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In this paper, we study locally strongly convex affine hyperspheres in the unimodular affine space ℝn+1which, as Riemannian manifolds, are locally isometric to the Riemannian product of two Riemannian manifolds both possessing constant sectional curvature. As the main result, a complete classification of such affine hyperspheres is established. Moreover, as direct consequences, 3- and 4-dimensional affine hyperspheres with parallel Ricci tensor are also classified.

Grain size, characterized by a combination of grain length, width, and thickness, is one of the major determinants of yield in rice. The present study identified TATA-box binding protein-associated factor 2 (TAF2) as an essential component regulating transcription and determining grain size in rice. Map-based cloning showed that a G/T substitution in TAF2resulted in a naturally occurring mutant called reduced grain size and plant height 1(rgh1). The mutants, with weak edited rgh1alleles, exhibited a small grain phenotype with reduced grain length and width, while the severe knockout mutant (rgh1-2s) was dwarf and completely sterile. Allelic test performed between rgh1and several edited alleles confirmed that the mutation in TAF2caused the rgh1phenotype. GUS staining showed that TAF2was mainly expressed in the vascular bundles of roots, stems, leaves, and grains. The cytological analysis revealed that reduced cell division in the glumes resulted in the small grain phenotype of rgh1. Further RNA-sequencing detected altered expression of genes involved in the basic biological processes in rgh1mutant. These findings provide novel insights into the TAF2-mediated genetic mechanism regulating grain size in rice.

Substorm processes have been studied in detail, and it is well known that interplanetary (IP) shock encountering the terrestrial magnetosphere causes global responses. However, how IP shock compression to the magnetosphere affects the development of an ongoing substorm remains uninvestigated. Herein, the simultaneous satellite and ground-based auroral evolutions associated with an IP shock impact on the magnetopause during an ongoing substorm on May 7th, 2005, were examined. The IMAGE satellite over the Southern Hemisphere captured the global development substorm, which was initiated at 17:38:47 UT. The poleward branch of the nightside auroral oval was fortuitously monitored by an all-sky camera at the Zhongshan Station (−74.5° magnetic latitude, ZHO) in Antarctica. The satellite imager observed continuous brightening and broadening of the nightside auroral oval after the IP shock arrival. The simultaneous ground-based optical aurora measurement displayed the intensification and expansion of a preexisting auroral surge poleward of the aurora oval. The geomagnetic field variations and the instantly increased PC indices indicated an elevated merging rate and enhanced the convection-related DP-2 currents. Therefore, this IP shock transient impact did not significantly change the ongoing development of the substorm, although it meets the magnetospheric precondition hypothesis.

We first classify Hopf hypersurfaces of both S2×S2and H2×H2which satisfy one of the three conditions: (1) constant mean curvature, (2) constant scalar curvature, (3) constant squared norm of the shape operator. It follows that these three conditions are equivalent for a Hopf hypersurface of both S2×S2and H2×H2. Then, we classify hypersurfaces of both S2×S2and H2×H2whose structure Jacobi operator is of Codazzi type. As its direct consequence, we obtain the classification of hypersurfaces in both S2×S2and H2×H2for which the structure Jacobi operator satisfies one of the six conditions: (1) vanishing, (2) parallel, (3) recurrent, (4) semi-parallel, (5) Lie parallel, (6) Killing type.

Heading date is an important agronomic trait in rice (Oryza sativaL.). We previously fine‐mapped two complementary genes, Late Heading Date 1and Late Heading Date 2(LH2), that control the late heading trait in rice. Here, we cloned and analyzed the function of LH2. LH2was fine‐mapped to a 53‐kb genomic region. Sequencing analysis revealed that there were differences in the coding sequence of LOC_Os08g07740between the varieties ‘Bo B’ and ‘Yuefeng B’. Therefore, LOC_Os08g07740was identified as a candidate gene for LH2and subsequently determined that LH2is a Type 3 allele of Days To Heading 8. Transgenic plants of Yuefeng B carrying LH2from Bo B significantly delayed the heading date under short‐day and long‐day conditions. A yeast two‐hybrid analysis revealed that LH2 physically interacted with Heme Activator Protein (HAP) 5A, ‐H, ‐I, ‐L, ‐K, and HAP5‐LIKE. The HAP5 domain of HAP5 family members has various functions. Further analysis revealed that LH2represses photoperiodic flowering by controlling the expression of Early Heading Date 1, Heading date 3a, and Rice Flowering Locus T1in rice. LH2delayed heading by 17.6 d in short‐day conditions and >32.7 d in long‐day conditions.LH2 physically interacted with HAP5A, ‐H, ‐I, ‐L, ‐K, and HAP5‐LIKE.The HAP5 domain of the HAP5 family exhibited functional differentiation.LH2is a Type 3 allele of DTH8.

Leaf‐color mutants have been extensively studied in rice (Oryza sativaL.) and many corresponding genes have been identified and cloned. However, the mechanism of complex leaf‐color mutations requires further study. In this study, we obtained an introgression line (TIL22) from a set of introgression lines raised using African cultivated rice (O. glaberrimaSteud.) as the donor parent and O. sativasubsp. indicaTeqing as the recipient. Compared with Teqing, TIL22 showed a yellow‐green leaf phenotype at the seedling stage, but the leaves gradually changed to green after the five‐leaf stage. The photosynthetic pigment contents of yellow‐green leaves at the seedling stage were significantly reduced and chloroplast development was retarded compared with those of Teqing. Genetic analysis indicated that the introgression line phenotype was controlled by a single nuclear gene, temporarily designated YGL22. Map‐based cloning and sequence analysis suggested that the candidate gene was likely to be LOC_Os01g15390, which encodes a chloroplast protein. Real‐time quantitative polymerase chain reaction (qPCR) analysis revealed that the YGL22transcript level was significantly lower in TIL22 than that of Teqing at the seedling stage. We generated the ygl22knockout mutant using the CRISPR/Cas9 system. The ygl22mutants showed a similar phenotype to that of TIL22 at the seedling stage, suggesting that YGL22may be involved in the early development of chloroplasts in rice. In addition, plant height, number of panicles per plant, and grain yield per plant of ygl22were not significantly affected. The results indicate that YGL22can be used as a trait marker gene in hybrid rice production.

