The Effect of Loop Curvature on Coronal Loop Kink Oscillations

We will review analytical and numerical efforts in modelling the influence of curvature on coronal loop oscillations. We will mainly focus our attention on fast kink mode oscillations. A curved slab model will be presented, where it becomes clear that curvature introduces wave leakage into the system, because of changes in the equilibrium. The importance of leakage will be assessed through the use of a slab and cylindrical model where lateral leakage is allowed. A full analytical model for a semi-toroidal loop will be constructed for a system with no leaking waves but with an inhomogeneous layer that introduces damping due to the process of resonant absorption. The model for a semi-toroidal loop will be extended to also include leakage, and will be studied numerically. The numerical results will be compared to the analytical model.     

Coronal Seismology by Means of Kink Oscillation Overtones

The detection of overtones of coronal loop kink oscillations has been an important advance in the development of coronal seismology. It has significantly increased the potential of coronal seismology and has thus initiated important theoretical and observational improvements. New detections of overtones have been made and a reduction of the error bars has been obtained. The efforts of theoreticians to extend eigenmode studies to more general coronal loop models is no longer a matter of checking the robustness of the model but now also allows for the estimation of certain equilibrium parameters. The frequencies of the detected (longitudinal) overtones are in particular sensitive to changes in the equilibrium properties along the loop, especially the density and the magnetic field expansion. Also, attempts have been made to use the limited longitudinal resolution in combination with the theoretical eigenmodes as an additional seismological tool.     

Modeling Nonstationary Random Processes with an Application to Gyro Drift Rate

The problem of estimating the a priori statistics of a nonstationary process is considered using finite-time averages of experimental data. A model of the form of a linear time-invariant difference equation with a stationary independent random sequence driving function is proposed and investigated. Finite-time averages are calculated and then used in a steepest descent method to determine the coefficients of the difference nce equation. Methods are presented for transforming this model to the statespace pace format necessary for Kalman filtering, and an example is given using actual gyro drift-rate data.     

A simultaneous X-ray and radio observation of a flare from Algol

An X-ray flare was observed from Algol using the low and medium energy detectors on the European Space Agency's EXOSAT observatory. Spectra obtained during the flare are well fitted by thermal continua while an Fe XXV emission feature was also detected. The strength of this feature indicates a cosmic abundance for iron. The data indicate that the flare occurred in a loop of height approximately 0.25 of the K star radius & with a magnetic field >300 Gauss.     

Initial experimental results from the Laboratory Biosphere closed ecological system facility.

An initial experiment in the Laboratory Biosphere facility, Santa Fe, New Mexico, was conducted May-August 2002 using a soil-based system with light levels (at 12 h per day) of 58-mol m-2 d-1. The crop tested was soybean, cultivar Hoyt, which produced an aboveground biomass of 2510 grams. Dynamics of a number of trace gases showed that methane, nitrous oxide, carbon monoxide, and hydrogen gas had initial increases that were substantially reduced in concentration by the end of the experiment. Methane was reduced from 209 ppm to 11 ppm, and nitrous oxide from 5 ppm to 1.4 ppm in the last 40 days of the closure experiment. Ethylene was at elevated levels compared to ambient during the flowering/fruiting phase of the crop. Soil respiration from the 5.37 m2 (1.46 m3) soil component was estimated at 23.4 ppm h-1 or 1.28 g CO2 h-1 or 5.7 g CO2 m-2 d-1. Phytorespiration peaked near the time of fruiting at about 160 ppm h-1. At the height of plant growth, photosynthesis CO2 draw down was as high as 3950 ppm d-1, and averaged 265 ppm h-1 (whole day averages) during lighted hours with a range of 156-390 ppm h-1. During this period, the chamber required injections of CO2 to continue plant growth. Oxygen levels rose along with the injections of carbon dioxide. Upon several occasions, CO2 was allowed to be drawn down to severely limiting levels, bottoming at around 150 ppm. A strong positive correlation (about 0.05 ppm h-1 ppm-1 with r2 about 0.9 for the range 1000-5000 ppm) was observed between atmospheric CO2 concentration and the rate of fixation up to concentrations of around 8800 ppm CO2.     

