References of "Chua, D. H"
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See detailSeeing the corona with the solar probe plus mission: the wide-field imager for solar probe+ (WISPR)
Vourlidas, A.; Howard, R. A.; Plunkett, S. P. et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2013)

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See detailOn the Characteristics and Source Regions of Dayside Proton Precipitation
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

Conference (2004, December 01)

The source regions of precipitating protons on the dayside and their dependence on solar wind conditions are studied using far-ultraviolet (FUV) spectral observations and imaging. The High-resolution ... [more ▼]

The source regions of precipitating protons on the dayside and their dependence on solar wind conditions are studied using far-ultraviolet (FUV) spectral observations and imaging. The High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) observes Doppler-shifted H Lyman-α emissions from precipitating protons with a spectral resolution of 1.5 Angstroms. The shapes of these Doppler spectra are indicative of the energy and pitch angle distributions of the proton precipitation. Global images of H Lyman-α emissions obtained by the SI-12 instrument on the IMAGE spacecraft are examined to relate the spectral observations to the dayside morphology of the proton aurora. During periods of sustained southward interplanetary magnetic field (IMF), the dayside proton aurora spectra exhibit broad Doppler shifts and are similar to those observed on the nightside with inferred mean energies typical of plasma sheet protons of magnetospheric origin. Global images of proton aurorae under these conditions show continuous regions of H Lyman-α emissions across the dayside extending from the nightside. In contrast, during periods of northward or variable IMF, proton aurora emissions on the dayside often appear in an isolated spot in the noon to late afternoon MLT sector. The Doppler-spectra of the proton emissions in these regions are narrow, indicating precipitation with low mean energies and from a different origin than that observed in the southward IMF cases. These spectra may be indicative of magnetosheath protons that have direct access to the ionosphere through high-latitude dayside reconnection. This study further quantifies the characteristics of dayside proton precipitation under various states of the magnetosphere and highlights the importance of IMF orientation on the coupling between the high-latitude, dayside ionosphere and its plasma sources at higher altitudes. [less ▲]

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See detailHigh-Resolution Limb Observations of Proton Aurora
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

Conference (2003, December 01)

The interaction of precipitating protons in the upper atmosphere involves charge exchange, ionization, elastic and inelastic collisions, and the deposition of energy from the bottom of the F-region to the ... [more ▼]

The interaction of precipitating protons in the upper atmosphere involves charge exchange, ionization, elastic and inelastic collisions, and the deposition of energy from the bottom of the F-region to the D-region of the ionosphere. These processes and the transport of incident protons through this range of altitudes has been described through a variety of modeling techniques but there has been a dearth of altitude-resolved observations of proton precipitation with which to validate such models. We present new limb observations of Doppler-shifted Lyman-α proton aurora emissions obtained by the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) that fill this niche. HITS performs limb scans that include tangent altitudes between 90 km and 400 km with approximately 5 km vertical resolution. The Doppler shifts of the proton aurora Lyman-α emissions are measured with 1.5 Angstrom resolution and are used to infer mean energies of the incident protons as a function of altitude. Observed energy-range (dE/dz) relations are compared to those predicted by a Monte Carlo simulation of proton transport in the upper atmosphere. [less ▲]

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See detailHigh resolution FUV observations of proton aurora
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

in Geophysical Research Letters (2003), 30(18),

We present new FUV observations of Doppler-shifted Lyman-alpha emissions from proton aurora obtained from the High Resolution Ionospheric and Thermospheric Spectrograph ( HITS) aboard the Advanced ... [more ▼]

We present new FUV observations of Doppler-shifted Lyman-alpha emissions from proton aurora obtained from the High Resolution Ionospheric and Thermospheric Spectrograph ( HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS). The HITS instrument observes the Doppler-shifted H Lyman-alpha emissions from proton precipitation with 1.5 Angstrom resolution. The high spectral resolution of these measurements allows the auroral Lyman-alpha emissions to be separated from the intense geocoronal background. The measured proton aurora Doppler spectra are modeled using a Monte Carlo simulation of proton flux transport. The forward modeling performed with this code allows us to infer the characteristic energies of the incident protons from the measured Lyman-alpha Doppler spectra. The inferred characteristics of dayside versus nightside proton precipitation are compared and used to identify the magnetospheric regions from which the particles likely originated. [less ▲]

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See detailDoppler Profiles of Proton Auroral Emissions Derived From High Resolution FUV Spectra
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

Conference (2002, December 01)

In this paper we present new FUV observations of Doppler-shifted Lyman-ë± emissions from proton aurorae obtained from the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the ... [more ▼]

In this paper we present new FUV observations of Doppler-shifted Lyman-ë± emissions from proton aurorae obtained from the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS). The Doppler profiles of the Lyman-ë± auroral emissions serve as proxies for the energy spectra of precipitating protons in the ionosphere. These observations remedy two previous shortcomings in proton aurora studies. There have been few spectral measurements of Doppler-shifted H/H[SUP]+[/SUP] emission profiles with which to validate existing models of proton flux transport in the ionosphere. Even fewer are spectral measurements of this kind over large spatial scales that would extend our understanding of proton aurora to a global level. The HITS instrument observes the Doppler shifted H Lyman-ë± emissions from proton precipitation at 0.5 Ì· resolution over the width of the auroral oval traversed by the ARGOS spacecraft. The measured Doppler spectra of proton emissions are then modeled using a Monte Carlo simulation of proton flux transport. The model parameters which include the incoming proton energy, pitch angle, and energy flux distributions are adjusted until the predicted Lyman-ë± Doppler profiles match the observations. This technique allows us to quantify the evolution of proton precipitation during varying levels of auroral activity with both spectral information and large-scale spatial coverage. We present our analysis of proton auroral observations for an isolated substorm event as an example. [less ▲]

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