Seminar – UCLA EPSS

Date: 2025-10-24 00:00:00

Time: 3:30 – 4:30pm

Location: 3853 Slichter Hall

Presented By:
Dr. Man Hua

Abstract:
Earth’s outer radiation belt is a doughnut-shaped region in space, containing stably trapped energetic electrons. Its outer boundary is closely related to the electron isotropy boundary (IB), which separates the outer radiation belt from the isotropic, precipitating electrons found further out, in the tail current sheet. Field-line curvature scattering (FLCS) is believed to play an important role in causing this isotropic electron precipitation and is effective when the electron gyroradius becomes comparable to the field line curvature radius in the equatorial current sheet region. However, the direct and quantitative impact of FLCS in controlling the outer belt electron lifetimes has never been directly assessed. In this talk, I will discuss the role of FLCS in controlling the outer belt electron lifetimes by combining observations and global radiation belt electron simulations. I will also reveal that this simple yet fundamental physical process which has been historically neglected in global radiation belt models, is sufficient to explain the outer electron belt configuration. Our findings transform our understanding of the dominant processes controlling radiation belt dynamics.

Date: 11/7/2025

Time: 12:00 – 1:00 pm

Location: 3853 Slichter Hall

Presented By: Dr. Ashley Schoenfeld – JPL

Abstract:

Surface observations of Saturn’s moon Titan revealed features characterized as dissected, elevated plateaus with high valley density known as labyrinth terrains. Of this terrain class, a subtype referred to as radial labyrinth is described as dome-shaped uplifts with radial channel patterns. Uplift of these radial labyrinths has been explained as cryomagmatic intrusions at the brittle-ductile transition zone. Here we propose an alternative hypothesis, that crustal heterogeneities in Titan’s upper clathrate crust introduce density differentials due to ethane-methane substitution, as ethane-rich liquids percolate into methane clathrate, inducing solid state flow and generating domal topography. This mechanism is analogous to salt tectonics on Earth and has similarly been evoked for dome formation on the dwarf planet Ceres. We show that the elevation and width of the observed radial labyrinths is consistent with domal uplift driven by a hydraulic head within the uppermost portion of Titan’s crust, given a plausible set of elastic parameters for clathrate hydrates. Additionally, the insulating effect of clathrate, combined with partial mixing with water-ice, allows for sufficiently low viscosity for geologic flow: uplift of the domes could have occurred early in Titan’s history, a billion years ago, or could have uplifted within the last 100 Myr during a recent phase of orbital excitation.

Date: 2025-10-17

Time: 3:30 – 4:30pm

Location: 3853 Slichter Hall

Presented By:
Dr. Leonid Olifer

Abstract:

Space is never empty. Instead, it is filled with high-energy particles originating at the Sun and trapped by Earth’s magnetic field, forming dynamic radiation environments that pose significant risks to satellites, astronauts, and future exploration missions. In this talk, I will discuss the evolution of Earth’s radiation belts during geomagnetic storms, the processes that limit their intensity, and how similar processes may operate under artificially created conditions. I will present recent work on fast plasma processes that substantially alter radiation levels around Earth. My approach integrates data analysis, simulations, and the development of advanced particle detectors derived from technology originally designed at CERN, tailored specifically for space missions. Additionally, I will showcase results from a student-led balloon mission conducted during the most intense geomagnetic storm of the past two decades.

Presented by: Prof. Jean-Philippe Avouac

Affiliation: California Institute of Technology

Location: 3853 Slichter Hall

Abstract: Earthquakes occur naturally driven by tectonic processes, but they can also be induced by human activities. In particular, earthquakes induced by extraction or injection of fluids in the subsurface — during gas production, CO2 storage of geothermal operations for example — provide an opportunity to investigate earthquake physics and to test earthquake forecasting models. Our research shows that, in such examples, spatial and temporal variations in seismicity rate can be predicted reliably from stress changes inferred from reservoir operations and surface deformation measurements. These advances can improve methods for time-dependent seismic hazard assessment. However, forecasting individual events remains a major challenge.

Presented by: Prof. Jun Korenaga

Affiliation: Yale University

Location: Young Hall 4222

Abstract:

The early evolution of the Earth-Moon system prescribes the tidal environment of the Hadean Earth and holds the key to the formation mechanism of the Moon. Estimating its early state by backtracking from the present, however, suffers from considerable uncertainties associated with ocean tides. Tidal evolution during the solidification of Earth’s magma ocean, on the other hand, has the potential to provide robust constraints on the Earth-Moon system before the appearance of a water ocean. To this end, it is of vital importance to understand how energy dissipates in a solidifying magma ocean and how tidal dissipation interacts with atmospheric evolution. These issues have turned out to be much more complicated than previously thought, and as it stands, many of the existing variations of the Moon-forming giant impact hypothesis appear to be unable to explain the present-day angular momentum of the Earth-Moon system, calling for further innovative ideas on the formation of the Moon.

