A5025956625- Ionosphere and magnetosphere dynamics
- Lightning and Electromagnetic Phenomena
- Earthquake Detection and Analysis
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Planetary Science and Exploration
- Electromagnetic Simulation and Numerical Methods
- GNSS positioning and interference
- Atmospheric aerosols and clouds
- Atmospheric Ozone and Climate
- Fire effects on ecosystems
- Seismic Waves and Analysis
- Meteorological Phenomena and Simulations
- Precipitation Measurement and Analysis
- Astrophysics and Cosmic Phenomena
- High voltage insulation and dielectric phenomena
- Spacecraft Design and Technology
- Polymer Science and PVC
- Geomagnetism and Paleomagnetism Studies
- Magneto-Optical Properties and Applications
- Geophysics and Sensor Technology
- Induction Heating and Inverter Technology
- Astronomical Observations and Instrumentation
- Ocular and Laser Science Research
- Plasma Diagnostics and Applications
University of Colorado Boulder
2015-2025
University of Colorado System
2011-2024
Stanford University
2007-2016
Vaughn College of Aeronautics and Technology
2014
American Institute of Aeronautics and Astronautics
2014
Boston University
2010-2011
Starlab (United States)
2005
Goodyear (United States)
1987-1998
Truman State University
1991
Extremely low frequency (ELF) and very (VLF) observations have formed the cornerstone of measurement interpretation effects lightning discharges on overlying upper atmospheric regions, as well near‐Earth space. ELF (0.3–3 kHz) VLF (3–30 wave energy released by is often agent modification lower ionospheric medium that results in conductivity changes excitation optical emissions constitute transient luminous events (TLEs). In addition, resultant are best (and uniquely) observable perturbations...
Abstract This article provides an overview of the experimental design, execution, education and public outreach, data collection, initial scientific results from Remote Sensing Electrification, Lightning, Mesoscale/Microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign. RELAMPAGO was a major campaign conducted in Córdoba Mendoza provinces Argentina western Rio Grande do Sul State Brazil 2018–19 that involved more than 200 scientists students United States,...
We present an improved time‐domain model of the lightning electromagnetic pulse (EMP) interaction with lower ionosphere. This inherently accounts for Earth's curvature, includes arbitrary number ion species, and uses a convolutional Perfectly Matched Layer (PML) boundary. apply electron heating due to EMP electrostatic fields, we include ionization, attachment, detachment. In addition modeling lightning, this can be used long‐distance VLF wave propagation in Earth‐ionosphere waveguide,...
The dual-wavelength Echidna lidar is a portable ground-based full-waveform terrestrial scanning for characterization of fine-scale forest structure and biomass content. While scanning, the instrument records full time series returns at half-nanosecond rate from two coaligned 5-ns pulsed lasers 1064 1548 nm wavelengths. Leaves absorb more strongly compared to stems, allowing discrimination composition milliradian scales ground canopy. This work describes design data products demonstrates...
The Earth's radiation belts are maintained by a number of acceleration, loss and transport mechanisms, the electron fluxes at any given time highly variable. Microbursts, which rapid (sub-second) bursts energetic electrons entering atmosphere from magnetosphere, one key mechanisms controlling belt fluxes. Such typically observed outer driven interactions with whistler mode chorus waves, but they can also occur in inner slot region, lightning-generated whistlers. This lightning-induced...
A 3‐D finite difference time domain model is used to simulate the lightning electromagnetic pulse (EMP) and its interaction with lower ionosphere. Results agree frequently observed, doughnut‐shaped optical signature of elves but show that structure exhibits asymmetry due presence Earth's ambient magnetic field. Furthermore, in‐cloud (horizontal) channels produce observable emissions without doughnut shape and, in fact, a much stronger output for same channel current. Electron density...
Accurate models of trans‐ionospheric propagation are needed to assess the role Earth‐originating very low frequency (VLF) electromagnetic waves in radiation belt dynamics. Recent studies have called relatively crude early into question, finding that they underestimate attenuation by 20–100 dB. A full wave model includes all relevant physics has recently become available and experimentally verified within a few decibels via comparison more extensive satellite data. Using this model, we...
The Dual-Wavelength Echidna® Lidar (DWEL), a ground-based, full-waveform lidar scanner designed for automated retrieval of forest structure, uses simultaneously-pulsing, 1064 nm and 1548 lasers to separate scattering by leaves from trunks, branches, ground materials. Leaf hits are separated others reduced response at due water absorption leaf cellular contents. By digitizing the full return-pulse waveform (full-width half maximum, 1.5 m) 7.5 cm intervals, can identify type event, as well...
