Astrophysics & Planetary Sciences Colloquia
The past several decades have brought a revolution in our understanding of the universe, its origin, and its constituent parts. While this transformation in our understanding has captured the imagination of the public as well as scientists, it has not strongly impacted how introductory college astronomy courses are taught; many still emphasize discoveries of the ancient Greeks and the Renaissance while giving little attention to recent advances.
The Earth’s magnetosphere is filled with various charged particle populations spanning orders of magnitude in energy, from the very cold (~eV) dense plasmasphere up to the high energy (~MeV) electrons trapped in the Van Allen radiation belts. Here we examine the coupled nature of these populations and the role of wave-particle interactions in transferring energy and momentum among them. In particular, we focus on the highly dynamic radiation belts, which often exhibit dramatic variations in intensity and spatial extent.
We live in a universe of waves. In astrophysical objects, in the clouds overhead, in the beat of our hearts, the transport of energy is often mediated by waves. In space plasmas, waves occur both on large scales, where magnetohydrodynamics (MHD) can describe their behavior, and on small scales, where kinetic effects must be considered.
Jupiter and Saturn’s internal magnetic fields carve out a cavity in the solar wind (and its embedded interplanetary magnetic field) to form two of the largest magnetospheres in our solar system. Their locations in the heliosphere are characterized by vastly different solar wind conditions than are available at Earth, thus affording, for example, the exploration of some of the highest Mach number shocks ever recorded in situ.
Aurora, optical emissions in the upper polar atmosphere, reflects a variety of space phenomena, and offers an opportunity for remote sensing of the space environment. Processes associated with aurora are not only important for Space Physics but also impact the human society such as radio communication and satellite operation during large space weather events. Recent studies have shown that localized structures in the Geospace system have major impacts on mass, momentum and energy transport in the system.
The precipitation of charged particles from space into planetary environments is as important as it is ubiquitous in the solar system, causing myriad effects on planetary atmospheres, surfaces, and biomatter. In this seminar I’ll focus on two environments in particular: Mars and icy moons.
Using a combination of the Hubble Space Telescope, the Keck telescopes, and the ALMA millimeter interferometer, we have begun to piece together a picture of the emergence of galactic structure: how the Universe evolved from its uniform state shortly after the Big Bang to the rich diversity of galaxies today. In this talk, I will discuss some of the results that have come out of my work and the impact they have had on our understanding of the formation and evolution of galaxies.
As techniques have improved over the last decade, observations have peered deep into the Universe’s history and begun to glimpse galaxies which formed in the first few billion years after the Big Bang. Evidence is mounting that galaxies in the early Universe appear and behave very differently from those nearby - for example, the most massive galaxies are extremely compact, and star-forming disks appear to have strange clumpy morphologies.
Measurements of the cosmic microwave background at redshift 1100 give us information about the initial density fluctuations that seeded structure formation. Observations of galaxies at redshift 7 give us information about the outcome of this structure formation. Between those redshifts lies a modern frontier of cosmology -- the cosmic dawn -- the formation of the first stars and the reionization of the intergalactic medium.