The geomagnetic storm is an intense geomagnetic activity, and one important research aspect is the storm time ultralow frequency (ULF) waves, which can resonate with injected particles and impact particle dynamics in the inner magnetosphere. This study focuses on analyzing ULF wave power during geomagnetic storms on the ground, in the magnetosphere and in the solar wind. During the Van Allen Probe era from year 2012–2019, we identified 94 geomagnetic storm events with 25 as strong storms and 69 as moderate storms based on the variation of SYM‐H index. The analysis revealed that for both satellite and ground‐based measurements during storms with different intensity, the ULF wave power was dramatically enhanced in the main phase. In addition, the ULF wave power of strong storms was significantly stronger than that of moderate storms within the magnetosphere and on the ground. While the finding is opposite in the solar wind. Furthermore, the ULF wave power of strong storms exhibited a higher intensity at higher L shell values and in some cases, it can last up to ∼2 days. Besides, the ULF wave power displayed a linear correlation with the absolute value of the SYM‐H index during the storm main phase while it exhibited an exponential association with the absolute value of the SYM‐H index during the recovery phase. This comprehensive analysis offers valuable insights into the evolution of ULF waves in the inner magnetosphere during geomagnetic storm events, shedding light on plasma waves and wave‐particle interactions in this region. We statistically analyzed the storm‐time Pc3‐5 ULF wave power using a combination of ground and satellite measurementsWithin the L shell of 3–6, higher ULF wave power is observed at higher L shell values around the SYM‐H index minimum timeULF wave power is linearly correlated with the SYM‐H index during the main phase and exponentially correlated during the recovery phase We statistically analyzed the storm‐time Pc3‐5 ULF wave power using a combination of ground and satellite measurements Within the L shell of 3–6, higher ULF wave power is observed at higher L shell values around the SYM‐H index minimum time ULF wave power is linearly correlated with the SYM‐H index during the main phase and exponentially correlated during the recovery phase

Associated with an immersion φ: S3→ ℂP3, we can define a canonical bundle endomorphism F: TS3→ TS3by the pull back of the Kahler form of ℂP3. In this article, related to F we study equivariant minimal immersions from S3into ℂP3under the additional condition (∇XF)X= 0 for all X∈ ker (F). As main result, we give a complete classification of such kinds of immersions. Moreover, we also construct a typical example of equivariant non-minimal immersion φ: S3→ ℂP3satisfying (∇XF)X= 0 for all X∈ ker (F), which is neither Lagrangian nor of CR type.

Homo (Au2)- and heterodinuclear coinage metal complexes (AuAg) ligated by a six-membered Janus-type ditopic N-heterocyclic carbene (NHC) have been prepared by deprotonation of aNHC (abnormal NHC) gold complex followed by complexation. The two ditopic NHC coinage metal complexes were structurally characterized by single crystal X-ray diffraction. The carbene character for the C2 carbon and C5 carbon of the ditopic NHC ligand in 3and 4was confirmed by the NMR and structural data.

Magnetosonic (MS) waves are common plasma waves in the Earth's magnetosphere. The self‐consistent excitation of MS waves has been studied by 2D particle‐in‐cell simulations in the meridian and equatorial planes of a dipole magnetic field. However, the direction of wave propagation is artificially limited in the previous 2D simulations. Therefore, the 3D simulation of MS waves needs to be investigated. In this paper, we investigate the excitation and evolution of MS waves in the Earth's dipole magnetic field based on a 3D general curvilinear particle‐in‐cell simulation. We find that the MS waves are excited primarily within 3° of the equator when the thermal velocity of the ring distribution is much less than the ring velocity of the ring distribution. These waves propagate along both the radial and azimuthal directions nearly perpendicular to the background magnetic field. In the linear stage, the growth rates of MS waves are almost equal in the radial and azimuthal directions. Compared with the waves propagating along the radial direction, the waves propagating along the azimuthal direction can grow for a longer time, resulting in a larger wave amplification in this direction after saturation. The simulation results provide a valuable insight to understand the self‐consistent evolution of MS waves in the Earth's dipole magnetic field, and the findings are useful for understanding the plasma wave‐particle interaction in the Earth's radiation belts. The Earth's magnetosphere is a natural plasma laboratory. Since the plasma in the magnetosphere is collisionless, electromagnetic waves are significant agents for the transport of energy and momentum among different particles. The MS waves are important electromagnetic waves in the magnetosphere, which have a frequency range from several Hertz to several hundred Hertz. Recently, these waves have been receiving an increasing interest due to their potential importance in accelerating radiation belt electrons and heating plasmaspheric ions. The 2D particle‐in‐cell simulations have been used to investigate MS waves in the meridian and equatorial planes of a dipole magnetic field. However, the direction of wave propagation is artificially limited in the previous 2D simulations. Thus, the 3D simulation of MS waves still needs to be studied. In this paper, we perform a 3D particle‐in‐cell simulation to investigate the excitation of the MS waves in a dipole magnetic field. A larger wave amplification is found in the azimuthal direction because they can grow for a longer time in this direction. Our results can contribute to the understanding of the spatial distribution of MS waves in the Earth's magnetosphere. Three‐dimensional particle‐in‐cell simulation of magnetosonic (MS) wave excitation in a dipole magnetic field has been studied for the first timeThe linear growth rates of MS waves are almost equal in the radial and azimuthal directionsA larger wave amplification is observed in the azimuthal direction since the waves can grow for a longer time in this direction Three‐dimensional particle‐in‐cell simulation of magnetosonic (MS) wave excitation in a dipole magnetic field has been studied for the first time The linear growth rates of MS waves are almost equal in the radial and azimuthal directions A larger wave amplification is observed in the azimuthal direction since the waves can grow for a longer time in this direction

