A bstTactCREME96 is an update of the Cosmic Ray Effects on Micro-Electronics code, a widely-used suite of programs for creating numerical models of the ionizingradiation environment in near-Earth orbits and for evaluating radiation effects in spacecraft. CREME96, which is now available over the World-Wide Web (WWW) at http://crsp3.nrl.navy.mil/creme96/, has many significant features, including (1) improved models of the galactic cosmic ray, anomalous cosmic ray, and solar energetic particle ("flare") components of the near-Earth environment;(2) improved geomagnetic transmission calculations; (3) improved nuclear transport routines; (4) improved singleevent upset (SEU) calculation techniques, for both protoninduced and direct-ionization-induced SEUs; and (5) an easy-to-use graphical interface, with extensive on-line tutorial information. In this paper we document some of these improvements. b ! ~ I I
Abstract. The geophysical significance of the thin nitrate-rich layers that have been found in both Arctic and Antarctic firn and ice cores, dating from the period 1561-1991, is examined in detail. It is shown that variations of meteorological origin dominate the record until the snow has consolidated to high-density firn some 30 years after deposition. The thin nitrate layers have a characteristic short timescale (<6 weeks) and are highly correlated with periods of major solar-terrestrial disturbance, the probability of chance correlation being less than 10 -9. A one-to-one correlation is demonstrated between the
Solar proton events have been routinely detected by satellites since the 20th solar cycle; however, before that time only very major proton events were detected at the Earth. Even though the detection thresholds differed between the 19th and more recent cycles, more than 200 solar proton events with a flux of over 10 particles (cm z s ster)-~ above 10 MeV have been recorded at the Earth in the last three solar cycles. At least 15 50 of these events had protons with energies greater than 450 MeV detected at the Earth. Other than an increase in solar proton event occurrence with increasing solar cycle, no recognizable pattern could be identified between the occurrence of solar proton events and the solar cycle. The knowledge we have gained from the data acquired over the past 40 years illustrates the difficulty in extrapolating back in time to infer the number and intensity of major solar proton events at the Earth.
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