Abstract We present a path forward on long-standing issue concerning the flux of small and slow meteoroids, which are believed to be dominant portion incoming meteoric mass into Earth’s atmosphere. Such flux, is predicted by dynamical dust models Zodiacal Cloud, not evident in ground-based radar observations. For decades this was attributed fact that radars used for meteor observations lack sensitivity detect population, due amount ionization produced slow-velocity meteors. hypothesis has...
Abstract Precipitation of energetic particles into the Earth's atmosphere can significantly change properties, dynamics, as well chemical composition upper and middle atmosphere. In this paper, using Monte Carlo models, we simulate, from first principles, interaction monoenergetic beams precipitating electrons with atmosphere, particular emphasis on process bremsstrahlung radiation its resultant ionization production atmospheric effects. The pitch angle dependence rate profile has been...
Abstract Quantifying radiation belt precipitation and its consequent atmospheric effects requires an accurate assessment of the pitch angle distribution precipitating electrons, as well knowledge dependence deposition on that distribution. Here Monte Carlo simulations are used to investigate incident electron energy for bounce period time scales, implications both loss from belts in upper atmosphere. Simulations conducted at discrete energies angles assess these parameters profiles estimate...
Abstract Accurate specification of ionization production by energetic electron precipitation is critical for atmospheric chemistry models to assess the resultant effects. Recent model‐observation comparison studies have increasingly highlighted importance considering fluxes in full range energy and pitch angle. However, previous parameterization methods were mostly proposed isotropically electrons with energies up 1 MeV, angle dependence has not yet been parameterized. In this paper, we...
Abstract In this concept study, we explore coded aperture imaging as a high‐angular resolution technique for suprathermal electron strahl observations in the solar wind. particular, studying relative contribution of pitch‐angle scattering to wind broadening near 1 AU requires very high‐resolution pitch angle. Coded is advantageous because it high‐signal method that can provide from simple, and compact platform. present an initial design achieve 40 field‐of‐view with 3.1 angular CubeSat‐sized...
Abstract Very Low Frequency (VLF, 3–30 kHz) waves propagate long distances in the waveguide formed by Earth and lower ionosphere. External sources such as solar flares lightning discharges perturb upper boundary thereby modify propagating within it. Therefore, studying propagation of VLF enables us to probe ionospheric response external forcing. However, wave also depends on property, that is, path conductivity. We tackle two main questions: how accurate should conductivity description be...
Observations on the night of 21 July 2003 ionospheric effects a thunderstorm in central France are reported. From 0200 to 0315 UT, camera system Pyrenees Mountains captured 28 sprites, triggered by +CG lightning as observed French METEORAGE detection system. A narrowband VLF receiver located Crete, at ∼2200 km southeast storm, subionospheric signals from six ground‐based transmitters. The amplitude one signals, originating transmitter ∼150 west storm and passing through region, exhibited...
Abstract We present evidence of ionospheric optical signatures lightning, known as elves, which sometimes occur in pairs separated time by ∼80–160 μs. demonstrate that these “elve doublets” are the signature compact intracloud discharges (CIDs), extremely powerful, thought to near tops thunderclouds. In this paper, using simple geometric calculations and full electromagnetic simulations, we show CIDs from altitudes 14–22 km explain delay observed elve doublets, consistent with typical CID...
Simulations of Very-low-frequency (VLF) transmitter signals are conducted using three models: the long-wave propagation capability, a finite-difference (FD) time-domain model, and an FD frequency-domain model. The models corrected Richardson extrapolation to minimize numerical dispersion inherent in these models. Using identical ionosphere ground parameters, shown agree very well their simulated VLF signal amplitude phase, within 1 dB few degrees for number different simulation paths...
Analysis of subionospheric VLF transmissions, observed in relation with sprites, has led to the identification a new category perturbations caused by direct effects tropospheric lightning on overlying lower ionosphere. They constitute large subset so‐called “early/fast” events where now term “fast,” which implies rapid onset durations less than ∼20 ms, does not apply. In contrast early/fast, have gradual growth and thus “slow” ranging from about 0.5 2.5 s; these are labeled herein as...
We propose a new mechanism for lightning‐induced perturbations to VLF transmitter signals known as Early events. This involves electron density changes due electromagnetic pulses (EMP) from successive in‐cloud lightning discharges associated with cloud‐to‐ground (CGs), which are likely the source of continuing current and much charge moment change in CGs. Through time‐domain modeling EMP we show that sequence can produce appreciable lower ionosphere, these primarily losses through...