Y. Q. Hao

Charged Particle Behavior in Localized Ultralow Frequency Waves: Theory and Observations

The formation and variability of the Van Allen radiation belts are highly influenced by charged particles accelerated via drift-resonant interactions with ultralow frequency (ULF) waves. In the prevailing theory of drift resonance, the ULF wave amplitude is assumed independent of magnetic longitude. This assumption is not generally valid in Earths magnetosphere, as supported by numerous observations that point to the localized nature of ULF waves. Here, we introduce a longitude dependence of the ULF wave amplitude, achieved via a von Mises function, into the theoretical framework of ULF wave-particle drift resonance. To validate the revised theory, the predicted particle signatures are compared with observational data through a best-fit procedure. It is demonstrated that incorporation of non-local effects in drift-resonance theory provides an improved understanding of charged particle behavior in the inner magnetosphere through the intermediary of ULF waves.

Radial propagation of magnetospheric substorm-injected energetic electrons observed using a BD-IES instrument and Van Allen Probes

In cases where substorm injections can be observed simultaneously by multiple spacecraft, they can help elucidate the potential mechanisms of particle transport and energization, of great importance to understanding and modeling the magnetosphere. In this paper, using data returned from the BeiDa-IES (BD-IES) instrument onboard a satellite in an inclined (55°) geosynchronous orbit (IGSO), in combination with two geo-transfer orbiting (GTO) satellite Van Allen Probes (A and B), we analyze a substorm injection event that occurred on the 16th of October 2015. During this substorm injection, the IGSO onboard BD-IES was outbound, while both Van Allen Probe satellites (A and B) were inbound, a configuration of multiple trajectories that provides a unique opportunity to simultaneously investigate both the inward and outward radial propagation of substorm injection. Indicated by AE/AL indices, this substorm was closely related to an IMF/solar wind discontinuity that showed a sharp change in IMF Bz direction to the north. The innermost signature of this substorm injection was detected by Van Allen Probes A and B at L-3.7, while the outermost signature was observed by the onboard BD-IES instrument at L~10. These data indicate that the substorm had a global, rather than just local, effect. Finally, we suggest that electric fields carried by fast-mode compressional waves around the substorm injection are the most likely candidate mechanism for the electron injection signatures observed in the inner- and outermost inner magnetosphere.

Electron dropout echoes induced by interplanetary shock: Van Allen Probes observations

On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ∼1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or “dropout echoes”, constitute a new phenomenon referred to as a “drifting electron dropout” with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from ∼1300 to 0100 LT. We conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. The dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.

The temporal dependence of GPS cycle slip in low-latitude region

Cycle slip is a typical anomaly phenomenon for GPS carrier phase measurements and frequent occurrence of cycle slip would greatly degrade the quality of GPS positioning. Although the degradation of GPS signal to noise or even the loss of lock related with radio wave interference have been found during severe solar radio burst event accompanying with solar flare, long-term studies show that for a given GPS receiver, loss of lock or cycle slip with higher satellite elevations is mainly caused by deep signal fade or strong phase fluctuation related to the ionospheric irregularities.