arXiv subjects

Zeping Jin

Publications and source records attributed to Zeping Jin.

2 recordsLinked to original sources

arXiv2026

Proton Temperature Anisotropy Across Interplanetary Shocks: A Statistical Analysis with WIND observations

Interplanetary (IP) shocks efficiently modify the proton temperature anisotropy of the solar wind. Analyzing ~800 IP shocks observed by the Wind spacecraft from 1997-2024, we present a statistical study of upstream and downstream proton temperature anisotropy and its dependence on shock geometry, compression, and distance from the shock. We find that (1) quasi-perpendicular shocks produce a pronounced enhancement of perpendicular temperature downstream (Tperp > Tpara), whereas parallel shocks remain near isotropic downstream due to typically stronger upstream Tpara; (2) comparisons with the Chew-Goldberger-Low (CGL) double-adiabatic model reveal geometry-dependent deviations. CGL overestimates downstream perpendicular heating and underestimates parallel heating at quasi-perpendicular shocks, with the opposite trend at quasi-parallel shocks, highlighting the importance of non-adiabatic processes beyond simple compression; (3) Shock-driven anisotropy is strongly localized near the shock and gradually relaxes toward typical solar wind conditions farther downstream as the shock's influence diminishes; and (4) downstream anisotropy is regulated by kinetic instabilities, with quasi-perpendicular shocks constrained by proton cyclotron and mirror instabilities and quasi-parallel shocks limited by the parallel firehose instability. Together, these results show that the evolution of temperature anisotropy at interplanetary shocks is controlled by shock geometry, localized processes, and instability driven regulation.

physics.space-ph↗

arXiv2023

Binary asteroid dissociation and accretion around white dwarfs

About 25-50% of white dwarfs (WDs) show metal lines in their spectra. Among the widely accepted explanations for this effect is that the these WDs are accreting asteroids that are perhaps flung onto the WDs by a planet via resonance, for instance. A number of theoretical works have looked into the accretion of asteroids onto WDs and obtained a fair agreement with the observed accretion rate. However, it is solely a very recent study (referenced in this work) that has taken asteroid binarity into consideration, examining the scattering between an asteroid binary and planets and showing that a dissociation and ejection of the former might result and the effect on WD metal accretion is likely to be weak. Here, we investigate the close encounter between an asteroid binary and the central WD and consider how the binary's dissociation may affect the WD's accretion. We find that depending on the orbital and physical properties, the components may acquire orbits that are significantly different (even on the order of unity) from that of the parent binary. We assumed all the inner main belt asteroids are binaries and we studied their accretion onto the solar WD under the perturbation of the giant planets. We find that compared to the case without binaries, the components' accretion may be postponed (or put forward) by millions of years or more, as the objects may be taken out of (or driven deeper into) the resonance due to the sudden orbital change upon dissociation. However, the overall influence of binary dissociation on the accretion rate is not very significant.

astro-ph.EP↗