arXiv subjects

Hongfei Liang

Publications and source records attributed to Hongfei Liang.

11 recordsLinked to original sources

arXiv2026

Anomalous Transverse Response and Multi-Field Ferrialtermagnetic-Ferroelectric Valve with CrSb Flakes

Altermagnets combine the zero-stray-field of antiferromagnets with the spin polarization of ferromagnets, showing great potential for spintronic applications. Here, we propose ferrialtermagnetism as a distinct subclass of altermagnetic family, where symmetry-inequivalent altermagnetic sublattices possess nonidentical Neel vectors, preventing mutual cancellation of alternating spin splitting and conferring intrinsic robustness against perturbations. This concept is realized in the three-atomic-layer CrSb (110) flakes, which exhibits spin splitting of 344 meV, moderate uniaxial magnetic anisotropy, and high Neel temperature of 657 K. The magneto-optical Kerr and the anomalous Hall effects are observed. Integrating this ferrialtermagnetic CrSb with ferroelectric Sc2CO2 and Cu spacer, we design an ferrialtermagnetic-ferroelectric valve. This device displays equilibrium tunneling magnetoresistance and electroresistance of ~10^3%, and non-equilibrium magnitudes under bias, thermal, or light field reaches ~10^4% with high spin filtering of 90%. The negative differential resistance and photogalvanic effects, and photocurrent extinction ratio of 283.8 are achieved. These findings establish ferrialtermagnetism as a fertile platform for multi-field-controlled, ultracompact, and self-powered spintronics and electronics.

cond-mat.mtrl-sci↗

arXiv2026

Fully compensated ferrimagnetic triferroics and multistate transport in hidden-phase wurtzite MnSe monolayer

Fully compensated ferrimagnets (fFIMs) have attracted interest due to their compensated moments and nonrelativistic spin splitting across the Brillouin zone. Known fFIMs, however, are mostly restricted to complex three-dimensional (3D) systems or require external fields in two-dimensional (2D) heterostructures, leaving intrinsic fFIM monolayers unexplored. We identify a hidden-phase MnSe monolayer, derived from the (001) planes of wurtzite, as an intrinsic fFIM featuring inequivalent sublattices not linked by any symmetry. It is a unipolar magnetic semiconductor (UMS) with perpendicular magnetic anisotropy (528.60 * 10^-3 eV per unit cell) and simultaneously exhibits ferroelectricity (polarization 4.63 * 10^-10 C/m) and ferroelasticity (signal 61%), with barriers of 7.6 * 10^-3 and 0.10 eV/f.u., respectively, establishing a single-phase triferroic system. The ground fFIM UMS characteristics are robust against strain up to 3%. The In2Se3/MnSe heterostructure enables nonvolatile electrical control between semiconducting and metallic states. Constructed tunnel junctions exhibit giant tunneling magnetoresistance (2.98 * 10^5%), electroresistance (6.97 * 10^14%), elastoresistance (7.95 * 10^4%), and near-perfect spin filtering (~100%). Collectively, this spontaneous 2D fFIM with coexisting triferroic orders provides a promising platform for ultrahigh-density, low-power, and miniaturized memory devices.

physics.app-ph↗

arXiv2026

Research on the Flat Field Measurement Method of Coronagraph

The solar corona has an extremely low density, and its brightness is only about one millionth of that of the photosphere. High-dynamic-range imaging of its faint structure is therefore essential for studying coronal heating, coronal mass ejections, and space weather. Quantitative coronagraph imaging requires flat-field measurement and calibration, which underpin intensity calibration, small-scale feature detection, and long-term cyclic analysis. This paper analyzes the coronagraph imaging chain and the origins of flat-field errors, including optical aberrations, stray light, and pixel-response non-uniformity, and summarizes the resulting calibration requirements of next-generation coronagraphs. On this basis, ground-based and space-based flat-fielding methods are systematically reviewed: the ground-based methods include integrating-sphere uniform light sources, opal glass/diffuser plates, clear-sky and thin-cloud backgrounds, and solar-disk scanning, while the space-based methods include internal light sources and diffuser plates, attitude-roll and off-corona offset observations, and multi-phase statistical self-consistent flat-fielding. Their accuracy, resource cost, and applicability are compared. The review shows that no single method is simultaneously high-precision, easy to update, and engineer-friendly; a hierarchical, multi-method calibration framework is therefore recommended. Finally, a new method is proposed in which lithographically generated structured light fields, combined with Fourier-optics and machine-learning inversion, are used to estimate the pixel-response function. Preliminary experiments show that this method achieves a lower residual error than the integrating-sphere and opal-glass methods, providing a high-precision reference for future wide-band, high-resolution coronagraph calibration.