High-performance EHA controls using an interior permanent magnetmotor

A controller for a high-performance electrohydrostatic actuator (EHA) using an interior permanent magnet (IPM) synchronous motor to produce servo motion is described. The buried-magnet design of the IPM motor yields desired characteristics such as high efficiency, robust rotor construction, and wide operating speed range. Power converter size is minimized by using insulated-gate bipolar transistor (IGBT) power switches combined with high-voltage integrated circuit (HVIC) gate drivers in phase-leg power modules. Experimental results for the demonstrator motor-controller hardware rated at 12 hp (continuous) are presented confirming the IPM motor drive's performance     

An EXOSAT observation of the morphology of the coronal X-ray emission from algol

The X-ray emission from Algol is thought to originate in a corona associated with the K star in this system. We report the results of a 35 hr continuous EXOSAT observation through secondary optical eclipse that was designed to measure the structure of the corona. No obvious X-ray eclipse was seen. The spectrum measured by the ME gives a temperature of 2.5 × 10⁷ K, consistent with the hard component previously seen by the Einstein SSS. The soft component previously reported by the SSS would only contribute at most 25% to the count rate seen in the LE (used with Al/P). The lack of a hard X-ray eclipse indicates the dimensions of the higher temperature emission region to be comparable to or greater than the size of the K star. An X-ray flare was detected with a peak luminosity of 1.4 × 10³¹ erg s^-1 and a total duration of 8 hours. The peak temperature was 5.0 keV with an emission measure of 9.4 × 10⁵³ cm^-3. The thermal nature of the flare is confirmed by the detection of an iron line with an EW of 2 keV. By equating the observed decay time of the flare to a known cooling law gives a dimension for the flaring loop of 0.3 stellar radii. This is much smaller than the dimensions of the hard component inferred from the lack of an eclipse. It seems probable that the flare occurred in one of the loops responsible for the lower temperature component seen by the SSS.     

Influence of gravitoinertial force on vestibular nystagmus in man observed in a centrifuge.

The influence of gravity load on the vestibular system in man was investigated in a centrifuge operating on the free swing principle. The vertical vestibular nystagmus induced by acceleration to 3G was analyzed and compared with reference measurements during 1G. Our data indicate that the effects of increased gravity load include a prolonged decay time constant of upbeat nystagmus and a subject-dependent persisting upbeat nystagmus. In an attempt to explain these findings, an extension of the velocity storage model is proposed, with gravity as a second stimulus function in addition to angular acceleration.     

Noise effects on centroid tracker aim point estimation

An investigation of errors due to noise in centroid tracker aim-point estimation is presented. The centroid tracker discussed is similar to the tracker described by A.L. Gilbert et al. (1980). Simplifications to this algorithm were made so that the derived models would be consistent with the actual tracker algorithm. Two statistical models are derived which relate image noise effects to computation of the target centroid. The first model, the simplified aim-point error model, is derived by assuming that the probabilities of incorrectly classifying target and background pixels are equal. The second model, the extended aim-point error model, is derived by assuming that the probability of incorrectly classifying a target pixel can differ from the probability of incorrectly classifying a background pixel. These models are described and their mathematical implication is discussed. Simulation results which verify the models are presented     

Atmospheric Science with InSight

In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP³), the InSight lander holds a highly sensitive pressure sensor (PS) and the Temperature and Winds for InSight (TWINS) instrument, both of which (along with the InSight FluxGate (IFG) Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated with the RADiometer (RAD) instrument which will measure the surface brightness temperature, and the Instrument Deployment Camera (IDC) which will be used to quantify atmospheric opacity, this will make InSight capable to act as a meteorological station at the surface of Mars. While probing the internal structure of Mars is the primary scientific goal of the mission, atmospheric science remains a key science objective for InSight. InSight has the potential to provide a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous in situ missions. In the paper, key results from multiscale meteorological modeling, from Global Climate Models to Large-Eddy Simulations, are described as a reference for future studies based on the InSight measurements during operations. We summarize the capabilities of InSight for atmospheric observations, from profiling during Entry, Descent and Landing to surface measurements (pressure, temperature, winds, angular momentum), and the plans for how InSight’s sensors will be used during operations, as well as possible synergies with orbital observations. In a dedicated section, we describe the seismic impact of atmospheric phenomena (from the point of view of both “noise” to be decorrelated from the seismic signal and “signal” to provide information on atmospheric processes). We discuss in this framework Planetary Boundary Layer turbulence, with a focus on convective vortices and dust devils, gravity waves (with idealized modeling), and large-scale circulations. Our paper also presents possible new, exploratory, studies with the InSight instrumentation: surface layer scaling and exploration of the Monin-Obukhov model, aeolian surface changes and saltation / lifing studies, and monitoring of secular pressure changes. The InSight mission will be instrumental in broadening the knowledge of the Martian atmosphere, with a unique set of measurements from the surface of Mars.