Mesospheric Response to Impacting Relativistic Electrons

Daily maps of the spatial distributions of precipitating energetic electrons were produced for the period 10-20 May 1992. These data will serve as the input for potential changes in upper atmosphere composition

The Mimas Ghost Revisited: An Analysis of the Electron Flux and Electron Microsignatures Observed in the Vicinity of Mimas at Saturn

An analysis of the electron absorption signature observed by the Cosmic Ray System on Voyager 2 near the orbit of Mimas is presented. We find that these observations cannot be explained as the absorption signature of Mimas. Combining Pioneer 11 and Voyager 2 measurements of the electron flux at Mimas's orbit (L = 3.1), we find an electron spectrum where most of the flux above ∼100 keV is concentrated near 1 to 3 MeV. This spectral form is qualitatively consistent with the band-pass filter model of Van Allen et al. (1980b). The expected Mimas absorption signature is calculated from this spectrum neglecting radial diffusion. Since no Mimas absorption signature was observed in the inbound Voyager 2 data, a lower limit on the diffusion coefficient for MeV electrons at L = 3.1 of D > 10^(−8) R_s^² s^(−1) is obtained. With a diffusion coefficient this large, both the Voyager 2 and the Pioneer 11 small-scale electron absorption signature observations in Mimas's orbit are enigmatic. Thus we refer to the mechanism for producing these signatures as the Mimas ghost. A cloud of material in orbit with Mimas may account for the observed electron signature if the cloud is at least 1% opaque to electrons across a region extending over a few hundred kilometers

Toward a descriptive model of solar particles in the heliosphere

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made

An analysis of the structure of Saturn's magnetic field using charged particle absorption signatures

A new technique is derived for determining the structure of Saturn's magnetic field. This technique uses the observed positions of charged particle absorption signatures due to the satellites and rings of Saturn to determine the parameters of an axially symmetric, spherical harmonic model of the magnetic field using the method of least squares. Absorption signatures observed along the Pioneer 11, Voyager 1, and Voyager 2 spacecraft trajectories are used to derive values for the orientation of the magnetic symmetry axis relative to Saturn's axis of rotation, the axial displacement of the center of the magnetic dipole from the center of Saturn, and the magnitude of the external field component. Comparing these results with the magnetic field model parameters deduced from analyses of magnetometer data leads us to prefer models that incorporate a northward offset of the dipole center by about 0.05 R_s

Instantaneous ionospheric global conductance maps during an isolated substorm

International audienceData from the Polar Ionospheric X-ray Imager (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite have been used to provide instantaneous global conductance maps. In this study, we focus on an isolated substorm event occurring on 31 July 1997. From the PIXIE and the UVI measurements, the energy spectrum of the precipitating electrons can be derived. By using a model of the upper atmosphere, the resulting conductivity values are generated. We present global maps of how the 5 min time-averaged height-integrated Hall and Pedersen conductivities vary every 15 min during this isolated substorm. The method presented here enables us to study the time development of the conductivities, with a spatial resolution of ~ 700 km. During the substorm, a single region of enhanced Hall conductance is observed. The Hall conductance maximum remains situated between latitudes 64 and 70 corrected geomagnetic (CGM) degrees and moves eastward. The strongest conductances are observed in the pre-midnight sector at the start of the substorm expansion. Toward the end of the substorm expansion and into the recovery phase, we find the Hall conductance maximum in the dawn region. We also observe that the Hall to Pedersen conductance ratio for the regions of maximum Hall conductance is increasing throughout the event, indicating a hardening of the electron spectrum. By combining PIXIE and UVI measurements with an assumed energy distribution, we can cover the whole electron energy range responsible for the conductances. Electrons with energies contributing most to the Pedersen conductance are well covered by UVI while PIXIE captures the high energetic component of the precipitating electrons affecting the Hall conductance. Most statistical conductance models have derived conductivities from electron precipitation data below approximately 30 keV. Since the intensity of the shortest UVI-wavelengths (LBHS) decreases significantly at higher electron energies, the UVI electron energy range is more or less comparable with the energy ranges of the statistical models. By calculating the conductivities from combined PIXIE and UVI measurements to compare with the conductivities from using UVI data only, we observe significant differences in the Hall conductance. The greatest differences are observed in the early evening and the late morning sector. We therefore suggest that the existing statistical models underestimate the Hall conductance

Order-Revealing Encryption: File-Injection Attack and Forward Security

Order-preserving encryption (OPE) and order-revealing encryption (ORE) are among the core ingredients for encrypted database (EDB) systems as secure cloud storage. In this work, we study the leakage of OPE and ORE and their forward security. We propose generic yet powerful file-injection attacks (FIAs) on OPE/ORE, aimed at the situations of possessing order by and range queries. The FIA schemes only exploit the ideal leakage of OPE/ORE (in particular, no need of data denseness or frequency). We also improve its efficiency with the frequency statistics using a hierarchical idea such that the high-frequency values will be recovered more quickly. Compared with other attacks against OPE/ORE proposed in recent years, our FIA attacks rely upon less demanding conditions and are more effective for attacking the systems with the function of data sharing or transferring like encrypted email system. We executed some experiments on real datasets to test the performance, and the results show that our FIA attacks can cause an extreme hazard on most of the existing OPE and ORE schemes with high efficiency and 100% recovery rate. In order to resist the perniciousness of FIA, we propose a practical compilation framework for achieving forward secure ORE. The compilation framework only uses some simple cryptographical tools like pseudo-random function, hash function and trapdoor permutation. It can transform most of the existing OPE/ORE schemes into forward secure ORE schemes, with the goal of minimizing the extra burden incurred on computation and storage. We also present its security proof and execute some experiments to analyze its performance

An integrated space physics instrument (ISPI) for Solar Probe

Instruments for the Solar Probe mission must be designed not only to address the unique scientific measurement requirements, but must be compatible with the modest resource dollars as well as tight constraints on mass and power. Another unique aspect of the Solar Probe mission is its constraint on telemetry and the fact that the prime science is conducted in a single flyby. The instrument system must be optimized to take advantage of the telemetry and observing time available. JPL, together with industry and university partners, is designing an Integrated Space Physics Instrument (ISPI) which will measure magnetic fields, plasma waves, thermal plasma, energetic particles, dust, and perform EUV/visible and coronal imaging for the Solar Probe mission. ISPI uses a new architecture and incorporates technology which not only eliminates unnecessary duplication of function, but allows sensors to share data and optimize science. The current ISPI design goal (for a flight package) is a 5 kilogram/10 watt payload. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87393/2/131_1.pd