Quasi-linear modeling of gyroresonance between different MLT chorus and geostationary orbit electrons

The contributions of dayside and nightside gyroresonance of chorus waves to electron radiation belt evolution at L = 6.6 are detailedly differentiated via fully solving the two-dimensional Fokker-Plank equation.The numerical results show that the chorus waves at different regions play signiffcantly different roles.The dayside chorus waves can cause obvious loss of energetic electrons at lower pitch angles and weak energization at larger pitch angles.The nightside chorus waves can yield significant energization at larger pitch angles,but cannot efficiently resonate with the energetic electrons at lower pitch angle.Due to the numerical difficulty in fully solving Fokker-Planck equation,the cross diffusion terms are often ignored in the previous work.Here the effect of cross diffiusion at different regions is further analyzed.On the dayside,ignoring cross diffusion overestimates the electron phase space density by several orders of magnitude at lower pitch angles,and consequently the dayside chorus waves are incorrectly regarded as an effective energization mechanism.On the nightside,ignoring cross diffusion overestimates the electron phase space density(PSD) by about one order of magnitude at larger pitch angles.These numerical results suggest that cross diffusion terms can significantly affect gyroresonance of chorus waves on both the dayside and nightside,which should be included in the future radiation belt models.     

Upward propagation of lightning-generated whistler waves into the radiation belts

Lightning-generated whistler (LGW) waves which induce energetic electron precipitation provide an important coupling between the ionosphere and radiation belts. Using the ray-tracing technique, we examine the propagation behaviour of LGW waves and show that they can travel upward into the radiation belts during higher geomagnetic activities due to the plasmapause inward compression, particularly in cases of lower wave frequencies, lower wave normal angles and azimuthal angles. Both perpendicular and parallel group velocities of LGW waves remain in relatively small values inside the plasmasphere but change rapidly to high values outside the plasmasphere. The launching latitude increases with increasing LGW wave normal angle. These results here further reveal a detailed picture on how LGW waves escape out of the plasmasphere and onto the radiation belts.     

Generation of simultaneous H+ and He+ band EMIC waves in the nightside radiation belt

Science China Technological Sciences - Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere. Here we report obliquely propagating H+ and He+...     

Butterfly distribution of Earth’s radiation belt relativistic electrons induced by dayside chorus

Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth’s radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high-resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 11–13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52, corresponding to the presence of enhanced dayside chorus. Using a Gaussian distribution fit to the observed chorus spectra, we calculate the bounce-averaged diffusion rates and solve two-dimensional Fokker-Planck equation. Numerical results demonstrate that acceleration by dayside chorus can yield the electron flux evolution both in the energy and butterfly pitch angle distribution comparable to the observation, providing a further evidence for the formation of butterfly distribution of relativistic electrons driven by very low frequency (VLF) plasma waves.     

Correlated observations linking loss of energetic protons to EMIC waves

Electromagnetic ion cyclotron (EMIC) emission is an efficient mechanism for scattering loss of energetic protons. Here, we report an event that provides both in-situ observation of energetic proton differential fluxes in the inner magnetosphere and precipitation of protons at ionospheric altitudes. During the 7–8 September 2015 geomagnetic storm the Van Allen Probes observed strong EMIC waves around L = 5 and a distinct decrement in fluxes of tens of keV protons around pitch angles 0°–45°. Meanwhile, precipitating protons at ionospheric altitudes were found to significantly enhanced (by several orders of magnitude), measured by NOAA 18 and 19 when they magnetically linked to the Van Allen Probe-A. By solving the Fokker-Planck diffusion equation, we show that EMIC waves can efficiently produce loss of energetic protons within about 2 h in the pitch angle range of ∼ 0°–45°, comparable to the satellite observations.

     

Identification of Free Radical Scavengers from Brazilian Green Propolis Using Off‐Line HPLC‐DPPH Assay and LC‐MS

Brazilian green propolis is known as an appreciable natural antioxidant with abundant polyphenolic compounds. For quality control, a fingerprint‐efficacy study of Brazilian green propolis was carried out in this work. Chemical fingerprints of Brazilian green propolis from 22 different sources were determined by HPLC and investigated by similarity analysis. The fingerprint‐efficacy relationships between chemical fingerprint and DPPH radical‐scavenging activity were established. The results showed that 14 characteristic common peaks were identified, and 9 compounds were discovered with free radical‐scavenging activities. Caffeoylquinic acids and artepillin C might be the major effective components for quality control of Brazilian green propolis due to their specificity and strong antioxidant activity. This study provides new markers for the quality assessment of Brazilian green propolis and its derived products.     

工艺参数对直流电沉积纳米晶Ni-Fe合金箔的影响

采用直流电沉积的方法在氯化物-硫酸盐体系中制备纳米晶Ni-Fe合金箔,研究了不同质量浓度硫酸亚铁、硼酸、NaCl、十二烷基硫酸钠、糖精、1,4-丁炔二醇、柠檬酸钠对镀层含铁量的影响,采用SEM、XRD、EDS分析Ni-Fe合金箔的形貌、结构和成分.结果表明:体系中组分含量对镀层含铁量有较大的影响;Ni-Fe合金箔表面光滑平整,镀层质量较好,为纳米晶态结构.     

Multi-satellite observations on the storm-time enhancements of energetic outer zone electron fluxes driven by chorus waves

The evolution of energetic outer zone electron fluxes during the strong magnetic storm on September 28, 2002 is investigated based on the observations of SAMPEX and GOES-10 satellites. The observations of both satellites showed that energetic electron fluxes increased significantly during the storm recovery phase, and reached the maximum on October 6. The 1.5–14 MeV and 2.5–14 MeV electron fluxes observed by SAMPEX peaked around L=3.5 with values of 6×10 2 cm -2 s -1 sr -1 keV -1 and 5×10 3 cm -2 s -1 sr -1...