A5033059935- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Earthquake Detection and Analysis
- Geomagnetism and Paleomagnetism Studies
- GNSS positioning and interference
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Magnetic confinement fusion research
- Geophysics and Gravity Measurements
- Laser-induced spectroscopy and plasma
- Oceanographic and Atmospheric Processes
- Planetary Science and Exploration
- Seismic Waves and Analysis
- Plasma Diagnostics and Applications
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Geophysical and Geoelectrical Methods
- Astronomy and Astrophysical Research
- Impact of Light on Environment and Health
- Magnetic Field Sensors Techniques
- Methane Hydrates and Related Phenomena
- Lightning and Electromagnetic Phenomena
- Geophysics and Sensor Technology
- Radiation Detection and Scintillator Technologies
- Electrostatic Discharge in Electronics
Boston University
2016-2025
The University of Texas at Dallas
2024
University of California, Los Angeles
2012-2021
University Corporation for Atmospheric Research
2018
NOAA Oceanic and Atmospheric Research
2013-2016
Nagoya University
2009-2012
Tohoku University
2005-2010
Institute of Space Science - INFLPR Subsidiary
2003-2004
Max Planck Institute for Plasma Physics
2003
Max Planck Society
2002
Pulsating aurora, a spectacular emission that appears as blinking of the upper atmosphere in polar regions, is known to be excited by modulated, downward-streaming electrons. Despite its distinctive feature, identifying driver electron precipitation has been long-standing problem. Using coordinated satellite and ground-based all-sky imager observations from THEMIS mission, we provide direct evidence naturally occurring electromagnetic wave, lower-band chorus, can drive pulsating aurora....
A critical, long‐standing problem in substorm research is identification of the sequence events leading to auroral onset. Based on event and statistical analysis THEMIS all‐sky imager data, we show that there a distinct repeatable onset, having similarities important differences from previous ideas. The initiated by poleward boundary intensification (PBI) followed north‐south (N‐S) arc moving equatorward toward onset latitude. Because linkage fast magnetotail flows PBIs N‐S auroras, results...
Abstract Plasmaspheric hiss is known to play an important role in controlling the overall structure and dynamics of radiation belt electrons inside plasmasphere. Using newly available Van Allen Probes wave data, which provide excellent coverage entire inner magnetosphere, we evaluate global distribution frequency spectrum intensity for different levels substorm activity. Our statistical results show that observed peak frequencies are generally lower than commonly adopted value (~550 Hz), was...
A glowing ribbon of purple light running east-west in the night sky has recently been observed by citizen scientists. This narrow, subauroral, visible structure, distinct from traditional auroral oval, was largely undocumented scientific literature and little known about its formation. Amateur photo sequences showed colors distinctly different common types aurora occasionally indicated magnetic field-aligned substructures. Observations Swarm satellite as it crossed arc have revealed an...
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 statistical survey of plasma densities and electron distributions (0.5–100 keV) is performed using data obtained from the Time History Events Macroscale Interactions During Substorms spacecraft in near‐equatorial orbits 1 July 2007 to May 2009 order investigate optimum conditions for whistler mode chorus excitation. The density calculated potential, together with situ magnetic field, used construct global maps cyclotron Landau resonant energies under quiet, moderate, active geomagnetic...
Statistical results on the global distribution of suprathermal electron (0.1–10 keV) fluxes are shown both outside and inside plasmasphere separately, using data from THEMIS. Significant found within plasmasphere, although they nevertheless smaller than populations plasmasphere. Electron plasmapause increase with stronger magnetic activity nightside decrease as a function increasing local time (MLT). Inside just plasmapause, particularly midnight to dawn sector during active times, while...
[1] Chorus waves, which have received intense attention recently due to their significant role in radiation belt electron dynamics, frequently exhibit rising and falling tones. Lower-band chorus observed using THEMIS wave burst data, are analyzed obtain the typical properties of either class emissions. Our results show that tones more likely be quasi field-aligned, whereas typically very oblique, close resonance cone. Furthermore, occur significantly often than tones, magnetic amplitudes...
The characteristics of the Poynting flux and wave normal vectors whistler‐mode waves outside plasmapause are investigated for lower (0.1–0.5 f ce ) upper bands (0.5–0.8 ), where is equatorial electron cyclotron frequency. To analyze properties, we utilized high‐resolution waveform data from multiple THEMIS spacecraft in near‐equatorial magnetosphere June 2008 to November 2012. Full measurements electric magnetic fields used calculate fluxes construct vectors, which then polar azimuthal...
Abstract Interactions between the solar wind and Earth's magnetosphere manifest many important space weather phenomena. In this paper, magnetosphere‐ionosphere drivers of intense d B /d t produced during geomagnetic storms that occurred on 9 March 2012 17 2015 are analyzed. A multi‐instrument approach combining Time History Events Macroscale Substorms (THEMIS) mission space‐borne ground‐based observations was adopted to examine signatures associated with extremes each storm. To complement...
Abstract We present the first observations of ionospheric phenomena using newly deployed Transition Region Explorer (TREx) Spectrograph. On night 10 April 2018, STEVE (Strong Thermal Emission Velocity Enhancement) and Picket Fence optical structures were observed by spectrograph in Lucky Lake, Saskatchewan. contains an enhancement OI red‐line (630‐nm) emission a continuum which spans visible wavelengths. Based upon its spectrum, we assert that characteristic mauve color is result this...
