We explore analytically the structure of relativistic shock and solitary wave
solutions in collisionless plasmas. In the wave frame of reference, a cold
plasma is flowing from one end and impacting ...on a low velocity plasma. First we
show that under astrophysical conditions, a cold electron-positron plasma is
unstable with respect to a two-stream instability in the interface between
these regions. The instability heats the inflowing cold plasma rapidly, on a
timescale comparable to the inverse of its plasma frequency. We then derive
time-independent equations to describe the resulting hot state of the pair
plasma, and describe the conditions under which the spatially uniform solution
is the unique stable solution for the post shock conditions. We also examine
plasmas composed of cold protons and hot electrons, and show that the spatially
uniform solution is the unique stable solution there as well. We state the
shock jump conditions which connect a cold, electron-proton plasma to a hot
electron-proton plasma. The generic feature evident in all of these models is
that the plasma's initial, directed kinetic energy gets almost completely
converted into heat. The magnetic field plays the role of catalyst which can
induce the plasma instability, but our solutions indicate that the macroscopic
field only gets amplified by a factor of approximately three in the frame of
the shock.
High-Speed Network Traffic Acquisition for Agent Systems Celeda, Pavel; Krmicek, Vojtech; Rehak, Martin ...
Proceedings of the 2007 IEEE/WIC/ACM International Conference on Intelligent Agent Technology,
11/2007
Conference Proceeding
This paper presents a design of high-speed network traffic acquisition subsystem suitable for agent-based intrusion detection systems. To match the performance requirements and to improve network ...traffic measurement, wire-speed data acquisition layer is based on hardware-accelerated probes, which provide real-time network traffic statistics. The network traffic is stored in collector servers and preprocessed data is then sent to detection agents that use heterogenous anomaly detection methods. These methods are correlated by means of trust and reputation models, and the conclusions regarding the maliciousness of the traffic is presented to the operator. Presented system is designed to improve the performance of agent-based intrusion detection systems and allow them to efficiently identify malicious traffic. The main contribution of presented system is its ability to aggregate real-time network-wide statistics from geographically dispersed probes. Traffic acquisition system is designed for deployment on high-speed backbone networks.
We consider element diffusion during the linear growth of structure in the intergalactic medium (IGM) before the redshift of reionization. The elements produced during big bang nucleosynthesis (such ...as D, He-4 or Li-7) condensed in collapsing regions more readily than hydrogen. Diffusion was most effective when the IGM was neutral since the collisional cross-section between neutral species is smaller than the corresponding Coulomb cross-section in an ionized gas. We find that diffusion led to small deviations in element abundances of up to 0.1%. Abundance measurements to this level of precision in low-metallicity environments could provide information about the thermal and ionization history of the primordial gas during the early formation of structure in the IGM.
We explore analytically the structure of relativistic shock and solitary wave solutions in collisionless plasmas. In the wave frame of reference, a cold plasma is flowing from one end and impacting ...on a low velocity plasma. First we show that under astrophysical conditions, a cold electron-positron plasma is unstable with respect to a two-stream instability in the interface between these regions. The instability heats the inflowing cold plasma rapidly, on a timescale comparable to the inverse of its plasma frequency. We then derive time-independent equations to describe the resulting hot state of the pair plasma, and describe the conditions under which the spatially uniform solution is the unique stable solution for the post shock conditions. We also examine plasmas composed of cold protons and hot electrons, and show that the spatially uniform solution is the unique stable solution there as well. We state the shock jump conditions which connect a cold, electron-proton plasma to a hot electron-proton plasma. The generic feature evident in all of these models is that the plasma's initial, directed kinetic energy gets almost completely converted into heat. The magnetic field plays the role of catalyst which can induce the plasma instability, but our solutions indicate that the macroscopic field only gets amplified by a factor of approximately three in the frame of the shock.
This paper presents a design of high-speed network traffic acquisition subsystem suitable for agent-based intrusion detection systems. To match the performance requirements and to improve network ...traffic measurement, wire-speed data acquisition layer is based on hardware-accelerated probes, which provide real-time network traffic statistics. The network traffic is stored in collector servers and pre-processed data is then sent to detection agents that use heterogeneous anomaly detection methods. These methods are correlated by means of trust and reputation models, and the conclusions regarding the maliciousness of the traffic is presented to the operator. Presented system is designed to improve the performance of agent-based intrusion detection systems and allow them to efficiently identify malicious traffic. The main contribution of presented system is its ability to aggregate real-time network-wide statistics from geographically dispersed probes. Traffic acquisition system is designed for deployment on high-speed backbone networks.
