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Dennis J. Chornay

Bio: Dennis J. Chornay is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Solar wind & Magnetosphere. The author has an hindex of 19, co-authored 56 publications receiving 3194 citations. Previous affiliations of Dennis J. Chornay include University of Maryland, College Park.


Papers
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Journal ArticleDOI
TL;DR: The solar wind experiment (SWE) on the WIND spacecraft is a comprehensive, integrated set of sensors which is designed to investigate outstanding problems in solar wind physics as discussed by the authors, which consists of two Faraday cup (FC) sensors; a vector electron and ion spectrometer (VEIS); a strahl sensor, which is especially configured to study the electron ‘strahl’ close to the magnetic field direction; and an on-board calibration system.
Abstract: The Solar Wind Experiment (SWE) on the WIND spacecraft is a comprehensive, integrated set of sensors which is designed to investigate outstanding problems in solar wind physics. It consists of two Faraday cup (FC) sensors; a vector electron and ion spectrometer (VEIS); a strahl sensor, which is especially configured to study the electron ‘strahl’ close to the magnetic field direction; and an on-board calibration system. The energy/charge range of the Faraday cups is 150 V to 8 kV, and that of the VEIS is 7 V to 24.8 kV. The time resolution depends on the operational mode used, but can be of the order of a few seconds for 3-D measurements. ‘Key parameters’ which broadly characterize the solar wind positive ion velocity distribution function will be made available rapidly from the GGS Central Data Handling Facility.

1,206 citations

Journal ArticleDOI
Craig J. Pollock1, T. E. Moore1, A. D. Jacques1, James L. Burch2, U. Gliese1, Yoshifumi Saito, T. Omoto, Levon A. Avanov3, Levon A. Avanov1, A. C. Barrie1, Victoria N. Coffey4, John C. Dorelli1, Daniel J. Gershman3, Daniel J. Gershman5, Daniel J. Gershman1, Barbara L. Giles1, T. Rosnack1, C. Salo1, Shoichiro Yokota, M. L. Adrian1, C. Aoustin, C. Auletti1, S. Aung1, V. Bigio1, N. Cao1, Michael O. Chandler4, Dennis J. Chornay3, Dennis J. Chornay1, K. Christian1, George Clark6, George Clark1, George Clark7, Glyn Collinson7, Glyn Collinson1, T. Corris1, A. De Los Santos2, R. Devlin1, T. Diaz2, T. Dickerson1, C. Dickson1, A. Diekmann4, F. Diggs1, C. Duncan1, A. Figueroa-Vinas1, C. Firman1, M. Freeman2, N. Galassi1, K. Garcia1, G. Goodhart2, D. Guererro2, J. Hageman1, Jennifer Hanley2, E. Hemminger1, Matthew Holland1, M. Hutchins2, T. James1, W. Jones1, S. Kreisler1, Joseph Kujawski1, Joseph Kujawski8, V. Lavu1, J. V. Lobell1, E. LeCompte, A. Lukemire, Elizabeth MacDonald1, Al. Mariano1, Toshifumi Mukai, K. Narayanan1, Q. Nguyan1, M. Onizuka1, William R. Paterson1, S. Persyn2, Benjamin M. Piepgrass2, F. Cheney1, A. C. Rager1, A. C. Rager7, T. Raghuram1, A. Ramil1, L. S. Reichenthal1, H. Rodriguez2, Jean-Noël Rouzaud, A. Rucker1, Marilia Samara1, Jean-André Sauvaud, D. Schuster1, M. Shappirio1, K. Shelton1, D. Sher1, David Smith1, Kerrington D. Smith2, S. E. Smith7, S. E. Smith1, D. Steinfeld1, R. Szymkiewicz1, K. Tanimoto, J. Taylor2, Compton J. Tucker1, K. Tull1, A. Uhl1, J. Vloet2, P. Walpole1, P. Walpole2, S. Weidner2, D. White2, G. E. Winkert1, P.-S. Yeh1, M. Zeuch1 
TL;DR: The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics as mentioned in this paper.
Abstract: The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory’s Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.

