Engineering topics

Waite, J. Hunter, Jr.

Publications and source records attributed to Waite, J. Hunter, Jr..

18 records

NASA NTRS2007

First Terrestrial Soft X-Ray Auroral Observation by the Chandra X-Ray Observatory

Northern auroral regions of Earth were imaged with energetic photons in the 0.1-10keV range using the High-Resolution Camera (HRC-I) aboard the Chandra X-ray Observatory at 10 epochs (each approx.20 min duration) between mid- December 2003 and mid-April 2004. These observations aimed at searching for Earth's soft (< 2 keV) X-ray aurora in a comparative study with Jupiter's X-ray aurora, where a pulsating X-ray "hot-spot" has been previously observed by Chandra. The first Chandra soft X-ray observations of Earth's aurora show that it is highly variable 0ntense arcs, multiple arcs, diffuse patches, at times absent). In at least one of the observations an isolated blob of emission is observed near the expected cusp location. A fortuitous overflight of DMSP satellite F13 provided SSJ/4 energetic particle measurements above a bright arc seen by Chandra on 24 January 2004, 20:01-20:22 UT. A model of the emissions expected strongly suggests that the observed soft X-ray signal is bremsstrahlung and characteristic K-shell line emissions of nitrogen and oxygen in the atmosphere produced by electrons.

Bhardwaj, Anil↗

NASA NTRS2006

Low- to Middle-Latitude X-Ray Emission from Jupiter

The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for approx. 40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each -8.5 hours long, were separated by an HRC-I exposure of approx. 20 hours. The low- to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low- to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to middle-latitude X-ray emission does not show any oscillations similar to the approx. 45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low- to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.

Bhardwaj, Anil↗

NASA NTRS2006

Low- to Mid-Latitude X-Ray Emission from Jupiter

The Chandra X-ray Observatory (CXO) observed Jupiter during the period 2003 February 24-26 for approx.40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each approx.8.5 hr long, were separated by an HRC-I exposure of approx.20 hr. The low- to mid-latitude non-auroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to mid-latitude X-ray count rate shows a small but statistically significant hour angle dependence, and is higher in regions of relatively low surface magnetic field strength, confirming ROSAT results. In addition, the spectrum from the low surface field region shows an enhancement in the energy band 1.14- 1.38 keV, perhaps partly due to line emission from that region. Correlation of surface magnetic field strength with count rate is not found for the 2000 December HRC-I data, at a time when solar activity was high. The low- to mid-latitude disk X-ray count rate observed by the HRC-I in the 2003 February observation is about 50% of that observed in 2000 December, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to mid-latitude X-ray emission does not show any oscillations similar to the -45 minute oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's non-auroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2 keV low- to mid-latitude X-ray spectra are harder than the auroral spectrum, and are different from each other at energies above 0.7 keV, showing variability in Jupiter s non-auroral X-ray emission on a time scale of a day. The 0.3-2.0 keV X-ray power emitted at low- to mid-latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by solar X-rays resonantly and fluorescently scattered in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the correlation of higher count rate with low surface magnetic-field strength indicates the presence of some secondary component, possibly ion precipitation from radiation belts closer to the planet than elsewhere at low- to mid-latitudes.

Bhardwaj, Anil↗

NASA NTRS2005

Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions

Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one full Saturn rotation (10.7 hr) at each epoch. We report here the first observation of an X-ray flare from Saturn s non-auroral (low-latitude) disk, which is seen in direct response to an M6-class flare emanating from a sunspot that was clearly visible from both Saturn and Earth. Saturn s X-ray emissions are found to be highly variable on time scales of tens of minutes to weeks. Unlike Jupiter, X-rays from Saturn s polar (auroral) region have characteristics similar to those from its disk and varies in brightness inversely to the FUV auroral emissions observed by the Hubble Space Telescope. This report establishes that disk X-ray emissions of the giant planets Saturn and Jupiter are directly regulated by processes happening on the Sun. We suggest that these emissions could be monitored to study X-ray flaring from solar active regions when they are on the far side and not visible to Near-Earth space weather satellites.

Bhardwaj, Anil↗

NASA NTRS2005

Discovery of Oxygen Kalpha X-ray Emission from the Rings of Saturn

Using the Advanced CCD Imaging Spectrometer (ACIS), the Chandra X-ray Observatory (CXO) observed the Saturnian system for one rotation of the planet (approx.37 ks) on 20 January, 2004, and again on 26-27 January, 2004. In this letter we report the detection of X-ray emission from the rings of Saturn. The X-ray spectrum from the rings is dominated by emission in a narrow (approx.130 eV wide) energy band centered on the atomic oxygen Ka fluorescence line at 0.53 keV. The X-ray power emitted from the rings in the 0.49-0.62 keV band is about one-third of that emitted from Saturn disk in the photon energy range 0.24-2.0 keV. Our analysis also finds a clear detection of X-ray emission from the rings in the 0.49-0.62 keV band in an earlier (14-15 April, 2003) Chandra ACIS observation of Saturn. Fluorescent scattering of solar X-rays from oxygen atoms in the H20 icy ring material is the likely source mechanism for ring X-rays, consistent with the scenario of solar photo-production of a tenuous ring oxygen atmosphere and ionosphere recently discovered by Cassini.

