A5077116611- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Magnetic confinement fusion research
- Astro and Planetary Science
- Earthquake Detection and Analysis
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Plasma Diagnostics and Applications
- Magnetic Field Sensors Techniques
- Planetary Science and Exploration
- GNSS positioning and interference
- Particle accelerators and beam dynamics
- Inertial Sensor and Navigation
- Electromagnetic Launch and Propulsion Technology
- Advanced Frequency and Time Standards
- nanoparticles nucleation surface interactions
- Magnetic Properties of Alloys
- Gamma-ray bursts and supernovae
- Geophysics and Sensor Technology
- Geophysical and Geoelectrical Methods
- Electron and X-Ray Spectroscopy Techniques
- Quantum and electron transport phenomena
- Magnetic properties of thin films
- Lightning and Electromagnetic Phenomena
University of California, Los Angeles
2015-2024
Planetary Science Institute
1990-2022
UCLA Health
2020-2022
Space Science Institute
2020
KU Leuven
2020
Princeton Plasma Physics Laboratory
1990
Princeton University
1990
The analysis of the dual magnetic field profile obtained by ISEE mission provides a unique opportunity to study earth's magnetospheric boundaries. A survey magnetopause thickness over dayside magnetosphere is carried out using measurements from twin 1 and 2 magnetometers. Since reliable are possible only for small separations (<1000 km) between our data set restricted thirty crossings in range local time 0800 1700 at GSM latitude 2° 35°. We find that constant rapid irregular motion with...
This paper discusses kinetic modeling of the properties magnetotail formation from a plasma mantle source and develops unified view structure central part sheet as well its boundary layer. Trajectories protons in presence uniform dawn‐dusk electric field have been traced using Tsyganenko magnetic model for quiet periods magnetospheric activity. The most important portion particle trajectories is each particle's first interaction with sharp reversal tail midplane, because this results...
Abstract Spacecraft observations and global hybrid (kinetic ions fluid electrons) simulations have demonstrated that ion dissipation processes at the quasi‐parallel bow shock are associated with formation of structures called spontaneous hot flow anomalies (SHFAs). Previous recent spacecraft also established SHFAs result in magnetosheath filamentary (MFS). In this paper we demonstrate addition to MFS, cavities decreases density, velocity, magnetic field enhancements temperature. We use...
Abstract We report Magnetospheric Multiscale (MMS) observations of a reconnecting current sheet in the presence weak density asymmetry with large guide field at dayside magnetopause. An ion diffusion region (IDR) was detected associated this sheet. Parallel dominated over perpendicular IDR, as found previous studies component reconnection. Electrons were preferentially heated parallel to magnetic within IDR. The heating manifested flattop distribution below 400 eV. Two types electromagnetic...
Abstract We report Magnetospheric Multiscale observations of high‐frequency electrostatic waves in the vicinity reconnection ion diffusion region on dayside magnetopause. The is identified during two magnetopause crossings by Hall electromagnetic fields, slippage ions with respect to magnetic field, and energy dissipation. In addition electron beam modes that have been previously detected at separatrix magnetospheric side magnetopause, we report, for first time, existence cyclotron harmonic...
Abstract Electron acceleration in the magnetotail has been investigated intensively. A major location for this process is reconnection region. How electrons are accelerated to suprathermal energy a realistic three‐dimensional geometry, as opposed an idealized configuration, not fully understood. In study, we employed implicit particle‐in‐cell (iPIC3D) simulation and large‐scale kinetic address problem. We simulated near‐Earth event observed by THEMIS spacecraft using iPIC3D with initial...
MMS observations recently confirmed that crescent-shaped electron velocity distributions in the plane perpendicular to magnetic field occur diffusion region near reconnection sites at Earth's magnetopause. In this paper, we re-examine origin of light our new finding ions and electrons are drifting opposite directions when displayed magnetopause boundary-normal coordinates. Therefore, ExB drifts cannot cause crescent shapes. We performed a high-resolution multi-scale simulation capturing...
Solar wind ion trajectories were computed using the Tsyganenko magnetic field model and assuming presence of a uniform dawn‐dusk electric field. As result energization scattering produced by stochastic processes near tail midplane, two distinct regions are formed, plasma sheet boundary layer (PSBL) addition to these large scale structures existence new small structures, called beamlets, in PSBL predicted. Beamlets correspond structuring distributions both configuration velocity space....
The motion of a heavy ion in the presence an intense ultralow‐frequency electromagnetic wave propagating along dc magnetic field is analyzed. Starting from basic equations and their associated two invariants, velocity‐space trajectories are drawn. It shown that after certain time, particles whose initial phase angles randomly distributed tend to bunch together, provided intensity, b 1 sufficiently large. maximum perpendicular velocity υ which particle reaches during bunching process can be...
In this paper the steady‐state proton distribution in Earth's magnetotail is derived both configuration and velocity space, taking into account proton's energization dawn‐dusk electric field its motion due to deterministic chaos. This stochastic effectively leads pitch angle scattering a redistribution of protons between central plasma sheet boundary, boundary layer. Knowledge these effects allows us explain previously observed features ion predict others for future experimental work.
