A5038250086- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Earthquake Detection and Analysis
- Astro and Planetary Science
- Dust and Plasma Wave Phenomena
- Magnetic confinement fusion research
- GNSS positioning and interference
- Seismic Waves and Analysis
- Lightning and Electromagnetic Phenomena
- Laser-induced spectroscopy and plasma
- Underwater Acoustics Research
- Plasma Diagnostics and Applications
- Planetary Science and Exploration
- Atomic and Subatomic Physics Research
- Tropical and Extratropical Cyclones Research
- Space Satellite Systems and Control
- Geophysics and Sensor Technology
- Acoustic Wave Phenomena Research
- Astrophysics and Cosmic Phenomena
- Spacecraft and Cryogenic Technologies
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Magnetic Field Sensors Techniques
- Aerodynamics and Acoustics in Jet Flows
University of Iowa
2012-2022
Ames National Laboratory
2004
Cornell University
2001
Starmet Corporation (United States)
1960
We discuss chorus emissions measured by the four Cluster spacecraft at close separations during a geomagnetically disturbed period on 18 April 2002. analyze lower band of below one half electron cyclotron frequency, radial distance 4.4 Earth's radii, within 2000 km long source region located to equator. The characteristic wave vector directions in this are nearly parallel field lines and multipoint measurement demonstrates dynamic character region, changing Poynting flux direction time...
The POLAR plasma wave instrument often detects coherent electric field structures in the high altitude polar magnetosphere. appear to be positively charged potentials which are found move both up and down ambient magnetic field. Typical estimated velocities parallel scale sizes order of 1000 km/s 100–1000 meters, respectively. We have observed at radial distances 2.02 8.5 Re L shells 6 − 12+, although they likely occur over a broader range space than suggested by this initial study....
Whistler mode chorus has been shown to play a role in the process of local acceleration electrons outer Van Allen radiation belt. Most quasi‐linear and nonlinear theoretical studies assume that waves propagate parallel terrestrial magnetic field. We show case where this assumption is invalid. use data from Cluster spacecraft characterize propagation spectral properties chorus. The recorded high‐resolution waveforms source region can be formed by succession discrete wave packets with...
The Cluster spacecraft were favorably positioned on the nightside near equatorial plasmapause of Earth at L ∼ 4.3 30 March 2002 to observe electromagnetic ion cyclotron (EMIC) rising tone emissions in association with Pc1 waves 1.5 Hz. EMIC found be left‐hand, circularly polarized, dispersive, and propagating away from equator. Their burstiness dispersion ∼30s/Hz out Hz are consistent their identification as triggered chorus emissions, first reported through situ observations plasmapause....
The Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) on board the Polar spacecraft observed 75 energetic particle events in 1996 while satellite was at apogee. All of these were associated with a decrease magnitude local magnetic field measured by Magnetic Field (MFE) Polar. These new showed several unusual features: (1) They detected dayside polar cusp near apogee about 79% total afternoonside 21% morningside; (2) an individual event could last for hours; (3) helium ion...
We investigate intense whistler‐mode chorus emissions which occurred during the geomagnetic storm on 31 March 2001. use multipoint measurements obtained by Cluster spacecraft in premidnight equatorial region outside plasmasphere at a radial distance of 4 Earth radii ( L = 4.0 − 4.2). Observed spatio‐temporal variations direction Poynting flux manifest consistent pattern: central position source fluctuates time scales minutes within 1000–2000 km equator. demonstrate that estimates...
We report a multipoint case study of the electromagnetic equatorial noise observed by Cluster project. High‐resolution data were measured in three close points space located morning sector outer plasmasphere. demonstrate narrow latitudinal extent emissions with typical width 2°, centered near minimum‐B equator. Power spectra recorded different satellites show complex structure emission lines whose relative intensities and positions vary at timescales 1–2 min and/or spatial scales tens...
Abstract. Isolated electrostatic structures are observed throughout much of the 4RE by 19.6RE Cluster orbit. These in Wideband plasma wave instrument's waveform data as bipolar pulses (one positive and one negative peak electric field amplitude) tripolar (two peak, or vice versa). at all boundary layers, solar wind magnetosheath, along auroral lines 4.5-6.5RE. Using from various spacecraft we have carried out a survey amplitudes time durations these how quantities vary with local magnetic...
We develop a nonlinear wave growth theory of electromagnetic ion cyclotron (EMIC) triggered emissions observed in the inner magnetosphere. first derive basic equations from Maxwell's and momentum for electrons ions. then obtain that describe dynamics resonant protons interacting with an EMIC wave. The frequency sweep rate plays important role forming current controls growth. Assuming optimum condition maximum as absolute instability at magnetic equator self‐sustaining propagating equator, we...
