C. J. Xiao

Semiochemicals from ovaries of gravid females attract ovipositing female houseflies, Musca domestica.

Chemical signals originating from the ovaries of gravid females of Musca domestica (Diptera: Cyclorrhapha: Muscidae) attract ovipositing females to common egg-laying sites. Behavioral experiments indicated that females preferred to oviposit in fermented wheat bran containing ovaries from reproductively mature houseflies. Females preferred to oviposit in fermented wheat bran than wet wheat bran. This effect was additive with the attraction to housefly ovaries. Solvent extracts from housefly ovaries were attractive to gravid females. Extracts obtained with hexane were most attractive to gravid females for egg laying, and extracts obtained with ethyl acetate attracted more egg laying than extracts obtained by dichloromethane. Gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC-MS) analysis showed that tricosane and (Z)-9-tricosene were the main components of the hexane extracts. Both tricosane and (Z)-9-tricosene were shown to elicit dose-dependent aggregation of gravid females in oviposition bioassays, but high doses of either chemical were not attractive.

Electron trapping around a magnetic null

Magnetic reconnection is an important process in astrophysical, space and laboratory plasmas. The magnetic null pair structure is theoretically suggested to be a crucial feature of the three-dimensional magnetic reconnection. The physics around the null pair, however, has not been explored in combination with the magnetic field configuration deduced from in situ observations. Here, we report the identification of the configuration around a null pair and simultaneous electron dynamics near one null of the pair, observed by four Cluster spacecraft in the geo-magnetotail. Further, we propose a new scenario of electron dynamics in the null region, suggesting that electrons are temporarily trapped in the central reconnection region including electron diffusion region resulting in an electron density peak, accelerated possibly by parallel electric field and electron pressure gradient, and reflected from the magnetic cusp mirrors leading to the bi-directional energetic electron beams, which excite the observed high frequency electrostatic waves.

Interaction Between CME and Magnetosphere Observed by Cluster on Nov. 6, 2001: (1) Waves Excitation

Very few in situ measurements so far show the details of the interactions between CME and magnetosphere. Here we report a fortuitous observation that the Cluster spacecraft were located at the dusk-side magnetopause, meandering back and forth four times between the ICME and the magnetosphere, and observed part process of the interaction between the CME and the magnetosphere. The primarily analysis showed that: (1) a fast ion beam other than the ambient plasma was observed almost perpendicular to the magnetic field; (2) The left-hand-polarized kinetic Alfven waves excitation by the ion beam; and (3) the resonances between the kinetic Alfven waves and part of the beam particles lead to the pitch angle diffusion of resonant particles and formating of a monospheric distribution with nearly constant kinetic energy. The wave-particle resonance may pay an important role in the energy transfer and particle exchange across the magnetopause between the magnetosheath and magnetosphere during the CME impulsion.