Engineering topics

Fung, Shing

Publications and source records attributed to Fung, Shing.

7 records

NASA NTRS2010

Cluster in the Auroral Acceleration Region

Due to a fortuitous evolution of the Cluster orbit, the Cluster spacecraft penetrated for the first time in its mission the heart of Earth's auroral acceleration region (AAR) in December 2009 and January 2010. During this time a special AAR campaign was carried out by the various Cluster instrument teams with special support from ESA and NASA facilities. We present some of the first multi-spacecraft observations of the waves, particles and fields made during that campaign. The Cluster spacecraft configuration during these AAR passages was such that it allowed us to explore the differences in the signatures of waves, particles, and fields on the various spacecraft in ways not possible with single spacecraft. For example, one spacecraft was more poleward than the other three (C2), one was at higher altitude (C1), and one of them (0) followed another (C4) through the AAR on approximately the same track but delayed by three minutes. Their separations were generally on the order of a few thousand km or less and occasionally two of them were lying along the same magnetic field line. We will show some of the first analyses of the data obtained during the AAR campaign, where upward and downward current regions, and the waves specifically associated with those regions, as well as the auroral cavities, were observed similarly and differently on the various spacecraft, helping us to explore the spatial, as well as the temporal, aspects of processes occurring in the AAR.

Pickett, Jolene S.↗

NASA NTRS2009

Investigating Changes in the High-Latitude Topside Ionosphere During Large Magnetic Storms

A search was conducted to locate periods of nearly simultaneous solar-wind and high latitude topside-ionospheric data during magnetic storms. The focus was on the 20-yr interval from 1965 to 1985 when both solar-wind and Alouette/ISIS topside-sounder data are potentially available. The search yielded 125 large magnetic storms (minimum Dst less than 100) and 280 moderate magnetic storms (minimum Dst between -60 and -100). Solar wind data were available for most, but not all, of these storms. A search of the available high-latitude topside electron-density Ne(h) profiles available from the National Space Science Data Center (NSSDC), both from manual inspection of 35-mm film ionograms in the 1960s and more recent auto-processing of ISIS-2 topside digital ionograms using the TOPIST software, during 9-day intervals associated with the 125 large magnetic storm minimum Dst times yielded the following results: 31 intervals had 10 or more manual-scaled profiles (21 intervals had more than 100 profiles and 5 of these had more than 1,000 profiles), and 34 intervals had 10 or more TOPIST profiles (2 intervals had more than 100 profiles). In addition, a search of the available Alouette-2, ISIS-1 and ISIS-2 digital ionograms during the above periods has yielded encouraging initial results in that many ISIS-1 ionograms were found for the early time intervals. Future work will include the search for 35-mm film ionograms during selected intervals. This presentation will illustrate the results of this investigation to date.

Fainberg, Joseph↗

NASA NTRS2008

The User Community and a Multi-Mission Data Project: Services, Experiences and Directions of the Space Physics Data Facility

From a user's perspective, the multi-mission data and orbit services of NASA's Space Physics Data Facility (SPDF) project offer a unique range of important data and services highly complementary to other services presently available or now evolving in the international heliophysics data environment. The VSP (Virtual Space Physics Observatory) service is an active portal to a wide range of distributed data sources. CDAWeb (Coordinate Data Analysis Web) enables plots, listings and file downloads for current data cross the boundaries of missions and instrument types (and now including data from THEMIS and STEREO). SSCWeb, Helioweb and our 3D Animated Orbit Viewer (TIPSOD) provide position data and query logic for most missions currently important to heliophysics science. OMNIWeb with its new extension to 1- and 5-minute resolution provides interplanetary parameters at the Earth's bow shock as a unique value-added data product. SPDF also maintains NASA's CDF (common Data Format) standard and a range of associated tools including translation services. These capabilities are all now available through webservices-based APIs as well as through our direct user interfaces. In this paper, we will demonstrate the latest data and capabilities now supported in these multi-mission services, review the lessons we continue to learn in what science users need and value in this class of services, and discuss out current thinking to the future role and appropriate focus of the SPDF effort in the evolving and increasingly distributed heliophysics data environment.

Fung, Shing F.↗

NASA NTRS2007

Drift-Resonant Interaction of Magnetospheric Relativistic Electrons with Ultra-Low Frequency (ULF) Waves: Comparison between Observations and Simulations

By analyzing CRRES and GOES observations on Aug. 27 1991, Tan et al. [2004] reported evidence of magnetospheric relativistic electron acceleration by resonant interactions with PC5 ULF waves. The event showed strong ULF wave activities after a storm sudden commencement (SSC) and energetic electron fluxes were enhanced in 2 hours. The electron flux peak observed in energy channels (0.6 - 1.1 MeV) were modulated by local electric field observed by CRRES. In this study, we set up a drift-resonant interaction model between ULF wave and magnetospheric relativistic electrons to model the observed electron flux in the event. In this model, the poloidal mode wave is concentrated in the dayside and the toroidal mode wave is concentrated in two flanks. The toroidal mode waves in the dawn and dusk flanks are in anti-phase. We found that electron can be accelerated jointly by the poloidal wave in the dayside and toroidal wave in flanks. The dayside poloidal wave serves as the dominant source of electron acceleration. The simulated electron flux variations agree well with observations both in fine details and long period behavior. These agreements in electron behavior indicate that the ULF wave plays an important role in accelerating MeV relativistic electrons around the geosynchronous orbit.

