The spatial extent and the ionization profiles within the extended oval‐shaped regions irradiated by the intense solar particle events (SPE) of August 1972 have been derived from high‐energy proton data obtained with the 1971‐089A polar‐orbiting satellite and from several balloon flights. The particle ionization during the most intense 10‐hour period of the event on August 4 greatly enhanced the concentrations of short‐lived HOx and long‐lived NOx constituents, which in turn were responsible for the creation of a polar ozone cavity (POC) that has been identified and tracked with the backscattered ultraviolet (BUV) ozone sensors on the Nimbus 4 satellite. At the end of the peak irradiation period the ozone concentrations within the northern hemisphere POC were reduced by 46, 16, and 4% at altitudes of 49.5, 41, and 32 km, respectively. The total columnar ozone is estimated to have been reduced by ∼2% at this time. Above ∼45 km the ozone recovered on the time scale of several days. At 38.7 km in the northern hemisphere, however, the POC persisted and rotated as a semirigid mass in an east‐to‐west direction for some 53 days until the autumnal changes in wind patterns finally prevented further tracking. Time‐dependent chemistry calculations have been performed to explain the cause, magnitude, and temporal features of the ozone reductions. Using the calculated diurnal and particle‐induced behavior of the ozone during the SPE, the changes in heating rate and temperature expected in the stratosphere have been estimated. As a result of the initial large HOx‐caused ozone reduction, the temperature at 45 km should have decreased by ∼4°K several days after the event. Attempts to verify the predicted temperature changes have been unsuccessful due to limitations in the temperature measurement techniques.
CUTLER, RICHARD G. (University of Houston, Houston, Tex.), AND JOHN E. EVANS. Synchronization of bacteria by a stationary-phase method. J. Bacteriol. 91:469-476. 1966.-Cultures of Escherichia coli and Proteus vulgaris have been synchronized, with a high percentage phasing, in large volumes and at high cell densities by a method which takes advantage of a tendency of cells to synchronize themselves when entering the stationary phase of growth. The method consists of growing the bacteria to an early stationary phase, harvesting them quickly under minimal conditions of stress, and inoculating them into fresh medium at a dilution of about sevenfold. Cellular division is then partially synchronized. Four-generation cycles of a high percentage of phasing are obtained by repeating this procedure on the partially synchronized culture. Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein analyses were made throughout all phases of the growth curve. Advantage has been taken of this method of synchrony to isolate selected segments of the bacterial genome in significant amounts. A working hypothesis to explain the synchrony suggests that the unfavorable conditions of growth as the bacteria near the stationary phase are detected by a decrease in the amino acid pool size, and that this results in a gradual decrease of DNA transcription activity through the inhibition of RNA polymerase by transfer RNA. The synchronizing method may be unique in producing cultures that grow both in cellular division and in genomic synchrony.
The Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload that operated from January 2016 through July of 2017 on the European Space Agency's LISA Pathfinder spacecraft. The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observatory targeting the source-rich milliHertz band. The two primary components of ST7-DRS are a micropropulsion system based on colloidal micro-Newton thrusters (CMNTs) and a control system that simultaneously controls the attitude and position of the spacecraft and the two free-flying test masses (TMs). This paper presents our main experimental results and summarizes the overall the performance of the CMNTs and control laws. We find that the CMNT performance to be consistent with pre-flight predictions, with a measured system thrust noise on the order of 100 nN/ √ Hz in the 1 mHz ≤ f ≤ 30 mHz band. The control system maintained the TM-spacecraft separation with an RMS error of less than 2 nm and a noise spectral density of less than 3 nm/ √ Hz in the same band. Thruster calibration measurements yield thrust values consistent with the performance model and ground-based thrust-stand measurements, to within a few percent. We also report a differential acceleration noise between the two test masses with a spectral density of roughly 3 fm/s 2 / √ Hz in the 1 mHz ≤ f ≤ 30 mHz band, slightly less than twice as large as the best performance reported with the baseline LISA Pathfinder configuration and below the current requirements for the Laser Interferometer Space Antenna (LISA) mission.
The solar particle event (SPE) of August 1972 is one of the largest that has occurred in the last 20 years. Since it is so well documented, it can serve as a good example of a major perturbation to the atmospheric electric system. In this paper, ion production rates and conductivities from the ground to 80 km at the peak intensity of the event on August 4 and for 30, 35, and 40 km for the 6‐day duration of the event are presented. At the peak of the event, the proton and electron precipitation currents, the ohmic current, and the vertical electric field are calculated inside the polar cap. The particle precipitation currents at this time greatly exceed the normal air earth current at altitudes above 30 km and produce reversals in the vertical electric field at 28 km and above. Calculations are presented of the vertical electric field at altitudes near 30 km where balloon measurements were made. Good agreement between the calculated and the measured vertical electric field verifies our ability to calculate disturbed conductivities at these altitudes from satellite measurements of proton spectra incident on the atmosphere. Despite the fact that at the peak of the event the vertical electric field near 30 km was shorted out by the solar particles and that the current carried by the solar particles exceeded the fair weather air‐earth current density in the stratosphere by large factors, it is concluded that the largest effect of an SPE of this magnitude on the atmospheric electric circuit is due to the Forbush decrease in the galactic cosmic ray flux rather than to the large increase in solar proton flux.
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