ALBERT

Description: The first International Symposium on Strain Gauge Balances was sponsored under the auspices of the NASA Langley Research Center (LaRC), Hampton, Virginia. Held at the LaRC Reid Conference Center, the Symposium provided an open international forum for presentation, discussion, and exchange of technical information among wind tunnel test technique specialists and strain gauge balance designers. The Symposium also served to initiate organized professional activities among the participating and relevant international technical communities. The program included a panel discussion, technical paper sessions, tours of local facilities, and vendor exhibits. Over 130 delegates were in attendance from 15 countries. A steering committee was formed to plan a second international balance symposium tentatively scheduled to be hosted in the United Kingdom in 1998 or 1999. The Balance Symposium was followed bv the half-day, Workshop on Angle of Attack and Model Deformation on the afternoon of October 25. The thrust of the Workshop was to assess the state of the art in angle of attack (AoA) and model deformation measurement techniques and to discuss future developments.

Description: Overcoat protection schemes for thin film devices have typically focused on inhibiting the growth of native oxides formed on the sensor surface, rather than on improving the passivating nature of these native oxides. Here, thin sputtered Cr overcoats and heat treatments in varying oxygen partial pressures enhanced the passivating nature of native Cr203 films formed on PdCr thin film strain gages. Results of strain tests using sensors protected using this approach are presented and the implications are discussed. PdCr gages with sputtered Cr overcoats withstood 12,000 dynamic strain cycles of 1100 micro-epsilon during 100 hours of testing at a temperature of 1000 C in air. Gage factors of 1.3 with drift rates as low as 0.1 Omega/hr were achieved for devices having a nominal resistance of approximately 100 Omega's. TCR's ranging from +550 ppm/C to +798 ppm/C were realized depending on the overcoat and thermal history. Possible mechanisms for an anomaly in the electrical characteristics of these films at 800 C and improvements in stability due to the use of overcoats are presented.

Description: Instrumentation systems have always been essential components of world class wind tunnels and laboratories. Langley continues to be on the forefront of the development of advanced systems for aerospace applications. This paper will describe recent advances in selected measurement systems which have had significant impact on aerospace testing. To fully understand the aerodynamics and aerothermodynamics influencing aerospace vehicles, highly accurate and repeatable measurements need to be made of critical phenomena. However, to maintain leadership in a highly competitive world market, productivity enhancement and the development of new capabilities must also be addressed aggressively. The accomplishment of these sometimes conflicting requirements has been the challenge of advanced measurement developers. However, several new technologies have recently matured to the point where they have enabled the achievement of these goals. One of the critical areas where advanced measurement systems are required is flow field velocity measurements. These measurements are required to correctly characterize the flowfield under study, to quantify the aerodynamic performance of test articles and to assess the effect of aerodynamic vehicles on their environment. Advanced measurement systems are also making great strides in obtaining planar measurements of other important thermodynamic quantities, including species concentration, temperature, pressure and the speed of sound. Langley has been on the forefront of applying these technologies to practical wind tunnel environments. New capabilities in Projection Moire Interferometry and Acoustics Array Measurement systems have extended our capabilities into the model deformation, vibration and noise measurement arenas. An overview of the status of these techniques and recent applications in practical environments will be presented in this paper.

Description: We examine 10 coronal mass ejections from the in-ecliptic portion of the Ulysses mission. Five of these CMEs are magnetic clouds. In each case we observe an inverse relationship between electron temperature and density. For protons this relationship is less clear. Earlier work has shown a similar inverse relationship for electrons inside magnetic clouds and interpreted it to mean that the polytropic index governing the expansion of electrons is less than unity. This requires electrons to be heated as the CME expands. We offer an alternative view that the inverse relationship between electron temperature and density is caused by more rapid cooling of the denser plasma through collisions. More rapid cooling of denser plasma has been shown for 1 AU measurements in the solar wind. As evidence for this hypothesis we show that the denser plasma inside the CMEs tends to be more isotropic indicating a different history of collisions for the dense plasma. Thus, although the electron temperature inside CMEs consistently shows an inverse correlation with the density, this is not an indication of the polytropic index of the plasma but instead supports the idea of collisional modification of the electrons during their transit from the sun.

Description: Mean values of a number of parameters of the most powerful coronal mass ejections (CMEs) and interplanetary shocks generated by these ejections are estimated using an analysis of data obtained by the cosmic coronagraphs and spacecrafts, and geomagnetic storm measurements. It was payed attention that the shock mass and mechanical energy, averaging 5 x 10(exp 16) grm and 2 x 10(exp 32) erg respectively, are nearly 10 times larger than corresponding parameters of the ejections. So, the CME energy deficit problem seems to exist really. To solve this problem one can make an assumption that the process of the mass and energy growth of CMEs during their propagation out of the Sun observed in the solar corona is continued in supercorona too up to distances of 10-30 solar radii. This assumption is confirmed by the data analysis of five events observed using zodiacal light photometers of the HELIOS- I and HELIOS-2 spacecrafts. The mass growth rate is estimated to be equal to (1-7) x 10(exp 11) grm/sec. It is concluded that the CME contribution to mass and energy flows in the solar winds probably, is larger enough than the value of 3-5% adopted usually.

