Publications (124)
RHESSI Observations of a Simple Large X-ray Flare on 11-03-2003
Wei Liu, Yan Wei Jiang, Siming Liu +1
We present data analysis and interpretation of a simple X-class flare observed with RHESSI on November 3, 2003. In contrast to other X-class flares observed previously, this flare…
Contactless Modulation of Intralayer and Interlayer Excitons in MoS2/WSe2 heterostructures with Acoustoelectric Fields
Yueyi Sun, Dexing Liu, Jiefei Zhu +9
This work presents a platform that enables surface acoustic wave (SAW) modulation of both intralayer and interlayer excitons in MoS2/WSe2 heterostructures. Harnessing the coupled p…
Evolution of High-energy Particle Distribution in Supernova Remnants
Houdun Zeng, Yuliang Xin, Qi Fu +1
The spectra fits to a sample of 34 supernova remnants (Zeng et al., 2019) are updated. -ray spectra of 20 supernova remnants (SNRs) with a soft TeV spectrum are further analyze…
Discrete treatment of inverse Compton scattering: implications on parameter estimation in gamma-ray astronomy
Junji Xia, Xingjian Lv, Kun Fang +1
In gamma-ray astronomy and cosmic-ray physics, the continuous approximation of inverse Compton scattering (ICS) is widely adopted to model the evolution of electron energy. However…
Stochastic Electron Acceleration in SNR RX J1713.7-3946
Zhonghui Fan, Siming Liu
Stochastic acceleration of charged particles due to their interactions with plasma waves may be responsible for producing superthermal particles in a variety of astrophysical syste…
The Nature of Linearly Polarized Millimeter and Sub-millimeter Emission in Sagittarius A*
Siming Liu, Lei Qian, Xue-Bing Wu +2
The linearly polarized millimeter and sub-millimeter emission in Sagittarius A* is produced within 10 Schwarzschild radii of the supermassive black hole at the Galactic Center and…
-Cygni supernova remnant in -rays: signatures of trapped and escaped Cosmic Rays
Yuan Li, Gwenael Giacinti, Siming Liu +1
We reanalyze 15 years of data recorded by the Fermi Large Area Telescope in a region around supernova remnant (SNR) -Cygni from 100 MeV to 1 TeV, and find that the spectra of t…
Stochastic Acceleration in the Western Hotspot of Pictor A
Zhong-Hui Fan, Siming Liu, Jian-Min Wang +2
Chandra's high resolution observations of radio galaxies require a revisit of the relevant electron acceleration processes. Although the diffusive shock particle acceleration model…
A Systematic Chandra study of Sgr A: II. X-ray flare statistics
Qiang Yuan, Q. Daniel Wang, Siming Liu +1
The routinely flaring events from \sgras\ trace dynamic, high-energy processes in the immediate vicinity of the supermassive black hole. We statistically study temporal and spectra…
Correlated Sub-mm and X-ray Variability in Sgr A*
Fulvio Melia, Siming Liu, Marco Fatuzzo
PAPER WITHDRAWN. The recent detection of Sgr A* in the X-ray band, together with the radio polarization measurements conducted over the past few years, offer the best constraints y…
Evolution of High-Energy Particle Distribution in Mature Shell-Type Supernova Remnants
Houdun Zeng, Yuliang Xin, Siming Liu +3
Multi-wavelength observations of mature supernova remnants (SNRs), especially with recent advances in gamma-ray astronomy, make it possible to constrain energy distribution of ener…
Stochastic Electron Acceleration in Shell-Type Supernova Remnants
Siming Liu, Zhong-Hui Fan, Christopher L. Fryer +2
We study the stochastic electron acceleration by fast mode waves in the turbulent downstream of weakly magnetized collisionless astrophysical shocks. The acceleration is most effic…
A statistical model for the -ray variability of the Crab nebula
Qiang Yuan, Peng-Fei Yin, Xue-Feng Wu +3
A statistical scenario is proposed to explain the -ray variability and flares of the Crab nebula, which were observed recently by the Fermi/LAT. In this scenario electrons are…
GeV gamma-ray emission from pulsar wind nebula HESS J1356-645 with Fermi-LAT
