Space Physics Seminar - winter-2024

Jan. 12, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Qianli Ma - UCLA/Boston University

Resonant interactions between whistler-mode waves and electrons contribute to diffuse auroral precipitation in Jupiter’s atmosphere and relativistic electron acceleration in Jupiter’s outer radiation belts. Juno has collected wave and particle data in Jupiter’s magnetosphere for more than 7 years, providing spatial coverage of M > 5 over a wide latitudinal range. Using Juno measurements during an injection event, we first evaluate the relationship between chorus wave intensities and 1–300 keV electron fluxes due to local wave generation. After the event analysis, we conduct a survey of electron flux and phase space density distributions at the magnetic equator in the outer radiation belt and plasma sheet. The phase space density profile implies the < 1 MeV electron source from radial diffusion, as well as collisional loss at low M shells and precipitation loss to Jupiter’s atmosphere. We also conduct a survey of whistler-mode wave intensity in the outer radiation belts. The wave survey suggests a local generation source for chorus waves and a remote propagation source for hiss waves. Finally, we simulate the impacts of chorus and hiss waves on energetic and relativistic electrons at M ~ 11 using quasilinear theory. Whistler-mode waves cause pitch angle scattering loss of < 1 MeV electrons, contributing to a significant total precipitating energy flux towards Jupiter’s atmosphere. Chorus waves with average intensities could cause > 5 MeV electron acceleration in about 10 days. Our studies unveil the energy transfer processes among the electron injections, whistler-mode waves, and relativistic electrons in Jupiter’s outer radiation belts.

Jan. 19, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Benjamin P. Brown - CU Boulder

Seminar Description coming soon.

Jan. 26, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Yasong Ge - CAS

Mars’ magnetic field has been measured at large scale by orbiting spacecraft and at very small scale via Martian meteorites. Here we report on a ground magnetic survey on metre to kilometre scales. The Zhurong rover made vector measurements at 16 sites along a 1,089 m track in the Utopia Basin on Mars. It recorded an extremely weak magnetic field, with an order of the average intensity less than that inferred from orbit, in contrast to the large magnetic field in Elysium Planitia measured by InSight. A spacecraft measurement samples an area with radius comparable to its altitude, while a ground measurement samples an area with radius comparable to the depth of the magnetized body. The weak magnetic field measured by Zhurong indicates no magnetization anomalies for a depth of many kilometres around and below the rover’s traverse. We suggest two possible explanations for the weak magnetic field: the entire Utopia Basin may have remained unmagnetized since its formation about 4 billion years ago or that the 5-km-radius ghost crater where Zhurong landed may have been demagnetized by impact.

Feb. 2, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• David Miles - U Iowa & PI of TRACERS

The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) is an upcoming NASA small-explorer (SMEX) mission, scheduled for launch in 2025. TRACERS comprises two identically instrumented small satellites in a string-of-pearls sun- synchronized circular orbit that intersect the polar magnetospheric cusp. TRACERS’ overarching science goal to: Connect the cusp to the magnetosphere – discover how spatial or temporal variations in magnetic reconnection drive cusp dynamics. This goal is achieved through three science objectives: Determine whether magnetopause reconnection is primarily spatially or temporally variable; Determine how the reconnection rate evolves; Determine the connection between dynamic structures in the cusp and reconnection variability. We present the science requirements, the driving constraints, and the technical implementation of the mission. TRACERS also carries the MAGIC payload – a technology demonstration of new magnetic field sensing technology. Finally, we summarize the unique science data products that will be made available to the scientific community for the launch and commissioning of TRACERS.

Feb. 9, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Solène Lejosne - Berkeley/SSL

Measured radiation belt intensity can present transient fluctuations at trapped particles’ drift frequency. While indicative of the occurrence of non-diffusive radial transport events, these drift-periodic fluctuations tend to be viewed as playing little to no role in large-scale radiation belt dynamics. In fact, an essential assumption in radiation belt science is that the typical effect of trapped particle transport on radiation belt intensity is well represented by a purely diffusive model, namely, the radial diffusion equation. This talk will provide observational and theoretical reasons that call into question this consensus. Drift-periodic fluctuations have been reported in the Earth’s inner radiation belt, in the outer belt, and even at Saturn. Their observations have become more and more common over the last decade, facilitated by the use of instruments with high-energy resolution channels. Thus, drift-periodic fluctuations may be a ubiquitous radiation belt feature. Yet, because drift-periodic fluctuations are expected to dissipate rapidly once generated, their contributions to large-scale radiation belt dynamics have been discarded in traditional radiation belt modeling efforts. I will show that the drift-periodic fluctuation lifetime is in fact much longer than expected (measured in hours in the Earth’s radiation belts). I will also explain why the observed magnitude and lifetime of a drift-periodic fluctuation is always an underestimation of the natural magnitude and lifetime of the structure. From the theoretical standpoint, these findings call into question the applicability of the standard, drift-averaged formulation of radial diffusion used to model the effect of radial transport on radiation belt intensity. I will propose a way forward by introducing a drift-diffusion model capable of retaining drift phase information and rendering drift-periodic fluctuations. By using this model, it will be possible to determine, in a systematic way, the role played by non-diffusive radial transport events in radiation belt acceleration, transport and loss.

