A5023109408- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Earthquake Detection and Analysis
- Astro and Planetary Science
- Magnetic confinement fusion research
- Geophysics and Gravity Measurements
- Seismic Waves and Analysis
- Dust and Plasma Wave Phenomena
- GNSS positioning and interference
- Laser-induced spectroscopy and plasma
- Planetary Science and Exploration
- Gamma-ray bursts and supernovae
- Ocean Waves and Remote Sensing
- Atmospheric Ozone and Climate
- Tropical and Extratropical Cyclones Research
- Geophysics and Sensor Technology
- Stellar, planetary, and galactic studies
- Gyrotron and Vacuum Electronics Research
- Geophysical and Geoelectrical Methods
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Coastal and Marine Dynamics
- Computational Fluid Dynamics and Aerodynamics
University of Minnesota System
1996-2025
University of Minnesota
2015-2024
Goddard Space Flight Center
2023
Twin Cities Orthopedics
2010-2020
University of California, Berkeley
1984-2011
University of California, Los Angeles
2003
University of Iowa
2003
Johns Hopkins University
1991
Centre National de la Recherche Scientifique
1988
Conditions Extrêmes et Matériaux Haute Température et Irradiation
1988
Using four months of tail data obtained by the three‐dimensional plasma instrument on board AMPTE/IRM satellite in 1986, we have done a statistical survey behavior ion and electron moments central sheet. Almost 80,000 spin averages density, bulk velocity, temperature, β were analyzed with respect to differences between their values inner outer sheet as well dependence magnetic activity. The temperature increases increasing activity while density decreases during disturbed intervals, except...
We report observations of “fast solitary waves” that are ubiquitous in downward current regions the mid‐altitude auroral zone. The single‐period structures have large amplitudes (up to 2.5 V/m), travel much faster than ion acoustic speed, carry substantial potentials ∼100 Volts), and associated with strong modulations energetic electron fluxes. amplitude speed distinguishes them from ion‐acoustic waves or weak double layers. electromagnetic signature appears be an positive charge (electron...
The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed Van Allen Probes) are designed to measure three dimensional quasi-static low frequency electric fields waves associated with major mechanisms responsible for acceleration of energetic charged particles in inner magnetosphere Earth. For this measurement, instrument uses pairs spherical double probe sensors at ends orthogonal centripetally deployed booms spin plane...
Three-dimensional particle simulations of magnetic reconnection reveal the development turbulence driven by intense electron beams that form near x-line and separatrices. The collapses into localized three-dimensional nonlinear structures in which density is depleted. predicted structure these holes compares favorably with satellite observations at Earth's magnetopause. birth death their associated electric fields lead to strong scattering energization, whose understanding critical...
Abstract Launched on 12 Aug. 2018, NASA’s Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The mission’s primary science goal is to determine structure and dynamics Sun’s coronal magnetic field, understand how solar corona wind are heated accelerated, what processes accelerate energetic particles. returned a treasure trove data that far exceeded quality, significance, quantity expectations, leading significant number discoveries reported in nearly...
Recent studies have shown that most Earthward transport hi the midtail, high‐beta plasma sheet takes place in form of short‐lived, high‐speed flow bursts. Bursty bulk flows are observed both when is thin, such as during substorm expansion, and it thick, recovery. We present multi‐instrument observations from ISEE1 ISEE 2 spacecraft to argue becomes thick close its equilibrium state, magnetic field signatures events consistent with theoretically predicted plasma‐depleted flux tubes or...
We present evidence based on measurements from the Polar spacecraft for existence of small‐scale, large‐amplitude kinetic Alfvén waves/spikes at plasma sheet boundary layer (PSBL) altitudes 4–6 R E . These structures coincide with larger‐scale Alfvénic waves that carry a large net Poynting flux along magnetic field lines toward Earth. Both are typically observed in PSBL but have also been deeper sheet. The small‐scale spikes electric amplitudes up to 300 mV m −1 and associated variations...
Observations of plasma particles and fields by the FAST satellite find evidence acceleration intense upgoing electron beams quasi‐static parallel electric fields. The beam characteristics include a broad energy spectrum with peak energies between 100 eV 5 keV, perpendicular temperatures less than 1 eV, fluxes greater 10 9 /cm²sec. Diverging electrostatic shocks associated have integrated potentials that match energy. These are found in regions downward Birkeland current account for total...