Xi Liu, Xiaolei Guo, Yuliang Xin +2
HESS J1356-645 is considered to be a pulsar wind nebula (PWN) associated with the pulsar PSR J1357-6429. We reanalyze the GeV gamma-ray emission in the direction of HESS J1356-645…
Enabling Multi-Agent Transfer Reinforcement Learning via Scenario Independent Representation
Ayesha Siddika Nipu, Siming Liu, Anthony Harris
Multi-Agent Reinforcement Learning (MARL) algorithms are widely adopted in tackling complex tasks that require collaboration and competition among agents in dynamic Multi-Agent Sys…
MedSAM-based lung masking for multi-label chest X-ray classification
Brayden Miao, Zain Rehman, Xin Miao +2
Chest X-ray (CXR) imaging is widely used for screening and diagnosing pulmonary abnormalities, yet automated interpretation remains challenging due to weak disease signals, dataset…
Magnetic Flux Tubes Illuminated by Pulsar Winds
Yifan Sun, C. -Y. Ng, Siming Liu
Observations of linear structure connecting pulsars to gamma-ray halos reveal injection of TeV electrons into the interstellar medium (ISM). In some cases, this could be attributed…
On the Power-Law Distributions of X-ray Fluxes from Solar Flares Observed with GOES
You-ping Li, Li Feng, Ping Zhang +2
Power-law frequency distributions of the peak flux of solar flare X-ray emission have been studied extensively and attributed to a system of self-organized criticality (SOC). In th…
Co-evolving Real-Time Strategy Game Micro
Navin K Adhikari, Sushil J. Louis, Siming Liu +1
We investigate competitive co-evolution of unit micromanagement in real-time strategy games. Although good long-term macro-strategy and good short-term unit micromanagement both im…
Unified Performance Analysis of Hybrid FSO/RF System with Diversity Combining
Long Huang, Siming Liu, Pan Dai +4
Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable links for high-data-rate wireless backhauls. In this paper, we present a unified perfor…
Development of a Swarm UAV Simulator Integrating Realistic Motion Control Models For Disaster Operations
Kazi Tanvir Ahmed Siddiqui, David Feil-Seifer, Tianyi Jiang +3
Simulation environments for Unmanned Aerial Vehicles (UAVs) can be very useful for prototyping user interfaces and training personnel that will operate UAVs in the real world. The…
Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes
Yan Wei Jiang, Siming Liu, Wei Liu +1
We present a study of the spatial and spectral evolution of the loop-top (LT) sources in a sample of 6 flares near the solar limb observed by {\it RHESSI}. A distinct coronal sourc…
Hadronic vs leptonic models for -ray emission from VER J2227+608
Siming Liu, Houdun Zeng, Yuliang Xin +1
Recent observations of VER J2227+608 reveal a broken power -ray spectrum with the spectral index increasing from in the GeV energy range to in the TeV ran…
Elementary Energy Release Events in Flaring Loops: Effects of Chromospheric Evaporation on X-rays
Siming Liu, Feiran Han, Lyndsay Fletcher
With the elementary energy release events introduced in a previous paper (Liu & Fletcher 2009) we model the chromospheric evaporation in flaring loops. The thick-target hard X-ray…
The Apparent Asymmetric Outflows of TeV Particles from Pulsar Winds
HongYu Pu, Siming Liu
Observations of X-ray filaments attached to a couple of powerful pulsars suggest escape of TeV electrons and/or positrons (e) from pulsar bow shocks into surrounding large…
Comprehensive Analog Signal Processing Platform Enabled with Acoustic Charge Transport in Two-dimensional Materials
Yueyi Sun, Siming Liu, Yingjie Luo +3
Two-dimensional Acoustic Charge Transport (2D-ACT) devices, which integrate two dimensional semiconductor field-effect transistor (FET) with high-frequency surface acoustic wave (S…
Discovery of a spatially extended GeV source in the vicinity of the TeV halo candidate 2HWC J1912+099: a TeV halo or supernova remnant ?
