Space Physics Seminar - winter-2020
Merging in situ and remote observations to investigate CMEs with upcoming solar observations
Jan. 16, 2020
3:30 p.m. - 5 p.m.
Slichter 6850
Presented By:
- This Seminar is Cancelled -
- Yeimy Rivera - University of Michigan
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Our recent modeling work reconstructed the thermodynamic evolution of several plasma structures (prominence, prominence-coronal transition region, and coronal-like plasma) within the radial expansion of a coronal mass ejection (CME) by examining heliopsheric ion composition within the ejecta. This study suggested that the components experienced rapid, continuous, and non-uniform heating as they travelled away from the Sun. The work indicated that comprehensive CME studies require multi-wavelength plasma observations along with a wide off-limb field of view to capture the extent of the evolution. However, the dynamic nature of the eruption makes it difficult to capture the plasma’s temporal and spatial evolution with a single narrowband imager or high resolution spectrometer
Probing Solar Chromospheric Temperatures and Dynamics with ALMA and IBIS
Jan. 17, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- Kevin Reardon - National Solar Observatory
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Even after decades of detailed study, many mysteries about the solar chromosphere remain. Making progress on these questions will be a key focus of solar physics in the coming years. In this talk, I will show recent work in this area combining imaging spectroscopy in the optical using the Interferometric Bidimensional Spectrometer (IBIS) and millimeter diagnostics from the Atacama Large Millimeter Array (ALMA). Using these instruments, we can probe the chromospheric temperature structure and dynamics on time scales of tens of seconds and at spatial scales of a few 100 km. We find evidence that spectral-line parameters of H-alpha and Ca II are closely correlated with the ALMA brightness temperatures. I will discuss how this changes our understanding of chromospheric dynamics and the interpretation of the observed spectral intensities. Finally, I will provide an overview of advances we expect on these questions from the soon-to-be-operational DKI Solar Telescope (DKIST).
How do Dipolarzing Flux Bundles Impact the cis-GEO Inner Magnetosphere
Jan. 24, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- Jiang Liu - UCLA EPSS
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Dipolarizing flux bundles (DFBs) are flux tubes in Earth’s magnetotail, which have larger Bz than the background. These bundles are most likely generated by near-earth tail reconnection. After they are generated, they propagate earthward (as bursty bulk flows) and carry strong electric fields. Their strong electric field can energize particles. If DFBs can bring these energized particles into the inner magnetosphere, they can impact the particle population of the ring current and the radiation belt. Even if a DFB cannot reach the inner magnetosphere, it may still impact the particle population there by sending ultra-low-frequency waves. In this talk, I explore the possible ways that DFBs can transport their energy to the inner magnetosphere.
Kinetics of solar wind discontinuities TBA
Jan. 31, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- Anton Artemyev - EPSS, UCLA
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Because solar wind plasma flow transports the entire spectrum of magnetic field fluctuations (from low-frequency inertial range to electron kinetic range), it is a natural laboratory for plasma turbulence investigation. Among the various wave modes and coherent plasma structures that contribute to this spectrum, one of the most important solar wind elements is ion-scale solar wind discontinuities. These structures, which carry very intense current, have been considered as a free energy source for plasma instabilities that contribute to solar wind heating. Investigations of such discontinuities have been mostly focused on their magnetic field signatures; much less is known about plasma kinetics around them. This presentation discusses statistics of such discontinuities observed around the Earth (~1 AU) by ARTEMIS and MMS mission and around the Mars (~1.5AU) by Maven mission. The main focus is on their kinetic structure and force balance.
The Making of the Space Weather Modeling Framework
Feb. 7, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- Tamas Gombosi - University of Michigan
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A successful example of research code development, community use and transition to operations is the University of Michigan's multiphysics MHD code called BATS-R-US and the Space Weather Modeling Framework (SWMF) that couples together regional domain models. The development of BATS-R-US started in the early 1990s, while SWMF was developed a decade later. Both BATS-R-US and SWMF were developed from the beginning with high parallel performance and portability in mind. The SWMF provides the software environment and tools to couple the various models with each other. It is a fully functional, documented software framework that allows the parallel execution and efficient coupling of multiple models. The SWMF provides a high-performance computational capability to simulate the space-weather environment from the upper solar chromosphere to the Earth's upper atmosphere and/or the outer heliosphere. Currently there are more than a dozen physics domains in the SWMF, but in an actual simulation one can use any meaningful subset of the components. In the early 2010s the CCMC evaluated three physics-based and three empirical magnetosphere (geospace) models at the request of NOAA/SWPC. Among the six models was the SWMF/Geospace configuration that included three coupled models: the global magnetosphere described by BATS-R-US, the inner magnetosphere simulated by the Rice Convection Model (RCM) and ionospheric electrodynamics solved by the Ridley Ionosphere Model (RIM). In 2014 NOAA/SWPC selected SWMF/Geospace as the first physics-based global magnetosphere model to be transitioned to operations. This presentation will outline the current state of space weather modeling and recent developments that pave the way for new and exciting capabilities.
