A5045317568- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Earthquake Detection and Analysis
- Geomagnetism and Paleomagnetism Studies
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Magnetic confinement fusion research
- Electron and X-Ray Spectroscopy Techniques
- Gamma-ray bursts and supernovae
- Plasma Diagnostics and Applications
- Spacecraft Design and Technology
- Laser-Plasma Interactions and Diagnostics
- GNSS positioning and interference
- Particle Accelerators and Free-Electron Lasers
- Laser-induced spectroscopy and plasma
- Geophysics and Gravity Measurements
- Particle accelerators and beam dynamics
- Space Satellite Systems and Control
- Astrophysics and Cosmic Phenomena
- Photocathodes and Microchannel Plates
- Planetary Science and Exploration
- Seismic Waves and Analysis
- Meteorological Phenomena and Simulations
- Space Science and Extraterrestrial Life
- earthquake and tectonic studies
Johns Hopkins University Applied Physics Laboratory
2019-2025
University of California, Los Angeles
2011-2024
Thomas Jefferson National Accelerator Facility
2015-2024
University of America
2023-2024
Catholic University of America
2023-2024
The Aerospace Corporation
2015-2023
Planetary Science Institute
2012-2023
University of California, Berkeley
2021-2023
University of Colorado Boulder
2008-2023
University of Iowa
2022-2023
Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy converted into heat and kinetic of charged particles. Reconnection occurs many astrophysical plasma environments laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization acceleration at sites along the sunward boundary Earth's magnetosphere where interplanetary field reconnects...
The Van Allen radiation belts contain ultrarelativistic electrons trapped in Earth's magnetic field. Since their discovery 1958, a fundamental unanswered question has been how can be accelerated to such high energies. Two classes of processes have proposed: transport and acceleration from source population located outside the (radial acceleration) or lower-energy relativistic energies situ heart (local acceleration). We report measurements NASA's Radiation Belt Storm Probes that clearly...
Abstract We study the effect of electromagnetic ion cyclotron (EMIC) waves on loss and pitch angle scattering relativistic ultrarelativistic electrons during recovery phase a moderate geomagnetic storm 11 October 2012. The EMIC wave activity was observed in situ Van Allen Probes conjugately ground across Canadian Array for Real‐time Investigations Magnetic Activity throughout an extended 18 h interval. However, neither enhanced precipitation >0.7 MeV nor reductions Probe 90° electron flux...
Earth's magnetotail contains magnetic energy derived from the kinetic of solar wind. Conversion that back to particle ultimately powers auroras, heats magnetospheric plasma, and energizes Van Allen radiation belts. Where how such electromagnetic conversion occurs has been unclear. Using a conjunction between eight spacecraft, we show this takes place within fronts recently reconnected flux, predominantly at 1- 10-electron inertial length scale, intense electrical current sheets (tens...
Abstract Energetic particle injections are critical for supplying particles and energy to the inner magnetosphere. Recent case studies have demonstrated a good correlation between transient, narrow, fast flow channels as well earthward reconnection (dipolarization) fronts in magnetotail, but statistical observations beyond geosynchronous orbit (GEO) verify findings were lacking. By surveying trans‐geosynchronous using Time History of Events Macroscale Interactions during Substorms (THEMIS),...
We present observations of the radiation belts from Helium Oxygen Proton Electron and Magnetic Ion Spectrometer particle detectors on Van Allen Probes satellites that illustrate energy dependence L shell belt enhancements decays. survey events in 2013 analyze an event 1 March more detail. The show following: (a) at all shells, lower electrons are enhanced often than higher energies; (b) fill slot region common (c) inner zone (d) even when do not fully region, energies tend to extend shells...
The coupling of compressional and transverse hydromagnetic waves is studied in the cold inhomogeneous outer magnetosphere. A general computer program has been developed for a dipole model. This model allows realistic spatial variation Alfven speed includes geometric effects. propagation structure each mode are analyzed on two‐dimensional map meridian plane. properties also investigated through time histories wave frequency spectra. highly spatially structured form shown theory global damping...
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...
Abstract Recent observations have suggested that spatially localized flows of high‐temperature, low‐density plasma carrying a dipolarized magnetic field (dipolarizing flux bundles, DFBs) play key role in hot transport toward the inner magnetosphere. What controls heating DFBs and how do thermodynamic parameters (such as density, temperature, pressure, specific entropy) spectral properties DFB population depend on ambient sheet geocentric distance R remains unknown. By statistical analysis...
