Found 9 entries in the Bibliography.

Showing entries from 1 through 9


Relation Between Shock-Related Impulse and Subsequent ULF Wave in the Earth s Magnetosphere

The generation of Pc4-5 ultralow frequency (ULF) waves after interplanetary shock-induced electric field impulses in the Earth s magnetosphere is studied using Van Allen Probes measurements by investigating the relationship between the first impulses and subsequent resonant ULF waves. In the dayside, the relevant time scales of the first impulse is correlated better with local Alfvén speed than with local eigenfrequency, implying that the temporal scale of the first impulse is more likely related to fast-mode wave propagati ...

Zhang, Dianjun; Liu, Wenlong; Li, Xinlin; Sarris, Theodore; Wang, Yongfu; Xiao, Chao; Zhang, Zhao; Wygant, John;

YEAR: 2020     DOI:

ULF wave; interplanetary shock; Magnetosphere; Field line resonance; electric field; wave excitation; Van Allen Probes

Simulations of Electron Flux Oscillations as Observed by MagEIS in Response to Broadband ULF Waves

Coherent electron flux oscillations of hundreds of keV are often observed by the Van Allen Probes in the magnetosphere during quiet times in association with ultralow frequency (ULF) waves. They are observed in the form of periodic flux fluctuations, with a drift frequency that is energy dependent, but are not associated with drift echoes following storm- or substorm-related energetic particle injections. Instead, they are associated with the resonant interaction of electrons with ULF waves and are an indication of ongoing e ...

Sarris, Theodore; Li, Xinlin; Temerin, Michael; Zhao, Hong; Khoo, Leng; Turner, Drew; Liu, Wenlong; Claudepierre, Seth;

YEAR: 2020     DOI:

electron flux oscillations; ULF waves; Magnetosphere; Radiation belts; radial diffusion; particle tracing simulations; Van Allen Probes


On the Initial Enhancement of Energetic Electrons and the Innermost Plasmapause Locations: CME-Driven Storm Periods

Using Van Allen Probes\textquoteright observations and established plasmapause location (Lpp) models, we investigate the relationship between the location of the initial enhancement (IE) of energetic electrons and the innermost (among all magnetic local time sectors) Lpp over five intense storm periods. Our study reveals that the IE events for 30 keV to 2MeV electrons always occurred outside of the innermost Lpp. On average, the inner extent of the IE events (LIE) for <800 keV electrons was closer to the innermost Lpp when c ...

Khoo, Leng; Li, Xinlin; Zhao, Hong; Sarris, Theodore; Xiang, Zheng; Zhang, Kun; Kellerman, Adam; Blake, Bernard;

YEAR: 2018     DOI: 10.1029/2018JA026074

energetic electron; enhancements; plasmasphere; Radiation belt; Van Allen Probes

Observations of impulsive electric fields induced by Interplanetary Shock

We investigate the characteristics of impulsive electric fields in Earth\textquoterights magnetosphere, as measured by the Van Allen Probes, in association with interplanetary shocks, as measured by ACE and Wind spacecraft in the solar wind from January 2013 to July 2016. It is shown that electric field impulses are mainly induced by global compressions by the shocks, mostly in the azimuthal direction and the amplitudes of the initial electric field impulses are positively correlated with the rate of increase of dynamic pres ...

Zhang, Dianjun; Liu, Wenlong; Li, Xinlin; Sarris, Theodore; Xiao, Chao; Wygant, J.;

YEAR: 2018     DOI: 10.1029/2018GL078809

electric field; inner magnetosphere; interplanetary shock; particle accelaration; Van Allen Probes


On the Relationship Between Electron Flux Oscillations and ULF Wave-Driven Radial Transport

The objective of this study is to investigate the relationship between the levels of electron flux oscillations and radial diffusion for different Phase Space Density (PSD) gradients, through observation and particle tracing simulations under the effect of model Ultra Low Frequency (ULF) fluctuations. This investigation aims to demonstrate that electron flux oscillation is associated with and could be used as an indicator of ongoing radial diffusion. To this direction, flux oscillations are observed through the Van Allen Pro ...

Sarris, Theodore; Li, Xinlin; Temerin, Michael; Zhao, Hong; Califf, Sam; Liu, Wenlong; Ergun, Robert;

YEAR: 2017     DOI: 10.1002/2016JA023741

Flux Oscillations; MAGEis; EMFISIS; EFW; Phase space density; radial diffusion; Radiation belts; Van Allen Probes

The role of the convection electric field in filling the slot region between the inner and outer radiation belts

The Van Allen Probes have reported frequent flux enhancements of 100s keV electrons in the slot region, with lower energy electrons exhibiting more dynamic behavior at lower L shells. Also, in situ electric field measurements from the Combined Release and Radiation Effects Satellite, Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Van Allen Probes have provided evidence for large-scale electric fields at low L shells during active times. We study an event on 19 February 2014 where hundre ...

Califf, S.; Li, X.; Zhao, H.; Kellerman, A.; Sarris, T.; Jaynes, A.; Malaspina, D.;

YEAR: 2017     DOI: 10.1002/2016JA023657

convection; electric field; electrons; Slot region; Van Allen Probes


Calculating ultra-low-frequency wave power of the compressional magnetic field vs. L and time: multi-spacecraft analysis using the Van Allen probes, THEMIS and GOES

Ultra-low-frequency (ULF) pulsations are critical in radial diffusion processes of energetic particles, and the power spectral density (PSD) of these fluctuations is an integral part of the radial diffusion coefficients and of assimilative models of the radiation belts. Using simultaneous measurements from two Geostationary Operational Environmental Satellites (GOES) geosynchronous satellites, three satellites of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft constellation and the ...

Sarris, Theodore; Li, Xinlin;

YEAR: 2016     DOI: 10.5194/angeo-34-565-2016

energetic particles trapped; magnetospheric configuration and dynamics; Magnetospheric physics; storms and substorms; Van Allen Probes


Estimates of the power per mode number of broadband ULF waves at geosynchronous orbit

In studies of radial diffusion processes in the magnetosphere it is well known that ultralow frequency (ULF) waves of frequency mωd can resonantly interact with particles of drift frequency ωd, where m is the waves\textquoteright azimuthal mode number. Due to difficulties in estimating m, an oversimplifying assumption is often made in simulations, namely that all ULF wave power is located at a single mode number. In this paper a technique is presented for extracting information on the distribution of ULF power in a range o ...

Sarris, T.;

YEAR: 2014     DOI: 10.1002/2013JA019238

Magnetosphere; mode number; radial diffusion; Radiation belts; ULF waves; ultralow frequency


Simulating radial diffusion of energetic (MeV) electrons through a model of fluctuating electric and magnetic fields

In the present work, a test particle simulation is performed in a model of analytic Ultra Low Frequency, ULF, perturbations in the electric and magnetic fields of the Earth\textquoterights magnetosphere. The goal of this work is to examine if the radial transport of energetic particles in quiet-time ULF magnetospheric perturbations of various azimuthal mode numbers can be described as a diffusive process and be approximated by theoretically derived radial diffusion coefficients. In the model realistic compressional electroma ...

Sarris, T.; Li, X.; Temerin, M.;

YEAR: 2006     DOI: 10.5194/angeo-24-2583-2006

Radial Transport