Magnetic Energy Storage and Conversion in the Solar Corona and Inner Heliosphere
Feb. 14, 2020
3:30 p.m. - 4:30 p.m.
Geology 6704
Presented By:
- Marco Velli - EPSS, UCLA
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Solar magnetic activity provides the dynamic, pulsating heart of the Heliosphere. The transformations of energy that accompany solar magnetic activity remain a mysterious, complex phenomenon, with ramifications that extend beyond space physics into astrophysics as a whole. This seminar will provide a pedagogical overview to the question of coronal stability and the roles of magnetic reconnection, waves and turbulence in magnetic energy release. It will also briefly describe the objectives of a recently funded phase I DRIVE science center whose goals are to use the Heliophysics Systems Observatory, i.e. the fleet of solar, heliospheric, geospace, and planetary spacecraft, together with ground based Observatories, to make progress on magnetic energy conversion processes throughout the Heliosphere.
Magnetotail dipolarizations at Mercury: Lessons from a miniature magnetosphere
Feb. 21, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- Ryan Dewey - University of Michigan
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Dipolarizations in Earth’s magnetotail play a major role in plasma and magnetic flux transport, particle heating and acceleration, and substorm current wedge formation. Mercury, whose magnetosphere closely resembles Earth’s topologically, also experiences dipolarizations despite Mercury’s shorter spatiotemporal scales and lack of an ionosphere. In light of these magnetospheric differences, we investigate the nature of dipolarizations at Mercury using MESSENGER spacecraft observations. We discuss how differences between the magnetospheres influence dipolarization dynamics and how the implications of our results may shape our understanding of the substorm process at terrestrial planets.
The ACATMOS Group Research on FAIRIES in South America with LEONA Network
Feb. 26, 2020
3:30 p.m. - 5 p.m.
Slichter Hall 6850
Presented By:
- Eliah F. M. T. São Sabbas - National Institute for Space Research INPE, Brazil
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LEONA is the Transient Luminous Event and ThunderstOrm High Energy EmissioN CollAborative Network. It was created in 2012 to study the EFfects SignAlIng the ElectRodynamic CouplIng between the AtmospherE and Space – FAIRIES. FAIRIES are composed by two categories of phenomena, one type are High Energy Emissions from Thunderstorms – HEETs: X-Ray, Gamma-Ray, Neutron, Electron, and Positron Emissions, i.e. anti-matter, and most probably other particles and subatomic particles that have not been detected yet. The other category is constituted by transient plasmas, with low-light level optical emissions, excited by lightning and spanning the whole region from the cloud tops to the border between Earth’s atmosphere and space (~20-100 km): the sprites and other Transient Luminous Events (TLEs). HEETs are naturally produced in our planet’s atmosphere by lightning and thunderstorm electric fields, with energies of a few hundred keV to 100 MeV, i.e. energies comparable to astrophysical events like supernovae explosions. Recently discovered, they have been detected by instrumentation on the ground, onboard airplanes, and onboard astrophysical satellites, such as CGRO, RHESSI, FERMI and AGILE, designed to measure Gamma-Ray Bursts (GRBs) and other energetic radiation/particles from space. TLEs are excited in the upper atmosphere above thunderstorms by electric and electromagnetic fields from lightning discharges. Together, HEET and TLEs, i.e. the FAIRIES, signal the electrodynamic coupling of all atmospheric layers and of the Earth System with the Near-Earth Space, and compose a natural laboratory to investigate fundamental particle, atomic and molecular physics, in the “lightning electric field atmospheric accelerator”, as well as astrophysical GRBs and plasma physics. In this talk we will discuss the importance of the LEONA network to study FAIRIES in South America, the successful observation of TLEs in 2 nights of the RELAMPAGO project campaign in Nov-Dec 2018 in Argentina, and in 7 nights during the LEONA 2019 campaign, and we will make a brief overview of the ACATMOS group achievements in leading this new multidisciplinary research area in Brazil and South America as a whole.
Magnetotail reconnection: Observation-motivated particle-in-cell simulations
Feb. 28, 2020
3:30 p.m. - 5 p.m.
