A5011734134- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Earthquake Detection and Analysis
- Geomagnetism and Paleomagnetism Studies
- Astro and Planetary Science
- Seismic Waves and Analysis
- Lightning and Electromagnetic Phenomena
- Magnetic confinement fusion research
- GNSS positioning and interference
- Atmospheric Ozone and Climate
- Plasma Diagnostics and Applications
- earthquake and tectonic studies
- Ocean Waves and Remote Sensing
- Underwater Acoustics Research
- Meteorological Phenomena and Simulations
- Atmospheric aerosols and clouds
- Atomic and Subatomic Physics Research
- Tropical and Extratropical Cyclones Research
- Astrophysics and Cosmic Phenomena
- Advanced Optical Sensing Technologies
- Geophysics and Gravity Measurements
- Ocular and Laser Science Research
- Geophysics and Sensor Technology
- Gamma-ray bursts and supernovae
- Seismology and Earthquake Studies
University of California, Los Angeles
2016-2025
NOAA Oceanic and Atmospheric Research
2015-2025
UCLA Health
2020-2024
Nagoya University
2023
King University
2023
University of California System
2023
University of Iowa
2023
Natural Environment Research Council
2023
British Antarctic Survey
2019-2023
Southwest Research Institute
2022
A quantitative analysis is presented of the resonant scattering plasma sheet electrons (∼100 eV–20 keV) at L = 6 due to interactions with whistler‐mode chorus. Using wave parameters modeled from observations under geomagnetically disturbed conditions, it demonstrated that rate pitch angle can exceed level strong diffusion over a broad energy range (200 eV–10 containing bulk injected population. Scattering by chorus appears be more effective than previous analyses interaction electrostatic...
Whistler mode chorus waves are receiving increased scientific attention due to their important roles in both acceleration and loss processes of radiation belt electrons. A new global survey whistler‐mode is performed using magnetic field filter bank data from the THEMIS spacecraft with 5 probes near‐equatorial orbits. Our results confirm earlier analyses strong dependence wave amplitudes on geomagnetic activity, confinement nightside emissions low latitudes, extension dayside high latitudes....
Pulsating aurora, a spectacular emission that appears as blinking of the upper atmosphere in polar regions, is known to be excited by modulated, downward-streaming electrons. Despite its distinctive feature, identifying driver electron precipitation has been long-standing problem. Using coordinated satellite and ground-based all-sky imager observations from THEMIS mission, we provide direct evidence naturally occurring electromagnetic wave, lower-band chorus, can drive pulsating aurora....
[1] The global distribution of chorus wave amplitudes and their normal angles is investigated using high-resolution spectra waveform data from THEMIS for lower-band upper-band separately. Statistical results show that large amplitude (>300 pT) occurs predominantly premidnight to postdawn preferentially observed at lower L shells (<8) near the magnetic equator. However, strong or moderate extends further into afternoon sector higher shells. For chorus, waves (>50 tend have <20° become even...
Electromagnetic ion cyclotron (EMIC) waves are transverse plasma generated by anisotropic proton distributions with T perp > para . They believed to play an important role in the dynamics of ring current and potentially, radiation belts. Therefore it is know their localization magnetosphere magnetospheric solar wind conditions which lead generation. Our earlier observations from three Time History Events Macroscale Interactions during Substorms (THEMIS) probes demonstrated that strong...
Abstract Local acceleration driven by whistler‐mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus‐driven during 17 March 2013 storm, when Van Allen Probes observed very rapid up several MeV within ~12 hours. A clear radial peak phase space density (PSD) near L * ~4 indicates that an internal local process was operating. We construct global...
We perform a comprehensive analysis to evaluate hiss‐induced scattering effect on the pitch angle evolution and associated decay processes of relativistic electrons. The results show that by equatorial, highly oblique hiss component is negligible. Quasi‐parallel approximation good for evaluation hiss‐driven electron rates ≤ 2 MeV. However, realistic wave propagation angles as function latitude must be considered accurately quantify above MeV, ambient plasma density also critical parameter....
Abstract To improve our understanding of the role electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis EMIC wave‐induced resonant scattering outer zone relativistic (>0.5 MeV) electrons and resultant loss time scales with respect to wave band, L shell, normal angle model. The results demonstrate that while H + ‐band dominate losses ~1–4 MeV electrons, it is He O prevail over pitch diffusion ultrarelativistic at higher...
Abstract Plasmaspheric hiss is known to play an important role in controlling the overall structure and dynamics of radiation belt electrons inside plasmasphere. Using newly available Van Allen Probes wave data, which provide excellent coverage entire inner magnetosphere, we evaluate global distribution frequency spectrum intensity for different levels substorm activity. Our statistical results show that observed peak frequencies are generally lower than commonly adopted value (~550 Hz), was...