In this paper, we present measurements from two passes of the Polar spacecraft intense electric and magnetic field structures associated with Alfven waves at within outer boundary plasma sheet geocentric distances 4–6 R E near local midnight. The variations have maximum values exceeding 100 mV/m are typically polarized approximately normal to boundary. investigated vary over timescales (in frame) ranging 1 30 s. They strong fluctuations amplitudes 10–40 nT which lie predominantly in plane...
During a passage through the Earth's dawn‐side outer radiation belt, whistler‐mode waves with amplitudes up to more than ∼240 mV/m were observed by STEREO S/WAVES instrument. These are an order of magnitude larger previously for whistlers in belt. Although peak frequency is similar whistler chorus, there distinct differences from addition amplitudes, including lack drift and oblique propagation large longitudinal electric field component. Simulations show that these amplitude can energize...
Measurements from the Cluster spacecraft of electric fields, magnetic and ions are used to study structure dynamics reconnection region in tail at distances ∼18 R E near 22.4 MLT on 1 October 2001. This paper focuses measurements large amplitude normal component field observed ion decoupling x‐line, associated potential drops across current sheet, role electrostatic ballistic acceleration sheet. The thinnest sheet during this interval was bifurcated into a pair sheets measured width...
Electric field and energetic particle observations by the Fast Auroral Snapshot (FAST) satellite provide convincing evidence of acceleration quasi‐static, magnetic‐field‐aligned (parallel) electric fields in both upward downward current regions auroral zone. We demonstrate this comparing inferred parallel potentials electrostatic shocks with energies. also report nonlinear structures which may play a role supporting fields. These include large‐amplitude ion cyclotron waves region, intense,...
A comparative study of upstreaming energetic ions in the kilovolt energy range and electrostatic hydrogen cyclotron (EHC) waves has been made using ion mass spectrometer plasma wave receiver data sets for first 1200 orbits S3‐3 spacecraft. The EHC are found to coincide over 90% events studied. In addition, both with energies greater than 500 eV exhibit a lower border their altitude distribution near 5000 km. nearly exact correlation suggests either that producing or heating ions. One example...
Large‐amplitude (up to ∼50 mV/m) solitary waves, identified as electron holes, have been observed during waveform captures on two of the four Cluster satellites several plasma sheet encounters that passage a magnetotail reconnection x line. The holes were seen near outer edge sheet, within and density cavity, at distances order few ion inertial lengths from center current sheet. occur intervals when there narrow beams but not distributions more isotropic or contained broad in pitch angle....
The Polar Satellite carries the first three-axis electric field detector flown in magnetosphere. Its direct measurement of components perpendicular and parallel to local magnetic has revealed new classes features structures associated with plasma acceleration that produces discrete auroras populates magnetosphere ionospheric origin. These structures, hydrogen ion cyclotron mode, include very large solitary waves, spiky wave envelopes fields, amplitude, nonlinear, coherent waves.
Characteristics of solitary waves observed by Polar in the high altitude cusp, polar cap and plasma sheet boundary are reported compared to observations auroral zone. The study presented herein shows that, at altitudes, positive potential structures (electron holes), with scale sizes order 10's Debye lengths, which usually propagate velocities a few thousand km/s. At boundary, direction propagation can be either upward or downward; whereas leading edge cusp energetic particle injections, it...
Using four months of tail data obtained by the three‐dimensional plasma instrument on board AMPTE/IRM satellite in 1986, we have done a statistical survey behavior ion moments and related parameters sheet boundary layer immediately adjacent outer central sheet. The more than 40,000 spin averages density, bulk velocity, temperature, temperature anisotropy β were analyzed with respect to differences between their values We also looked into dependence magnetic activity, possible interrelations...
Measurements of dc electric fields, field‐aligned currents, the plasma density, and wave fields density fluctuations have been made for first time at auroral zone altitudes between 1000 8000 km on S3‐3 satellite. The design operation various detectors that these measurements is described, some typical scientific results are presented. These include observations high altitude typically 5–50 particles/cm³, currents exceeding electrostatic ion cyclotron instability threshold often observed in...
Drift‐resonance wave‐particle interaction is a fundamental collisionless plasma process studied extensively in theory. Using cross‐spectral analysis of electric field, magnetic and ion flux data from the Van Allen Probe (Radiation Belt Storm Probes) spacecraft, we present direct evidence identifying generation mode standing poloidal wave through drift‐resonance interactions inner magnetosphere. Intense azimuthal field (E φ ) oscillations as large 10mV/m are observed, associated with radial...
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...