Bhardwaj, Anil↗

NASA NTRS2004

Solar Control on Jupiter's Equatorial X-ray Emissions: 26-29 November 2003 XMM-Newton Observation

During November 26-29,2003 XMM-Newton observed X-ray emissions from Jupiter for 69 hours. The 0.7-2.0 keV X-ray disk of Jupiter is observed to be brightest at the subsolar point, and limb darkening is seen in the 0.2-2.0 keV and 0.7-2.0 keV images. We present simultaneous lightcurves of Jovian equatorial X-rays and solar X-rays measured by the GOES, SOHO/SEM, and TIMED/SEE satellites. The solar X-ray flares occurring on the Jupiter-facing side of the Sun are matched by corresponding features in the Jovian X- rays. These results support the hypothesis that X-ray emissions from Jovian low-latitudes are solar X-rays scattered and fluoresced from the planet's upper atmosphere, and confirm that the Sun directly controls the non-auroral X-rays fiom Jupiter's disk. Our study suggest that Jovian equatorial X-rays; during certain Jupiter phase, can be used to predict the occurrence of solar flare on the hemisphere of the Sun that is invisible to space weather satellites.

Bhardwaj, Anil↗

NASA NTRS2004

First Terrestrial Soft X-ray Aurora Observations by Chandra

Northern polar "auroral" regions of Earth was observed by High-Resolution Camera in imaging mode (T32C-I) aboard Chandra X-Ray Observatory (CXO) during mid December 2003 - mid April 2004. Ten CXO observations, each approximately 20 min duration, were made in a non-conventional method (due to CXO technical issues), such that Chandra was aimed at a fixed point in sky and the Earth's polar cusp was allowed to drift through the HRC-I field-of-view. The observations were performed when CXO was near apogee and timed during northern winter mostly near midnight (6 hr), except two observations which occurred around 1200 UT, so that northern polar region is entirely in dark and solar fluoresced x-ray contamination can be avoided. These observations were aimed at searching the Earth's soft x-ray aurora and to do a comparative study with Jupiter's x-ray aurora, where a pulsating x-ray hot-spot near the northern magnetic pole has been observed by Chandra that implies a particle source region near Jupiter's magnetopause, and entry of heavy solar wind ions due to high-latitude reconnection as a viable explanation for the soft x-ray emissions. The first Chandra soft (0.1-2 keV) x-ray observations of Earth's aurora show that it is highly variable (intense arc, multiple arcs, diffuse, at times almost absent). In at least one of the observations an isolated blob of emission is observed where we expect cusp to be: giving indication of solar wind charge-exchange signature in x-rays. We are comparing the Chandra x-ray observations with observations at other wavelengths and particle data from Earth-orbiting satellites and solar wind measurements from near-Earth ACE and SOH0 spacecraft. Preliminary results from these unique CXO-Earth observations will be presented and discussed.

Bhardwaj, Anil↗

NASA NTRS2004

Biomark/Organic Analysis with Time-of-Flight Mass Spectrometry

The concept of a Comprehensive 2-Dimensional Gas Chromatography coupled with Time-of-Flight Mass Spectrometry (GCxGC-TOWS) for the analysis of organic compounds has been proven with commercially available instrumentation (LECO Corp). The performance of a GCxGC instrument has been characterized in various stages using two independent breadboard systems. The GCxGC separation systems, including the thermal modulator, have been miniaturized to the size of a benchtop configuration. One breadboard system employs a Flame Ionization Detector (FID), whereas the second breadboard system employs a Time-of-Fight mass spectrometer (TOFWS) as a detection system.

Waite, J. Hunter, Jr.↗

NASA NTRS2004

First Terrestrial Soft X-ray Auroral Observation by the Chandra X-Ray Observatory

Northern auroral regions of Earth were imaged using the High-Resolution Camera (HRC-1) aboard the Chandra X-Ray Observatory (CXO) at 10 epochs (each approx.20 min duration) between mid-December 2003 and mid-April 2004. These observations aimed at searching for Earth s soft (<2 keV) x-ray aurora in a comparative study with Jupiter s x-ray aurora, where a pulsating x-ray "hot-spot" has been previously observed by Chandra. The first Chandra soft x-ray observations of Earth s aurora show that it is highly variable (intense arcs, multiple arcs, diffuse patches, at times absent). In at least one of the observations an isolated blob of emission is observed near the expected cusp location. A fortuitous overflight of DMSP satellite F13 provided SSJ/4 energetic particle measurements above a bright arc seen by Chandra on 24 January 2004, 20:01-20:22 UT. A model of the emissions expected strongly suggests that the observed soft x-ray signal is produced by electron bremsstrahlung.