We interpret observations of low‐altitude electromagnetic ELF hiss observed on the dayside at subauroral latitudes. A divergent propagation pattern has been reported between 50° and 75° geomagnetic latitude. The waves propagate with downward directed wave vectors which are slightly equatorward inclined lower magnetic latitudes poleward higher Reverse ray tracing using different plasma density models indicates a possible source region near equator radial distance 5 7 Earth radii by mechanism...
We present a survey of whistler mode chorus emissions based on high‐telemetry rate data the Plasma Wave Instrument board Polar spacecraft. Using simultaneous measurements full vectors electric field and magnetic we calculate Poynting chorus, parameterize observations by their L * coordinate. Our new analysis angle between direction vector line confirms previous results propagation main band away from equator. systematic also prove existence magnetospherically reflected component found...
Abstract A Polar magnetosonic wave (MSW) study was conducted using 1 year of 1996–1997 data (during solar minimum). Waves at and inside the plasmasphere were detected all local times with a slight preference for occurrence in midnight‐postmidnight sector. Wave (and intensities) peaked within~±5° magnetic equator, half maxima ~±10°. However, MSWs also as far from equator +20° 60° MLAT but lower intensities. An extreme MSW intensity event amplitude B w = ~± nT E 25 mV/m detected. This occurred...
Abstract In the region between L = 2 to 7 at all Magnetic Local Time (MLTs) plasmaspheric hiss was detected 32% of time. limited 3 6 and 15 21 MLT (dusk sector), wave percentage detection highest (51%). The latter is most likely due energetic ~10–100 keV electrons drifting into dusk bulge region. On average, intensities are an order magnitude larger on dayside than nightside. Plasmaspheric considerably more intense coherent during high‐solar wind ram pressure intervals. A hypothesis for this...
We report four different types of plasma waves detected in and near the dayside polar cap boundary layer (PCBL) region at high altitudes (>6 R E ). One wave type is narrowband whistler‐mode emission frequencies just below f ce (5.5 kHz). These emissions could be locally generated by resonant wave‐particle interactions involving an electron beam ∼100 eV energy. A second a low frequency (200–300 Hz) whistler mode wave, which may ∼25 keV electrons or ∼45 ions. It also possible that these...
Abstract. Bipolar pulses of ~ 25-100 µs in duration have been observed the wave electric field data obtained by Wideband plasma instrument on Cluster spacecraft dayside magnetosheath. These are similar almost all respects to those several over last few years. They represent solitary potential structures, and this case, electron phase space holes. When time series containing bipolar transformed frequency domain a windowed FFT, appear as typical broad-band features, extending from...
Abstract. We report on recent measurements of solitary waves made by the Wideband Plasma Wave Receiver located each four Cluster spacecraft at 4.5-6.5RE (well above auroral acceleration region) as they cross field lines that map to zones. These are observed in data isolated bipolar and tripolar waveforms. Examples two types pulses provided. The time durations majority both this region range from about 0.3 up 5ms. Their peak-to-peak amplitudes 0.05 20mV/m, with a few reaching almost 70mV/m....
We study in detail high‐frequency (HF) plasma waves between the electron cyclotron and frequencies within a reconnection diffusion region (DR) encountered by Cluster magnetotail using continuous electric field waveforms. identify three wave types, all observed separatrix regions: Langmuir (LW), electrostatic solitary (ESWs), (ECWs). This is first time ECWs have been inside this region. Direct comparison waveforms distributions are made at timescale of one energy sweep detector (125 ms)....
Abstract. In this case study we investigate the source region of whistler-mode chorus located close to geomagnetic equator at a radial distance 4.4 Earth radii. We use measurements from four Cluster spacecraft separations less than few hundreds km, recorded during storm 18 April 2002. The waveforms electric field fluctuations were obtained by WBD instruments in frequency range 50Hz-9.5kHz. Using these data, calculate linear and rank correlation coefficients averaged power-spectral density...
We report observations of waves near the local proton cyclotron frequency and its lowest harmonics, made by Plasma Wave Instrument on board Polar spacecraft, orbits for which perigee (at an altitude 1 Earth radius) was in or southern auroral zone. The electromagnetic nature these revealed measuring their magnetic components simultaneously with two independent antenna systems, one a single loop other set triaxial search coils. Waves this kind were found zone about third examined. Peaks field...
Abstract. Through case studies involving Cluster waveform observations, solitary waves in the form of bipolar and tripolar pulses have recently been found to be quite abundant near-Earth dayside magnetosheath. We expand on results those previous by examining distribution from bow shock magnetopause using data. Cluster's orbit allows for measurement magnetosheath about 10 RE 19.5 RE. Our clearly show that within magnetosheath, are likely observed at any distance this has no dependence time...
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