Motivated by recent observations of intense electric fields and elevated energetic particle fluxes within flow bursts beyond geosynchronous altitude (Runov et al., 2009, 2011), we apply modeling guiding centers in prescribed but realistic to improve our understanding acceleration transport toward the inner magnetosphere through model‐data comparisons. Representing vortical nature an earthward traveling burst, a localized, westward‐directed transient field flanked on either side eastward...
We report on internal, magnetospheric processes related to markedly different storm‐time responses of phase space density (PSD) in invariant coordinates corresponding equatorially mirroring, relativistic electrons Earth's outer radiation belt. Two storms are studied detail, selected from a database 53 events (Dst min < −40 nT) during the THEMIS era thus far (December 2007–August 2012). These well covered by number situ spacecraft and complemented additional ground‐based observatories,...
Using multipoint in situ observations upstream of Earth's bow shock from the THEMIS mission, we present first foreshock bubbles (FBs) and compare them to hot flow anomalies (HFAs). FBs are recently conceptualized kinetic phenomena that can form under commonplace condition a rotational discontinuity interplanetary magnetic field interacting with backstreaming energetic ions quasi‐parallel foreshock. may have remained elusive until now due their many observational similarities HFAs lack...
Abstract From a survey of the first nightside season NASA's Van Allen Probes mission (December 2012 to September 2013), 47 energetic (tens hundreds keV) electron injection events were found at L shells ≤ 4, all which are deeper than any previously reported substorm‐related injections. Preliminary details from these presented, including how occurred shortly after dipolarization signatures and injections observed higher shells, deepest was ~ 2.5, and, surprisingly, 4 limited in energy ≤250...
Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the can be investigated situ by spacecraft. On 11 July 2017, four Magnetospheric Multiscale spacecraft encountered a site magnetotail, involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvénic electron jets reaching 15,000 kilometers per second; (ii) meandering motion and acceleration electric field, producing...
Abstract On 30 September 2012, a flux “dropout” occurred throughout Earth's outer electron radiation belt during the main phase of strong geomagnetic storm. Using eight spacecraft from NASA's Time History Events and Macroscale Interactions Substorms (THEMIS) Van Allen Probes missions NOAA's Geostationary Operational Environmental Satellites constellation, we examined full extent timescales dropout based on particle energy, equatorial pitch angle, radial distance, species. We calculated space...
Abstract We present observations that provide the strongest evidence yet discrete whistler mode chorus packets cause relativistic electron microbursts. On 20 January 2016 near 1944 UT low Earth orbiting CubeSat Focused Investigations of Relativistic Electron Bursts: Intensity, Range, and Dynamics (FIREBIRD II) observed energetic microbursts (near L = 5.6 MLT 10.5) from its lower limit 220 keV, to 1 MeV. In outer radiation belt magnetically conjugate, Van Allen Probe A rising‐tone, band waves...
We present phase space density (PSD) observations using data from the Magnetic Electron Ion Spectrometer instrument on Van Allen Probes for 17 March 2013 electron acceleration event. confirm previous results and quantify how PSD gradients depend first adiabatic invariant. find a systematic difference between lower-energy electrons (<few 100 keV) originating plasma sheet higher-energy >1 MeV with source region within radiation belts. Our show that process begins enhancements to 10s–100s keV...
Abstract A statistical study was conducted of Earth's radiation belt electron response to geomagnetic storms using NASA's Van Allen Probes mission. Data for electrons with energies ranging from 30 keV 6.3 MeV were included and examined as a function L‐shell, energy, epoch time during 110 SYM‐H ≤−50 nT September 2012 2017 (inclusive). The revealed clear energy L‐shell dependencies, tens enhanced at all L‐shells (2.5 ≤ L 6) in the storm commencement main phase then quickly decaying away early...
Abstract Drastic variations of Earth's outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave‐particle interactions are critically important. Using 15 spacecraft including NASA's Van Allen Probes, THEMIS, SAMPEX missions NOAA's GOES POES constellations, we investigated the evolution during strong geomagnetic storm 30 September 3 October 2012. This storm's main phase dropout exhibited enhanced losses atmosphere at L* <...
The ion foreshock is a source of energy for magnetospheric ULF waves, but it usually only considered effective at driving waves with frequencies above the Pc5 (2–7 mHz) range. We present observations an 8 h high speed solar wind interval on 14 July 2008 during which three distinct types transient phenomena (TIFP) were observed just upstream dayside bow shock. demonstrate that TIFP generate global amplitudes as large 10 mV/m in electric field and nT magnetic field. characterize response to...