Bhardwaj, Anil↗

NASA NTRS2001

Chandra ACIS Observations of Jovian X-Ray Emission

On November 25 and 26, 1999, the Chandra X-ray spacecraft conducted a set of four 19,000 sec observations of Jupiter. The ACIS-S instrument configuration was used for its good low energy efficiency and spatial resolution. An anomalous response was obtained which was subsequently attributed to strong jovian infrared radiation penetrating the detector and piling up spurious events across the entire X-ray range. However, the pre-observation establishment of an offsetting bias field has allowed the recovery of data from that portion of Jupiter's disc which remained within the elevated portion of the bias field during the observation. This ranges from fewer than 3000 sec to the entire observing time for about 10% of the planet. Auroral emission is seen near both poles in each observation. The northern aurora ia overall more intense than the southern, consistent with prior Einstein and ROSAT Observatory results. The southern aurora shows more modulation with Jupiter's rotation than the northern. Spatial resolution has been improved by at least a factor of two over prior measurements but convincing evidence of structure has not been seen. Lower latitude emission, first observed by ROSAT, is confirmed with flux levels averaging more than a factor of five below peak auroral values. Pronounced variation in the observed emission has occurred over the observing period. The spectral response extends from 0.24 keV, below which noise dominates, to about 1.2 keV. For all four observations the spectrum is clearly enhanced between 0.45 and 0.85 keV. This is apparently unequivocal evidence that Jupiter's X-ray emission is the result of oxygen and perhaps sulfur ions precipitating into the planet's atmosphere, where they undergo charge exchange interactions. The identification of specific transitions lines in the spectrum is among the ongoing efforts. A bremsstrahlung component has not yet been identified.

Garmire, Gordon↗

NASA NTRS1997

Generation Mechanisms UV and X-ray Emissions During SL9 Impact

The purpose of this grant was to study the ultraviolet and X-ray emissions associated with the impact of comet Shoemaker-Levy 9 with Jupiter. The University of Michigan task was primarily focused on theoretical calculations. The NAGW-4788 subtask was to be largely devoted to determining the constraints placed by the X-ray observations on the physical mechanisms responsible for the generation of the X-rays. Author summarized below the ROSAT observations and suggest a physical mechanism that can plausibly account for the observed emissions. It is hoped that the full set of activities can be completed at a later date. Further analysis of the ROSAT data acquired at the time of the impact was necessary to define the observational constraints on the magnetospheric-ionospheric processes involved in the excitation of the X-ray emissions associated with the fragment impacts. This analysis centered around improvements in the pointing accuracy and improvements in the timing information. Additional pointing information was made possible by the identification of the optical counterparts to the X-ray sources in the ROSAT field-of-view. Due to the large number of worldwide observers of the impacts, a serendipitous visible plate image from an observer in Venezuela provided a very accurate location of the present position of the X-ray source, virtually eliminating pointing errors in the data. Once refined, the pointing indicated that the two observed X-ray brightenings that were highly correlated in time with the K and P2 events were brightenings of the X-ray aurora (as identified in images prior to the impact).Appendix A "ROSAT observations of X-ray emissions from Jupiter during the impact of comet Shoemaker-Levy 9' also included.

Waite, J. Hunter, Jr.↗

NASA NTRS1994

Hubble Space Telescope Goddard high-resolution spectrograph H2 rotational spectra of Jupiter's aurora

We have observed the emission spectrum from Jupiter's north auroral atmosphere with 0.57 A spectral resolution over 1204-1241 A. Bright emissions have been detected from 50 deg to 60 deg latitude at locations consistent with 6 to 30 R (sub J) auroral ovals, with much fainter emissions away form the auroral ovals. The emission spectrum is well fitted by both laboratory spectra and theoretical models of optically thin electron excited H2, with added Doppler-broadened Lyman Alpha emission. The observed Lyman Alpha emission wings extend more than 1 A from line center and appear correlated in strength with the H2 brightness. Individual rotational lines in the H2 Werner band system are resolved, allowing a determination of the H2 rotational temperature at the altitude of the emission. We derive best-fit temperatures from 400-450 to 700-750 K, with the auroral emission layer temperature changing either across the auroral oval or over several days' time. These observations demonstrate for the first time the ability to measure the observed rapid H2 temperature variations across Jupiter's auroral atmosphere.

