Space Physics Seminar - fall-2024

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)

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.

Oct. 11, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853

Presented By:

• Asti Bhatt - SRI

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.

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

Presented By:

• Roger Varney - UCLA AOS

Seminar Description coming soon.

Oct. 25, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853

Presented By:

• Jia Huang - SSL

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.

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

Presented By:

• Fran Bagenal - CU Boulder/LASP

Seminar Description coming soon.

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

Presented By:

• Sohpia Zomerdijk-Russell - JPL

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.

Nov. 22, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853

Presented By:

• Mike Hartinger - SSI/UCLA

"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.

Dec. 6, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853

Presented By:

• Xuzhi Zhou - PKU

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.