Presented by: Prof. Xinting Yu

Affiliation: University of Texas at San Antonio

Location: Young Hall 4222

Abstract:

The field of exoplanets is evolving with astronomical speed, with over 6000 exoplanets discovered to date, including many planets that have no counterparts in the Solar System. More recently, the James Webb Space Telescope has revolutionized our understanding of exoplanet atmospheres by delivering unprecedented spectroscopic constraints on their atmospheric compositions.

In this talk, I will talk about my journey as a planetary scientist who started in the lab working with organic materials on Titan, and how I transitioned to working on some fun theoretical problems for exoplanet atmospheres. Specifically, I will discuss how we can use atmospheric composition to understand the nature and potential habitability of temperate sub-Neptunes, planets with sizes ranging between Earth and Neptune, which also represent the most common type of exoplanets discovered to date. I will also highlight my recent work addressing the emerging population of “missing methane” exoplanets.

Presented by: Dr. Samuel Yee

Affiliation: Harvard

Location: 3853 Slichter Hall

Abstract:

Hot Jupiters — giant planets on short-period (< 10 days) orbits around their host stars — represent the most extreme outcome of planet formation. Even though they were the first type of exoplanet around Sun-like stars to be discovered, their origins remain unclear. One challenge is our limited understanding of hot Jupiter statistics, as most of them were discovered by a heterogeneous collection of ground-based surveys with a variety of biases. NASA’s Transiting Exoplanet Survey Satellite, a uniform all-sky transit search, presents the opportunity to revolutionize hot Jupiter demographics by unifying these previous planet searches. Over the past few years, I led the TESS Grand Unified Hot Jupiter Survey to confirm and characterize hundreds of planet candidates from TESS with facilities like Keck and Magellan. I will present the 4-sigma detection of a pile-up in the period distribution, the dependence of hot Jupiter occurrence on host star properties, and new evidence that they are found around a kinematically young galactic population. I will also discuss how our survey is enabling new lines of inquiry including the discovery of giant planets in the galactic thick disk, as well as detailed characterization of benchmark systems to test key physical processes like tidal inflation and orbital decay.

Presented by: Prof. Katherine de Kleer

Affiliation: Caltech

Location: 3853 Slichter Hall

Abstract: The heat flow of a planetary body plays a major role in defining its evolution and current composition, driving processes from internal differentiation during its formation through geological activity at the current time. In this talk, I will describe how the ALMA (sub-)millimeter observatory and the James Webb Space Telescope are shedding light on the heat flow histories of satellites and small bodies. Thermal emission observations of asteroids provide information on the abundance and form of metals (ALMA) and minerals (JWST) on their surfaces. I will present ongoing asteroid programs aimed at providing a more complete compositional picture of asteroid surfaces, with implications for the early heating and differentiation of planetesimals. ALMA can also measure the isotopes of the volatile-forming elements, a key tool for studying the formation and evolution of objects in the Solar System. I will discuss sulfur and chlorine isotopes in the volcanic gasses of Jupiter’s moon Io in particular, and how they place constraints on the tidal heating and volcanism that Io experienced over the age of the Solar System.

Presented by: Prof. Jonathan Lunine

Affiliation: NASA JPL

Location: 3853 Slichter Hall

Abstract: The Juno spacecraft has been orbiting Jupiter since July 2016 and is completing its first extended mission. My personal list of the five most important things we’ve learned from the Juno mission during its prime and extended missions goes something like this: 1. Jupiter has a fuzzy core. 2. Moist convection really is a dominant feature of Jovian atmospheric dynamics 3. Water seems to be supersolar in abundance, at least down hundreds of bars pressure. 4. Europa has a platypus-shaped crustal melt region. 5. There is an active lava flow at Zal Montes on Io.

Presented by: Dr. Ceci Lopez-Gamundi

Affiliation: JPL

Location: 3853 Slichter Hall

Abstract:

Recent advances in Earth observation and computational techniques allow for the rigorous examination of climate and coastal sediment dynamics at scale. Leveraging these novel methods, we investigate how severe storms and oscillations in Earth’s climate affect Great Bahama Bank (GBB), the world’s largest modern isolated carbonate platform. High-fidelity hydrodynamic simulations suggest that a single hurricane has a negligible effect on the broad-scale distribution of sediments on the platform top, which is predominately sculpted by fair-weather conditions. Nevertheless, multi-decadal satellite monitoring intimates that catastrophic hurricanes, when occurring in quick succession, may be responsible for the remobilization of mud months to years after their passage. On longer time scales still, interannual and decadal variations in suspended sediment are linked to windy El-Niño events, tidal-forcing Lunar Nodal Cycles, and the weakening of the Atlantic Meridional Overturning Circulation. Spatial variations abound too. Surprisingly, sediment lofting along the leeward margin is linked to wind, while tide dictates resuspension on the windward margin. Finally, we present evidence others have found in the Holocene sedimentary record of the same climate signals we observe in the modern – linking platform top sediment dynamics to slope sedimentation. In doing so, we shed light on how modern analogues can be used to constrain past climate signals and predict sedimentological responses in the future.