Hai-Ming Zhang, Shao-Qiang Xi, Ruo-Yu Liu +3
Observations by HAWC and Milagro have detected spatially extended TeV sources surrounding middle-aged () pulsars like Geminga and PSR B0656+14, which have…
Radial Profiles of Non-thermal Emission from Supernova Remnant RX J1713.7-3946
Yunyong Tang, Siming Liu
Supernova remnant RX J1713.7-3946 (also named as G347.3-0.5) has exhibited largest surface brightness, detailed spectral and shell-type morphology, it is one of the brightest TeV s…
Derivation of the Electron Distribution in SNR RX J1713.7-3946 via a Spectral Inversion Method
Hui Li, Siming Liu, Yang Chen
We show that the radio, X-ray and gamma-ray spectrum of the supernova remnant RX J1713.7-3946 can be accounted for with the simplest emission model, where all of these emissions ar…
A Giant Peanut-shaped Ultra-High-Energy Gamma-Ray Emitter Off the Galactic Plane
Zhen Cao, Felix Aharonian, Yunxiang Bai +312
Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes…
Observational Signatures of Tearing Instability in the Current Sheet of a Solar Flare
Lei Lu, Li Feng, Alexander Warmuth +7
Magnetic reconnection is a fundamental physical process converting magnetic energy into not only plasma energy but also particle energy in various astrophysical phenomena. In this…
Multi-objective evolution for 3D RTS Micro
Sushil J. Louis, Siming Liu
We attack the problem of controlling teams of autonomous units during skirmishes in real-time strategy games. Earlier work had shown promise in evolving control algorithm parameter…
Anomalous distributions of primary cosmic rays as evidence for time-dependent particle acceleration in Supernova remnants
Yiran Zhang, Siming Liu, Qiang Yuan
Recent precise measurements of cosmic ray (CR) spectra show that the energy distribution of protons is softer than those of heavier nuclei, and there are spectral hardenings for al…
Fermi Large Area Telescope Detection of Supernova Remnant RCW 86
Qiang Yuan, Xiaoyuan Huang, Siming Liu +1
Using year Fermi-LAT data, we report the detection of GeV -ray emission from the shell-type supernova remnant RCW 86 (G315.4-2.3) with a significance of . The…
Cascade and Damping of Alfvén-Cyclotron Fluctuations: Application to Solar Wind Turbulence Spectrum
Yan Wei Jiang, Siming Liu, Vahé Petrosian +1
With the diffusion approximation, we study the cascade and damping of Alfvén-cyclotron fluctuations in solar plasmas numerically. Motivated by wave-wave couplings and nonlinear ef…
Stochastic Electron Acceleration in the TeV Supernova Remnant RX J1713.7-3946: The High-Energy Cut-off
Zhonghui Fan, Siming Liu, Christopher L. Fryer
In the leptonic scenario for TeV emission from a few well-observed shell-type TeV supernova remnants (STTSNRs), very weak magnetic fields are inferred. If fast-mode waves are produ…
Measuring the Black Hole Spin in Sgr A*
Fulvio Melia, Benjamin C. Bromley, Siming Liu +2
The polarized mm/sub-mm radiation from Sgr A* is apparently produced by a Keplerian structure whose peak emission occurs within several Schwarzschild radii (r_S=2GM/c^2) of the bla…
EduBench: A Comprehensive Benchmarking Dataset for Evaluating Large Language Models in Diverse Educational Scenarios
Bin Xu, Yu Bai, Huashan Sun +10
As large language models continue to advance, their application in educational contexts remains underexplored and under-optimized. In this paper, we address this gap by introducing…
Twisted-pair unilateral reconnection: A unifying driver for magnetically powered astrophysical bursts
Shu-Ping Yan, Wenhui Yu, Jing Ye +11
Magnetic reconnection in twisted loops has long been invoked as an engine powering energetic transients from black hole accretion to neutron star mergers, yet never directly observ…
Fermi Large Area Telescope observations of the supernova remnant HESS J1731-347
Rui-zhi Yang, Xiao Zhang, Qiang Yuan +1
Context: HESS J1731-347 has been identified as one of the few TeV-bright shell-type supernova remnants (SNRs). These remnants are dominated by nonthermal emission, and the nature o…
From period to quasi-period to chaos: A continuous spectrum of orbits of charged particles trapped in a dipole magnetic field
Yuxin Xie, Siming Liu
Via evaluation of the Lyapunov exponent, we report the discovery of three prominent sets of phase space regimes of quasi-periodic orbits of charged particles trapped in a dipole ma…
Electron Acceleration around the Supermassive Black Hole at the Galactic Center
Siming Liu, Vahe' Petrosian, Fulvio Melia
The recent detection of variable infrared emission from Sagittarius A*, combined with its previously observed flare activity in X-rays, provides compelling evidence that at least a…
Method for testing diffusive shock acceleration and diffusion propagation of 1-100 TeV cosmic electrons with multiwavelength observations of the Geminga halo and pulsar wind nebula
Weikang Gao, Li-Zhuo Bao, Kun Fang +3
Diffusive shock acceleration and diffusion propagation are essential components of the standard cosmic ray model. These theories are based on extensive observations of high-energy…
A statistical model to explain the gamma-ray variability and flares of the Crab nebula
Qiang Yuan, Peng-Fei Yin, Xue-Feng Wu +3
Recently the AGILE and Fermi/LAT detectors uncovered giant -ray flares from the Crab nebula. The duration of these flares is a few days. The Fermi/LAT data with monthly time bi…
GeV emission around SS 433 with 17 years Fermi-LAT observation
Qiwang Sun, Dmitry Khangulyan, Jiren Liu +1
We present an analysis of 17 years of Fermi-LAT observations of the microquasar SS~433. We detect four GeV sources in the region: a newly identified source, PS J1910+0550, located…
Is PSR J08554644 responsible for the 1.4 TeV electron spectral bump hinted by DAMPE?
