The authors report the synthesis of Mg-based metallic glass composite reinforced with Nb particles which are simply added during melting process. The ductile Nb particles effectively impede shear band propagation and upon yielding, deformed Nb particles distribute the load uniformly to the surrounding glassy matrix to promote the initiation and branching of abundant secondary shear bands. In contrast to the previous Mg-based metallic glass composites which fracture with very little plasticity, the composite shows great resistance to crack growth. The high strength of 900MPa and large plasticity of 12.1±2% have made it comparable to excellent Zr- or Ti-based metallic glass composite.

We use the Magnetospheric Multiscale mission to investigate electron‐scale structures at a dipolarization front. The four spacecraft are separated by electron scales and observe large differences in plasma and field parameters within the dipolarization front, indicating strong deviation from typically assumed plane or slightly curved front surface. We attribute this to ripples generated by the lower hybrid drift instability (LHDI) with wave number of kρe≃0.4 and maximum wave potential of ∼1 kV ∼kBTe. Power law‐like spectra of E⊥ with slope of −3 indicates the turbulent cascade of LHDI. LHDI is observed together with bursty high‐frequency parallel electric fields, suggesting coupling of LHDI to higher‐frequency electrostatic waves.

Dipolarizing flux bundles transport magnetic flux to the inner and dayside magnetosphere, heat the plasma sheet, and provide a seed population to the radiation belt. The magnetic perturbation ahead of them, often referred to as a dipolarization front (DF), is asymmetric with a small Bz dip followed by a sharp Bz enhancement. The Bz dip is thought to be generated from dawnward currents carried by DF‐reflected ions; after reflection, these earthward moving ions gyrate clockwise and contribute to dawnward diamagnetic currents ahead of the front. Using observations of hundreds of DFs, we investigate this hypothesis. We find that the depth of the Bz dip as a function of the front azimuth depends on DF propagation speed and ambient plasma density. These statistical signatures support the hypothesis that the Bz dip is caused by ion reflection and suggest that secondary currents carried by these reflected ions can reshape the front significantly.

Jupiter’s rapidly rotating, strong magnetic field provides a natural laboratory that is key to understanding the dynamics of high-energy plasmas. Spectacular auroral x-ray flares are diagnostic of the most energetic processes governing magnetospheres but seemingly unique to Jupiter. Since their discovery 40 years ago, the processes that produce Jupiter’s x-ray flares have remained unknown. Here, we report simultaneous in situ satellite and space-based telescope observations that reveal the processes that produce Jupiter’s x-ray flares, showing surprising similarities to terrestrial ion aurora. Planetary-scale electromagnetic waves are observed to modulate electromagnetic ion cyclotron waves, periodically causing heavy ions to precipitate and produce Jupiter’s x-ray pulses. Our findings show that ion aurorae share common mechanisms across planetary systems, despite temporal, spatial, and energetic scales varying by orders of magnitude.

Dipolarization fronts (DFs), earthward propagating structures in the Earth's magnetotail with sharp enhancements of the northward magnetic field, can reflect and accelerate ions in the ambient plasma sheet. The ion reflection and acceleration process, which generates earthward flows ahead of the DF, also imposes a dynamic pressure on the DF to decelerate its earthward motion. It has been shown that the ion reflection process is not symmetric, with stronger ion accelerations at the evening side of the DF than at its morning side, which implies dawn-dusk asymmetric reaction of the ambient plasma and consequently dawnward deflection of DFs. In this paper, we examine this scenario in detail, by carrying out statistical studies based on Time History of Events and Macroscale Interactions during Substorms observations from 2008 to 2011. We demonstrate the important role of the ion reflection process in the longstanding problems regarding DF evolution and bursty flow braking in the near-Earth plasma sheet.

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formed by using both Zr-based BMG (Vit 1) and Mg-based BMG (Mg-Cu-Gd) as cores and Al-5056 and Mg-AZ31 as sleeves. After processing, the interfaces seem to be particularly free of defects except in the case of the Vit1-AZ31 rod for which a large difference in viscosity is observed between the glass and the sleeve alloy at the extrusion temperature. The good quality of the interfaces is confirmed by mechanical properties of the MEGA rods tested in compression which suggest that the rule of mixtures can be used, in a first approximation, to predict the fracture stress of the composites. This first report concerning the manufacture of MEGA rods by co-extrusion supports the idea that this process could be particularly attractive to combine bulk metallic glasses with conventional metallic alloys. Work is in progress to study in more details the co-extrusion process and the geometry of the resulting MEGA rods as a function of the extrusion parameters. In addition it is necessary to evaluate more deeply the advantages of such MEGA rods over conventional unidirectionally reinforced alloys, in particular from the viewpoint of the resulting mechanical properties.In 1990s, the preparation of bulk metallic glasses (BMGs, typically referred to a minimum casting dimension larger than 1mm) in some multicomponent alloy systems brought a whole new concept to the metallic glasses research field and greatly widened the application of metallic glasses. [1][2][3][4][5] Meanwhile, it is considered that the complexity of their constituents thought to be conducive to the high glass-forming abil- ADVANCED ENGINEERING MATERIALS 2006, 8, No. 10 COMMUNICATIONS

In the terrestrial inner radiation belt, the energy spectrogram of energetic electrons (10-100s keV) sometimes contains one or multiple peaks (Datlowe et al., 1985;Imhof & Smith, 1966;Imhof et al., 1981aImhof et al., , 1981b. These peaks form regular patterns that map on constant bounce-averaged drift frequencies across the entire inner radiation belt (Sauvaud et al., 2013). These features were named "zebra stripes" by Ukhorskiy et al. (2014). Ukhorskiy et al. (2014) first suggested that the stripes are produced by a global process modulating particles' drift motion. Later in Van Allen Probes era, the patterns are observed to be tightening and narrowing during consecutive inner belt crossings (Lejosne & Roederer, 2016;Liu et al., 2016). Liu et al. ( 2016) have shown that a single monochromatic uniform electric field is sufficient for reproducing the key characteristics of the stripes. The authors pointed out that the electric field distorts the electrons' drift shell, so that the electrons detected by the spacecraft at different times are actually originating from different L-shells with different Phase Space Density (PSD). Lejosne and Mozer (2020) further studied the relation of zebra stripes and geomagnetic activity and revealed that zebra stripes are usually triggered during substorm onsets when the penetration electric field is enhanced in the plasmasphere. Similar zebra stripe patterns have been distinguished in Saturn's electron radiation belt (Müller et al., 2010;Paranicas et al., 2007), but only recently it became apparent that their occurrence in the  E 100 keV to few MeV range can be explained by global-scale electric fields as at Earth (Hao et al., 2020). Similarly, Hao et al. (2020 attributed this pattern to a convective electric field with an approximate noon-to-midnight orientation and reproduced the stripe patterns seen by Cassini. Indirect evidence in Juno and Galileo data hinted that zebra stripes may also exist at Jupiter but at much higher energies (  E 1 MeV) due to the stronger magnetic field and faster rotation of the planet compared to Saturn and Earth. Noncorotational convection flows at Saturn have long been a candidate among the key sources of the Saturnian electron radiation belt. There are a variety of loss mechanisms in the radiation belt, such as wave-particle scattering into the atmospheric loss cone and electron absorption or energy loss at the Saturnian massive ring system, moons, neutral gas cloud, and dusty rings (