1,038 citations

Journal ArticleDOI
TL;DR: HYDRA is an experimental hot plasma investigation for the POLAR spacecraft of the GGS program as discussed by the authors, with a suite of particle analyzers that sample the velocity space of electron and ions between 2 keV/q and 35 keV /q in three dimensions, with a routine time resolution of 05 s.
Abstract: HYDRA is an experimental hot plasma investigation for the POLAR spacecraft of the GGS program A consortium of institutions has designed a suite of particle analyzers that sample the velocity space of electron and ions between ≃2 keV/q – 35 keV/q in three dimensions, with a routine time resolution of 05 s Routine coverage of velocity space will be accomplished with an angular homogeneity assumption of ≃16°, appropriate for subsonic plasmas, but with special ≃15° resolution for electrons with energies between 100 eV and 10 keV along and opposed to the local magnetic field This instrument produces 49 kilobits s−1 to the telemetry, consumes on average 14 W and requires 187 kg for deployment including its internal shielding The scientific objectives for the polar magnetosphere fall into four broad categories: (1) those to define the ambient kinetic regimes of ions and electrons; (2) those to elucidate the magnetohydrodynamic responses in these regimes; (3) those to assess the particle populations with high time resolution; and (4) those to determine the global topology of the magnetic field In thefirst group are issues of identifying the origins of particles at high magnetic latitudes, their energization, the altitude dependence of the forces, including parallel electric fields they have traversed In thesecond group are the physics of the fluid flows, regimes of current, and plasma depletion zones during quiescent and disturbed magnetic conditions In thethird group is the exploration of the processes that accompany the rapid time variations known to occur in the auroral zone, cusp and entry layers as they affect the flow of mass, momentum and energy in the auroral region In thefourth class of objectives are studies in conjunction with the SWE measurements of the Strahl in the solar wind that exploit the small gyroradius of thermal electrons to detect those magnetic field lines that penetrate the auroral region that are directly ‘open’ to interplanetary space where, for example, the Polar Rain is observed

205 citations

Journal ArticleDOI
TL;DR: The IBEX-Lo sensor as discussed by the authors is a large geometric factor single pixel camera that maximizes the relatively weak heliospheric neutral signal while effectively eliminating ion, electron, and UV background sources.
Abstract: The IBEX-Lo sensor covers the low-energy heliospheric neutral atom spectrum from 0.01 to 2 keV. It shares significant energy overlap and an overall design philosophy with the IBEX-Hi sensor. Both sensors are large geometric factor, single pixel cameras that maximize the relatively weak heliospheric neutral signal while effectively eliminating ion, electron, and UV background sources. The IBEX-Lo sensor is divided into four major subsystems. The entrance subsystem includes an annular collimator that collimates neutrals to approximately 7°×7° in three 90° sectors and approximately 3.5°×3.5° in the fourth 90° sector (called the high angular resolution sector). A fraction of the interstellar neutrals and heliospheric neutrals that pass through the collimator are converted to negative ions in the ENA to ion conversion subsystem. The neutrals are converted on a high yield, inert, diamond-like carbon conversion surface. Negative ions from the conversion surface are accelerated into an electrostatic analyzer (ESA), which sets the energy passband for the sensor. Finally, negative ions exit the ESA, are post-accelerated to 16 kV, and then are analyzed in a time-of-flight (TOF) mass spectrometer. This triple-coincidence, TOF subsystem effectively rejects random background while maintaining high detection efficiency for negative ions. Mass analysis distinguishes heliospheric hydrogen from interstellar helium and oxygen. In normal sensor operations, eight energy steps are sampled on a 2-spin per energy step cadence so that the full energy range is covered in 16 spacecraft spins. Each year in the spring and fall, the sensor is operated in a special interstellar oxygen and helium mode during part of the spacecraft spin. In the spring, this mode includes electrostatic shutoff of the low resolution (7°×7°) quadrants of the collimator so that the interstellar neutrals are detected with 3.5°×3.5° angular resolution. These high angular resolution data are combined with star positions determined from a dedicated star sensor to measure the relative flow difference between filtered and unfiltered interstellar oxygen. At the end of 6 months of operation, full sky maps of heliospheric neutral hydrogen from 0.01 to 2 keV in 8 energy steps are accumulated. These data, similar sky maps from IBEX-Hi, and the first observations of interstellar neutral oxygen will answer the four key science questions of the IBEX mission.