Yiwei Bao, Yang Chen, Siming Liu
DAMPE observation on the cosmic ray electron spectrum hints a narrow excess at 1.4 TeV. Although the excess can be ascribed to dark matter particles, pulsars and pulsar wind…
Elementary Energy Release Events in Solar Flares
Siming Liu, Lyndsay Fletcher
Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenologic…
Stochastic Electron Acceleration in Shell-Type Supernova Remnants II
Siming Liu, Zhong-Hui Fan, Christopher L. Fryer
We discuss the generic characteristics of stochastic particle acceleration by a fully developed turbulence spectrum and show that resonant interactions of particles with high speed…
Vector meson dominance in photon structure functions at small from holography
Wei Gao, Siming Liu, Wenbin Lin +1
We investigate the photon structure functions via the photon-photon and photon-vector meson scattering within the framework of holographic QCD, focusing on the small Bjorken re…
Spin-Induced Disk Precession in the Supermassive Black Hole at the Galactic Center
Siming Liu, Fulvio Melia
Sgr A* is a compact radio source at the Galactic Center, thought to be the radiative manifestation of a supermassive black hole. At least a portion of its…
Discovery of diffuse gamma-ray emission in the vicinity of G172.8+1.5: An old supernova remnant with different turbulence properties
Yuan Li, Gwenael Giacinti, Siming Liu
We report the detection of high-energy -ray emission in the vicinity of G172.8+1.5, which is debated as a Supernova remnant (SNR) or an ionized hydrogen (H) region.…
Neuroevolution for RTS Micro
Aavaas Gajurel, Sushil J Louis, Daniel J Mendez +1
This paper uses neuroevolution of augmenting topologies to evolve control tactics for groups of units in real-time strategy games. In such games, players build economies to generat…
Small-Scale Anisotropies of Cosmic Rays from Turbulent Flow
Yiran Zhang, Siming Liu
Within the classical convection--diffusion approximation, we show that the angular distribution of cosmic rays (CRs) in a highly turbulent flow may exhibit significant small-scale…
The Large High Altitude Air Shower Observatory (LHAASO) Science Book (2021 Edition)
Zhen Cao, D. della Volpe, Siming Liu +87
Since the science white paper of the Large High Altitude Air Shower Observatory (LHAASO) published on arXiv in 2019 [e-Print: 1905.02773 (astro-ph.HE)], LHAASO has completed the tr…
Constraining anisotropic diffusion between Geminga and Earth with the cosmic-ray electron and positron spectrum
Junji Xia, Xiaojun Bi, Kun Fang +1
The gamma-ray halo surrounding Geminga suggests a notable reduction in cosmic-ray diffusion. One potential explanation for this phenomenon is the projection effect of slow diffusio…
Line Emission from Cooling Accretion Flows in the Nucleus of M31
Siming Liu, Michael J. Fromerth, Fulvio Melia
The recent Chandra X-ray observations of the nucleus of M31, combined with earlier VLA radio and HST UV spectral measurements, provide the strictest constraints on the nature of ac…
Discovery of diffuse -ray emission in the vicinity of G213.0-0.6: Supernova remnant versus massive star-forming region
Yuan Li, Gwenael Giacinti, Siming Liu
We report the discovery of high-energy -ray emission in the vicinity of G213.0-0.6, which is debated as a supernova remnant (SNR) or an ionized hydrogen (H) region.…
A Three-component Model for Cosmic-ray Spectrum and Dipole Anisotropy
Yiran Zhang, Siming Liu, Houdun Zeng
Using a three-component, multi-scale diffusion model, we show that the cosmic-ray (CR) proton and helium spectra and the dipole anisotropy can be explained with reasonable paramete…
MAIDCRL: Semi-centralized Multi-Agent Influence Dense-CNN Reinforcement Learning
Ayesha Siddika Nipu, Siming Liu, Anthony Harris
Distributed decision-making in multi-agent systems presents difficult challenges for interactive behavior learning in both cooperative and competitive systems. To mitigate this com…
