Title: Investigation of Solar Influence on Thermospheric Density Variation
Abstract: Due to undulations in the heliospheric current sheet, the Earth’s orbit is divided into sectors where the sun’s interplanetary magnetic field (IMF) at the Earth is primarily directed towards or away from the sun. During the year 2003, the IMF direction at the Earth changes with a nearly consistent periodicity of 12-15 days, leading to well defined IMF sectors. During this same period, thermospheric neutral particle densities and electron content are higher during times when the IMF is directed towards the sun, and lower when the IMF is directed away from the sun. Possible links between the IMF polarity and thermospheric densities were investigated, with a focus on the spatial distribution of thermospheric density variations between IMF sectors, as well as the temporal changes of solar wind and IMF parameters and geomagnetic activity indices during the Earth’s transition between IMF sectors.
Soft x-ray spectroscopy is an experimental technique that provides a unique perspective on many
important material properties. When combined with first principles electronic structure calculations, everything from the bulk band gap, to site-specific charge densities can be determined and understood. This talk will look at the application of these techniques to several technologically important nitrides and oxides, and emphasize how they can provide information on the structure-property relationships that are key to engineering new materials
There is intense activity in the search of glueballs, light hybrids and multiquark states, either as supernumerary states with ordinary quantum numbers JPC, or as genuine exotics with JPC that cannot be matched by ordinary quantum numbers. In particular, evidence has been found for 1-+ states between 1 and 2 GeV by VES at Serpukhov, by E852 at Brookhaven, and by COMPASS at CERN, and the search continues at JLab by GLUEX. The structure of these states are still ambiguous. Four-quark states and hybrid states are the most possible explanations. To study these non-qq resonances beyond the conventional quark model, the Wilson coefficients of dimension-8 condensate contribution to the current-current correlator of 1−+ light hybrid current gq(x)γνiGμν(x)q(x) are calculated. With inclusion of these higher-power corrections and updating the input parameters, the mass of the 1−+ light hybrid meson are re-analyzed from Monte-Carlo based QCD sum rules. In this talk, the basic idea of the quark model and QCD sum rules will be briefly reviewed and then the results of calculation and numerical analysis will be presented.
Abstract: The majority of matter in the universe is nonluminous and of unknown composition. It has been dubbed ‘dark matter’ for these reasons. The dark matter problem is one of the most pressing problems in both particle physics and astrophysics. This talk will provide an overview of the study of dark matter from a particle physics perspective. The evidence for the existence of dark matter will be reviewed, and the motivations for particle models of dark matter will be discussed. The talk will conclude with a description of experimental and observational searches for dark matter, including nuclear recoil searches, cosmic ray signals, and production in particle colliders.
Abstract: Ion heating by friction with neutral particles is known to have a significant impact on the F-region ion temperature in the presence of large electric fields, particularly when the ions become supersonic relative to the neutral background population with which they collide. However, what has not been fully characterized is the impact this heating has on ion temperature anisotropy, as well as the influence of these non-Maxwellian velocity distributions on the shape and interpretation of incoherent radar spectra. To study this, reconstructions of incoherent radar spectra made from Monte-Carlo simulations of velocity distributions are being analyzed along-side radar campaigns capable of giving insight into such things as the collision cross-section of different collisions (such as the resonant charge exchange of O+ ions with O). For this research, an experiment was devised to scrutinize the plasma along the magnetic meridian so as to extract electric field and ion temperature information at altitudes where frictional heating plays an important role. The results of this work indicate that, as expected, the line-of-sight component of the plasma drift extracted from different altitudes is consistent throughout the ionosphere above 150 km. However, owing to competition with processes such as heat exchange with electrons, neutral atmospheric uncertainties, and heat conduction from above, extracting information about the effect of frictional heating is difficult unless the electric field is very strong. Here, the first electric field and ion temperature results from these special magnetic meridian scanning modes will be shown.
Title: Space Weather: Finding Field-Aligned Currents during Substorms
Abstract: Near-Earth space is a region whose dynamics are best described by plasmas and the currents they form. To understand the chain of events that leads to space weather phenomena, the connections of the solar wind to the magnetosphere to the ionosphere by such currents need to be understood. In particular, during substorms currents are formed between the magnetosphere and the ionosphere, and a view of incoming and outgoing currents would illustrate the structure of what is called the substorm current wedge. Two scientific tools are considered to do just that in this presentation: the magnetometers aboard the Iridium satellite constellation in the AMPERE project and the radar network SuperDARN. A comparison between AMPERE and SuperDARN methods will be given, as well as the results for a superposed epoch analysis for AMPERE (SuperDARN results up-and-coming).