195 citations

Journal ArticleDOI
TL;DR: In this paper, Sittler et al. showed that water molecules are the dominant source of ions within the inner magnetosphere of Saturn's magnetosphere, and they used the radio and plasma wave science (RPWS) electron density observations from previous publications to indirectly confirm usage of the above temperature anisotropies for water group ions and protons.

140 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors analyzed hourly averaged interplanetary magnetic field (IMF) and plasma data from the Advanced Composition Explorer (ACE) and Wind spacecraft, generated from 1 to 4 min resolution data time-shifted to Earth.
Abstract: [1] Hourly averaged interplanetary magnetic field (IMF) and plasma data from the Advanced Composition Explorer (ACE) and Wind spacecraft, generated from 1 to 4 min resolution data time-shifted to Earth have been analyzed for systematic and random differences. ACE moments-based proton densities are larger than Wind/Solar Wind Experiment (SWE) fits-based densities by up to 18%, depending on solar wind speed. ACE temperatures are less than Wind/SWE temperatures by up to ∼25%. ACE densities and temperatures were normalized to equivalent Wind values in National Space Science Data Center's creation of the OMNI 2 data set that contains 1963–2004 solar wind field and plasma data and other data. For times of ACE-Wind transverse separations <60 RE, random differences between Wind values and normalized ACE values are ∼0.2 nT for ∣B∣, ∼0.45 nT for IMF Cartesian components, ∼5 km/s for flow speed, and ∼15 and ∼30% for proton densities and temperatures. These differences grow as a function of transverse separation more rapidly for IMF parameters than for plasma parameters. Autocorrelation analyses show that spatial scales become progressively shorter for the parameter sequence: flow speed, IMF magnitude, plasma density and temperature, IMF X and Y components, and IMF Z component. IMF variations have shorter scales at solar quiet times than at solar active times, while plasma variations show no equivalent solar cycle dependence.

1,062 citations

Journal ArticleDOI
Craig J. Pollock1, T. E. Moore1, A. D. Jacques1, James L. Burch2, U. Gliese1, Yoshifumi Saito, T. Omoto, Levon A. Avanov1, Levon A. Avanov3, A. C. Barrie1, Victoria N. Coffey4, John C. Dorelli1, Daniel J. Gershman5, Daniel J. Gershman3, Daniel J. Gershman1, Barbara L. Giles1, T. Rosnack1, C. Salo1, Shoichiro Yokota, M. L. Adrian1, C. Aoustin, C. Auletti1, S. Aung1, V. Bigio1, N. Cao1, Michael O. Chandler4, Dennis J. Chornay3, Dennis J. Chornay1, K. Christian1, George Clark6, George Clark1, George Clark7, Glyn Collinson1, Glyn Collinson6, T. Corris1, A. De Los Santos2, R. Devlin1, T. Diaz2, T. Dickerson1, C. Dickson1, A. Diekmann4, F. Diggs1, C. Duncan1, A. Figueroa-Vinas1, C. Firman1, M. Freeman2, N. Galassi1, K. Garcia1, G. Goodhart2, D. Guererro2, J. Hageman1, Jennifer Hanley2, E. Hemminger1, Matthew Holland1, M. Hutchins2, T. James1, W. Jones1, S. Kreisler1, Joseph Kujawski1, Joseph Kujawski8, V. Lavu1, J. V. Lobell1, E. LeCompte, A. Lukemire, Elizabeth MacDonald1, Al. Mariano1, Toshifumi Mukai, K. Narayanan1, Q. Nguyan1, M. Onizuka1, William R. Paterson1, S. Persyn2, Benjamin M. Piepgrass2, F. Cheney1, A. C. Rager1, A. C. Rager6, T. Raghuram1, A. Ramil1, L. S. Reichenthal1, H. Rodriguez2, Jean-Noël Rouzaud, A. Rucker1, Marilia Samara1, Jean-André Sauvaud, D. Schuster1, M. Shappirio1, K. Shelton1, D. Sher1, David Smith1, Kerrington D. Smith2, S. E. Smith6, S. E. Smith1, D. Steinfeld1, R. Szymkiewicz1, K. Tanimoto, J. Taylor2, Compton J. Tucker1, K. Tull1, A. Uhl1, J. Vloet2, P. Walpole2, P. Walpole1, S. Weidner2, D. White2, G. E. Winkert1, P.-S. Yeh1, M. Zeuch1 
TL;DR: The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics as mentioned in this paper.
Abstract: The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory’s Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.

