Space Physics Seminar - fall-2024
Multi-scale Ionospheric Dynamics during Geomagnetic Storms: Physical Processes, Forecasting, and Impacts
Oct. 4, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Dr. Shasha Zou - Univ. of Michigan (UCLA AOS alumna)
Subscribe to Calendar
The terrestrial ionosphere serves as the closest natural laboratory for studying space plasma physics. It is a vital component of the near-Earth space environment and plays an essential role in modern radio communication and navigation systems. The ionosphere responds dynamically to solar radiation and geomagnetic disturbances, especially during geomagnetic storms. During storms, ionospheric density structures of various spatiotemporal scales can form. Notable density features such as storm-enhanced density (SED), plumes, and polar cap patches often emerge in the mid to high-latitude ionosphere, while plasma depletions, commonly referred to as bubbles, can develop near the equator. Ionospheric irregularities frequently occur at the edges of these density structures, leading to severe radio scintillations. In my talk, I will discuss the formation and evolution of these multiscale structures, our efforts to improve their characterization and forecasting, and their impact on ion upflow and outflow from the ionosphere to the magnetosphere.
Using all-sky cameras to investigate coupling between the lower and the upper atmosphere
Oct. 11, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Asti Bhatt - SRI
Subscribe to Calendar
The sun-earth system is complex where energy and momentum transport from one region of the atmosphere to the other with varying effects. The earth’s upper atmosphere is sandwiched between two regions – the magnetosphere above and the lower atmosphere below. The energetic events in the sun drives the magnetosphere and in turn the ionospheric response. The lower atmosphere also has energetic events in the form of thunderstorms and hurricanes. These tropospheric weather events also tend to launch energy into the upper atmosphere impacting the ionosphere. How the energy and momentum propagation from both these sources impact the ionospheric dynamics is a subject of active research. In this talk, I will talk about various ways to investigate this coupling between lower and upper atmosphere and focus on a specific technique of using all-sky cameras. The all-sky cameras observing the nighttime emissions from the earth’s thermosphere and ionosphere, when used in a network fashion can shed light on coupling processes that take place over 1000s of kms. One such network of all-sky cameras exists in the continental united states called the ‘Mid-latitude All-sky-imaging Network for Geospace Observations (MANGO)’. I will discuss the application of this network to investigate the energy and momentum coupling processes.
Proton Temperature Observed by Parker Solar Probe and Its Variations in Different Solar Wind Conditions
Oct. 25, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Jia Huang - SSL
Subscribe to Calendar
In this seminar, I will introduce the proton temperature variations observed by Parker Solar Probe (PSP) mission. First, I will present a technique for deriving the proton temperature components based on the comparison of radial proton temperature measured by the SWEAP/SPC with the orientation of the local magnetic field measured by the FIELDS fluxgate magnetometer. Second, I will show the temperature evolution from the inner heliosphere to 1 AU with a combination of PSP, Helios, and Wind data. Third, I will discuss the temperature variations in different solar wind conditions including switchbacks, streamer belt solar wind, and Alfvénic slow solar wind, etc.
Juno in Jupiter’s Magnetosphere
Nov. 1, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Dr. Fran Bagenal - CU Boulder/LASP
Subscribe to Calendar
The Juno spacecraft has been orbiting Jupiter for eight years, passing over Jupiter's poles 66 times. The Juno mission resolves critical questions regarding the processes that drive Jupiter's dramatic aurora and tests the universality of the processes that generate aurora and couple magnetized planets to their space environments. Jupiter's magnetosphere is known to be powered very differently than for Earth. The volcanic moon Io injects ~1 ton/s of sulfur and oxygen which becomes ionized, trapped in Jupiter's magnetic field and forms a plasma torus that corotates with Jupiter's 10 hour spin period. As the iogenic plasma spreads out to fill Jupiter’s vast magnetosphere, the dynamics are dominated by strong planetary rotation rather than by the interplanetary environment controlled by the solar wind. Moreover, the plasma is heated as it moves outward, the high plasma pressure inflating the magnetosphere. And yet, we see hints that some of the fundamental processes that drive Jupiter's aurora are similar to those that drive Earth's aurora. Is the global aurora regulated by a quasi-static global pattern of electric currents that connects Jupiter's magnetosphere to its polar ionosphere along magnetic field lines? Are the dominant acceleration processes the same as those that dominate at Earth or do other processes prevail? Where does the acceleration occur? Juno addresses these and other critical questions by flying a capable suite of in situ particles and fields magnetospheric instruments through Jupiter's low-altitude polar regions, and combining those measurements with UV and IR imaging of the polar auroral displays. This seminar will summarize the critical issues and questions regarding Jupiter's magnetosphere, and review what we have learned from the Juno mission. p.s. Hot news! Yes, Jupiter also experienced this month’s strong solar storm!