Feb. 16, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Bruce T. Tsurutani - JPL

I will start with a paper published before the space age (Heppner JGR 1955) that I read as a graduate student and end my talk with where we are today: this same paper and viscous interaction (Axford and Hines, Can. J. Phys. 1961). Solar Flares, Disappearing Filaments, Coronal Holes, CMEs/Driver Gases, CIRs, Magnetic Clouds, Filaments, High-Speed Streams, Nonlinear Alfvén Waves, Magnetic Reconnection, Viscous Interaction, Forward and Reverse Shocks, Storm Sudden Commencements/Sudden Impulses, Auroras, Substorms, HILDCAAs, Chorus Waves, Relativistic Electrons, Magnetic Storms, Superstorms, The Carrington Event, Supersubstorms, and GICs will be discussed.

Feb. 23, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Porf. Martin Connors - Athabasca University, Athabasca Canada

One facet of space weather technological effects arises from the ability of changing magnetic fields to generate electric fields, as discovered by Michael Faraday in the 1830s. In 1859 the most advanced technological system of the day, the telegraph, was greatly affected by the Carrington Event. In 1989 a smaller event took down the Hydro-Québec power grid, dramatically showing that distributed metallic conductors at ground level are subject to geomagnetically-induced currents (GIC) which generally have bad effects. Understanding potential effects on the coupled conductor-Earth system requires good understanding of Earth conductivity structure, which may be obtained with magnetotelluric (MT) surveys, now nearly complete for the entire USA. On the other hand, much MT interpretation is based on an assumption of vertically incident electromagnetic waves, which would have only horizontal component magnetic fields. Large geomagnetic disturbances often have large or even dominant vertical magnetic fields. Examples of this and studies on the potential impact of “B-zee” will be presented.

March 1, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Meng Jin - SETI/LM

This presentation delves into the origins of space weather - solar activities in the form of solar wind, coronal mass ejections (CMEs), CME-driven shocks, and Solar Energetic Particles (SEPs). These elements are crucial for accurate space weather forecasting, prompting extensive development of sophisticated physics-based models. The first part of the talk will highlight our recent efforts of high-fidelity solar eruption modeling from the Sun to Earth, which emphasizes how integrating advanced modeling with observational data facilitates our understanding of fundamental processes in space and astrophysics. Subsequently, I will explore how insights into solar phenomena aid in the investigation of exo-solar systems and potentially habitable planets, alongside pioneering techniques for detecting stellar CMEs. I will conclude by discussing future missions (e.g., MUSE, PUNCH), when combined with existing remote- sensing and in-situ observations (e.g., SDO, Parker Solar Probe, Solar Orbiter), will significantly improve the data-constrained CME modeling and eventually lead to a better space weather forecast capability.

March 8, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Harriet George - CU Boulder

Parker Solar Probe (PSP) performs Venus gravity assists (VGAs) in order to lower its perihelion. PSP carries a full plasma wave package (FIELDS) that provides the rare opportunity to study plasma wave activity in Venus’s induced magnetosphere. These plasma waves provide key insight to the overall dynamics of the system, including the occurrence of kinetic instabilities, magnetotail reconnection, magnetosheath turbulence and the possible presence (or lack) of lightning. I will discuss the plasma wave observations from PSP FIELDS during VGAs 1 – 5, specifically the Langmuir, ion acoustic, ion cyclotron and whistler mode waves that we comprehensively identified and mapped throughout near-Venus space. We compared the FIELDS instrumentation capabilities to the capabilities of the plasma wave instruments onboard Pioneer Venus Orbiter’s (PVO) and Venus Express (VEX). We found that these previous Venus missions were often unable to conclusively identify plasma wave modes or measure important characteristics of these waves, such as the propagation direction, bandwidth and maximum power. These results highlight the value of a plasma wave instrument on a new Venus mission. I will also discuss a case study of whistler-mode waves detected in Venus’s induced magnetotail during PSP’s fourth VGA. We find that these whistler-mode waves propagate towards the planet and were likely generated by magnetotail reconnection. Whistler-mode waves in Venus’s ionosphere and near-Venus space are often attributed to lightning as a generation mechanism, but the magnetotail whistler-mode waves detected by PSP are incompatible with a lightning source. I will discuss the implications of these results for lightning occurrence rates on Venus.

March 15, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

• Dr. Corey J. Cochrane - JPL, Caltech

Many moons in the solar system are thought to potentially harbor hidden oceans based on the features observed at their surfaces. The best evidence for the existence of subsurface oceans arises from interpretation of magnetic field measurements collected by the magnetometer on the Galileo spacecraft in the vicinity of Europa. The Europa Clipper mission, set to launch in 2024, will revisit Europa to confirm the presence of the ocean and will characterize its thickness and salinity to assess its habitability using a phenomenon known as magnetic induction. In this presentation, this phenomenon will be explained as well as the approaches that can be used to better understand the interior properties of Europa and other icy worlds in the solar system with putative subsurface oceans. Additionally, a brief introduction will be given regarding the next- generation quantum magnetometers that are currently being developed.