We report results from the analysis of a case of conjugate polar cap arcs (PCAs) observed on 5 February 2006 in the Northern Hemisphere by the ground‐based Yellow River Station all‐sky imager (Svalbard) and in both hemispheres by the space‐based DMSP/SSUSI and TIMED/GUVI instruments. The PCA's motion in dawn‐dusk direction shows a clear dependence on the interplanetary magnetic field (IMF) Bycomponent and presents a clear asymmetry between Southern and Northern Hemispheres, that is, formed on the duskside and moving from dusk to dawn in the Northern Hemisphere and vice versa in the other hemisphere. The already existing PCAs' motion is influenced by the changes in the IMF Bywith a time delay of ~70 min. We also observed strong flow shears/reversals around the PCAs in both hemispheres. The precipitating particles observed in the ionosphere associated with PCAs showed properties of boundary layer plasma. Based on these observations, we might reasonably expect that the topological changes in the magnetotail can produce a strip of closed field lines and local processes would set up conditions for the formation and evolution of PCAs. Polar cap arcs have been observed in both hemispheres by space‐based imagers simultaneouslyThe PCA motion shows a clear dependence on the IMF Byand presents a clear asymmetry between the two hemispheresStrong flow shears/reversals are around the PCAs with boundary layers precipitating particles observed from DMSP

We show that isotropic Lagrangian submanifolds in a 6-dimensional strict nearly Kähler manifold are totally geodesic. Moreover, under some weaker conditions, a complete classification of the J-isotropic Lagrangian submanifolds in the homogeneous nearly Kähler S3× S3is also obtained. Here, a Lagrangian submanifold is called J-isotropic, if there exists a function λ, such that g((∇h)(v, v, v), Jv) = λholds for all unit tangent vector v.

Results from a 1D kinetic simulation, for the first time, reveal the important role of modified electron acoustic wave (MEAW) in auroral electron acceleration. Parallel electric fields, generated due to the mode coupling between kinetic Alfven waves (KAWs) and MEAWs in the transition region from the magnetosphere and the ionosphere, can be sustained by continuous energy input carried by Alfven waves from the magnetosphere. Under the incidence of long‐period Alfven waves carrying upward field‐aligned currents, a parallel potential drop can be formed in the transition region, leading to mono‐energetic electron acceleration. Such a mechanism provides a possible link between shear Alfven waves and the mesoscale mono‐energetic auroral electron acceleration. Discrete aurora is supposed to be caused by precipitated electrons accelerated by parallel electric field. The mode coupling between modified electron acoustic waves (MEAWs), which received little attention, and kinetic Alfven waves is an effective mechanism of the generation of parallel electric field. The present simulation results show that the generation of parallel electric field, due to the mode coupling in the transition region, could be important or even dominant under certain circumstances. Our findings point out the importance of the MEAWs on the auroral electron acceleration. Simulation results indicate that modified electron acoustic waves (MEAWs) strongly affect the auroral electron accelerationKinetic Alfven waves under certain circumstances lead to mono‐energetic acceleration through mode coupling to MEAWsSuch a mechanism provides a possible link between Alfven waves and mono‐energetic electron acceleration Simulation results indicate that modified electron acoustic waves (MEAWs) strongly affect the auroral electron acceleration Kinetic Alfven waves under certain circumstances lead to mono‐energetic acceleration through mode coupling to MEAWs Such a mechanism provides a possible link between Alfven waves and mono‐energetic electron acceleration

Interplanetary (IP) shock‐driven sudden compression of the Earth's magnetosphere produces electromagnetic disturbances in the polar ionosphere. Several studies have examined the effects of IP shock on magnetosphere‐ionosphere coupling systems using all‐sky cameras and radars. In this study, we examine responses and drivers of the polar ionosphere following an IP shock compression on 16 June 2012. We observe the vertical drift and concurrent horizontal motion of the plasma. Observations from digisonde located at Antarctic Zhongshan station (ZHO) showed an ionospheric thick Eregion ionization and associated vertical downward plasma motion at Fregion. In addition, horizontal ionospheric convection reversals were observed on the Super Dual Auroral Radar Network ZHO and McMurdo radar observations. Findings suggest that the transient convective reversal breaks the original shear equilibrium, it is expected that the IP shock‐induced electric field triggers an enhanced velocity shear mapping to the Eregion. The horizontal motion of the plasma was attributed to only the dusk‐to‐dawn electric field that existed during the preliminary phase of sudden impulse. We also found that ionospheric convection reversals were driven by a downward field‐aligned current. The results of these observations reveal, for the first time, the immediate and direct cusp ionosphere response to the IP shock, which is critical for understanding the global response of the magnetosphere following an abrupt change in Interplanetory Magnetic Field (IMF) and solar wind conditions. On 16 June 2012, an interplanetary (IP) shock hit near‐Earth space (geospace), resulting in enhanced plasma convection, auroral intensifications, and altering electric current systems in the high‐ and polar‐latitude ionosphere. We present a case study characterizing the effect of IP shock‐driven sudden impulse (SI) impact on geospace systems that changes vertical drift and horizontal convection observed by digital ionosonde and Super Dual Auroral Radar Network high‐frequency radars. We found an SI‐driven immediate vertical downward plasma motion, the sudden appearance of sporadic E‐layer, and an ionospheric convection reversal following the IP shock. We discuss the possible impact of SI on magnetospheric‐ionospheric coupling systems and possible driving mechanisms that are attributed to the observations reported in the study. Ionosonde ZHO detected enhanced Eregion ionization and vertical plasma motion following the arrival of an interplanetary shockEvidence suggests that the strong Elayers are the result of sudden impulse (SI)‐driven E‐field drift‐convergence and particle precipitationIP shock‐triggered SI alters the dusk‐to‐dawn electric field that drives a brief downward plasma motion at the dayside polar ionosphere Ionosonde ZHO detected enhanced Eregion ionization and vertical plasma motion following the arrival of an interplanetary shock Evidence suggests that the strong Elayers are the result of sudden impulse (SI)‐driven E‐field drift‐convergence and particle precipitation IP shock‐triggered SI alters the dusk‐to‐dawn electric field that drives a brief downward plasma motion at the dayside polar ionosphere