Solar Wind Driving at the Innermost and Outer Planetary Magnetospheres
Nov. 8, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Sohpia Zomerdijk-Russell - JPL
Subscribe to Calendar
Extensive studies of Earth’s magnetosphere have shaped our current understanding of how the solar wind drives planetary magnetospheres throughout our solar system. These studies have led to the standard paradigm that global magnetic reconnection is the dominant process in the solar wind driving of a magnetosphere and that a viscous-like interaction is negligible as an external driver. However, questions still remain as to how much solar wind-magnetospheric interactions will differ at the other planets in our solar system. In this work we start at the innermost planet, where MESSENGER observations of large numbers of flux ropes (FRs) at Mercury’s dayside magnetosphere have revealed a highly dynamic magnetosphere that is strongly driven by frequent and intense magnetic reconnection. Here, we investigate what conditions reconnection occurs under on Mercury’s magnetopause by modeling 201 FRs, that are the products of magnetic reconnection processes. We found our work supports the hypothesis that there is enhanced reconnection driven formation of FRs at Mercury that can occur over a wider range of magnetic shear angles than those typical at Earth. Moving to the outer solar system, however, different solar wind conditions suggest a viscous-like interaction may start to dominate over reconnection. The Uranian system provides a unique place in which to test this hypothesis and a missing link to resolve it with a Uranus mission would be to provide a step change in our understanding of magnetic reconnection in the Uranian system. Here, we test the effectiveness of global magnetic reconnection in the Uranian system by presenting model predictions of dayside reconnection voltages that are applied to the system under different magnetospheric configurations. The typical dayside reconnection voltage that is applied to Uranus’ magnetosphere was found to be on the order of 10 kV, lower than that typical at the Earth. By continuing to develop our understanding of solar wind-magnetospheric interactions at the very different planets throughout our own solar system, we can hope to more broadly understand how magnetospheres will interact with their host stars in exoplanetary systems.
Mesoscale Structures in the Polar Cap Ionosphere and Polar Wind
Nov. 15, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Roger Varney - UCLA AOS
Subscribe to Calendar
The ionosphere provides significant ion outflows to the magnetosphere, and during geomagnetic storms ions of ionospheric origin become the dominant constituents of the magnetosphere. This ionospheric source is not steady or uniform. Many competing processes in the ionosphere and thermosphere cause the outflow rates to highly structured in space and time. This talk reviews our current understanding of the causes of structured ion outflow and discusses outstanding challenges for future research. The polar cap ionosphere frequently contains mesoscale plasma density structures, such as tongues of ionization and polar cap patches. These density structures modulate the source of ions available for outflow into the magnetosphere. Ion outflow can be divided into classical polar wind outflow, consisting of mostly H+, and energetic heavy ion outflow, consisting of O+, N+, and sometimes molecular ions. The H+ in the classical polar wind is primarily produced by charge exchange from heavy ions. Using high- resolution models under development by the Center for Geospace Storms (CGS), we show that simulations that create mesoscale ionospheric density structures will also create mesoscale structures in the polar wind ion outflow. We contrast these simulations with polar cap observations from the Resolute Bay Incoherent Scatter Radar (RISR).
The Many Faces of Geomagnetic Induction: Tracing Multiscale Space Weather Hazards from Sun to Mud
Nov. 22, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Mike Hartinger - SSI/UCLA
Subscribe to Calendar
"At almost the exact moment when the magnetograph traces leaped and the aurora flared up, huge currents in the Earth induced by the heavenly turbulence, manifested themselves not only in power lines in Canada, but in cables under the North Atlantic." As Brooks noted in a 1959 New Yorker article, the February 1958 geomagnetic storm created a range of space weather impacts at different locations that were linked to periods of geomagnetic disturbance. Since 1958, our understanding of space weather, geomagnetic induction, and the puzzle of why technology impacts are felt in some locations/storms and not others has developed considerably. Magnetic field variations originating from a variety of sources in the solar wind-magnetosphere-ionosphere system induce electric fields in the Earth that ultimately drive geomagnetically induced currents (GIC) in power lines/systems. We now know there are many faces of geomagnetic induction due to the rich variety of possible interactions across these different domains. To determine whether a particular magnetosphere-ionosphere (M-I) current system represents a hazard, it’s critical to consider the whole chain of factors from the spatial and temporal scale of the M-I current, to local geology and water depth, to power system configuration; these can all dramatically alter the expectation for power system damage or disruptions in each event/location. In this seminar, I’ll discuss several recent observational and modeling studies exploring the interplay between these different factors, highlighting conditions that have led to the largest geoelectric fields, GIC, and impacts on North American power grids and submarine telecommunication cables in major geomagnetic storms, including the recent 10-11 May 2024 storm. I’ll further discuss gaps in our understanding of geomagnetic induction-related hazards and how they can be addressed, including limited and heterogeneous historical ground magnetometer records that affect our understanding of high-impact/low-frequency geomagnetic disturbances.
Cross-scale chain of wave-particle resonances in space plasmas
Dec. 6, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Xuzhi Zhou - PKU
Subscribe to Calendar
Wave-particle resonance, a ubiquitous process in the plasma universe, occurs when resonant particles observe a constant wave phase to enable sustained energy transfer. In this talk, we will present spacecraft observations in the terrestrial foreshock region where macroscale waves in the ultra-low-frequency band and microscale whistler waves resonate simultaneously with the ions. The ion acceleration from ultra-low-frequency waves leads to velocity distributions unstable to the growth of whistler waves, which in turn resonate with the electrons and dissipate energy at electron-scales. These observations demonstrate that the chain of wave-particle resonance is an efficient mechanism for cross-scale energy transfer, which could redistribute the kinetic energy and accelerate the particles upstream of the shocks.