Abstract Motivated by the observed high concentration of oxygen ions in magnetotail during enhanced geomagnetic activity, we investigated acceleration reconnection using 2.5‐D implicit particle‐in‐cell simulations. We found that lobe can enter downstream outflow region, i.e., region dipolarization fronts (DFs) or jet fronts. Without entering exhaust, they are accelerated Hall electric field. They populate before DFs arrive there. This is addition to exhaust and fields. Oxygen preexisting...
Abstract In the Earth's dayside reconnection boundary layer, whistler mode waves coincide with magnetic field openings and formation of resultant anisotropic electrons. Depending on energy range electrons, whistlers can grow at frequencies in upper and/or lower band. Observations show that modulate Langmuir wave amplitude as they propagate toward X line. phase packets, well coincident electron measurements, reveal accelerate electrons via Landau resonance locations where E || is antiparallel...
We examine the consequences of magnetic reconnection at high‐latitude magnetopause using a three‐dimensional global magnetohydrodynamic simulation solar wind interaction with Earth's magneto sphere. Magnetic field lines from reveal formation flux ropes during periods northward interplanetary field. These result multiple processes between lobes and draped magnetosheath that are convected around flank magnetosphere. The identified in consistent features observed measured by Hawkeye‐1 some crossings.
We have developed a 2½‐dimensional ( x , y υ z ) electromagnetic code to study the formation and stability of magnetopause current layer. This computes trajectories ion electron particles in their self‐consistently generated field an externally imposed two‐dimensional vacuum dipolar magnetic field. The results presented here are obtained for simulation solar wind‐magnetosphere interaction subsolar region equatorial plane. observe self‐consistent establishment layer resulting from both...
Abstract We present an analysis of the energy partitioning in magnetotail during a substorm at 03:58:00 UT on 7 February 2009. The employs multiscale approach where we use state from global magnetohydrodynamics (MHD) model to spawn kinetic particle‐in‐cell (PIC) simulation large portion tail. directly investigate fluxes resulting magnetic reconnection. run provides information additional processes absent MHD description. ion bulk and enthalpy carry greatest energy, but Poynting flux electron...
Earth's magnetotail is an excellent laboratory to study the interplay of reconnection and turbulence in determining electron energization. The process formation a power law tail during turbulent documented fact still need comprehensive explanation. We conduct massively parallel, particle cell 3D simulation use enhanced statistical resolution high energy range velocities how creates conditions for be formed. not direct acceleration by coherent, laminar reconnection-generated electric field....
Abstract A historic challenge to understanding geomagnetic activity is determining where in Earth's magnetotail magnetic energy converted into particle and heat by reconnection. Key unravel this fundamental process the location extent of electron diffusion region (EDR) conversion initiated. We have located EDR during a substorm on 15 February 2008 using combination global magnetohydrodynamic (MHD) particle‐in‐cell (PIC) simulations. Solar wind data were used as input MHD simulation, which...
We have combined global magnetohydrodynamic (MHD) simulations of the solar wind and magnetosphere interaction with an implicit particle-in-cell simulation (PIC) used this approach to model magnetic reconnection at both dayside magnetopause in magnetotail plasma sheet. In approach, we first magnetospheric configuration driven by using MHD simulation. At a time interest (usually when thin current sheet has formed simulation), load large fields based on state. use results set boundary...
Abstract Numerous questions remain about how solar wind directional discontinuities, for example, rotational discontinuities (RDs), affect energy and transport processes at the magnetopause. The impact on dayside magnetosphere of a RD is studied. study shows that leads to complex structures magnetopause, boundary layer, mantle, cusp even though geomagnetic activity level remains low. At low altitudes, Defense Meteorological Satellite Program spacecraft observe double signature magnetic...
Two‐dimensional numerical simulations have been carried out in order to study the injection and propagation of a nonrelativistic electron beam from spacecraft into fully ionized plasma magnetic field. Contrary earlier results one dimension, high‐density whose density is comparable ambient can propagate plasma. A strong radial electric field resulting net charges causes electrons spread radially, reducing density. When current exceeds return current, significant charging observed along with...
Abstract We have carried out global magnetohydrodynamics (MHD) simulations together with large‐scale kinetic to investigate the response of dayside magnetospheric ion precipitation a large rotation (135°) interplanetary magnetic field (IMF). The study uses simplified MHD model (no dipole tilt and constant ionospheric conductance) idealized solar wind conditions where IMF rotates smoothly from southward toward northward direction ( B X = 0) clearly identify effects impact discontinuity on...
Abstract We have used a global magnetohydrodynamic simulation and embedded particle‐in‐cell (PIC) to analyze magnetotail reconnection in near the electron diffusion region (EDR). Results from were set initial boundary conditions for large‐scale implicit PIC simulation. examined proxies EDR (the nongyrotropy of distribution function, slippage, nonideal terms Ohm's law work done [ J · E ′] frame). The was well organized by B x = 0 surface. All gave false positive values but together, along...
Electron cyclotron harmonics and broadband electrostatic noise (BEN) are often observed in the Earth's outer plasma sheet. While it is well known that ion beams sheet boundary layer can generate BEN, new two dimensional simulations show field‐aligned with a small perpendicular ring distribution drive not only but also electron harmonic (ECH) waves simultaneously. Simulation results presented here using detailed diagnostics of wave properties, including dispersion relations all modes.