Modeling the Multi-Wavelength Emission of Shell-Type Supernova Remnant RX J1713.7-3946
Qiang Yuan, Siming Liu, Zhonghui Fan +2
Emission mechanisms of the shell-type supernova remnant (SNR) RX J1713.7-3946 are studied with multi-wavelength observational data from radio, X-ray, GeV -ray to TeV -ray b…
Origin of Strong Linear Polarization from Fast Radio Bursts
Runna Wang, Siming Liu, Anda Xiong +2
The detection of almost 100% linearly polarized emission from the fast radio burst source FRB 121102 implies coherent emission of relativistic electrons moving in perpendicular to…
Probing the Density in the Galactic Center Region: Wind-Blown Bubbles and High-Energy Proton Constraints
Christopher L. Fryer, Siming Liu, Gabriel Rockefeller +2
Recent observations of the Galactic center in high-energy gamma-rays (above 0.1TeV) have opened up new ways to study this region, from understanding the emission source of these hi…
VER J2227+608: A Hadronic PeVatron Pulsar Wind Nebula?
Yuliang Xin, Houdun Zeng, Siming Liu +2
We report the detection of GeV -ray emission from the very-high-energy (VHE) -ray source VER J2227+608 associated with the "tail" region of SNR G106.3+2.7. The GeV -ray…
Is Supernova Remnant Cassiopeia A a PeVatron?
Xiao Zhang, Siming Liu
Cassiopeia A, a well-observed young core-collapse supernova remnant (SNR), is considered as one of the best candidates for studying very high-energy particle acceleration up to PeV…
Proton and Helium Heating by Cascading Turbulence in a Low-beta Plasma
Zhaodong Shi, P. A. Muñoz, J. Büchner +1
How ions are energized and heated is a fundamental problem in the study of energy dissipation in magnetized plasmas. In particular, the heating of heavy ions (including ${}^{4}\mat…
Is Thermal Expansion Driving the Initial Gas Ejection in NGC 6251?
Fulvio Melia, Siming Liu, Marco Fatuzzo
In this paper, we explore the possibility that the radiative properties of the most compact region in NGC 6251* may be understood in the same sense as Sgr A*, though with some tell…
Evolutionary Multi-objective Optimization of Real-Time Strategy Micro
Rahul Dubey, Joseph Ghantous, Sushil Louis +1
We investigate an evolutionary multi-objective approach to good micro for real-time strategy games. Good micro helps a player win skirmishes and is one of the keys to developing be…
Relativistic Charged Balls
Yunqiang Yu, Siming Liu
It is proven that the relativistic charged ball with its charge less than its mass (in natural units) cannot have a non-singular static configuration while its radius approaches it…
Unified model for the gamma-ray emission of supernova remnants
Qiang Yuan, Siming Liu, Xiao-Jun Bi
Shocks of supernova remnants (SNRs) are important (and perhaps the dominant) agents for production of the Galactic cosmic rays. Recent -ray observations of several SNRs have ma…
Shadowing of the Nascent Jet in NGC 4261 by a Line-Emitting Supersonic Accretion Disk
Siming Liu, Michael J. Fromerth, Fulvio Melia
NGC 4261 (3C 270) is a low-luminosity radio galaxy with two symmetric kiloparsec-scale jets. Earlier Hubble Space Telescope observations indicated the presence of a hundred-parsec…
Cosmic-Ray Convection-Diffusion Anisotropy
Yiran Zhang, Siming Liu, Dejin Wu
Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These…
Limitation of the Least Square Method in the Evaluation of Dimension of Fractal Brownian Motions
Bingqiang Qiao, Siming Liu, Houdun Zeng +2
With the standard deviation for the logarithm of the re-scaled range of simulated fractal Brownian motions given in a previous paper \cite{q1…
New Constraints on the Nature of Radio Emission in Sagittarius A*
Siming Liu, Fulvio Melia
The mm to sub-mm spectrum of Sgr A* at the Galactic center, as well as its polarization characteristics, are consistent with the inner 10 Schwarzschild radii of a tight Keplerian e…
Stochastic Acceleration of 3He and 4He by Parallel Propagating Plasma Waves
Siming Liu, Vahé Petrosian, Glenn M. Mason