This paper reviews key properties and major unsolved problems about Strong Thermal Emission Velocity Enhancement (STEVE) the picket fence. We first introduce basic characteristics of STEVE historical observations STEVE-like emissions, particularly case on 11 September 1891. Then, we discuss open questions STEVE: 1) Why does preferentially occur in equinoxes? 2) How do solar wind storm/substorm conditions control STEVE? 3) is rare, despite that not seem to require extreme driving conditions?...
[1] A multievent study was performed using conjugate measurements of the Time History Events and Macroscale Interactions during Substorms (THEMIS) spacecraft an all-sky imager periods intense lower-band chorus waves. The thirteen identified cases support our previous finding, based on two events, that intensity modulation near magnetic equator is highly correlated with quasiperiodic pulsating auroral emissions spacecraft's footprint, indicating driver aurora. Furthermore, we a fortuitous...
[1] Using observations from the THEMIS spacecraft, we investigate modulation of whistler mode chorus waves in magnetosphere by compressional Pc4–5 pulsations (i.e., with periods tens seconds to a few minutes) an anticorrelation between total electron density and background magnetic field intensity. We find that such are associated modulations resonant fluxes Changes density, field, flux anisotropy electrons could all be responsible for triggering excitation waves. To quantitatively which...
We address the long‐standing problem of location and origin equatorwardmost Pre‐Breakup auroral Arc (PBA) by combining energetic particle observations from NOAA Polar Operational Environmental Satellites (POES) overpasses prebreakup arcs with imaging magnetospheric Time History Events Macroscale Interactions during Substorms (THEMIS) mission. The arc was observed within a few minutes breakup ∼1–2 hours in MLT meridian. For three ideal conjunctions out 16 PBA crossings, we also construct...
We present simultaneous measurements of dayside diffuse aurora and whistler‐mode waves made by the South Pole all‐sky imager two THEMIS spacecraft. found a high correlation between intensity at 557.7 nm near footprint latitudes wave measured on board. The power in other modes was negligibly small most cases, indicating that is driven precipitating energetic electrons resonating with waves. over wide L * range (6 < 11) further allowed us to magnetically link magnetospheric plasma...
Recent THEMIS spacecraft observations have shown longitudinally narrow, earthward moving, plasma sheet flow channels with large, abrupt magnetic field dipolarizations that been referred to as dipolarization fronts. We undertake a detailed study of the subset these events had good quality auroral imaging. find many occurred during substorm expansion phase after onset (determined by intensification) and were related streamers. Both fronts' relation streamers their changes are similar what has...
[1] Modulation of whistler mode chorus waves, which plays an important role in driving the pulsating aurora and other processes related to energetic electron dynamics, is interesting but a long-standing unresolved problem. Here we utilize situ observations from THEMIS spacecraft investigate density variations modulation wave amplitude, forms complementary study by compressional Pc4–5 pulsations presented companion paper. We show that these are correlated remarkably well with modulated...
[1] Recent ground-based imager observations have provided evidence of precursor auroral activity leading to substorm onset, where the is initiated by a poleward boundary intensification (PBI) followed an streamer moving equatorward toward onset latitude onset. However, since many streamers do not lead substorms, question arises as what conditions are required for Using 382 events detected THEMIS all-sky imagers during 2007–2009, we examined properties latitudinally thin, quiet arcs that...
During times of enhanced magnetospheric convection, cold dense plasma from the plasmasphere can form a plume extending sunward toward dayside magnetopause. A statistical study is presented high‐density plasmaspheric at Observations Time History Events and Macroscale Interactions (THEMIS) spacecraft show to be present magnetopause during 12.5 % (148 1184) crossings. Its most common location in magnetic local time when contacting 13.6 h. The crossings evidence for reconnection 68 events with...
This paper presents THEMIS measurements of two substorm events to show how the current wedge (SCW) is generated. In late growth phase when an earthward flow burst in near‐Earth magnetotail brakes and diverted azimuthally, pressure gradients X‐ Y‐directions are observed increase pileup diverting regions flow. The enhanced gradient Y‐direction dawnward (duskward) on dawnside (duskside) where a clockwise (counter‐clockwise) vortex forms. dawn‐dusk drives downward (upward) field‐aligned (FAC)...
Abstract Observational properties of throat aurora are investigated in detail by using 7 year continuous auroral observations obtained at Yellow River Station (magnetic latitude 76.24°N). From our inspection, is often observed under the condition stripy diffuse contacting with persistent discrete oval, and long‐period generally consist intermittent subsequences brightening followed poleward moving form dimming. We also noticed that orientation aligned along ionospheric convection flow, its...
Abstract We present multispacecraft observations of enhanced flow/electric field channels in the inner magnetosphere and conjugate subauroral ionosphere, i.e., polarization streams (SAPS) near dusk ion drifts (SAID) midnight. The collocate with ring current (RC) injections lagging onset substorms by a few to ∼20 min, significantly shorter than gradient‐curvature drift time tens keV ions. lag is order propagation reconnection‐injected hot plasma jets premidnight plasmasphere substorm wedge...