Fung, Shing↗

NASA NTRS2007

Scientific Uses and Directions of SPDF Data Services

From a science user's perspective, the multi-mission data and orbit services of NASA's Space Physics Data Facility (SPDF) project perform as a working and highly functional heliophysics virtual observatory. CDAWeb enables plots, listings and file downloads for current data across the boundaries of missions and instrument types (and now including data from THEMIS and STEREO), VSPO access to a wide range of distributed data sources. SSCWeb, Helioweb and our 3D Animated Orbit Viewer (TIPSOD) provide position data and query logic for most missions currently-important to heliophysics science. OMNIWeb with its new extension to 1- and 5- minute resolution provides interplanetary parameters at the Earth's bow shock as a unique value-added data product. To enable easier integrated use of our capabilities by developers and by the emerging heliophysics VxOs, our data and services are available through webservices-based APls as well as through our direct user interfaces. SPDF has also now developed draft descriptions of its holdings in SPASE-compliant XML In addition to showcasing recent enhancements to SPDF capabilities, we will use these systems and our experience in developing them: to demonstrate a few typical science use cases; to discuss key scope and design issues among users, service providers and end data providers; and to identify key areas where existing capabilities and effective interface design are still inadequate to meet community needs.

Fung, Shing↗

NASA NTRS2007

Long-term Average Spectral and Spatial Distributions of Plasmaspheric Hiss Observed by the Akebono and IMAGE Satellites

The radiation belt slot region is known to result from losses of energetic electrons by enhanced pitch-angle scattering by whistler mode waves associated with plasmaspheric hiss emission. The distributions of whistler mode waves in the slot L range are therefore important for understanding the electron radiation belt. The sources and distributions of the waves are, however, still controversial. In the present study, using the Akebono/MCA data [1989-20051 and the IMAGE/RPI data [2000-20051, we have constructed the average plasmaspheric hiss spectral distributions over a broad frequency range. In addition, we have investigated the spatial distributions of plasmaspheric hiss with the wave map technique [Green et a1.(2005)]. Our study shows that the broadband plasmaspheric hiss are distributed in the frequency range of 100Hz to several kHz, and exhibit a broad intensive peak. The frequency of the intensity peak tends to increase with magnetic latitude. The frequencies of the most intense waves in the nominal slot L range (2<3) during quiet times (Dst>-50nT) are found to be between 300Hz and 600Hz on average. During high storm activity (Dst <-150nT), however, the peak frequencies become slightly lower. The intensity of plasmaspheric hiss clearly depends on substorm activity as measured by the AE index, consistent with Meredith et a1.(2004). The hiss wave intensity maps also show a strong local time asymmetry. The large amplitude waves are observed at 6:OO-19:OO MLT. From our extensive analysis, we have also found an L dependence of hiss activity, with the larger amplitude waves being observed at lower L during substorm active conditions. The same tendency can be found for solar activity. The average intensities of the waves during 1989-1991 and 2000-2001 are a few dB larger than those during 1992-1997 and 2005. The most intense waves are observed at lower L during high solar activity. The statistical study on spectrum features of the plasmaspheric hiss together with the spatial distribution show clear dependences of storm, substorm and solar activities.

Fung, Shing↗

NASA NTRS2004

Considerations for a Radar System to Detect an Ocean Underneath the Icy Shell of Europa

The detection of an ocean underneath Europa is one of the primary objectives of the Jupiter Icy Moons Orbiter (JIMO) mission. An orbiting surface penetrating radar has the potential of providing that measurement thus yielding information regarding the possibility of life support on Europa. Radars in the MHz range have successfully monitored the kilometer-deep ice shelves of Greenland and Antarctica, including the detection of Lake Vostok (and others) below an ice sheet thickness of about 4 km. The performance of a radar system orbiting Europa will be subject to several potential complications and unknowns. Besides ionospheric dispersion and the actual depth of the ocean, which is estimated between 2 and 30 km, major unknowns affecting radar performance are the temperature profile, the amount of salt and other impurities within the ice crust as well as the surface roughness. These impurities can in part be produced at the highly irradiated surface by magnetospheric interactions and transported downward into the ice crust by geologic processes. The ionospheric interference must also be modeled from effects of these interactions on production of the thin neutral atmosphere and subsequent ionization of the neutrals. We investigated these uncertainties through radar simulations using different surface and ice characteristics over a frequency range from 10 to 50 MHz. The talk will present results from these simulations discussing potential limitations.

Markus, Thorsten↗