Plasma in the inner magnetosphere is affected by various processes, such as substorms. In this study, we have statistically investigated the ring current properties based on the observations of Van Allen Probes from 2012 to 2019 to examine the substorm effects on the plasma pressure and current system in the inner magnetosphere. The results show that the plasma pressure increases significantly, leading to a ∼3 nT/hr geomagnetic depression during intense substorms. The contribution of <100 keV H+ions to the plasma pressure increases during substorms, which is more significant at lower L‐shells. Opposite to the H+ions, the proportion of >10 keV O+ions contributing to the plasma pressure increases as substorm intensity increases. In addition, the rise of plasma pressure is mainly distributed from dusk to midnight, resulting in the enhancement of asymmetric ring current and the region II field‐aligned currents connecting to the ionosphere. Our results provide a comprehensive view of the variation of plasma pressure and current system in the inner magnetosphere during quiet periods and intense substorms. The pressure increase caused by intense substorms can lead to 3 nT/hr magnetic field depressionThe pressure contribution of both <100 keV H+and >10 keV O+increase during intense substormsThe ring current densities from dusk to midnight and region II FACs increase dramatically during intense substorms The pressure increase caused by intense substorms can lead to 3 nT/hr magnetic field depression The pressure contribution of both <100 keV H+and >10 keV O+increase during intense substorms The ring current densities from dusk to midnight and region II FACs increase dramatically during intense substorms

Interplanetary (IP) shocks have substantial impact on particles and electromagnetic fields when arriving at the Earth's magnetosphere. In this study, we have examined the dynamics of cross‐energy ions and plasma waves observed by Van Allen Probe B near the equator at the noon sector inside the geosynchronous orbit after the impact of an IP shock on 27 February 2014. We found that the Ultra‐Low Frequency (ULF) and electromagnetic ion cyclotron (EMIC) waves are induced, and the differential fluxes of protons of various energies have different responses after the IP shock arrival. The perpendicular flux increased dramatically for low‐energy ions (10–100 eV) due to the electric field drift and betatron acceleration. These adiabatic processes also accounted for the evident proton flux decrease at 30–80 keV energies and increase at energies higher than 100 keV, caused by the positive or negative gradient in phase space density before the IP shock arrival. The short‐lived ULF waves triggered by the IP shock also interacted with the ∼100 keV protons, resulting in the stripes in their pitch angle distribution. The anisotropic distribution of >50 keV protons excited EMIC waves after the shock arrival. This study provides a comprehensive picture of the IP shock effects on the ions of different energies and plasma waves inside the geosynchronous orbit, which shed new lights on the cross‐energy responses of ions and plasma waves in the inner magnetosphere to solar wind discontinuities. We analyzed simultaneous cross‐energy ion response through adiabatic and non‐adiabatic processes after the impact of an Interplanetary shockIons with different energies experienced the same adiabatic processes but underwent different evolutions depending on initial distributionsUltra‐Low Frequency and electromagnetic ion cyclotron waves could be generated simultaneously and affect different energy ions We analyzed simultaneous cross‐energy ion response through adiabatic and non‐adiabatic processes after the impact of an Interplanetary shock Ions with different energies experienced the same adiabatic processes but underwent different evolutions depending on initial distributions Ultra‐Low Frequency and electromagnetic ion cyclotron waves could be generated simultaneously and affect different energy ions

We investigated the dawn–dusk asymmetrical distribution of quasi‐dc earthward Poynting flux (EPF) in the dayside polar cap of the Northern Hemisphere based on 3 years of observations at ∼850 km made by the Defense Meteorological Satellite Program (DMSP) F17. The satellite data have been sorted by low (Kp ≤ 2) and high (Kp > 2) geomagnetic activity, as well as the orientation and strength of interplanetary magnetic field (IMF) By and Bz components, binned by magnetic latitude, and magnetic local time. Statistical results show that the enhanced convection electric field favors the asymmetrical EPF distribution. Asymmetrical distribution characteristics are summarized as (a) there are mainly two enhanced EPF regions, near dawn and cusp and the mean EPF is 28% larger on the dawn than on the dusk for all IMF and Kp conditions. (b) The mean EPF for high Kp is 3 times greater than that for low Kp in the dayside polar cap. The enhanced EPF shifted from near the dawn for low Kp to near the cusp for high Kp. The EPF is also larger on the dawn than on the dusk for high Kp. (c) The EPF of the dayside polar cap is significantly enhanced as the IMF strength increases. Under IMF By+, EPF is greater on the dawn than on the dusk. The opposite is true under IMF By−. The IMF Bz− favors enhanced EPF and the EPF on the dawn (dusk) reaches its maximum for IMF By+ and Bz− (IMF By− and Bz−). The dawn–dusk asymmetrical distribution of earthward Poynting flux (EPF) in the dayside polar cap of the Northern Hemisphere is presentedDependence of the asymmetrical distribution of EPF on geomagnetic activities and interplanetary magnetic field By/Bz orientations and strengths has been studiedStatistical results indicate that the asymmetrical distribution of EPF is strongly related to the convection electric field The dawn–dusk asymmetrical distribution of earthward Poynting flux (EPF) in the dayside polar cap of the Northern Hemisphere is presented Dependence of the asymmetrical distribution of EPF on geomagnetic activities and interplanetary magnetic field By/Bz orientations and strengths has been studied Statistical results indicate that the asymmetrical distribution of EPF is strongly related to the convection electric field