astro-ph.SR↗

arXiv2025

Two-sided-loop jet originates from the filament internal reconnection

Magnetic reconnection driving two-sided-loop jet is typically associated with interactions between an emerging bipole and the overlying horizontal magnetic field, or between filaments from separate magnetic systems. Leveraging high temporal and spatial resolution observations from ground-based and space-borne instruments, we have identified a two-sided-loop jet originating from magnetic reconnection between threads within a single filament. Our observations show that as two initially crossing filamentary threads within the filament converge, reconnection takes place at their intersection. In the Doppler images, distinct redshift and blueshift signals are observed at the locations where the filament threads intersected. This process generates a two-sided-loop jet with outflow speeds of \speed{22.2} and \speed{62.5}. Following reconnection, the original crossing threads transform into two parallel threads that subsequently separate at speeds of \speed{2.8} and \speed{8.3}. This observation offers a new perspective on the mechanisms responsible for jet formation.

astro-ph.SR↗

arXiv2025

3D fast-mode Wave Propagation from Corona to Chromosphere: Triggering Mechanism for 3D Oscillations of filaments

Moreton waves are widely regarded as the chromospheric counterpart of extreme ultraviolet (EUV) waves propagating in the corona. However, direct observational evidence confirming their simultaneous propagation across multiple atmospheric layers from the corona through the transition region to the chromosphere has been lacking. In this study, we present comprehensive observational evidence of a three-dimensional (3D) fast-mode wave propagating from the corona through the transition region into the chromosphere, exhibiting a gradual deceleration. Additionally, this wave interacts with three filaments (F1, F2, and F3) along its path, inducing oscillation with multiple amplitudes: Filaments F1 and F2 exhibit simultaneous horizontal and vertical large-scale oscillations ($\sim$\speed{20}), while Filament F3 only exhibits vertical small-scale oscillation ($\sim$\speed{4}). Interestingly, F1 displays a similar oscillation period of about 500\,s in both horizontal and vertical directions, whereas F2 shows significantly different periods in these two dimensions (1100\,s and 750\,s), and F3 exhibits only a vertical oscillation with a period of about 450\,s. Based on this kinematic behavior, we propose that their oscillations were likely triggered by compression from the flanks of the dome-shaped wavefront. We further estimate the magnetic fields of the filaments. The radial (axial) magnetic fields for F1 and F2 are estimated to be 14.9\,G (28.6\,G) and 9.9\,G (18.6\,G), respectively. For F3, we estimate its radial magnetic field to be 16.6\,G.

astro-ph.SR↗

arXiv2025

Moving Plasma Structures and Possible Driving Mechanisms of Solar Microflares Observed with High-Resolution Coronal Imaging

Solar microflares are ubiquitous in the solar corona, yet their driving mechanisms remain a subject of ongoing debate. Using high-resolution coronal observations from the Solar Orbiter's Extreme Ultraviolet Imager (EUI), we identified about a dozen distinct moving plasma structures (hereafter, `` tiny ejections'') originating from the centers of three homologous microflares out of four successive events. These tiny ejections propagate roughly perpendicular to the flaring loops. They often originate as dot-like structures with a length scale of approximately $10^{3}$ km. While these initial dot-like shapes are observable in EUI images, they remain undetectable in the images captured by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. As they propagate, these dot-like structures consistently evolve into loop-like formations, possibly due to the heating of the surrounding magnetic field. Rather than being generated by a series of flux rope eruptions, the tiny ejections appear to result from small-angle magnetic reconnections within a bipolar field. Thus, the microflares associated with these ejections may be driven by magnetic reconnection within braided fields, a process similar to the proposed nanoflare mechanism and distinct from the standard large-scale flare model.

astro-ph.SR↗

arXiv2024

Broad and Bi-directional narrow quasi-periodic fast-propagating wave trains associated with a filament-driven halo CME on 2023 April 21

This paper presents three distinct wave trains that occurred on 2023 April 21: a broad quasi-periodic fast-propagating (QFP) wave train and a bi-directional narrow QFP wave train. The broad QFP wave train expands outward in a circular wavefront, while bi-directional narrow QFP wave trains propagate in the northward and southward directions, respectively. The concurrent presence of the wave trains offers a remarkable opportunity to investigate their respective triggering mechanisms. Measurement shows that the broad QFP wave train's speed is 300- 1100 km/s in different propagating directions. There is a significant difference in the speed of the bi-directional narrow QFP wave trains: the southward propagation achieves 1400 km/s, while the northward propagation only reaches about 550 km/s accompanied by a deceleration of about 1- 2 kms-2. Using the wavelet analysis, we find that the periodicity of the propagating wave trains in the southward and northward directions closely matches the quasi-periodic pulsations (QPPs) exhibited by the flares. Based on these results, the narrow QFP wave trains were most likely excited by the intermittent energy release in the accompanying flare. In contrast, the broad QFP wave train had a tight relationship with the erupting filament, probably attributed to the unwinding motion of the erupting filament or the leakage of the fast sausage wave train inside the filament body.