Description: Solar wind proton temperatures lower than expected for 'normal' solar wind expansion are a common signature of 'ejecta' (i.e. interplanetary coronal mass ejections). We have surveyed the OMNI solar wind data base for 1965-1991, and Helios data for 1974-1980, to identify regions of abnormally low temperatures. Their occurrence rate is clearly dependent on solar activity levels, in particular when the minority of events associated with encounters with the heliospheric plasma sheet are excluded. The analysis of the OMNI data may provide an indication of the rate of ejecta at the Earth, and hence of the CME rate, extending back to before spacecraft coronagraph observations became available in the early 1970's. We discuss the association of these solar wind structures with cosmic ray depressions bidirectional particle flows, and other ejecta signatures. Our impression is that no one ejecta signature provides a truly comprehensive indication of the presence of ejecta, but that abnormally low temperature depressions encompass most of the regions identified by these other individual signatures.

Description: We have been carrying out the interplanetary scintillation observations at a frequency of 327 MHz. The IPS measurements at this frequency can probe the distance range of 0.1-1 AU. We will report on source regions of the low-speed winds which were observed within 0.3 AU by the IPS method. The source regions of low-speed winds have been studied. In 1991, two spacecraft of Sakigake and IMP observed two low-speed streams in one solar rotation, which originated from a magnetic neutral line on the source surface. However speeds are slightly different from each other: one is 300 km/s while the other one is 400 km/s. Similar speed difference was also observed by the IPS method. We examined differences of these source regions in the soft X-ray images observed by the Yohkoh satellite. At the source region of the lower speed wind, sun spots were found under the neutral line, while nothing except the neutral line was found for the higher speed wind. We made a synoptic chart of the solar wind speeds which were observed within 0.3 AU. In this chart, compact regions of very low speed can be found clearly, and the amplitude of a low-speed belt is smaller than that of a magnetic neutral line. Distribution of the low-speed belt is rather suited above active regions than on a neutral line calculated by the potential field model.

Description: The radial distance dependence of solar wind speeds, which were measured by interplanetary scintillation method, has been studied especially for a high-speed solar wind, and large increase of the IPS speeds (300 km/s) was observed at the distance range of 0.1 - 0.3 AU. When the streams are mapped back onto the source surface, they distribute in polar coronal holes or their boundaries. Since the IPS measurement can be biased by several effects such as of line-of-sight integration, strong scattering and random velocities, we examined these biasing effects and have found difficulty to explain the large IPS speed increase with the biasing effects.

Description: Two-antenna scintillation (IPS) observations can provide accurate measurements of the velocity with which electron density fluctuations drift past the line of sight. We will present recent IPS measurements made with the EISCAT and VLBA arrays. It is common, particularly during declining activity. for the line of sight to pass through plasma with a wide range of speed. Therefore it is important to account for the line of sight integration. It is clear from ULYSSES measurements that the speed is bimodal in nature, i.e., either 'fast' or 'slow.' Thus it is not necessary to model a continuous velocity distribution - one need only locate the 'fast-slow' interface. In addition one must consider the possibility that the density fluctuations are moving with respect to the flow of particles. Alfven waves propagating through field-aligned density fluctuations can mimic a sound wave in this respect, so the apparent IPS velocity can be the flow speed plus the Alfven speed. In modeling the IPS it is important that the scattering be 'weak,' because the weak scattering model requires only 1 spatial parameter instead of 3. Furthermore the effect of multiple velocities in much more distinct in weak scattering. EISCAT can only operate near 933 MHz, which limits the observations to outside of 17R(solar mass). The VLBA is the only facility with the combination of high frequency operation and long baselines required to observe inside of 15R(solar mass). A simple bimodal model has been successfully used to interpret our IPS observations near the sun. Farther out interaction regions have built up significantly and a two speed model is no longer valid. An apparent deceleration in the fast polar wind is sometimes evident when compared to the ULYSSES observation. The density variance delta N(exp 2)e in the fast wind appears to decrease from equator to pole.

Description: Recent observations of coronal holes made with the soft X-ray telescope aboard Yohkoh have indicated a temperature of 1.8 approximately 2.1 x 10(exp 6) K and an emission measure of 10(exp 25.7 approximately 26.2) cm (exp -5). This is almost the same as in quiet regions of the Sun. Numerical simulations of the temperature density and velocity structure in a coronal hole. using a parameterized heating distribution have been used for a comparison with the Yohkoh observations. Models are obtained which fit the observed temperature and emission measure. with heating fluxes which are consistent with other measurements. However, the final velocity of the solar wind is very slow which indicates the necessity of another acceleration mechanism such as alfven waves.