1,038 citations

Journal ArticleDOI
TL;DR: The THEMIS instrument as discussed by the authors is designed to measure the ion and electron distribution functions over the energy range from a few eV up to 30 keV for electrons and 25 kV for ions, and it consists of a pair of electrostatic analyzers with common 180°×6° fields-of-view that sweep out 4π steradians each 3 s spin period.
Abstract: The THEMIS plasma instrument is designed to measure the ion and electron distribution functions over the energy range from a few eV up to 30 keV for electrons and 25 keV for ions. The instrument consists of a pair of “top hat” electrostatic analyzers with common 180°×6° fields-of-view that sweep out 4π steradians each 3 s spin period. Particles are detected by microchannel plate detectors and binned into six distributions whose energy, angle, and time resolution depend upon instrument mode. On-board moments are calculated, and processing includes corrections for spacecraft potential. This paper focuses on the ground and in-flight calibrations of the 10 sensors on five spacecraft. Cross-calibrations were facilitated by having all the plasma measurements available with the same resolution and format, along with spacecraft potential and magnetic field measurements in the same data set. Lessons learned from this effort should be useful for future multi-satellite missions.

1,031 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined wind observations of inertial and dissipation range spectra in an attempt to better understand the processes that form the dissipation ranges and how these processes depend on the ambient solar wind parameters (interplanetary magnetic field intensity, ambient proton density and temperature, etc.).
Abstract: The dissipation range for interplanetary magnetic field fluctuations is formed by those fluctuations with spatial scales comparable to the gyroradius or ion inertial length of a thermal ion. It is reasonable to assume that the dissipation range represents the final fate of magnetic energy that is transferred from the largest spatial scales via nonlinear processes until kinetic coupling with the background plasma removes the energy from the spectrum and heats the background distribution. Typically, the dissipation range at 1 AU sets in at spacecraft frame frequencies of a few tenths of a hertz. It is characterized by a steepening of the power spectrum and often demonstrates a bias of the polarization or magnetic helicity spectrum. We examine Wind observations of inertial and dissipation range spectra in an attempt to better understand the processes that form the dissipation range and how these processes depend on the ambient solar wind parameters (interplanetary magnetic field intensity, ambient proton density and temperature, etc.). We focus on stationary intervals with well-defined inertial and dissipation range spectra. Our analysis shows that parallel-propagating waves, such as Alfven waves, are inconsistent with the data. MHD turbulence consisting of a partly slab and partly two-dimensional (2-D) composite geometry is consistent with the observations, while thermal paxticle interactions with the 2-D component may be responsible for the formation of the dissipation range. Kinetic Alfven waves propagating at large angles to the background magnetic field are also consistent with the observations and may form some portion of the 2-D turbulence component.

747 citations

Journal ArticleDOI
03 Jun 2016-Science
TL;DR: For example, NASA's magnetospheric multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field as discussed by the authors.
Abstract: Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region

579 citations