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:

• Dr. 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.

April 29, 2025
11 a.m. - noon
Zoom

Presented By:

• Dr. Ameneh Mousavi - Space Science Institute

The discovery of the Energetic Neutral Atom (ENA) ribbon by the Interstellar Boundary Explorer (IBEX) has reshaped the understanding of the outer heliosphere and its interaction with the local interstellar medium (LISM). A key component in current explanations for the ribbon is the population of pickup ions (PUIs) beyond the heliopause, through charge exchange between local interstellar ions and neutral solar wind (SW) atoms. These PUIs are believed to produce the observed ENAs through a sequence of interactions known as the secondary ENA mechanism. A key open question is whether PUIs maintain their initial anisotropic ring-like distributions or become isotropized through interactions with self-generated waves/turbulence before contributing to the ENA ribbon. Competing scenarios have been proposed: one assumes weak scattering allows anisotropic PUIs to survive, while the other argues for spatial confinement of the PUIs via strong wave-particle interactions. Resolving this question requires realistic modeling of the outer heliosheath PUI distributions beyond the idealized forms used in earlier studies. This seminar presents recent findings on the stability and evolution of a multi-component PUI velocity distribution derived from a 3D global simulation of the SW-LISM interaction using linear instability analysis and hybrid simulations. The study investigates the roles of mirror and Alfvén-cyclotron modes in scattering PUIs. Unlike earlier studies, the results show that mirror waves primarily reduce the thermal anisotropy of PUIs rather than scatter them effectively in pitch angle. The Alfvén-cyclotron waves quickly scatter the PUIs with pitch angles away from 90°, while the PUIs near 90° pitch angle maintain a degree of anisotropy within our simulation timeframe. These results have significant implications for understanding the IBEX ENA ribbon. Join Zoom Meeting https://ucla.zoom.us/j/93607696242?pwd=Kbz3FGUPPryE9352UuGTpDkkLd02Nv.1 Meeting ID: 936 0769 6242 Passcode: 752762 (or dial "plasma" on your telephone keypad)

May 2, 2025
9 a.m. - 10 a.m.
Zoom only

Presented By:

• Qi Zhang - Swedish Institute of Space

Mars lacks a global magnetic field, allowing the solar wind to directly interact with its atmosphere. The solar wind’s convective electric field induces currents in Mars’ ionosphere, generating an induced magnetosphere that deflects the solar wind and drives atmospheric escape. This study aims to understand the Martian climate evolution and water loss. We here apply a new method to estimate heavy ion (O⁺, O2⁺, CO2⁺) escape rates by coupling a hybrid plasma model with spacecraft observations. External factors—solar EUV flux, solar wind dynamic pressure, interplanetary magnetic field (IMF) strength, and IMF cone angle—significantly influence escape rates. Escape increases with higher EUV and dynamic pressure but decreases with stronger IMF or larger cone angles. In extreme cases of near-radial IMF alignment, the induced magnetosphere collapses (termed a degenerate induced magnetosphere), eliminating the dayside bow shock and accelerating sunward ion escape. Comparative analysis with Venus under similar conditions exhibits shared solar wind interaction modes for unmagnetized planets, advancing understanding of atmospheric erosion and space weather effects. Join Zoom Meeting https://ucla.zoom.us/j/93607696242?pwd=Kbz3FGUPPryE9352UuGTpDkkLd02Nv.1 Meeting ID: 936 0769 6242 Passcode: 752762 (or dial "plasma" on your telephone keypad)

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

Presented By:

• Dr. 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 interpreting their data."

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

Presented By:

• Xueling Shi - VT

In the vast space surrounding Earth, unseen rhythms – known as ultra-low-frequency (ULF) waves – pulse through the geospace environment. These waves, vibrating at frequencies between 1 mHz and a few Hz, were first discovered in the 19th century when fluctuations in compass needles revealed their presence. Though invisible, ULF waves are powerful agents of energy transfer across space, influencing regions from Earth’s upper atmosphere to the radiation belts. They also generate magnetic fluctuations that induce electric fields at the Earth’s surface, driving geomagnetically induced currents (GICs) capable of disrupting power grids and other critical infrastructure. In this seminar, we will explore where ULF waves arise, what drives them, and how they contribute to space weather events. Through the integration of satellite and ground- based observations with numerical simulations, we will uncover the dynamics of ULF wave activity and its implications for both natural geophysical processes and modern technological systems. Understanding these effects is essential for improving space weather forecasting and protecting vital infrastructure from geomagnetic disturbances.

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

Presented By:

• Yue Deng - UTA

Space environment includes Sun, Solar wind (a.k.a. heliosphere), magnetosphere and ionosphere- thermosphere (a.k.a. upper atmosphere). The geomagnetic storms can be triggered by the activities on the Sun and in the heliosphere, which can strongly influence the coupling between magnetosphere and ionosphere, and the energy deposited into the upper atmosphere. The impact of geomagnetic storms on our geospace environment and society is the primary focus of space weather action. The typical space weather impacts include changing satellite orbits through increasing atmospheric drag, damaging the power lines and pipelines through geomagnetically induced currents (GICs), influencing the GPS and high-frequency (HF) communications through ionospheric variations. A recent significant change in our understanding of the ionosphere-thermosphere system is the frequent driving by dynamic multi-scale structures that couple to the magnetosphere in the polar cap region, the dayside cusp and along auroral oval and sub-auroral magnetic field lines. These structures play a critical role in Space Weather dynamics, interacting with the more slowly changing, large-scale structure that is more directly driven by interaction with the solar wind. The Global Ionosphere Thermosphere Model (GITM), a self-consistent non-hydrostatic model in the upper atmosphere with a flexible resolution, is suitable for studying transient meso-scale phenomena. To improve the description of multi-scale structures in geomagnetic forcing and to evaluate the influence of such structures on the global dynamics of the upper atmosphere and feedback to the magnetosphere, various data and models are utilized to investigate the variations of energy inputs from both above and below, and their influences on the coupled magnetosphere-ionosphere-thermosphere (MIT) system.

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

Presented By:

• Emile Saint-Girons - CentraleSupelec

This talk will present the development of an analytical model of the time-averaged omnidirectional electron flux in the inner magnetosphere. Thanks to spacecraft measurements resolved in energy and pitch-angle provided by the ELFIN mission at 400 km altitude, we used adiabatic invariants and Kennel and Petschek’s quasi-linear diffusion theory to infer this flux at all latitudes, for altitudes ranging from 150 to 20,000 km. The values obtained were then fitted using a stepwise optimization procedure, to construct a function of substorm activity, L-shell, altitude and energy. We finally obtained a model in agreement with direct spacecraft measurement performed at high and low altitudes by Van Allen Probes.

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

Presented By:

• Harriet George - CU

Magnetic reconnection in the Earth's magnetotail is a critical component of the energy flow through the Earth's magnetosphere. However, the cross-tail extent and coherence of X-lines in the magnetotail is not yet well understood. Analysis of the tail-wide extent of magnetic reconnection from in-situ observations has previously been confounded by the large spatial scale of the Earth's magnetotail. In this study, we leverage multi-constellation observations of the ejecta from magnetic reconnection sites to probe the cross-tail extent and coherence of reconnection sites in the magnetotail. We use observations of bursty bulk flows and tailward jets by MMS and THEMIS within the plasma sheet to analyse the cross-tail distribution of these reconnection ejecta, which provides insight to the tail-wide extent of the X-lines that they originated from.