UVCS Observations of Velocity Shear at Streamer Boundaries in the Corona

Space Science Reviews - Measurements of the intensities of the O?vi 1032and 1037&;nbsp;Å spectral lines in the southern solar hemisphere, from 1.5 to 5&;nbsp;R s, were made with...     

Source Region of High and Low Speed Wind during the Spartan 201-05 Flight

The large-scale coronal magnetic fields of the Sun are believed to play an important role in organizing the coronal plasma and channeling the high and low speed solar wind along the open magnetic field lines of the polar coronal holes and the rapidly diverging field lines close to the current sheet regions, as has been observed by the instruments aboard the Ulysses spacecraft from March 1992 to March 1997. We have performed a study of this phenomena within the framework of a semi-empirical model of the coronal expansion and solar wind using Spartan, SOHO, and Ulysses observations during the quiescent phase of the solar cycle. Key to this understanding is the demonstration that the white light coronagraph data can be used to trace out the topology of the coronal magnetic field and then using the Ulysses data to fix the strength of the surface magnetic field of the Sun. As a consequence, it is possible to utilize this semi-empirical model with remote sensing observation of the shape and density of the solar corona and in situ data of magnetic field and mass flux to predict values of the solar wind at all latitudes through out the solar system. We have applied this technique to the observations of Spartan 201-05 on 1–2 November, 1998, SOHO and Ulysses during the rising phase of this solar cycle and speculate on what solar wind velocities Ulysses will observe during its polar passes over the south and the north poles during September of 2000 and 2001. In order to do this the model has been generalized to include multiple streamer belts and co-located current sheets. The model shows some interesting new results. This revised version was published online in August 2006 with corrections to the Cover Date.     

Automatic Controller for a Sweeping Microwave Receiver

The Automatic System Controller (ASC) is a very simple automatic data processing system designed to provide unattended operation of the R-31 receiver, a sweeping microwave receiver. With the receiver set to operate in the scanning mode, its video output is processed by the ASC, which recognizes by thresholding the presence of a signal in the receiver pass band. When the threshold is exceeded, a receiver sweep stop is actuated, an appropriate receiver mode is selected, and an on-site tape recorder is turned on. To enhance signal acquisition, the ASC provides noise leveling gain control, the gating of undesirable signals, and useful aids for an operator attending the receiver.     

An endogenous growth pattern of roots is revealed in seedlings grown in microgravity

In plants, sensitive and selective mechanisms have evolved to perceive and respond to light and gravity. We investigated the effects of microgravity on the growth and development of Arabidopsis thaliana (ecotype Landsberg) in a spaceflight experiment. These studies were performed with the Biological Research in Canisters (BRIC) hardware system in the middeck region of the space shuttle during mission STS-131 in April 2010. Seedlings were grown on nutrient agar in Petri dishes in BRIC hardware under dark conditions and then fixed in flight with paraformaldehyde, glutaraldehyde, or RNAlater. Although the long-term objective was to study the role of the actin cytoskeleton in gravity perception, in this article we focus on the analysis of morphology of seedlings that developed in microgravity. While previous spaceflight studies noted deleterious morphological effects due to the accumulation of ethylene gas, no such effects were observed in seedlings grown with the BRIC system. Seed germination was 89% in the spaceflight experiment and 91% in the ground control, and seedlings grew equally well in both conditions. However, roots of space-grown seedlings exhibited a significant difference (compared to the ground controls) in overall growth patterns in that they skewed to one direction. In addition, a greater number of adventitious roots formed from the axis of the hypocotyls in the flight-grown plants. Our hypothesis is that an endogenous response in plants causes the roots to skew and that this default growth response is largely masked by the normal 1?g conditions on Earth.     

Electromagnetic Effects of Aircraft Wake-Active Feuillet Interaction

A mechanism by which an aircraft wake can interact strongly with the electromagnetic radiation present in an active elevated anomalous refractivity region (active feuillet) is analyzed. The aircraft wake structure, assumed to consist of twin contrarotating vortices plus entrained irrotational gas, trailing behind the wings of typical large aircraft is shown to be capable of descending a distance of approximately 3 wing span distances and attaining a length of the order of 10 km, prior to instability-induced disruption. The parcel of air such a descending coherent wake structure can convey into an active feuillet is demonstrated to alter significantly the local refractive index of the duct and induce substantial radiation spillage. The general characteristics of the electromagnetic radiation produced by this interaction process (i.e., scattering by diaphanous objects) is described.     

Synchronization effects on probability of pulse train interception

Expressions for the probability of coincidence between pairs of pulse trains are examined. The application to systems of interest in the field of electronic warfare is emphasized. Theoretical results for the limit of uncorrelated pulse trains are reviewed and new theory is developed to cover the case of coincidence between uniform pulse trains where the coincidence phenomena may be highly correlated. Monte Carlo experiments show that increasing the jitter level on one of the pulse trains causes a transition between the correlated and uncorrelated regimes     

The entropy in groups – a clue to galaxy formation

The entropy in the hot X-ray gas in groups of galaxies is a fossil of the process of galaxy formation The amount of entropy in these low mass systems considerably exceeds that predicted from structure formation models. To explain these results requires “extra” energy which is a relic of the process of star formation and active galaxy heating. We present new XMM results on the entropy and entropy profiles. These results are inconsistent with pre-heating scenarios which have been developed to explain the entropy floor in groups but are broadly consistent with models of structure formation which include the effects of heating and/or the cooling of the gas. The total entropy in these systems provides a strong constraint on all models of galaxy and group formation, and on the poorly defined feedback process which controls the transformation of gas into stars and thus the formation of structure in the universe.     

Smallsats for METOP: Design definition, heritage and performance

The results of a study by MMS for BNSC and the UK Meteorological Office into the potential use of Smallsats to support METOP are reported. A risk of degradation or failure of a mission critical instrument during the METOP lifetime has been identified. The scenario proposed uses a Smallsat flying in formation with METOP to replace a failed instrument with data being returned to METOP via an inter-satellite link. An assessment of small launcher and small platform availability and instrument interface requirements indicates that such a scenario is feasible. Minor modifications to METOP and a relative pointing correction during ground processing would be required. It is concluded that a Smallsat could provide a significant improvement to METOP programme reliability with low design and cost risk. Scenario attractiveness depends upon whether a critical instrument failure would justify replacement.