Clarke, John T.↗

NASA NTRS1992

Studies of interactive plasma processes in the polar cusp

The final report for NAGW-1657 (SwRI Project 15-2783) is presented. Several distinctly different areas of research are discussed: (1) studies of the thermal structure of polar outflows; (2) Prognoz-8 data analysis; and (3) the Ulysses Jupiter encounter.

Waite, J. Hunter, Jr.↗

NASA NTRS1992

Modeling the Jovian aurora

The Jovian aurora is the most powerful aurora in the solar system, over 100 times more powerful than the Earth's aurora. These magnificent visual displays can provide important information about the planetary magnetosphere which is responsible for the acceleration of energetic particles that produce aurora at any planet. Similarities and differences in planetary auroral emissions are thus a viable means of classifying and studying both comparative atmospheric and magnetospheric processes. For instance, at Earth the solar wind is the primary source of auroral power while at Jupiter it is conjectured that the rotation of the planet is the major source of magnetospheric and auroral power. The purpose of this IR project was to develop a model: (1) for use in interpreting the existing set of multispectral observations of Jupiter's aurora; and (2) to design new experiments based on the findings to improve understanding of the underlying auroral processes.

Waite, J. Hunter, Jr.↗

NASA NTRS1992

Studies of interactive plasma processes in the polar cusp

Progress during the reporting period is presented. Several distinctly different areas of research are presently being pursued: (1) studies of the thermal structure of polar outflows; (2) Prognoz data analysis; and (3) Ulysses Jupiter encounter.

Waite, J. Hunter, Jr.↗

NASA NTRS1992

Aeronomical modeling of the outer planets

The purpose is twofold: to report the programmatic issues of the project as to accomplishments and anticipated work statement for the next six months and to report the technical findings of the project. From the programmatic point of view the study was a clear success. Four talks were given on the work: (1) a talk on electron Bremsstrahlung X ray production at the annual American Astronomical Society, Division of Planetary Studies meeting in October of 1990 in Charlottesville, Virginia; (2) a poster on proton precipitation at the May, 1991 American Geophysical Union in Baltimore, Maryland; (3) an invited paper on multispectral time dependent modeling at the International Union of Geodosy and Geomagnetism in Vienna in August of 1991; and (4) a paper at the annual Division of Planetary Studies of the American Astronomical Society held in Palo Alto in November of 1991 entitled 'Jovian Bremsstrahlung X Rays: A Ulysses Prediction' which predicted the Jovian auroral X ray flux that should be measured by the Ulysses Gamma Ray Burst experiment during the Ulysses spacecraft's closest encounter with Jupiter in February 1992. The Ulysses' prediction paper generated much interest from people studying the Jovian aurora and from experimenters on the Ulysses spacecraft. As a result of this interest two things happened: (1) a paper of the same title was submitted and accepted for publication in the January issue of the Geophysical Research Letters; and (2) a massive observing campaign was organized to provide supporting ultraviolet and infrared observations at the time of the Ulysses encounter. This observational interest allowed personnel at the Southwest Research Institute (SwRI) (Alan Stern, PI; Hunter Waite Co-I) to obtain director's discretionary time on the Hubble Space Telescope to support the Ulysses encounter by obtaining ultraviolet observations. Once the multiple wavelength observations are obtained in February, the auroral model developed under this project will be used to analyze the data with hopes of providing new insight into the physical processes responsible for the Jovian aurora.

Waite, J. Hunter, Jr.↗

NASA NTRS1991

Bremsstrahlung x rays from Jovian auroral electrons

In a recent paper by D. D. Barbosa, it is argued that electron bremsstrahlung is the most likely source of the auroral x-ray emissions that have been observed at Jupiter. Barbosa bases his argument on observational and theoretical studies of the production of secondary electrons in the Earth's aurora. It is argued here that Barbosa's interpretation is flawed because it ignors the constraint that the primary electron distribution parameters place on the parameters for the secondary electron distribution. As a result, Barbosa's postulated secondary electron fluxes are over three orders of magnitude greater than the theory of auroral electrons permits.

Waite, J. Hunter, Jr.↗

NASA NTRS1989

Doppler shifted H Ly alpha emission from Jupiter's aurora

High-spectral-resolution IUE observations of the aurora on Jupiter were obtained in order to search for Doppler shifted H-Ly-alpha emission produced through charge exchange by fast precipitating protons. Although no emission has been observed corresponding to proton energies greater than 200 eV, a large fraction of the H-Ly-alpha emission has appeared Doppler shifted, mainly toward the blue, by about 50 km/s. These results show that the acceleration of ionospheric plasma in an H2 atmosphere can lead to bright Ly-alpha emission, setting constraints on the production of the outer planet airglow emissions.

Clarke, John T.↗