Stochastic acceleration of He and He from a thermal background by parallel propagating turbulent plasma waves with a single power-law spectrum of the wavenumber is studied.…
Lepton Models for TeV Emission from SNR RX J1713.7-3946
Zhonghui Fan, Siming Liu, Qiang Yuan +1
(Aims.) SNR RX J1713.7-3946 is perhaps one of the best observed shell-type supernova remnants with emissions dominated by energetic particles accelerated near the shock front. The…
Energy Flows in the Jupiter-Io System
Siming Liu
With the laws of mass conservation, momentum conservation and energy conservation, incorporating the processes of neutral gas ionization and ion diffusion, we develop a self-consis…
Impulsive Thermal X-ray Emission from a Low-lying Coronal Loop
Siming Liu, Youping Li, Lyndsay Fletcher
Understanding the relationship among different emission components plays an essential role in the study of particle acceleration and energy conversion in solar flares. In flares wh…
Polarized mm And sub-mm Emission From Sgr A* At The Galactic Center
Fulvio Melia, Siming Liu, Robert Coker
The recent detection of significant linear polarization at mm and sub-mm wavelengths in the spectrum of Sgr A* (if confirmed) will be a useful probe of the conditions within severa…
MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasi-Periodicity
Chi-kwan Chan, Siming Liu, Christopher L. Fryer +4
High resolution observations of Sgr A* have revealed a wide variety of phenomena, ranging from intense rapid flares to quasi-periodic oscillations, making this object an ideal syst…
Gravitational losses for the binary systems induced by the next-to-leading spin-orbit coupling effects
Hao Zhang, Wei Gao, Guansheng He +3
The orbital energy and momentum of the compact binary systems will loss due to gravitational radiation. Based on the mass and mass-current multipole moments of the binary system wi…
TeV cosmic ray nuclei acceleration in shell-type supernova remnants with hard -ray spectra
Houdun Zeng, Yuliang Xin, Shuinai Zhang +1
The emission mechanism for hard -ray spectra from supernova remnants (SNRs) is still a matter of debate. Recent multi-wavelength observations of TeV source HESS J1912+101 show…
Measure the Propagation of a halo CME and Its Driven Shock with the Observations from a Single Perspective at Earth
Lei Lu, Bernd Inhester, Li Feng +2
We present a detailed study of an earth-directed coronal mass ejection (Full halo CME) event happened on 2011 February 15 making use of white light observations by three coronagrap…
A Deep Chandra View of A Candidate Parsec-Scale Jet from the Galactic Center Super-massive Black Hole
Zhenlin Zhu, Zhiyuan Li, Mark R. Morris +2
We have investigated the linear X-ray filament, G359.944-0.052, previously identified as a likely X-ray counterpart of a parsec-scale jet from the Galactic Center super-massive bla…
Stochastic Electron Acceleration During the NIR and X-ray Flares in Sagittarius A*
Siming Liu, Fulvio Melia, Vahe Petrosian
Recent near-IR (NIR) and X-ray observations of Sagittarius A*'s spectrum have yielded several strong constraints on the transient energization mechanism, justifying a re-examinatio…
Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma
Yiran Zhang, Siming Liu
Recently, Zhang & Liu (2024) proposed a turbulent convection model for multiscale anisotropies of cosmic rays (CRs), with an assumption of isotropic diffusion such that the anisotr…
Polarized Emission of Sagittarius A*
Lei Huang, Siming Liu, Zhi-Qiang Shen +4
We explore the parameter space of the two temperature pseudo-Newtonian Keplerian accretion flow model for the millimeter and shorter wavelength emission from Sagittarius A*. A gene…
A Possible Link Between the Galactic Center HESS Source and Sgr A*
D. R. Ballantyne, Fulvio Melia, Siming Liu +1
Recently, HESS and other air Cerenkov telescopes have detected a source of TeV gamma-rays coincident with the Galactic center. It is not yet clear whether the gamma-rays are produc…