Cheng et al. recently (Results Math 76:144, 2021) established a complete classification of the n-dimensional C-totally real minimal submanifolds with constant sectional curvature in the (2n+1)-dimensional Sasakian space form N2n+1(c). In this paper, trying to extend the above result, we classify C-totally real minimal submanifolds in N2n+1(c)with parallel Ricci tensor for n=3,4. In particular, we show that 4-dimensional C-totally real minimal Einstein submanifolds in N9(c)are of constant sectional curvature.

Auroral spiral is one of the auroral vortex structures. Here, we propose a model to explain the formation of auroral spiral structure based on three‐dimensional particle‐in‐cell simulations. In our model, an auroral arc develops through precipitations of electrons accelerated during magnetic reconnection in the auroral acceleration region. The arc morphology at low altitudes can be modified by electron‐scale magnetic flux ropes, which are generated through secondary oblique tearing modes in the intensified current sheet along one particular branch of the primary reconnection separatrices. The resulting vortex structures agree well with high‐resolution observations of auroral spirals. We find that the rotational sense of these spirals is determined by electron kinetic processes and controlled by the guide field direction. Our study further suggests that when the field‐aligned length of the auroral acceleration region is shorter than a critical length, these auroral spiral structures will not form. Discrete aurorae, usually displayed as auroral arcs, are universal phenomena in the ionosphere of the Earth and other planets, and are generated by precipitations of electrons from the magnetosphere, ionosphere, and solar wind. Spirals, as frequently observed vortex structures in arcs, have drawn great attention. The formation of auroral spirals is considered to be related to the magnetosphere‐ionosphere coupling process during both magnetically active and quiet times. However, how the auroral spirals develop is still an open question. It is suggested that magnetic reconnection occurs in the auroral acceleration region, typically above ∼4,000 km altitude in the field‐aligned current sheet. Using kinetic simulations, we study the role of magnetic reconnection in the formation of auroral spirals. Auroral acceleration is modeled by considering magnetic reconnection in the field‐aligned current sheetPeriodic spiral structures can develop from an auroral arc modified by secondary oblique tearing instabilityThe characteristics of the spiral structures in our simulation agree well with observation Auroral acceleration is modeled by considering magnetic reconnection in the field‐aligned current sheet Periodic spiral structures can develop from an auroral arc modified by secondary oblique tearing instability The characteristics of the spiral structures in our simulation agree well with observation

A new technique for estimating quiet day curve (QDC) was suggested. To validate the new approach, QDCs were derived from data acquired by the imaging riometer installed at the Chinese Zhongshan Station in Antarctic. The evaluation was performed by comparing the difference between QDC derived by the new technique and those derived by Tanaka’s technique. The results were discussed in terms of the diurnal variation and discrepancy. Also, cosmic noise absorption (CNA) images were built using both techniques in order to evaluate the implications of the changes when obtaining them using different methods of the QDC determination. The influence of the multiplicative factor value on the QDC determination in Tanaka’s technique was evaluated.

Using high temporal resolution optical data obtained from three-wavelength all-sky imagers over six winters continuously at Yellow River Station (78.92°N, 11.93°E) in Arctic, we statistically investigated the dependence of location of poleward moving auroral forms (PMAFs) on the interplanetary magnetic field (IMF) Bzand Bycomponents as a function of MLT and MLAT under stable IMF conditions. It is found that more PMAFs occurred in lower latitude for Bz< 0 and there was less evident IMF By-related prenoon-postnoon asymmetry for Bz< 0 than for Bz> 0. We found that the PMAFs were distributed over a wide range of MLT when Bz< 0, which indicates that the reconnection X-line might spread like an ‘S’’ shape. However, during northward IMF, PMAFs were observed predominantly prenoon for IMF By> 0 and postnoon for IMF By< 0 associating with the effect of the high-latitude reconnection, which is largely consistent with the theoretical model of the convection flow.

Abstract: An immersed umbilic-free submanifold in the unit sphere is called Blaschke isoparametric if its Möbius form vanishes identically and all of its Blaschke eigenvalues are constant. In this paper, we give a complete classification for all Blaschke isoparametric hypersurfaces with three distinct Blaschke eigenvalues.

