^{ +}} being respectively the Doppler shifted and hydrogen ion gyro-frequencies), the growth rate increases with increasing negatively
charged oxygen ion densities while decreasing with increasing propagation angles, negative ion temperatures and negative ion
mass. 相似文献
9.
10.
Kiyoshi Ichimoto Takako T. Ishii Kenichi Otsuji Goichi Kimura Yoshikazu Nakatani Naoki Kaneda Shin’Ichi Nagata Satoru UeNo Kumi Hirose Denis Cabezas Satoshi Morita 《Solar physics》2017,292(4):63
A new solar imaging system was installed at Hida Observatory to observe the dynamics of flares and filament eruptions. The system (Solar Dynamics Doppler Imager; SDDI) takes full-disk solar images with a field of view of \(2520~\mbox{arcsec} \times 2520~\mbox{arcsec}\) at multiple wavelengths around the \(\mathrm{H}\alpha\) line at 6562 Å. Regular operation was started in May 2016, in which images at 73 wavelength positions spanning from \(\mathrm{H}\alpha -9~\mathring{\mathrm{A}}\) to \(\mathrm{H}\alpha +9~\mathring{\mathrm{A}}\) are obtained every 15 seconds. The large dynamic range of the line-of-sight velocity measurements (\({\pm}\,400~\mbox{km}\,\mbox{s}^{-1}\)) allows us to determine the real motions of erupting filaments in 3D space. It is expected that SDDI provides unprecedented datasets to study the relation between the kinematics of filament eruptions and coronal mass ejections (CME), and to contribute to the real-time prediction of the occurrence of CMEs that cause a significant impact on the space environment of the Earth. 相似文献
11.
The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) gives us a chance to investigate the theoretical Neupert effect using the correlation between the thermal-energy
derivative and the nonthermal energy, or the thermal energy and the integral nonthermal energy. Based on this concept, we
analyze four M-class RHESSI flares on 13 November 2003, 4 November 2004, 3 and 25 August 2005. According to the evolution
of the temperature [T], emission measure [EM], and thermal energy [E
th], each event is divided into three phases during the nonthermal-energy input [
\frac dEnthdt\frac {\mathrm{d}E_{\mathrm{nth}}}{\mathrm{d}t} in the units of erg s−1]. Phase 1 is identified as the interval before the temperature maximum, while after the thermal-energy maximum is phase 3,
between them is phase 2. We find that these four flares show the Neupert effect in phase 1, but not in phase 3. The Neupert
effect still works well in the second phase, although the cooling becomes slightly important. We define the parameter μ in the relation of
\fracdEthdt=m\fracdEnth(t)dt\frac{\mathrm {d}E_{\mathrm{th}}}{\mathrm{d}t}=\mu\frac{\mathrm{d}E_{\mathrm {nth}}(t)}{\mathrm{d}t} or
Eth(t0)=mò0t0\fracdEnth(t)dt dtE_{\mathrm{th}}(t_{0})=\mu\int_{0}^{t_{0}}\frac{\mathrm{d}E_{\mathrm{nth}}(t)}{\mathrm{d}t}\,\mathrm{d}t when the cooling is ignored in phase 1. Considering the uncertainties in estimating the energy from the observations, it
is not possible to precisely determine the fraction of the known energy in the nonthermal electrons transformed into the thermal
energy of the hottest plasma observed by RHESSI. After a rough estimate of the flare volume and the assumption of the filling
factor, we investigate the parameter μ in these four events. Its value ranges from 0.02 to 0.20, indicating that a small fraction (2% – 20%) of the nonthermal energy
can be efficiently transformed into thermal energy, which is traced by the soft X-ray emission, and the bulk of the energy
is lost possibly due to cooling. 相似文献
12.
