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Sun-as-a-star spectroscopic characteristics of solar flares can be used as a benchmark for the detection and analysis of stellar flares. Here, we study the Sun-as-a-star properties of an X1.0 solar flare, using high-resolution spectroscopic data obtained by the Chinese H α Solar Explorer (CHASE). A noise reduction algorithm based on discrete Fourier transformation is first employed to enhance the signal-to-noise ratio of the space-integral H α spectrum, with a focus on its typical characteristics. For the flare of interest, we find that the average H α profile displays a strong emission at the line center and an obvious line broadening. It also presents a clear red asymmetry, corresponding to a redshift velocity of around 50 km s ^−1 that slightly decreases with time, consistent with previous results. Furthermore, we study how the size of the space-integral region affects the characteristics of the flare's Sun-as-a-star H α profile. It is found that although the redshift velocity calculated from the H α profile remains unchanged, the detectability of the characteristics weakens as the space-integral region becomes larger. An upper limit on the size of the target region where the red asymmetry is detectable is estimated. It is also found that the intensity in H α profiles, measured by the equivalent widths of the spectra, are significantly underestimated if the H α spectra are further averaged in the time domain.

We present imaging and spectroscopic diagnostics of a long filament during its formation with the observations from the Chinese H α Solar Explorer and Solar Dynamics Observatory. The seed filament first appeared at about 05:00 UT on 2022 September 13. Afterward, it grew gradually and connected to another filament segment nearby, building up a long filament at about 20:00 UT on the same day. The CHASE H α spectra show an obvious centroid absorption with mild broadening at the main spine of the long filament, which is interpreted as evidence of filament material accumulation. More interestingly, near the footpoints of the filament, persistent redshifts have been detected in the H α spectra during the filament formation, indicating continuous drainage of filament materials. Furthermore, through inspecting the extreme-ultraviolet (EUV) images and magnetograms, it was found that EUV jets and brightenings appeared repeatedly at the junction of the two filament segments, where opposite magnetic polarities converged and canceled each other continuously. These results suggest the occurrence of intermittent magnetic reconnection that not only connects magnetic structures of the two filament segments but also supplies cold materials for the filament channel likely by the condensation of injected hot plasma, even though a part of the cold materials falls down to the filament footpoints at the same time.

The solidification microstructure and phase transition of ten La-Nd-Fe alloys were studied experimentally by scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) and differential thermal analysis (DTA). Phase compositions and phase transition temperatures of La-Nd-Fe alloys were measured and the formed phases were identified. The solidification behavior of La-Nd-Fe alloys was analyzed based on the experimental results of both solidification microstructure and phase transitions with the reported Nd-Fe, La-Fe and La-Nd sub-binary phase diagrams. The results indicated that the solidification processes of all La-Nd-Fe alloys begin with the precipitation of primary phase fcc( γ -Fe) and then follow by the formation of bcc( α -Fe) and/or Fe _17 Nd _2 phases through different peritectic reactions. The solidification microstructure of three Fe _65 La _29 Nd _6 , Fe _65 La _25 Nd _10 and Fe _65 La _22 Nd _13 alloys presents three-phase microstructure with bcc( α -Fe), Fe _17 Nd _2 and fcc(La,Nd) phases, while that of three Fe _65 La _19 Nd _16 , Fe _65 La _9 Nd _26 and Fe _65 La _15.5 Nd _19.5 alloys shows three-phase microstructure with bcc( α -Fe), Fe _17 Nd _2 and dhcp(La,Nd) phases. The two-phase micorstructure with Fe _17 Nd _2 and dhcp(La,Nd) ohases was formed in the solidification microstructure of four Fe _65 La _12 Nd _23 , Fe _65 La _6.5 Nd _28.5 , Fe _65 La _4 Nd _31 and Fe _65 La _1.5 Nd _33.5 alloys. Moreover, no stable ternary intermetallic compound was found in the present experiments. The solidification microstructure and phase transition of La-Nd-Fe alloys would provide a basis for the design of La-Nd-Fe-B magnetic alloys.

The phase formation of the (Nd _0.70 Pr _0.30−x Ce _x ) _2.28 Fe _13.58 B _1.14 (x = 0.10, 0.15, and 0.20; hereafter defined as Pr _20 Ce _10 , Pr _15 Ce _15 and Pr _10 Ce _20 , respectively) and (Nd _0.60 Pr _0.40−y Ce _y ) _2.28 Fe _13.58 B _1.14 (y = 0.10, 0.20, and 0.30; hereafter defined as Pr _30 Ce _10 , Pr _20 Ce _20 and Pr _10 Ce _30 , respectively) alloys that were prepared via the arc-melting method was investigated experimentally. The x-ray diffraction results revealed that all alloys annealed at 1173 K for 360 h consisted of a (NdPrCe) _2 Fe _14 B main phase with a tetragonal Nd _2 Fe _14 B-typed structure (space group P4 _2 /mnm) and an α -Fe minor phase, except for the Pr _10 Ce _30 alloy, which contained an additional CeFe _2 phase. The magnetic properties of the (Nd _0.70 Pr _0.30−x Ce _x ) _2.28 Fe _13.58 B _1.14 and (Nd _0.60 Pr _0.40−y Ce _y ) _2.28 Fe _13.58 B _1.14 ribbons that were prepared by melt spinning were examined. The remanence (B _r ) and maximum magnetic energy product ((BH) _max ) of the (Nd _0.70 Pr _0.30−x Ce _x ) _2.28 Fe _13.58 B _1.14 ribbons increased first and then decreased, whereas the coercivity (H _cj ) of the ribbons increased with an increase in Ce content. The B _r and (BH) _max of the (Nd _0.60 Pr _0.60−y Ce _y ) _2.28 Fe _13.58 B _1.14 ribbons increased, whereas the H _cj of the ribbons decreased gradually with an increase in Ce content. This changed behavior of magnetic properties is attributed to the variation of volume fraction of the α -Fe phase and different phase formations in the melt-spun ribbons. The Curie temperatures (T _c ) of all ribbons decreased slightly with Ce substitution, which results from the lower Curie temperatures of Pr _2 Fe _14 B and Ce _2 Fe _14 B. The Pr _10 Ce _30 ribbon with a higher Ce content exhibited optimal magnetic properties (B _r = 9.71 kGs, H _cj = 13.09 kOe, (BH) _max = 18.78 MGOe), which indicates that suitable magnetic properties of the Nd–Pr–Ce–Fe–B melt-spun ribbons can be achieved by alloy-composition and phase-formation design.