Laboratory for Atmospheric and Space Physics (LASP)

In this seminar, I present recent results on the structure, variability and energetics of the far upper atmosphere found by the method of solar occultation, where atmospheric properties are inferred using sunlight as it passes through an atmosphere. The extreme ultraviolet (EUV) band is strongly absorbed in the thermosphere, enabling EUV occultations to provide a unique window into a sparsely observed region of the atmosphere.

The dynamics of Earth’s radiation belts remain one of the central challenges in space weather research. Despite decades of satellite observations, predicting when and how the belts will intensify or decay remains difficult. This seminar will discuss recent work combining multi-mission datasets from 36 multi-agency satellites to produce the highest-resolution phase space density (PSD) observations of the outer belt to date, and how these have been used to identify dominant acceleration and loss mechanisms.

Wildfires are becoming increasingly frequent and intense in a warming climate, reversing decades of air quality improvements, as seen in the 2025 Los Angeles Fires and many other record-breaking events worldwide. Crucially, what burns locally doesn’t stay local—wildfire smoke often rises, travels, and affects the atmosphere and climate far beyond its source. I will share new insights into the far-reaching impacts of wildfire smoke based on aircraft measurements, satellite observations, and modeling.

Understanding the chemical composition of exoplanet atmospheres is key to identifying habitable worlds and potential biosignatures. Current instruments face challenges in detecting weak atmospheric signals from small-sized exoplanets due to telluric and stellar contamination, spectral overlap, and limited resolution.

We have entered a new era of studying the physics of planetary atmospheres. Powered by new facilities like the James Webb Space Telescope and upcoming 30-meter class telescopes, we can observe exoplanet atmospheres in exquisite detail for the first time. With these measurements, we can test our understanding of the physics and chemistry of atmospheres in exotic environments: heating planets up to thousands of degrees or placing them around stars with very different properties.

Solar irradiance variability models supplement the measurement record by extrapolating the observations to broader spectral range and longer time periods than directly observed. Version 1 of the NASA-NOAA-LASP (NNL) solar irradiance variability models are observation-based models that prescribe change in TSI and SSI based on change in solar magnetic activity features called faculae, that enhance solar irradiance at most wavelengths, and sunspots that reduce solar irradiance.

Mars lacks a global dipole magnetic field like Earth. As a result, the solar wind and interplanetary magnetic field (IMF) directly interact with its upper atmosphere, generating an induced magnetosphere and driving ion escape from the red planet. As a key atmospheric loss process, understanding ion escape is essential for studies of atmospheric evolution and the long-term climate history of Mars.

The evolutionary history, and likely habitability, of exoplanet atmospheres depends on the space weather of their host stars. Understanding the particle environment, including the wind density, magnetic field strength, and velocity field, impinging on exoplanet systems remains a significant open question. This unknown impacts the interpretation of exoplanet atmosphere observations and the ongoing search for biosignatures, with facilities like JWST.

The vicinity of small bodies such as the Moon and asteroids, as well as artificial satellites, forms a “plasma-solid boundary layer” where space plasma and solid surfaces come into direct contact without the mediation of a neutral atmosphere or magnetosphere. The importance of the research subject is being increasingly recognized along with the recent global surge in momentum for manned lunar exploration.

Io, the innermost Galilean satellite of Jupiter, is the most volcanically active body in the Solar System. Its atmosphere is primarily composed of SO₂, S, O, and SO, and is continuously bombarded by plasma from the Io torus at a relative velocity of ~ 60 km/s. As a result of this strong plasma–atmosphere interaction, Io constitutes a major source of neutrals for the Jovian magnetosphere, the ultimate source of its plasma and the main driver of its dynamics.