The effect of radial interplanetary magnetic field (IMF BX${\mathrm{B}}_{\mathrm{X}}$) has been ignored in the solar wind‐magnetosphere‐ionosphere (S‐M‐I) coupling. We present a statistical study of IMF Bx effects on the Heppner‐Maynard Boundary (HMB) midnight latitude calculated from SuperDARN measurements between January 2002 and December 2017. The HMB represents the equatorward extent of the ionospheric convection pattern and can be used as a proxy for the equatorward boundary of the auroral oval. That is, the HMB expands toward lower latitude when the level of S‐M‐I coupling is enhanced. It is found that the averaged HMB midnight latitudes during both sunward and antisunward radial IMFs are around 64–65° magnetic latitude (MLAT). HMB midnight latitude is negatively correlated with the magnitude of IMF Bx as well as solar wind speed, while no significant trend is found between HMB midnight latitude and IMF Bz or By during radial IMF. For antisunward radial IMF, the relationship between upstream parameters and HMB is more dependent than in sunward radial direction. As the first long‐term statistical study focused on HMB during radial IMF conditions, this work provides observational evidence that the IMF Bx plays an important role in the coupling process and the traditional coupling function could not be applicable in the case of radial IMF. The magnetic reconnection between solar wind and magnetosphere can drive a convection structure in the high‐latitude ionosphere. Heppner and Maynard developed a method to calculate the equatorward boundary of the ionospheric convection, which is called Heppner‐Maynard Boundary (HMB). HMB could be used as the monitor of the interaction process between the solar wind and geomagnetic field. In this paper, we report the effects of the radial (sunward or antisunward) interplanetary magnetic field (IMF) on HMB in the northern hemisphere. For normal cases, the Bz component o IMF is the most important. But our statistical results indicate that there is a decreasing trend between the strength of IMF Bx and HMB latitudes at midnight. No significant trend is found between HMB midnight latitude and IMF Bz or By during radial IMF. Moreover, the results provide observational evidence the Bx term should be considered in the coupling function during radial IMF. The HMB midnight latitude has a negative trend on the IMF Bx, especially for negative IMF BxThe averaged values of HMB during radial IMFs are larger than those for substorm periods and a long‐term period of 17 yearsThe traditional coupling function may not be applicable in the case of radial IMF The HMB midnight latitude has a negative trend on the IMF Bx, especially for negative IMF Bx The averaged values of HMB during radial IMFs are larger than those for substorm periods and a long‐term period of 17 years The traditional coupling function may not be applicable in the case of radial IMF

Sporadic E(Es) layers could be composed of metallic ions and formed, modified, or transported by the action of convective electric fields in the high latitude ionosphere. In this paper, by utilizing simultaneous observations from Digisonde and Super Dual Auroral Radar Network (SuperDARN) HF radars at Zhongshan Station (ZHS, 69.4°S, 76.4°E), Antarctica, a thin Es layer, which initially formed in the lower F region and descended into the lower Eregion, with wavelike structures, was recorded by Digisonde on 14 November 2019. The Es layer‐related concurrent ionospheric irregularities were also detected by the SuperDARN ZHS HF radar. By using a global‐scale 2‐D convection map, combined with images from the Special Sensor Ultraviolet Spectrographic Imager instruments onboard Defense Meteorological Satellite Program (DMSP) spacecraft, it is proposed that the flow shears associated with the duskside convective circulation are responsible for the evolution of the Es layer. Moreover, using the HF radar elevation angle data to measure the scatter height, it is strongly suggested that the Es layer was elongated with convection circulation. The electrodynamic processes responsible for the formation and evolution of the Es layer are discussed. An Es layer formed in the lower F region and descended to the Eregion, observed simultaneously by Digisonde and Super Dual Auroral Radar Network (SuperDARN) HF radarsThe formation and evolution of the Es layer related to the afternoon convection reversalSuperDARN HF radar measurements suggest the Es layer is elongated with convection circulation An Es layer formed in the lower F region and descended to the Eregion, observed simultaneously by Digisonde and Super Dual Auroral Radar Network (SuperDARN) HF radars The formation and evolution of the Es layer related to the afternoon convection reversal SuperDARN HF radar measurements suggest the Es layer is elongated with convection circulation

Recent studies have reported the simultaneous observation of Magnetosonic (MS) waves and Electromagnetic ion cyclotron (EMIC) waves. In this study, a detailed survey of the concurrent EMIC waves and MS waves is performed using the Van Allen Probes observations from 2012 to 2017. The results suggest that most of the concurrent EMIC waves and MS waves are H+band EMIC waves and MS waves. The favorable geomagnetic conditions for the concurrent EMIC waves and MS waves are AE* ≥ 500 nT inside the plasmapause and AE* ≥ 100 nT outside the plasmapause. Although EMIC waves are generally stronger than MS waves, stronger MS waves than EMIC waves are more likely to occur during moderate and active geomagnetic times. Our study is consistent with the most recent research, and provides more detailed information that helps us to deepen our understanding of the concurrent EMIC waves and MS waves. Electromagnetic ions cyclotron (EMIC) waves and magnetosonic (MS) waves are two common wave mode in the Earth radiation belts and play important roles in radiation belt dynamics. Recent studies have reported observations of concurrent EMIC waves and MS waves and conducted a brief statistic survey. To deepen our understanding of the concurrent EMIC waves and MS waves, this study aims to comprehensively analyze the statistical occurrence pattern and associated global distribution of concurrent EMIC waves and MS waves. Our study demonstrated that most of the concurrent EMIC waves and MS waves are H+ band EMIC waves and MS waves, which reveals the deep relationship between MS waves and the concurrent H+ band EMIC waves. Our study also demonstrated that the concurrent EMIC waves are generally stronger than MS waves, while the wave amplitudes of MS waves can exceed EMIC waves during geomagnetically turbulent times. This result indicates that the combined scattering effect of the concurrent EMIC waves and MS waves could vary significantly under different geomagnetic conditions. Most of the concurrent Electromagnetic ion cyclotron (EMIC) waves and Magnetosonic (MS) waves are H+band EMIC waves and MS wavesThe concurrent EMIC waves and MS waves are most frequently observed outside the plasmapause under geomagnetic moderate and active conditionsThe possibility of MS waves stronger than the concurrent EMIC waves is higher during geomagnetically moderate and active times Most of the concurrent Electromagnetic ion cyclotron (EMIC) waves and Magnetosonic (MS) waves are H+band EMIC waves and MS waves The concurrent EMIC waves and MS waves are most frequently observed outside the plasmapause under geomagnetic moderate and active conditions The possibility of MS waves stronger than the concurrent EMIC waves is higher during geomagnetically moderate and active times

We classify hypersurfaces of the hyperbolic space Hn+1(c) with constant scalar curvature and with two distinct principal curvatures. Moreover, we prove that if Mnis a complete hypersurfaces with constant scalar curvature n(n - 1) R and with two distinct principal curvatures such that the multiplicity of one of the principal curvatures is n- 1, then R = c. Additionally, we prove two rigidity theorems for such hypersurfaces.

