Interplanetary coronal mass ejections (ICMEs), the large-scale solar transients carrying flux ropes (FRs), may evolve in different ways, including erosion and/or accumulation of magnetic field lines while being involved in magnetic reconnection with ambient solar wind and often with other nearby ICMEs and solar wind structures. In this Letter, for the first time utilizing a rare alignment of spacecraft, we analyse the multiscale radial evolution of two ICMEs—observed by spacecraft pairs with minimal angular separations of 2 $\mathop{.}\limits^{{\unicode{x000b0}}}$ 2 and 1 $\mathop{.}\limits^{{\unicode{x000b0}}}$ 1, and radial separations of 0.15 and 0.05 au, respectively—due to erosion and accumulation. We derive their magnetic helicity and cross helicity, residual and average magnetic energy, FR radial size, temporal extension of their helical structures, and the core’s characteristic scale size, and compare these parameters at the radial distances of the lined-up spacecraft to obtain their radial scaling. We find that if an expanding FR undergoes erosion at its outer layer during heliospheric propagation, its overall size expansion rate is lower than that of its core, where field line helicity is maximum. Conversely, during field line accumulation or merging, the expansion rate of FR overall size is higher than that of its core. Furthermore, erosion is indicated by a decreasing dominance of magnetic energy relative to total energy and a higher rate of average magnetic energy decay than ideally expected. These results demonstrate that coordinated multispacecraft observations can distinguish between erosion and accumulation processes in ICME FRs and provide new constraints on their dynamical evolution in the heliosphere.
Space weathering progressively modifies lunar surface regolith, while impact gardening and related processes redistribute weathered materials within the upper regolith, generating depth-dependent variations in maturity. Although surface maturity has been extensively investigated, its variation within the uppermost few centimeters remains insufficiently characterized. In particular, whether shallow maturity profiles differ between nearside and farside, especially at mid-to-high latitudes, has yet to be systematically examined. Here, using multisource orbital and in situ observations together with sampling-derived information, we investigate the depth-dependent distribution of shallow maturity at the Chang’e-5 (CE-5) landing site on the nearside and the Chang’e-6 (CE-6) site on the farside, both located at mid-to-high latitudes. Prelanding orbital spectra characterize the undisturbed surface, whereas in situ spectra acquired after plume-induced erosion (∼0.4/0.7 cm depth) and sampling excavation (∼3.4/3.7 cm depth) provide information on deeper layers, enabling maturity comparisons across three shallow stratigraphic horizons. Maturity indicators consistently indicate that the shallow regolith of CE-6 is more mature than that of CE-5, with the postlanding in situ spectra yielding Is/FeO values of ∼78.13 and ∼31.40 for CE-6 and CE-5, respectively. Despite this difference in overall maturity, both sites exhibit similar depth-dependent patterns; the regolith becomes fresher with depth, showing relatively small maturity changes following plume erosion and more pronounced changes after sampling excavation. The similarity in these vertical patterns suggests broadly comparable intensities of two sites’ shallow regolith modification. These findings provide new observational constraints on the vertical distribution and evolution of shallow maturity and advance our understanding of regolith modification of CE-5 and CE-6 sites.
The origin of the near-critical rotation of classical Be stars remains uncertain. Binary mass transfer provides a formation channel, but it cannot explain Be stars that are observed without a close companion. We investigate V1371 Tau, a hierarchical triple containing an inner B+B binary and an outer Be star. With n -body simulations, we first show that the observed inclination variations of the B+B binary do not require von Zeipel–Lidov–Kozai (ZLK) oscillations, as nodal precession alone can produce substantial changes in inclination relative to the line of sight. We then consider whether V1371 Tau formed from a primordial 2+2 quadruple, in which a progenitor binary of the Be star underwent ZLK-driven eccentricity excitation and merged. We find that mergers occur over a broad range of progenitor binary parameters while leaving the observed B+B binary intact. The merger remnant is expected to retain the orbital angular-momentum direction at the time of merger, producing a potentially observable misalignment between the Be-star spin axis and its orbit around the surviving B+B binary. These results demonstrate that ZLK-driven mergers in higher-order multiple systems provide a viable formation pathway for rapidly rotating Be stars without present-day close companions.
Emerging flux regions (EFRs) are key sites of magnetic flux transport and energy release in the solar atmosphere, often hosting arch filament systems (AFSs). We present high-resolution observations of an EFR obtained during the Sunrise III mission, combining spectropolarimetric measurements from the Tunable Magnetograph (TuMag) and Sunrise Chromospheric Infrared Spectro-Polarimeter (SCIP) with complementary observations from the Solar Dynamics Observatory (SDO). The data set provides a continuous view of an AFS over nearly 4 hr. Line-of-sight (LOS) velocities derived from the Mg I b _2 line reveal three episodic plasma-flow events characterized by strong downflows reaching up to ∼17 km s ^−1 at the AFS footpoints and enhanced upflows near the loop tops. Although this pattern agrees with the classical emergence and draining scenario, the strongest upflows and downflows occur nearly simultaneously. Atmospheric Imaging Assembly (AIA) 304 and 171 Å observations reveal transient extreme-UV (EUV) brightenings in the surrounding emerging system; some occur during episodes of enhanced LOS velocities, while others do not, indicating that the temporal correspondence is not systematic. Multiline spectropolarimetric inversions reveal temperatures between ∼4000 and ∼10,000 K and a smooth variation of the magnetic field inclination along a representative AFS loop. Non-force-free-field extrapolations provide the large-scale magnetic context of the low-lying AFS loops and surrounding coronal structures. Together, the observations reveal a spatially and temporally complex evolution of the emerging system without establishing a direct causal connection between the local plasma-flow enhancements and the EUV brightenings.
Stellar coronal mass ejections (CMEs) play key roles in stellar evolution and planetary habitability. On the Sun, CMEs typically originate from preexisting prominences or filaments, while materials condensed via the evaporation–condensation process have only been observed to remain confined or fall back as rain—never to trigger reconnection or drive eruptions. Here, we present high-resolution spectroscopic observations of II Pegasi (II Peg) obtained by the NARVAL, which captured successive sequences of loop-top condensation, gravitational fallback, and subsequent ejection, associated with stellar flares. Three successive flares originating from the same active region exhibited similar early phase spectral evolution but diverged into distinct final outcomes. Two flares developed to show blueshifted emission in the H α line, with maximum velocities reaching 1.7 and 1.07 times the stellar surface escape velocity (∼306 km s ^−1 ), indicating mass ejections. In contrast, the third flare exhibited a redshifted emission feature in the H α line, signifying a confined event. We interpret these contrasting behaviors within an impact-triggered magnetic reconnection framework, in which the final trajectory—eruptive or confined—is set by whether the newly reconnected field lines open outward or remain closed. Our studies show that stellar CMEs can arise directly from coronal condensations that fall back, trigger reconnection, and are subsequently ejected, revealing a previously unrecognized eruption pathway.
