Calendar

Aug
28
Fri
Colloquium Thesis Proposal: Laura Mayorga
Aug 28 @ 3:15 pm – 4:15 pm
Colloquium Thesis Proposal: Laura Mayorga @ BX102

Probing Exoplanet Atmospheric Properties from Phase Variations and Polarization

Laura Mayorga, NMSU

The study of exoplanets is evolving past simple transit and Doppler method discovery and characterization. One of the many goals of the upcoming mission WFIRST-AFTA is to directly image giant exoplanets with a coronagraph. We undertake a study to determine the types of exoplanets that missions such as WFIRST will encounter and what instruments these missions require to best characterize giant planet atmospheres. We will first complete a benchmark study of how Jupiter reflects and scatters light as a function of phase angle. We will use Cassini flyby data from late 2000 to measure Jupiter’s phase curve, spherical albedo, and degree of polarization. Using Jupiter as a comparison, we will then study a sample of exoplanet atmosphere models generated to explore the atmospheric parameter space of giant planets and estimate what WFIRST might observe. Our study will provide valuable refinements to Jupiter-like models of planet evolution and atmospheric composition. We will also help inform future missions of what instruments are needed to characterize similar planets and what science goals will further our knowledge of giant worlds in our universe.

Oct
16
Fri
Colloquium: Doug Biesecker
Oct 16 @ 3:15 pm – 4:15 pm
Colloquium: Doug Biesecker @ BX102

Why Space Weather Matters and How Forecasting Will Improve in the DSCOVR Era

Doug Biesecker, NOAA/NWS/Space Weather Prediction Center

Space Weather is a growing enterprise, with growing recognition of its importance inside and outside government.  The largest concern is with the electric power grid, but impacts to Global Positioning Systems (GPS) are also significant.  Other areas of impact include satellites and human space flight, and high frequency communication for aviation, mariners, and emergency responders, among many.  The NOAA National Weather Service’s Space Weather Prediction Center (SWPC) is the nation’s official source of space weather watches, warnings and alerts.  SWPC does this with a 24×7 staffed operation that monitors the Sun, solar wind, and geospace environment taking advantage of a broad suite of observations and models to provide the best forecasts possible.  In conjunction with the growing recognition of space weather, NOAA launched its first mission, the Deep Space Climate Observatory (DSCOVR), out of the Earth’s orbit to an orbit about the L1 Lagrange point.  This is also NOAA’s first satellite mission where space weather is the primary mission and DSCOVR marks the first of what is expected to be a long series of space weather monitoring satellites.  NOAA is also bringing numerical space weather models into the mix of models running on the nation’s supercomputers.  Numerical space weather models have demonstrated the ability to improve the onset time of space weather storms and will, for the first time, allow regional geomagnetic forecasting.  Instead of describing conditions on Earth with a single number, customers will have forecasts tailored to their location.

 

Feb
12
Fri
Colloquium: Lauren Woolsey
Feb 12 @ 3:15 pm – 4:15 pm
Colloquium:  Lauren Woolsey @ BX102

Magnetic Influences on Coronal Heating and the Solar Wind

Lauren Woolsey, Harvard University

 

Abstract

The physical mechanism(s) that generate and accelerate the solar wind have not been conclusively determined after decades of study, though not for lack of possibilities. The long list of proposed processes can be grouped into two main paradigms: 1) models that require the rearranging of magnetic topology through magnetic reconnection in order to release energy and accelerate the wind and 2) models that require the launching of magnetoacoustic and Alfvén waves to propagate along the magnetic field and generate turbulence to heat the corona and accelerate the emanating wind. After a short overview of these paradigms, I will present my ongoing dissertation work that seeks to investigate the latter category of theoretical models and the role that different magnetic field profiles play in the resulting solar wind properties with Alfvén-wave-driven turbulent heating. I will describe the computer modeling in 1D and 3D that I have done of bundles of magnetic field (flux tubes) that are open to the heliosphere, and what our results can tell us about the influences of magnetic field on the solar wind in these flux tubes, including the latest time-dependent modeling that produces bursty, nanoflare-like heating. Additionally, I will present the latest results of our study of chromospheric network jets and the magnetic thresholds we are finding in magnetogram data.

Apr
1
Fri
Colloquium: Hwiyun Kim (Host: Rene Walterbos)
Apr 1 @ 3:15 pm – 4:15 pm
Colloquium:  Hwiyun Kim     (Host: Rene Walterbos) @ BX102

High Resolution Spectroscopy with Immersion Grating Infrared Spectrometer (IGRINS)

Hwihyun Kim, KASI/UT Austin

 

The Immersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution (R=45,000) in the near-infrared. IGRINS employs a silicon immersion grating as the primary disperser of the white pupil, and volume-phase holographic gratings cross-disperse the H and K bands onto Teledyne Hawaii-2RG arrays. IGRINS provides simultaneous wavelength coverage from 1.45 – 2.45 microns in a compact cryostat. I will summarize the performance and various science programs of IGRINS since commissioning in Summer 2014. With IGRINS we have observed such as Solar System objects, nearby young stars, star-forming regions like Taurus and Ophiuchus, the Galactic Center, and planetary nebulae.

The second half of my talk will be focused on the study of ionized and neutral gas in an ultracompact HII region Monoceros R2. We obtained the IGRINS spectra of Mon R2 to study the kinematic patterns in the areas where ionized and molecular gases interact. The position-velocity maps from the IGRINS spectra demonstrate that the ionized gases (Brackett and Pfund series, He and Fe emission lines;Δv ≈ 40km/s) flow along the walls of the surrounding clouds. This is consistent with the model by Zhu et al. (2005, 2008). In the PV maps of the H2 emission lines there is no obvious motion (Δv < ~10km/s) of the molecular hydrogen right at the ionization boundary. This implies that the molecular gas is not taking part in the flow as the ionized gas is moving along the cavity walls.

Mar
28
Tue
Joint Physics/Astronomy Colloquium: William Newman
Mar 28 @ 4:00 pm – 5:00 pm
Joint Physics/Astronomy Colloquium: William Newman @ Gardiner Hall 229, Physics. Dept. | Ames | Iowa | United States

Giant Planet Shielding of the Inner Solar System Revisited: Blending Celestial Mechanics with Advanced Computation

Dr. William Newman, UCLA

The Earth has sustained during the last billion years as many as five catastrophic collisions with asteroids and comets which led to widespread species extinctions. Our own atmosphere was literally blown away 4.5 billion years ago by a collision with a Mars-sized impactor. However, collisions with comets originating in the outer solar system accreted much of the present-day atmosphere. Relatively advanced life on our planet is the beneficiary of a number of impact events during Earth’s history which built our atmosphere without destroying a large fraction of terrestrial life. Using very high precision Monte Carlo integration methods to explore the orbital evolution over hundreds of millions of years followed by the application of celestial mechanical techniques, the presentation will explain directly how Earth was shielded by the combined influence of Jupiter and Saturn, assuring that only 1 in 100,000 potential collisions with the Earth will materialize.