In this paper we construct many examples of n-dimensionalWillmore Lagrangian submanifolds in the complex Euclidean space Cn. We characterize them as the only Willmore Lagrangian submanifolds invariant under the action of SO(n). The mostimportant contribution of our construction is that it provides examplesof Willmore Lagrangian spheres in Cnfor all n≥ 2.

Abstract.:  Let M m be a m-dimensional submanifold in the n-dimensional unit sphere S n without umbilic point. Two basic invariants of M m under the Möbius transformation group of S n are a 1-form Φ called Möbius form and a symmetric (0,2) tensor A called Blaschke tensor. In this paper, we prove the following rigidity theorem: Let M m be a m-dimensional (m≥3) submanifold with vanishing Möbius form and with constant Möbius scalar curvature R in S n , denote the trace-free Blaschke tensor by . If , then either ||Ã||≡0 and M m is Möbius equivalent to a minimal submanifold with constant scalar curvature in S n ; or and M m is Möbius equivalent to in for some c≥0 and .

A sodium Doppler lidar system with three‐directional measurements of sodium density, atmospheric wind field, and temperature was established at Zhongshan (69.4°S, 76.4°E), Antarctica. On November 14, 2019, a sporadic sodium layer (SSL) was observed at an altitude range of 93–103 km. The temporal/spatial sodium density variations of this SSL are associated with a strong sporadic E(Es) layer at nearly the same height, which is modulated by the convective electric field. By considering the structures and the time lags of the SSL's growth at three positions, the SSL appears to have a horizontal advection in an approximately westward direction with a velocity of the order of 80 m/s. This is consistent with the zonal wind velocity derived from the lidar system itself. The temporal/spatial sodium density variations strongly indicate that the formation and perturbation of SSLs are related to the evolution of ESlayers due to varied electric fields and atmospheric gravity waves, while it is advected by the horizontal wind. A sporadic Elayer (Es) could be formed by metallic ions and then modified or transported by the action of magnetospheric electric fields in the high latitude ionosphere. It has been widely proposed that Eslayers play an important role in the formation of sporadic sodium layers (SSL), but detailed studies of their dynamic process and evolution are still lacking. A three‐frequency Sodium (Na) resonance fluorescence Doppler lidar has been recently deployed by the Polar Research Institute of China, which could measure the sodium density, temperature, and wind profiles simultaneously in three directions. To clarify the dynamic properties of Es/SSL, we have performed observations of an event at Zhongshan Station (69.4°S, 76.4°E), Antarctica, which includes sodium density profiles and wind velocity measured by the multidirectional lidar system, detection of the Eslayer by a collocated Digisonde radar, Fregion ion velocity, that is, electric field, derived by the SuperDARN HF radar network, as well as gravity wave perturbations determined from the Davis medium frequency radar. Separation of temporal/spatial variations in sporadic sodium layer (SSLs) is observed by a three‐directional lidar system at Zhongshan, AntarcticaThe formation and perturbance of SSLs are associated with a sporadic Elayer at the same heightThe SSLs are advected by the background wind Separation of temporal/spatial variations in sporadic sodium layer (SSLs) is observed by a three‐directional lidar system at Zhongshan, Antarctica The formation and perturbance of SSLs are associated with a sporadic Elayer at the same height The SSLs are advected by the background wind

In general, lobe reconnection occurs under northward interplanetary magnetic field (IMF) Bz. However, what process can trigger lobe reconnection has not been fully understood. Using observations from SuperDARN radar and Defense Meteorological Satellite Program (DMSP) spacecraft, we found that (a) short‐term sunward ionospheric flow bursts observed by SuperDARN poleward of the cusp showed one‐to‐one correspondent with the sudden increase of the IMF Bz, (b) the sunward flow bursts observed by SurperDARN were associated with sunward ion drifts identified from the DMSP satellite, and (c) a cusp auroral spot, together with an inverse ion energy dispersion, was observed in association with one of the flow bursts. We suggest that these observations provide evidence that the lobe reconnections can be triggered by a sudden increase of the IMF Bz component. What’s more, we found that the reconnection signatures disappeared quickly after the IMF Bz enhancement being over, which indicates that the lobe reconnection triggered by the sudden increase of the IMF Bz is a transient process. The lobe reconnection between solar wind and magnetosphere occurs under a strong northward interplanetary magnetic field (IMF). And it will produce sunward ionospheric convection flow in the dayside polar cap. In this study, we find that short‐term sunward ionospheric convection flows in the dayside polar cap show one‐to‐one correspondence with the sudden increase of the IMF Bz under strong IMF Bx condition. By combining SuperDARN and Defense Meteorological Satellite Program data, we can identify that it is caused by transient lobe reconnection. The transient lobe reconnection may take place even if the increasing magnitude of the IMF Bz is not substantially large, and then disappears quickly after the finish of IMF Bz enhancement. Thus, we believe that the transient lobe reconnection is caused by sudden positive enhancement of IMF Bz. Sunward ionospheric convection flow bursts at the dayside polar cap showed one‐to‐one correspondent with the sudden increase of the interplanetary magnetic field (IMF) BzCusp auroral spot and inverse ion energy dispersion were confirmed to associate with one of the flow burstsEvidence of transient lobe reconnection triggered by sudden increase of the IMF Bz is presented Sunward ionospheric convection flow bursts at the dayside polar cap showed one‐to‐one correspondent with the sudden increase of the interplanetary magnetic field (IMF) Bz Cusp auroral spot and inverse ion energy dispersion were confirmed to associate with one of the flow bursts Evidence of transient lobe reconnection triggered by sudden increase of the IMF Bz is presented