Abstract Remote sensing of solar‐induced chlorophyll fluorescence (SIF) provides a powerful proxy for gross primary productivity (GPP). It is particularly promising in boreal ecosystems where seasonal downregulation photosynthesis occurs without significant changes canopy structure or content. The use SIF as GPP complicated by inherent non‐linearities due to both physical (illumination effects) and ecophysiological (light efficiencies) controls at fine spatial (tower/leaf) temporal...
The Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite frequently observes relativistic (> 1 MeV) electron precipitation in the radiation belts at L shells of 4–6 with bursty temporal structure lasting < s. This phenomenon can occur all local times but is most often seen between 0200 1000 magnetic time. VLF chorus also observed to preferentially these same times. Using observations from SAMPEX Heavy Ion Large Telescope data Polar plasma wave instrument, we show...
The effect of large amplitude chorus on energetic, radiation‐belt electrons is evaluated using a general, relativistic, oblique, test‐particle code. Three specific cases are examined: (A) Low‐amplitude waves interacting at low‐latitudes exhibit the expected, linear scattering which leads to large‐scale diffusive behavior. (B) Large‐amplitude result in monotonic decreases pitch‐angle and energy due resonance dislocation effect, leading de‐energization particle loss. (C) obliquely high...
A long-standing problem in the field of space physics has been origin plasmaspheric hiss, a naturally occurring electromagnetic wave high-density plasmasphere (roughly within 20,000 kilometers Earth) that is known to remove high-energy Van Allen Belt electrons pose threat satellites and astronauts. recent theory tied hiss seemingly different outer magnetosphere, but this was difficult test because challenging set observational requirements. Here we report on experimental verification theory,...
The relativistic electron dropout event on 20 November 2003 is studied using data from a number of satellites including SAMPEX, HEO, ACE, POES, and FAST. observations suggest that the may have been caused by two separate mechanisms operate at high low L ‐shells, respectively, with separation ∼ 5. At ‐shells ( > 5), approximately independent energy consistent losses to magnetopause aided Dst effect outward radial diffusion which can deplete electrons down lower ‐shells. < strongly...
A statistical survey of plasma densities and electron distributions (0.5–100 keV) is performed using data obtained from the Time History Events Macroscale Interactions During Substorms spacecraft in near‐equatorial orbits 1 July 2007 to May 2009 order investigate optimum conditions for whistler mode chorus excitation. The density calculated potential, together with situ magnetic field, used construct global maps cyclotron Landau resonant energies under quiet, moderate, active geomagnetic...
Abstract We adopt a physics‐based technique to infer chorus wave amplitudes from the low‐altitude electron population (30–100 keV) measured by multiple Polar Orbiting Environmental Satellites (POES), which provide extensive coverage over broad region in L‐shell and magnetic local time (MLT). This is validated analyzing conjunction events between Van Allen Probes measuring near equator POES satellites 30–100 keV at conjugate low altitudes. apply this construct distributions during 8–9 October...
A quantitative analysis is performed on the decay of an unusual ring relativistic electrons between 3 and 3.5 R E , which was observed by Relativistic Electron Proton Telescope instrument Van Allen probes. The formed September 2012 during main phase a magnetic storm due to partial depletion outer radiation belt for L > 3.5, this remnant persisted at energies above 2 MeV, exhibiting only slow decay, until it finally destroyed another 1 October. This long‐term stability electron associated...
Recent analysis using quasilinear theory (QLT) has shown that magnetosonic (MS) waves are able to accelerate electrons relativistic energies on fast time scales (∼1 day). However, the large obliquity of wave and typical equatorial confinement MS power create conditions bring into question fundamental applicability QLT this problem. In paper, a test particle code is used model interaction energetic with waves, results analysis, investigate any potential nonlinear effects. It found in expected...
The rapid loss of radiation belt electrons in the main phase geomagnetic storms is believed to be aided by EMIC waves, and usually analyzed with quasi‐linear theory. However, even moderate wave intensities easily cause resonant respond nonlinearly, drastically different results. We map out region nonlinear behavior a single parameter, show that both direction magnitude scattering can estimated analytical expressions. interactions typically lead advection toward large pitch angles, rather...
Both plasmaspheric hiss and chorus waves were observed simultaneously by the two Van Allen Probes in association with substorm‐injected energetic electrons. Probe A, located inside plasmasphere postdawn sector, intense hiss, whereas B outside just before dawn. Dispersed injections of electrons dayside outer associated significant intensification at frequencies down to ~20 Hz, much lower than typical wave 100–2000 Hz. In plasmasphere, upper energy injected agrees well minimum cyclotron...