Cascade and Damping of Alfvén-Cyclotron Fluctuations: Application to Solar Wind Turbulence
Yanwei Jiang, Siming Liu, Vahé Petrosian
It is well-recognized that the presence of magnetic fields will lead to anisotropic energy cascade and dissipation of astrophysical turbulence. With the diffusion approximation and…
Evolution of high-energy particle distribution in Supernova Remnants
Houdun Zeng, Yuliang Xin, Siming Liu
Supernova remnants (SNRs) have been considered as the dominant contributors to Galactic cosmic rays. However, the relation between high-energy particles trapped in SNRs and cosmic…
Morphological Evolution of Higher Order Nonlinear Kinetic Alfvén Waves in Structured Galactic Environments
Manpreet Singh, Siming Liu, N. S. Saini
Kinetic Alfven waves (KAWs) are fundamental to energy transport and small-scale structure formation in the turbulent, magnetized interstellar medium (ISM). While first-order Kortew…
Relative Spectra and Distributions of Fluences of 3He and 4He in Solar Energetic Particles
Vahe Petrosian, Yan Wei Jiang, Siming Liu +3
Solar Energetic Particles (SEPs) show a rich variety of spectra and relative abundances of many ionic species and their isotopes. A long standing puzzle has been the extreme enrich…
Electron Acceleration in Middle-age Shell-type -Ray Supernova Remnants
Xiao Zhang, Siming Liu
Over the past decade, -ray observations of supernova remnants (SNRs) and accurate cosmic-ray (CR) spectral measurements have significantly advanced our understanding of particl…
On the Gamma-Ray Nebula of Vela Pulsar. I. Very Slow Diffusion of Energetic Electrons within the TeV Nebula
Yiwei Bao, Siming Liu, Yang Chen
High-energy particle transport in pulsar wind nebulae (PWNe) plays an essential role in explaining the characteristics revealed in multiwavelength observations. In this paper, the…
An Accretion-Induced X-ray Flare in Sgr A*
Siming Liu, Fulvio Melia
The recent detection of a three-hour X-ray flare from Sgr A* by Chandra provides very strong evidence for a compact emitting region near this supermassive black hole at the Galacti…
Wave emission of non-thermal electron beams generated by magnetic reconnection
Xin Yao, Patricio Muñoz, Jörg Büchner +3
Magnetic reconnection in solar flares can efficiently generate non-thermal electron beams. The energetic electrons can, in turn, cause radio waves through microscopic plasma instab…
Modeling Emission from the Supermassive Black Hole in the Galactic Center with GRMHD Simulations
Kyle W. Martin, Siming Liu, Chris Fragile +2
Sagittarius A* is a compact radio source at the Galactic center, powered by accretion of fully ionized plasmas into a supermassive black hole. However, the radio emission cannot be…
Black Hole Accretion in Low States: Electron Heating
Siming Liu, Christopher L. Fryer, Hui Li
Plasmas in an accretion flow are heated by MHD turbulence generated through the magneto-rotational instability. The viscous stress driving the accretion is intimately connected to…
Polarimetric Imaging of the Massive Black Hole at the Galactic Center
Benjamin C. Bromley, Fulvio Melia, Siming Liu
The radio source Sgr A* in the Galactic center emits a polarized spectrum at millimeter and sub-millimeter wavelengths that is strongly suggestive of relativistic disk accretion on…
A Self-Consistent Model of Kinetic Alfven Solitons in Pulsar Wind Plasma: Linking Soliton Characteristics to Pulsar Observables
Manpreet Singh, Geetika Slathia, N. S. Saini +1
A self-consistent model is presented for the formation and propagation of kinetic Alfvén (KA) solitons in mass-loaded filaments within the pulsar wind, where a magnetized electron…
A Relativistic Disk in Sagittarius A*
Siming Liu, Fulvio Melia
The detection of a mm/Sub-mm ``bump'' in Sgr A*'s radio spectrum suggests that at least a portion of its overall emission is produced within a compact accretion torus. This inferen…