arXiv subjects

Gang Qin

Publications and source records attributed to Gang Qin.

4 recordsLinked to original sources

arXiv2024

Perpendicular Diffusion Effect of Cosmic Ray Dipole Anisotropy

Anisotropy is very important to understand cosmic ray (CR) source and interstellar environment. The theoretical explanation of cosmic rays anisotropy from experiments remains challenging and even puzzling for a long time. In this paper, by following the ideas of Jokipii 2007, we use a simple analytical model to study the CR dipole anisotropy amplitude, considering that CRs diffuse only in perpendicular direction, with the ratio between the secondary and primary cosmic rays omnidirectional particle distribution function as an input. We make power law fitting of the observed B/C ratio and use it as the input of the anisotropy model. We show that the modeling results can roughly describe the general trend of the observational data in energy range from $6\times 10^1$ to $3\times 10^{11}$ GeV. It is suggested that the perpendicular diffusion may play a significant role in CR anisotropy in the wide energy range.

astro-ph.HE↗

arXiv2017

Predicting the Popularity of Online Videos via Deep Neural Networks

Predicting the popularity of online videos is important for video streaming content providers. This is a challenging problem because of the following two reasons. First, the problem is both "wide" and "deep". That is, it not only depends on a wide range of features, but also be highly non-linear and complex. Second, multiple competitors may be involved. In this paper, we propose a general prediction model using the multi-task learning (MTL) module and the relation network (RN) module, where MTL can reduce over-fitting and RN can model the relations of multiple competitors. Experimental results show that our proposed approach significantly increases the accuracy on predicting the total view counts of TV series with RN and MTL modules.

cs.LG↗

arXiv2017

Modulation of Galactic Cosmic Rays in the Inner Heliosphere, Comparing with PAMELA Measurements

We develop a numerical model to study the time-dependent modulation of galactic cosmic rays (GCRs) in the inner heliosphere. In the model a time-delayed modified Parker heliospheric magnetic field (HMF) and a new diffusion coefficient model, NLGCE-F, from Qin \& Zhang (2014), are adopted. In addition, the latitudinal dependence of magnetic turbulence magnitude is assumed as $\sim (1+\sin^2θ)/2$ from the observations of Ulysses, and the radial dependence is assumed as $\sim r^S$, where we choose an expression of $S$ as a function of the heliospheric current sheet (HCS) tilt angle. We show that the analytical expression used to describe the spatial variation of HMF turbulence magnitude agrees well with the Ulysses, Voyager 1, and Voyager 2 observations. By numerically calculating the modulation code we get the proton energy spectra as a function of time during the recent solar minimum, it is shown that the modulation results are consistent with the PAMELA measurements.

physics.space-ph↗

arXiv2015

Simulations of the spatial and temporal invariance in the spectra of gradual solar energetic particle events

The spatial and temporal invariance in the spectra of energetic particles in the gradual solar events is reproduced in the simulations. Based on a numerical solution of the focused transport equation, we obtain the intensity time profiles of solar energetic particles (SEPs) accelerated by an interplanetary shock in the three-dimensional interplanetary space. The shock is treated as a moving source of energetic particles with a distribution function. The time profiles of particle flux with different energies are calculated in the ecliptic at $1$ AU. According to our model, we find that shock acceleration strength, parallel diffusion and adiabatic cooling are the main factors in forming the spatial invariance in SEP spectra, and perpendicular diffusion is a secondary factor. In addition, the temporal invariance in SEP spectra is mainly due to the effect of adiabatic cooling. Furthermore, a spectra invariant region, which agrees with observations but is different than the one suggested by Reames and co-workers, is proposed based on our simulations.

astro-ph.SR↗