Geology 6704
Presented By:
- San Lu - EPSS, UCLA
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Magnetic reconnection is an important process in plasmas because it reconfigures magnetic field and releases magnetic energy to accelerate charged particles. In Earth’s magnetotail, in particular, magnetic reconnection plays an important role in magnetospheric energy conversion. Because magnetotail reconnection occurs in the pre-reconnection current sheet, the characteristics of this current sheet controls properties of magnetotail reconnection. In-situ spacecraft observations show that the pre-reconnection current sheet has two important characteristics: 1) it has inhomogeneous temperature across the current sheet, and 2) it is a charged current sheet with the current predominantly carried by electrons. Particle-in-cell (PIC) models can well simulate the magnetotail reconnection with the most complete physics description. However, previous PIC simulations of magnetic reconnection were based on the simple neutral current sheets with homogeneous temperature and ions as current carriers. We perform a series of particle-in-cell simulations and find that the properties of magnetic reconnection are significantly changed after having included the two characteristics of the pre-reconnection current sheet. We hereby suggest that for better understanding and modeling magnetotail reconnection, the temperature inhomogeneity and charging effect need to be taken into account.
Merging in situ and remote observations to investigate CMEs with upcoming solar observations
March 5, 2020
4 p.m. - 5 p.m.
Slichter 6850
Presented By:
- Yeimy Rivera - University of Michigan
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Our recent modeling work reconstructed the thermodynamic evolution of several plasma structures (prominence, prominence-coronal transition region, and coronal-like plasma) within the radial expansion of a coronal mass ejection (CME) by examining heliopsheric ion composition within the ejecta. This study suggested that the components experienced rapid, continuous, and non-uniform heating as they travelled away from the Sun. The work indicated that comprehensive CME studies require multi-wavelength plasma observations along with a wide off-limb field of view to capture the extent of the evolution. However, the dynamic nature of the eruption makes it difficult to capture the plasma’s temporal and spatial evolution with a single narrowband imager or high resolution spectrometer
Solar Terrestrial Interactions: The Ionospheric Signatures
March 6, 2020
3:30 p.m. - 5:05 p.m.
Geology 6704
Presented By:
- Gerard Fasel - Pepperdine University
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Understanding space weather and how it affects the Earth’s terrestrial environment is as important to humankind as knowing what the global weather conditions are on any particular day. Yet, these Solar-Terrestrial interactions are still not well understood. The Sun generates a wind, which consists of charged particles, mostly protons and electrons, which are constrained to move along the Interplanetary Magnetic Field (IMF). The solar wind is constantly interacting with our terrestrial environment. Magnetic reconnection, first proposed by Dungee in 1961, is the most understood among these interactions. This occurs when the IMF reconnects to the Earth’s magnetic field, causing thermal energy to be transmitted down into the ionosphere and creating the aurora in both the northern (aurora borealis) and southern hemispheres (aurora australis). Polar-moving auroral forms are believed to be the ionospheric signatures of magnetic reconnection on the dayside magnetopause. Certain solar wind conditions, often resulting from solar storms such as coronal mass ejections, can create extremely active auroral displays known as geomagnetic storms. This talk will look at dayside ionospheric signatures due to solar-terrestrial interactions. A new aurora, foreshock aurora, due to a massive compression of the magnetosheath and bow shock will be introduced. Generally, when the IMF Bz-component is negative, the auroral oval generally expands equatorward. Several examples will be presented when the dayside auroral oval does not expand for Bz<0 conditions. Finally, some updated information regarding PMAFs and their connection to magnetic reconnection will be discussed.
Magnetic Curvature Force and the Physics of Current Sheets in the Magnetosheath
March 13, 2020
3:30 p.m. - 5 p.m.
Slichter 6850
Presented By:
- Robert J. Strangeway - EPSS, UCLA
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The Magnetospheric Multiscale mission (MMS), consisting of four closely spaced Earth-orbiting spacecraft, has provided unprecedented high quality and high temporal resolution data that has provided new insights into the process of reconnection at both the dayside magnetopause and the nightside current sheet. MMS has also shown that the magnetosheath itself can be highly structured. Several research groups have reported on strong current sheets observed within the magnetosheath itself that appear to be separate from the magnetopause current. Various hypotheses have been forwarded to explain these structures, including fast plasma jets from the bow shock, interacting flux ropes/flux transfer events (FTEs), and dusty plasma interactions. In order to elucidate the causes for these current sheets we analyze the force associated with magnetic field-line curvature and we find that the curvature force can offset the excess pressure force often observed at or near the current sheet. This suggests that the interacting flux-rope/FTE hypothesis best explains the events, but this leads to further questions. Specifically, the magnetic field signatures suggest that if the source is due to flux-rope/FTE entanglement then the current sheets are highly evolved. In addition, while the current is mainly field-aligned, it is not clear how this current closes as the entangled structures become un-entangled.