On 24 March 1991 instrumentation aboard CRRES observed the almost instantaneous injection of electrons and protons with energies above 15 MeV into the L‐region 2 < L < 3. The energy spectrum of the injected electrons, a power law (E−6) peaked at 15 MeV and continued to at least 50 MeV
High‐time‐resolution (0.5 s) measurements of the vehicle frame to ambient plasma potential were made with a 50‐m antenna experiment on the SCATHA satellite. Accurate measurements were limited to sunlight conditions or to low‐level eclipse charging periods. Significant variations in the spacecraft potential in sunlight occurred which depended on the orientation of the satellite with respect to the sun. Using the SCATHA data, statistical occurrence of charging at near‐geosynchronous orbit in daylight is studied. Charging greater than −10 V (in the negative sense) occurs only between 1900 LT and 0900 LT but at all altitudes and latitudes of the SCATHA orbit. High‐level (> −100 V) charging occurs only for magnetic activity, as measured by Kp, of 2+ or greater. Three “worst case” daylight charging event periods (−340 V to −740 V) show that the electron population that directly drives the vehicle potential on the SCATHA satellite has an energy typically greater than 30 keV. The vehicle potential (in the negative sense) is directly proportional to the electron flux carried by the population above 30 keV, although the linear regression coefficients change from case to case. The vehicle potential is insensitive to changes in the electron flux below 30 keV, even though the fluxes in this range are considerably more intense. To explain the data, we suggest that the low‐energy electron fluxes are essentially self‐balanced by the combination of their own secondary and backscattered emissions and that a substantial portion of the photoelectron emissions are returned to the satellite by the action of the surrounding magnetic field.
D TL C IPL-TR-93-2055 9. SPONSORING.i MONITORING AGENCY .4AN 8 D 10 .SPONSOR!,NG MONITORING AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES *Boston College, Chestnut Hill, MA Reprinted from XVth International Symposium on Discharges and Electrical Insulation in Vacuum-Darmstadt-1992 12a, DISTRIUTION AVAILABILITY STATEMENT j1 2 b. DISTRIBUT'IN CODE Approved for public release; Distribution unlimited 13. ABSTRACT (Maximum2 10 wcrds) Sixteen samples of standard insulating materials with electrodes were eposed to the full variety of the Earth's space radiation beus tor 14 months. Spontaneous discharges were recorded for each sample and are compared to the radiation levels which were simultaneously monitored. Samples with the most exposed insulator surface pulsed most frequently. Pulsing correlated with electron flux, but not at all with proton flux. The pulse rate per unit electron flux was initially small, rose continuously for 7 mutahs, and then fell slightly during the last seven months. A computer model predicts the charging of the inmulators by the high energy electron flux; It took I to 6 months for the electric fields to approach steady state levels. Most of the pulses were less than 50 volts on 50 ohms. The pulsing rate decays when the satellite leaves the electron belts; the decay became more rapid after 7 months. Pulsing during the first six months had different characteristics than later pulsing. 14. SUBJECT TERMS 15. NUMBER OF PAGES Electrical Discharging Radiation Insulating 5 16. PRICE CODE 17. SECURITY CLASSIFICATION 118. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ASSTRAC0. L ON OF ASTRA UNCLASSIFIED UNCLASSIFIED I UNCLASSIFIED SAR !NSN 7540-01,280-1500 Szarda'd '-orr'9 298 (Rev 2-89) IC
Proton flux maps of near-Earth space are presented using the Proton Telescope (PROTEL) detector on CRRES. The proton energy range covered is 1-100 MeV. Contamination of PROTEL measurements due to > 100 MeV protons is corrected using loss cone data, resulting in consistency with dosimeter measurements and a Monte Carlo computer model of PROTEL. Two states of the inner magnetosphere were found during the CRRES mission, a quiet state having a single proton belt, and an active state with a double belt. The properties of the new population in the second belt are presented. Comparisons with NASA proton codes are made.
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