Naveen Bijalwan 《Astrophysics and Space Science》2011,336(2):413-418
Recently, Bijalwan (Astrophys. Space Sci., doi:, 2011a) discussed charged fluid spheres with pressure while Bijalwan and Gupta (Astrophys. Space Sci. 317, 251–260, 2008) suggested using a monotonically decreasing function f to generate all possible physically viable charged analogues of Schwarzschild interior solutions analytically. They discussed
some previously known and new solutions for Schwarzschild parameter
u( = \fracGMc2a ) £ 0.142u( =\frac{GM}{c^{2}a} ) \le 0.142, a being radius of star. In this paper we investigate wide range of u by generating a class of solutions that are well behaved and suitable for modeling Neutron star charge matter. We have exploited
the range u≤0.142 by considering pressure p=p(ω) and
f = ( f0(1 - \fracR2(1 - w)a2) +fa\fracR2(1 - w)a2 )f = ( f_{0}(1 - \frac{R^{2}(1 - \omega )}{a^{2}}) +f_{a}\frac{R^{2}(1 - \omega )}{a^{2}} ), where
w = 1 -\fracr2R2\omega = 1 -\frac{r^{2}}{R^{2}} to explore new class of solutions. Hence, class of charged analogues of Schwarzschild interior is found for barotropic equation
of state relating the radial pressure to the energy density. The analytical models thus found are well behaved with surface
red shift z
s
≤0.181, central red shift z
c
≤0.282, mass to radius ratio M/a≤0.149, total charge to total mass ratio e/M≤0.807 and satisfy Andreasson’s (Commun. Math. Phys. 288, 715–730, 2009) stability condition. Red-shift, velocity of sound and p/c
2
ρ are monotonically decreasing towards the surface while adiabatic index is monotonically increasing. The maximum mass found
to be 1.512 M
Θ with linear dimension 14.964 km. Class of charged analogues of Schwarzschild interior discussed in this paper doesn’t have
neutral counter part. These solutions completely describe interior of a stable Neutron star charge matter since at centre
the charge distribution is zero, e/M≤0.807 and a typical neutral Neutron star has mass between 1.35 and about 2.1 solar mass, with a corresponding radius of about
12 km (Kiziltan et al., [astro-ph.GA], 2010). 相似文献
13.
S. K. El-Labany R. Sabry W. F. El-Taibany E. A. Elghmaz 《Astrophysics and Space Science》2012,340(1):77-85
The nonlinear ion-acoustic double layers (IADLs) in a warm magnetoplasma with positive-negative ions and nonthermal electrons
are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density
distribution, and the Poisson equation are used to derive a modified Zakharov–Kuznetsov (MZK) equation, in the small amplitude
regime. It is found that compressive and rarefactive IADLs strongly depend on the mass and density ratios of the negative-to-positive
ions as well as the nonthermal electron parameter. Also, it is shown that there are one critical value for the density ratio
of the negative-to-positive ions (ν), the ratio between unperturbed electron-to-positive ion density (μ), and the nonthermal electron parameter (β), which decide the existence of positive and negative IADLs. The present study is applied to examine the small amplitude
nonlinear IADL excitations for the (H+, O2-)(\mathrm{H}^{+}, \mathrm{O}_{2}^{-}) and (H+,H−) plasmas, where they are found in the D- and F-regions of the Earth’s ionosphere. This investigation should be helpful in
understanding the salient features of the nonlinear IADLs in either space or laboratory plasmas where two distinct groups
of ions and non-Boltzmann distributed electrons are present. 相似文献
14.
Théophile Tchakoua Mama Pamboundom Berthelot Said Duvalier Ramlina Vamhindi Serge Guy Nana Engo Ousmanou Motapon Mama Nsangou 《Astrophysics and Space Science》2018,363(3):48
The potential energy surface (PES) for the \(\mathrm{CP}(\mathrm{X}^{2}\varSigma^{+})\)-\(\mathrm{He}(^{1}S)\) complex has been calculated at the RCCSD(T)-F12/VTZ-F12 level of theory. The analytic fit of the PES was obtained by using global analytical method. The fitted PES was used subsequently in the close-coupling approach for the computation of the state-to-state collisional excitation cross sections of the fine-structure levels of the CP-He complex. Collision energies were taken up to 1500 cm?1 and they yield after thermal averaging, state-to-state rate coefficients up to 200 K. The propensity rules between the lowest fine-structure levels were studied. These rules show, on one hand, a strong propensity in favour of even \(\Delta N\) transitions, and the other hand, that cross sections and collisional rate coefficients for \(\Delta j =\Delta N\) transitions are larger than those for \(\Delta j\neq \Delta N\) transitions. 相似文献
15.
Arthur C. Reardon 《Astrophysics and Space Science》2011,336(2):369-377
Detailed analyses by independent research groups over several decades reveal a significant discrepancy between the observed
rate of periastron advance in the detached eclipsing binary star systems DI Herculis and V541 Cygni and the values theoretically
predicted from the combined classical and general relativistic effects. A modification to Newton’s gravitational theory is
proposed in this investigation to account for these discrepancies, and is represented by
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