astro-ph.SR↗

arXiv2022

Recurrent narrow quasi-periodic fast-propagating wave trains excited by the intermittent energy release in the accompanying solar flare

About the driven mechanisms of the quasi-periodic fast-propagating (QFP) wave trains, there exist two dominant competing physical explanations: associated with the flaring energy release or attributed to the waveguide dispersion. Employing Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 171 A images, we investigated a series of QFP wave trains composed of multiple wavefronts propagating along a loop system during the accompanying flare on 2011 November 11. The wave trains showed a high correlation in start time with the energy release of the accompanying flare. Measurements show that the wave trains phase speed is almost consistent with its group speed with a value of about 1000 km s-1, indicating that the wave trains should not be dispersed waves. The period of the wave trains was the same as that of the oscillatory signal in X ray emissions released by the flare. Thus we propose that the QFP wave trains were most likely triggered by the flare rather than by dispersion. We investigated the seismological application with the QFP waves and then obtained that the magnetic field strength of the waveguide was about 10 Gauss. Meanwhile, we also estimated that the energy flux of the wave trains was about 1.2X105 erg cm-2 s-1.

astro-ph.SR↗

arXiv2019

The Birth of a Jet-driven Twin CME and Its Deflection from Remote Magnetic Fields

We report the formation of a complicated coronal mass ejection (CME) on 2015 August 23 by using the high temporal and high spatial resolution multi-wavelength observations taken by the Solar Dynamic Observatory and the Solar and Heliospheric Observatory. The CME exhibited both jet-like and bubble-like components simultaneously, and therefore we call it a twin CME. Detailed imaging and kinematic analysis results indicate that the twin CME were evolved form the eruption of a mini-filament driven blowout jet at the east edge of an equatorial coronal hole, in which the activation of the mini-filament was tightly associated with the continuous flux cancellation and quasi-periodic jet-like activities in the filament channel. Due to the magnetic reconnection between the filament and the ambient open field lines, the filament broke partially at the northern part and resulted in an intriguing blowout jet in the south direction. It is interesting that the ejecting jet was deflected by a group of remote open field lines, which resulted in the significant direction change of the jet from southward to eastward. Based on the close temporal and spatial relationships among the jet, filament eruption, and the twin CME, we conclude that the jet-like CME should be the coronal extension of the jet plasma, while the bubble-like one should be originated from the eruption of the mini-filament confined by the closed magnetic fields at the jet-base.

astro-ph.SR↗

arXiv2010

Relationship between group sunspot number and Wolf sunspot number

Continuous wavelet transform and cross-wavelet transform have been used to investigate the phase periodicity and synchrony of the monthly mean Wolf ($R_{z}$) and group ($R_{g}$) sunspot numbers during the period of June 1795 to December 1995. The Schwabe cycle is the only one common period in Rg and Rz, but it is not well-defined in case of cycles 5-7 of Rg and in case of cycles 5 and 6 of $R_{z}$. In fact, the Schwabe period is slightly different in $R_{g}$ and $R_{z}$ before cycle 12, but from cycle 12 onwards it is almost the same for the two time series. Asynchrony of the two time series is more obviously seen in cycles 5 and 6 than in the following cycles, and usually more obviously seen around the maximum time of a cycle than during the rest of the cycle. $R_{g}$ is found to fit $R_{z}$ better in both amplitudes and peak epoch during the minimum time time of a solar cycle than during the maximum time of the cycle, which should be caused by their different definition, and around the maximum time of a cycle, $R_{g}$ is usually less than $R_{z}$. Asynchrony of $R_{g}$ and $R_{z}$ should somewhat agree with different sunspot cycle characteristics exhibited by themselves.

astro-ph.SR↗

arXiv2010

The Phase Shifts of the Paired Wings of Butterfly Diagrams

Sunspot groups observed by Royal Greenwich Observatory/US Air Force/NOAA from May 1874 to November 2008 and the Carte Synoptique solar filaments from March 1919 to December 1989 are used to investigate the relative phase shift of the paired wings of butterfly diagrams of sunspot and filament activities. Latitudinal migration of sunspot groups (or filaments) does asynchronously occur in the northern and southern hemispheres, and there is a relative phase shift between the paired wings of their butterfly diagrams in a cycle, making the paired wings spatially asymmetrical on the solar equator. It is inferred that hemispherical solar activity strength should evolve in a similar way within the paired wings of a butterfly diagram in a cycle, making the paired wings just and only keep the phase relationship between the northern and southern hemispherical solar activity strengths, but a relative phase shift between the paired wings of a butterfly diagram should bring about an almost same relative phase shift of hemispheric solar activity strength.

astro-ph.SR↗