Evaluation of the STORM model storm-time corrections for middle latitude

This paper presents results from the Storm-Time Ionospheric Correction Model (STORM) validation for selected Northern and Southern Hemisphere middle latitude locations. The created database incorporated 65 strong-to-severe geomagnetic storms, which occurred within the period 1995–2007. This validation included data from some ionospheric stations (e.g., Pruhonice, El Arenosillo) that were not considered in the development or previous validations of the model. Hourly values of the F2 layer critical frequency, foF2, measured for 5–7 days during the main and recovery phases of each selected storm were compared with the predicted IRI 2007 foF2 with the STORM model option activated. To perform a detailed comparison between observed values, medians and predicted foF2 values the correlation coefficient, the root-mean-square error (RMSE), and the percentage improvement were calculated. Results of the comparative analysis show that the STORM model captures more effectively the negative phases of the summer ionospheric storms, while electron density enhancement during winter storms and the changeover of the different storm phases is reproduced with less accuracy. The STORM model corrections are less efficient for lower-middle latitudes and severe geomagnetic storms.     

Solar Imprint on ICMEs, Their Magnetic Connectivity, and Heliospheric Evolution

Interplanetary outflows from coronal mass ejections (ICMEs) are structures shaped by their magnetic fields. Sometimes these fields are highly ordered and reflect properties of the solar magnetic field. Field lines emerging in CMEs are presumably connected to the Sun at both ends, but about half lose their connection at one end by the time they are observed in ICMEs. All must eventually lose one connection in order to prevent a build-up of flux in the heliosphere; but since little change is observed between 1 AU and 5 AU, this process may take months to years to complete. As ICMEs propagate out into the heliosphere, they kinematically elongate in angular extent, expand from higher pressure within, distort owing to inhomogeneous solar wind structure, and can compress the ambient solar wind, depending upon their relative speed. Their magnetic fields may reconnect with solar wind fields or those of other ICMEs with which they interact, creating complicated signatures in spacecraft data.     

The Noise Model of the SEIS Seismometer of the InSight Mission to Mars

The SEIS (Seismic Experiment for Interior Structures) instrument on board the InSight mission to Mars is the critical instrument for determining the interior structure of Mars, the current level of tectonic activity and the meteorite flux. Meeting the performance requirements of the SEIS instrument is vital to successfully achieve these mission objectives. The InSight noise model is a key tool for the InSight mission and SEIS instrument requirement setup. It will also be used for future operation planning. This paper presents the analyses made to build a model of the Martian seismic noise as measured by the SEIS seismometer, around the seismic bandwidth of the instrument (from 0.01 Hz to 1 Hz). It includes the instrument self-noise, but also the environment parameters that impact the measurements. We present the general approach for the model determination, the environment assumptions, and we analyze the major and minor contributors to the noise model.     

CIR Morphology, Turbulence, Discontinuities, and Energetic Particles

Corotating interaction regions (CIRs) in the middle heliosphere have distinct morphological features and associated patterns of turbulence and energetic particles. This report summarizes current understanding of those features and patterns, discusses how they can vary from case to case and with distance from the Sun and possible causes of those variations, presents an analytical model of the morphological features found in earlier qualitative models and numerical simulations, and identifies aspects of the features and patterns that have yet to be resolved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nuclear fragmentation database for GCR transport code development

A critical need for NASA is the ability to accurately model the transport of heavy ions in the Galactic Cosmic Rays (GCR) through matter, including spacecraft walls, equipment racks, etc. Nuclear interactions are of great importance in the GCR transport problem, as they can cause fragmentation of the incoming ion into lighter ions. Since the radiation dose delivered by a particle is proportional to the square of (charge/velocity), fragmentation reduces the dose delivered by incident ions. The other mechanism by which dose can be reduced is ionization energy loss, which can lead to some particles stopping in the shielding. This is the conventional notion of shielding, but it is not applicable to human spaceflight since the particles in the GCR tend to be too energetic to be stopped in the relatively thin shielding that is possible within payload mass constraints. Our group has measured a large number of fragmentation cross sections, intended to be used as input to, or for validation of, NASA’s radiation transport models. A database containing over 200 charge-changing cross sections and over 2000 fragment production cross sections has been compiled. In this report, we examine in detail the contrast between fragment measurements at large acceptance and small acceptance. We use output from the PHITS Monte Carlo code to test our assumptions using as an example ⁴⁰Ar data (and simulated data) at a beam energy of 650 MeV/nucleon. We also present preliminary analysis in which isotopic resolution was attained for beryllium fragments produced by beams of ¹⁰B and ¹¹B. Future work on the experimental data set will focus on extracting and interpreting production cross sections for light fragments.     

Effects of repeated long duration +2Gz load on man's cardiovascular function

Usefulness of a short-arm human centrifuge is expected when it is used in space as a countermeasure against cardiovascular deconditioning, problem of bone-calcium metabolism, etc. However, nothing is solidly established regarding the most desirable program for artificial G application. Accordingly, this study was designed to analytically evaluate the effects of repeated long duration +Gz load on human cardiovascular function. Recently heart rate spectral analysis has been recognized as a powerful tool for quantitatively evaluating parasympathetic and sympathetic activity separately in human. It is reported that power of the high frequency component (HF-p) is mediated selectively by parasympathetic activity and the power ratio of low to high frequency components(LF/HF) is indicative of cardiac sympathetic activity or cardiac sympathovagal balance. Sequence method is developed to examine spontaneous baroreceptor reflex sensitivity (BRS). We studied cardiovascular control function by using these methods in 9 healthy men before and after 7 days of daily repeated 1hour +2Gz load. When compared with the data of pre-G load period, post-G load period, decrease of HR, increases of HF-p and BRS were statistically significant. SBP, DBP and LF/HF tended to decrease, however, these changes were not statistically significant. This results indicate that repeated +2Gz load increases parasympathetic activity and arterial baroreceptor-cardiac reflex sensitivity. In recent years, many investigators suggest that space flight and head-down bedrest leads to impaired baroreceptor-cardiac reflex responses and decrease of parasympathetic activity, which may contribute to orthostatic intolerance. So our results suggest that daily repeated 1hour +2Gz load would be useful in preventing post-flight orthostatic intolerance.     

Helium-3: Status and Prospects

We report on our continuing efforts to determine 3He abundances in H II regions and planetary nebulae. Our detections of 3He in some PNe show that some stars produce large amounts of 3He. However the H II region abundances show no evidence for this production. From our sample of > 40 H II regions, the subsample which should yield the most reliable abundances has 3He/H abundances which scatter between 1-2 × 10-5. There is no trend with either galactocentric distance or metallicity. Even if we do not understand the underlying mechanisms, we see empirically that stars neither produce nor destroy 3He in a major way. We thus suggest that the level of the "3He Plateau" (3He/H = 1.5 _-0.5 ^+1.0 × 10^-5) is a reasonable estimate for the primordial 3He.     

Derating Concerns for Microprocessors Used in Safety-Critical Applications

The use of commercial-off-the-shelf (COTS) microprocessors for safety-critical applications usually implies derating of the device to make it work in harsh environments. We discuss derating concerns for state-of-the-art microprocessors. Issues addressed herein include noise margins due to low voltage levels, multiple power supplies, frequency and current derating concerns, error sources, timing degradation, power-aware architectures, and new advanced microprocessor derating features.