Events at Physics
Events on Monday, December 3rd, 2012
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Gyrokinetic Simulations of Solar Wind Turbulence and Dissipation
- Time: 12:00 pm
- Place: 1310 Sterling Hall
- Speaker: Jason TenBarge, University of Iowa
- Abstract: Turbulence plays an important role in space and astrophysical plasmas by mediating the transfer of energy from large-scale motions to the small scales at which the turbulence can be dissipated. Recent advances in solar wind data extending to sub-electron scales have increased the focus on turbulence and dissipation at kinetic scales. Due to the nature of plasma turbulence, gyrokinetics is well suited to study weakly collisional kinetic plasmas, such as the solar wind. We present nonlinear gyrokinetic simulation results in- cluding: (1) energy spectra spanning the entire dissipation range from ion to sub-electron scales that show striking agreement with in situ solar wind data, (2) identification of a dissipation range anisotropic cascade of energy in agreement with predictions of critical balance, and (3) constraints on the physical origin of energy dissipation at kinetic scales.
- Special Lunch Astronomy Talk
- "H-alpha Dots: A Catalog of Faint Emission-line Objects Discovered in Narrowband Images"
- Time: 12:00 pm
- Place: 4421 Sterling Hall
- Speaker: Jessica Kellar, Darthmouth College
- Abstract: I discovered a number of isolated and compact sources of emission (aEurooeH-alpha dotsaEuro) in a narrow-band H-alpha survey. These H-alpha dots could be (1) isolated extra-galactic HII regions associated with a nearby larger galaxy, (2) dwarf star-forming galaxies, or (3) background galaxies, where another strong emission-line such as [OIII]5007 has redshifted into the H-alpha filter. Based on follow-up spectra taken at the MDM 2.4 meter telescope and HET, I determined that the H-alpha dots are a combination of nearby (z~0.01) dwarf star-forming galaxies and intermediate-redshift (mostly at z~0.3) starforming galaxies and AGN. I will discuss the star-formation properties, environments, and metallicities of the dwarf galaxies. The star-forming galaxies at z~0.3 are very metal-poor, which suggests that they may be recently formed. I will discuss the insights this diverse sample of galaxies from the H-alpha dot survey can give us about galaxy evolution.