Using the full relativistic test particle (TP) simulation code, we investigate the parametric dependence of electron scattering and phase space density evolution driven by magnetosonic (MS) waves at L= 4.5 both inside and outside the plasmapause. The scattering effects caused by Landau resonance, bounce resonance, and the transit‐time effect are all involved in the study. The net scattering effects are evaluated in the form of diffusion coefficients with different combinations of MS wave parameters, such as frequency bandwidth and wave normal angle, and ambient plasma density. The results demonstrate that (1) Landau resonance and the transit‐time effect dominate the electron scattering inside and outside the plasmapause, respectively, while both are modulated by bounce resonant scattering; (2) bounce resonant scattering becomes more important with narrowband MS waves; (3) electron scattering induced by MS waves is highly sensitive to wave normal angle. The temporal phase space density (PSD) evolution obtained from 2‐D kinetic Fokker‐Planck simulations shows that MS waves with larger wave normal angles are more likely to generate electron butterfly pitch angle distributions (PADs) for hundreds of keV electrons outside the plasmapause. Our study suggests that the electron butterfly distribution has important implications for revealing the combined scattering of MS wave‐particle interactions, and the combination of the multiple scattering mechanisms should be carefully incorporated in future global modeling of radiation belt dynamics. The transit‐time effect with bounce resonance by MS waves dominates the electron scattering outside the plasmapauseElectron scattering by MS waves is sensitive to frequency bandwidth, wave normal angle, and plasma densityMS waves generate electron butterfly pitch angle distributions more efficiently outside the plasmapause

Developing a computational model for aurora image classification is an important task for polar research. However, the design of the handcrafted features in the traditional methods has insufficient descriptive ability for auroral morphology and is dependent on expert knowledge. In this paper, an automatic aurora image classification framework based on deep learning is proposed to solve the problem. In this framework, three basic deep learning networks—AlexNet, VGG, and ResNet—are used to automatically classify all‐sky aurora images via convolution and pooling processes and a back‐propagation mechanism, without requiring manual intervention. As shown in the class activation mapping (CAM), the proposed framework can extract the complex auroral feature representations automatically and discriminatively. The results obtained with all‐sky aurora images from the Yellow River Station demonstrate that the proposed framework has effective transfer ability and can achieve real‐time classification. It is also shown that the proposed method can achieve higher average classification accuracy than the AI‐MFLDA method. The statistical auroral occurrence distribution can be obtained based on the classification results. There are dominant morphological characteristics in the four magnetic local time (MLT) regions of the dayside aurora oval, which confirms the effectiveness of the proposed method. The established automatic deep learning framework for aurora image classification shows a definite accuracy improvementThe proposed framework has the capability of efficient transfer and fast classification for real‐time generated aurora imagesThe auroral occurrence distribution validates the rationality of the auroral morphology division and the effectiveness of the proposed framework

Low‐frequency hiss is known to play an important role in the precipitation of radiation belt electrons by cyclotron, Landau, and bounce resonances. To investigate the potential combined scattering effect caused by these resonant processes, we analyze the resonant conditions and develop a full relativistic test particle code to quantify the net pitch angle scattering efficiency. It is indicated that the three resonance processes can coexist to scatter electrons at different energies and pitch angles, with the net pitch angle scattering rates up to ~10−3s−1for low‐frequency hiss ~175 pT at L= 4.5. Comparisons with the quasi‐linear theory results demonstrate that the cyclotron resonance is mainly responsible for the pitch angle scattering of electrons < ~ 80°, while both Landau and bounce resonances can affect the scattering of near‐equatorially mirroring electrons and their combined diffusion produces smaller scattering coefficients compared to quasi‐linear theory calculations. The radiation belt electrons are believed to resonate with low‐frequency plasmaspheric hiss in ways of cyclotron, Landau, and bounce resonances. In previous quasi‐linear approximations, the wave‐particle interactions were separately evaluated through numerical calculations, where the cyclotron resonance is mainly responsible for pitch angle scattering of nonequatorially mirroring electrons with pitch angles <80°, and both Landau and bounce resonance are believed to effectively scatter near‐equatorially mirroring electrons. To examine the net scattering effect and determine the dominant scattering mechanism for near‐equatorially mirroring electrons, we simulate the electron scattering coefficients by test particle code and compare the results with quasi‐linear theory. Besides validating the contribution of low‐frequency hiss to radiation belt electron losses and the applicability of quasi‐linear theory, our investigation emphasizes the importance of combined scattering effect of cyclotron, Landau, and bounce resonances. Our results also suggest that the combined scattering cannot be treated by quasi‐linear formulism but should be incorporated into future simulations of radiation belt electron dynamics. Cyclotron, Landau, and bounce resonances induced by low‐frequency hiss can coexist to scatter radiation belt electronsTest particle simulations validate the feasibility of quasi‐linear theory in that hiss‐induced pitch angle scattering of electrons < ~ 80° is mainly predominated by cyclotron resonanceCombined Landau and bounce resonances by low‐frequency hiss produce smaller pitch angle scattering coefficients for near‐equatorially mirroring electrons than previous quasi‐linear theory predictions

In this paper, we propose a lossless compression method to resolve the limitations in the real-time transmission of aurora spectral images. This method bi-dimensionally decorrelates the spatial and spectral domains and effectively removes side information of recursively computed coefficients to achieve high quality rapid compression. Experiments on data sets captured from the Antarctic Zhongshan Station show that the proposed algorithm can meet real-time requirements by using parallel processing to achieve outstanding compression ratio performance with low computational complexity. [ABSTRACT FROM AUTHOR]