Space Physics Seminar - spring-2025

April 4, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Louis Richard - IRF

Magnetic reconnection is a fundamental plasma process that converts electromagnetic energy into particle acceleration and bulk plasma motion, driving some of the most energetic events in the Universe. In this study, we investigate how reconnection outflows transfer energy to the surrounding plasma using data from NASA’s Magnetospheric Multiscale (MMS) spacecraft in Earth’s magnetotail. Our analysis shows that turbulence generated within the reconnection outflow plays a key role in energy dissipation. Specifically, thermal ions are rapidly scattered and heated due to their interaction with strongly curved magnetic fields, while the convective electric field further accelerates higher-energy ions. Additionally, we find that electrons are efficiently heated by a magnetic field-aligned electric field, which arises to maintain charge neutrality. These findings provide new insights into energy dissipation and particle energization mechanisms in magnetic reconnection, improving our understanding of plasma dynamics in space and astrophysical environments.

April 11, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Jinxing Li - AOS/UCLA

The present study uncovers the fine structures of magnetosonic waves by investigating the EFW waveforms measured by Van Allen Probes. 1) We show that each harmonic of the magnetosonic wave may consist of a series of elementary rising-tone emissions, with a frequency sweep rate proportional to the frequency, implying a nonlinear wave generation. 2) Each harmonic consists of a series of mini harmonics spaced around the O+ gyrofrequency. By investigating the ion distributions, we suggest that the ring distribution of protons provides free energy to excite the waves, and O+ ions prevent waves from being amplified around multiples of O+ gyrofrequency, resulting in the formation of mini harmonics. 3) Furthermore, we show an observation of nonlinear multi-band magnetosonic waves with each band consisting of multiple harmonics. The odd harmonics in the 2nd band are not the nonlinear harmonics of the 1st band. The discoveries of these fine structures provide new insights into wave-particle interactions and energy conversion among multiple species.

April 16, 2025
noon - 1 p.m.
Slichter Hall # 6850

Presented By:

• Zijin Zhang and Yuliang Ding -

Seminar Description coming soon.

April 18, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Paulo Alves - P&A

Relativistic astrophysical jets, such as those emanating from the centers of active galaxies, shine across the entire electromagnetic spectrum and are among the most powerful particle accelerators in the Universe. Yet, the mechanisms underlying their particle acceleration are not well understood. Global magnetohydrodynamic (MHD) simulations of the propagation of astrophysical jets suggest that the development of hydromagnetic instabilities can play an important role in the dissipation of the jet’s internal magnetic field. However, it remains unclear if the dissipated energy is efficiently channeled into nonthermal particles, as is required to explain observations. In this talk, I will discuss how fully kinetic particle-in-cell (PIC) simulations (in 3D and quasi-3D geometries) are enabling new insights into the conditions under which hydromagnetic instabilities in jets can efficiently accelerate nonthermal particles. In particular, I will highlight the importance of how different plasma and magnetic field configurations that are believed to occur in jets (which combine relativistically rotating plasma flows and relativistic magnetic energy densities, with different field geometries) strongly affect the nonlinear development of hydromagnetic instabilities and their associated nonthermal particle acceleration efficiency. I will also discuss how emerging techniques from scientific machine learning have the potential to aid in the development of reduced statistical models of nonthermal particle acceleration from the data of first-principles PIC simulations, further advancing our understanding of physical processes that control nonthermal particle acceleration efficiency in these complex environments.

April 25, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Anthony Sciola - APL

The stormtime ring current has a major influence on global geospace dynamics, as it both shapes and is shaped by its interactions with other domains including the magnetotail and ionosphere, and plasma populations such as the plasmasphere. While the global-scale behavior of the ring current is generally well-understood, many questions remain regarding how mesoscale phenomena impact ring current formation and evolution. The major source of the ring current is plasma transported from the tail, however it remains unknown to what extent this plasma is supplied by mesoscale burst bulk flows (BBFs) vs global-scale convection. The evolution of lower-energy ring current particles, as well as the plasmasphere, are dependent on the convective electric field, which is itself influenced by ring current pressure gradients. These pressure gradients help establish the global-scale shielding of lower latitudes from the high latitude electric field. However, Stable Auroral Red (SAR) arcs have been observed to exhibit high spatiotemporal variability during storms, revealing structured and dynamic overlap of the ring current and plasmasphere which are responsible for these emissions. It remains unknown which population is the primary driver of this variability, and how both global and mesoscale transport processes contribute. Advancing our understanding of ring current dynamics requires an understanding of mesoscale processes and their effect on system-scale coupling, which is a challenging task using observations alone. In this presentation, we discuss recent work towards this goal which leverages advancements in global geospace modeling combined with data validation and contextualization. Using the Multiscale Atmosphere-Geospace Environment (MAGE) model developed by the NASA DRIVE Center for Geospace Storms (CGS), we first target ring current formation by quantifying the contribution of BBFs and demonstrating their effect on the evolution of the ring current energy spectra. We then investigate the evolution of the stormtime ring current and plasmasphere, validated by a synthetic SAR arc proxy compared with ground observations. We find that multiple injections contribute to ring current structuring which can form multiple simultaneous SAR arcs, while undulation-like SAR arc patterns can be formed by the structuring of the plasmapause via dynamic electric fields.

May 2, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Heidi Haviland - MSFC

Here we review the electromagnetic geophysical methods used to probe the lunar interior and highlight key challenges including contamination from plasma and crustal magnetic fields. Within conducting layers of the Moon, changing electric and magnetic fields produce induced fields in proportion to the electrical conductivity at depth. The electromagnetic sounding transfer function requires two observations: a reference measurement capturing the driving field change, and a surface or near surface measurement which captures the total field (induction, external, and any local noise sources). Isolation of induction allows for the extrapolation of interior electrical conductivity. Lunar electromagnetic sounding was performed during the Apollo program with surface magnetometers, Apollo 12, 15 and 16, and orbiters including Explorer 35, Apollo 15 and 16 subsatellites. Following, the Kaguya and Lunar Prospector missions have also been used to study the lunar interior using fields measured in orbit. Modeling results suggest plasma and induce magnetic fields couple within the nightside wake cavity. Crustal magnetic fields are known to generate mini magnetospheres suggesting a dynamic interaction between the local plasma and fields at the surface. Recently, Firefly’s Blue Ghost 1 mission contained the Lunar Magnetotelluric Sounder experiment measuring magnetic and electric fields in the Mare Crisium basin. We will discuss the challenges this mission will face in interrupting their data.

May 9, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Sachin Reddy - JPL

TBA

May 16, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Xueling Shi - VT

TBA

May 23, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Yue Deng - UTA

TBA

May 30, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Emile Saint-Girons - CentraleSupelec

TBA

June 6, 2025
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Harriet George - CU

TBA