Space Physics Seminar - spring-2023
Scientific applications of atmospheric and ionospheric remote sensing with GNS
April 7, 2023
3:30 p.m. - 4:30 p.m.
Slichter 3853
Presented By:
- Dr. Olga P. Verkhoglyadova - NASA Jet Propulsion Laboratory (JPL)
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Introduction into utilizing GNSS (Global Navigation Satellite System) measurements for the upper Earth’s atmospheric science and space weather research will be made. Approaches for Total Electron Content (TEC) estimations and global ionospheric mapping performed at JPL will be discussed. Recent results on classification of ionospheric maps and evaluation of TEC prediction with the first principles models will be presented. The GNSS radio-occultation (RO) technique will be briefly introduced. Several related science applications and recent research performed at JPL will be reviewed. Current directions in development of remote sensing techniques with satellite for Earth science and heliophysics research will be outlined.
An Acoustically Controlled Steady State Desk Top Plasma for Studying Communications Blackout, Thermal Convection in a Central Force Field and Pulsating Motion with Mach Numbers Matching Cepheids
April 14, 2023
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Dr. Seth Putterman - P&A, UCLA
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Oscillating sound waves can exert a force known as acoustic radiation pressure. These forces can trap a bubble or levitate a particle. We have uncovered a term in the Navier-Stokes equation for gas/fluid dynamics which gives an acoustic radiation force that is enhanced by a density gradient. In a spherical geometry a standing wave in a plasma leads to an acoustic gravity that is over 1,000 times earth’s gravity ‘g’ in the lab. This enables ground-based observation of thermal convection in a spherical geometry. Previous efforts took place in space because they were dependent on a fluid with a temperature dependent permittivity. With an applied electric field their effective gravity was less than g/10. Our plasma is excited in sulfur with microwave radiation. By pulsing the microwaves at the frequency of a spherical acoustic resonance the acoustic forces create a confined hot region near the center and a convecting region beyond the velocity antinode. The non-stationary nature of the convection is also representative of the plasma that forms on the surface of hypersonic vehicles and accounts for communications blackout. The Mach number of the spherical pulsation matches a Cepheid. We hope to modify the parameters of our system so that the plasma’s opacity causes it to become a natural oscillator. In this way continuous energy input will lead to high amplitude oscillations and confinement of the hot region. Thanks to DARPA and the AFOSR and the Dean of Physical Sciences for Support!
Extrasolar Analogs: Aurorae and Radiation Belts
April 21, 2023
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Dr. Melodie Kao - UCSC
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Planetary magnetic fields influence atmospheric evolution from space weather and yield insights into planet interiors. The most direct way of characterizing magnetic fields on exoplanets and their brown dwarf cousins is by observing exo-aurorae at radio frequencies. Additionally, a non-auroral quiescent radio component accompanies all known examples of substellar exo-aurorae and provides an alternative means for assessing the physics occurring in substellar magnetospheres. Low-frequency radio arrays will soon be sensitive to exoplanet radio emission and provide a new means of exoplanet detection and characterization. Now is a critical time to prepare for these upcoming searches by harnessing detailed studies of radio emission on observationally accessible exoplanet analogs: planetary-mass and cold brown dwarfs. I will synthesize the state of the art for radio star-planet interactions as well as brown dwarf magnetospheric radio studies, discuss implications for exoplanet magnetism, and highlight opportunities for the next generation of ground- and space-based radio facilities.
How much do we understand CME evolution in the corona and heliosphere?
May 12, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Dr. Erika Palermio - PSI
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Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic fields that are regularly expelled from the Sun into the heliosphere, and are amongst the major drivers of space weather effects at Earth and other solar system bodies. The evolution of CMEs as they propagate through the solar corona and interplanetary space is one of the major topics of heliophysics research. Far from being static, solid structures, CMEs travel away from the Sun through a structured ambient solar wind and interplanetary magnetic field that can lead to varied evolutionary outcomes, including deflections, rotations, deformations, and erosion. The complexity of the myriad processes affecting CME evolution in the solar corona and in interplanetary space makes full characterisation of the journey of a CME a particularly arduous task. In this presentation, we will first provide a brief review of the current status of research and understanding of the evolution of CMEs in the solar corona and inner heliosphere. We will explore the major breakthroughs that have been obtained via multi-spacecraft measurements realised via fortuitous alignments of the observing probes throughout the heliosphere. Then, we will tackle the major open questions on CME evolution, with an additional focus on what knowledge gaps need to be filled in order to improve space weather forecasts. Finally, we will conclude by addressing the need for dedicated multi-spacecraft missions for CME science realised e.g. via satellite constellations, which have been gaining increasing interest over recent years.
Energetic electron precipitation: Magnetospheric drivers and atmospheric impacts
May 19, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Dr. Lauren Blum - CU/LASP
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The outer radiation belt is a highly dynamic region of the Earth’s magnetosphere, with often-unpredictable variations in intensity and spatial extent. Characterization of this variable radiation environment is critical to mitigating spacecraft anomalies often caused by energetic particles. Precipitation into the atmosphere has been shown to be an important loss process for energetic particles in Earth’s magnetosphere, as well as a key energy input to Earth’s atmosphere, modifying atmospheric chemistry and ozone content. Here we explore the nature and extent of electron loss to the atmosphere as well as what electromagnetic wave modes may be causing it. In particular, we examine the detailed properties of rapid sub-second precipitation, termed microbursts. Microburst precipitation has long been associated with whistler mode chorus wave activity, due to their similar global distributions and sub-second structure. However, despite decades of observations, large gaps remain in our understanding of how, where, and when chorus waves can produce relativistic electron microbursts. We’ll highlight some recent results providing a more complete picture of the complex relationship between chorus waves and microburst precipitation. Finally, we’ll end by highlighting some upcoming efforts, including balloon and CubeSat measurements currently under development, that will help reveal the nature of the interaction between precipitating energetic particles and Earth’s atmosphere.
Adventures in machine learning prediction of solar flares: small victories and agonizing defeats
May 26, 2023
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Dr. Tom Berger - SWX, TREC, CO
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The prediction of solar magnetic eruptions, the root cause of solar flares, coronal mass ejections, and radiation storms, and hence the drivers of all severe space weather impacts, remains one of the highest priority challenges in space weather forecasting. Currently, manual analysis of sunspot images and magnetograms followed by climatology prediction and forecaster-in-the-loop judgements is the state of the art. NASA’s Solar Dynamics Observatory (SDO) has now accumulated over 20 PB of photospheric magnetic field, chromospheric, and coronal images over Solar Cycle 24, enabling the development of machine learning (ML) solar flare prediction models and holding out hope that these models will achieve the sort of breakthroughs in skill demonstrated by ML models in other fields such as image classification. In this talk, I discuss three stages of development of ML solar flare prediction models at the CU Space Weather Technology, Research, and Education Center (SWx TREC): topological data analysis of magnetogram data, Convolutional Neural Network (CNN) analysis of magnetogram images, and Self-Attention Network (SAN) analysis of Extreme Ultraviolet (EUV) chromospheric and coronal images. Our models perform comparably to other ML flare prediction models as well as to the state-of-the-art manual methods, and we demonstrate conclusively that pattern recognition can predict eruptions as skillfully as physics-based methods. But our models, like all other ML flare predictions models to date, fail to achieve breakthrough performance in predictive skill. We discuss possible reasons for this as well as several common errors that lead to deceptively high skill scores occasionally reported in the literature.