The July 1974 solar events: A possible lower limit for microwave activity

The active region McMath 10433 was the source of several flares and radio outbursts during the early part of July 1974. This region was tracked continuously, for several periods during the month at 22.2 GHz using a telescope with a 4 beam. Comparison with the results obtained simultaneously with a normal 7 GHz solar patrol instrument indicate that there is important burst activity occurring at levels below the detection limit of normal solar patrol instruments. The time-development morphology of these bursts is similar to those normally observed and has enabled the simple events to be re-interpreted. A completely new type of event - the fast absorption - has also been recognized. The correlation of the microwave events with SPA events observed on VLF propagation is also discussed.Spending a sabbatical year at CRAAM, São Paulo, Brazil.     

Operational requirements and the geometry of a station-keeping maneuver

In this paper station-keeping is regarded as the specialization of relative motion referred to a moving, orbiting origin. For this study a well-known linear solution to this problem serves as a base formulation from which the investigation begins.Even though the overall problem could be separated into three parts—necessitating two distinct studies for coverage—this paper examines only the last phase of the operation. That is, it is the continuation, or retention, of a relative motion sub-orbit which is of interest in this analysis.The situation becomes one of determining what is needed to maintain the sub-orbit, and/or to adjust it. In addition, the consequences of these actions, and the results predicted from theory are established, examined, and commented upon. In the presentation of information gathered from this study, various graphs have been prepared; however, these are expressed in a dimensionless format so that the results apply equally to all reasonable reference orbits.For this analysis the separate and combined influences, due to both the initial relative motion state and to a thrusting condition, are examined. Also, the consequences of referencing the acquired sub-orbits to an inertially aligned frame of reference (rather than the familiar rotating one) are illustrated, discussed, and commented upon.Formerly: Sr. Analyst and Manager, Seabrook Office, AMA, Inc., Seabrook, Md., U.S.A.     

Coronal holes,solar wind streams,and geomagnetic activity during the new sunspot cycle

We have extended our previous study of coronal holes, solar wind streams, and geomagnetic disturbances from the declining phase (1973–1975) of sunspot cycle 20 through sunspot minimum (1976) into the rising phase (1977) of cycle 21. Using daily He I 10830 Å spectroheliograms and photospheric magnetograms, we found the following results:

1. As the magnetic field patterns changed, the solar atmosphere evolved from a structure having a few, large, long-lived, low-latitude coronal holes to one having numerous small, short-lived, high-latitude holes (in addition to the polar holes which persisted throughout this 5-year interval).
2. The high-latitude holes recurred with a synodic rotation period of 28–29 days instead of the 27-day period already known to be characteristic of low-latitude holes.
3. During 1976–1977 many coronal holes were intrinsically ‘weak’ in the sense that their average intensities did not differ greatly from the intensity of their surroundings. Such low-contrast holes were rare during 1973–1975.

An updated Bartels display of the occurrence of holes, wind speed, and geomagnetic activity summarizes the evolution of their characteristics and interrelations as the sunspot cycle has progressed. Long-lived, low-latitude holes have become rare but remain terrestrially effective. The more common high-latitude holes are effective only when the Earth lies at a relatively high heliographic latitude in the same solar hemisphere.     

Longevity of fluorine-bearing tremolite on Venus

There is a general belief that hydrous minerals cannot exist on Venus under current surface conditions. This view was challenged when Johnson and Fegley (2000, Icarus 146, 301-306) showed that tremolite (Ca₂Mg₅Si₈O₂₂(OH)₂), a hydrous mineral, is stable against thermal decomposition at current Venus surface temperatures, e.g., 50% decomposition in 4 Ga at 740 K. To further explore hydrous mineral thermal stability on Venus, we experimentally determined the thermal decomposition kinetics of fluorine-bearing tremolite. Fluor-tremolite is thermodynamically more stable than OH-tremolite and should decompose more slowly. However how much slower was unknown. We measured the decomposition rate of fluorine-bearing tremolite and show that its decomposition is several times to greater than ten times slower than that of OH-tremolite. We also show that F-bearing tremolite is depleted in fluorine after decomposition and that fluorine is lost as a volatile species such as HF gas. If tremolite ever formed on Venus, it would probably also contain fluorine. The exceptional stability of F-bearing tremolite strengthens our conclusions that if hydrous minerals ever formed on Venus, they could still be there today.     

Dynamics of Two Planets in the 3/2 Mean-motion Resonance: Application to the Planetary System of the Pulsar PSR B1257+12

This paper considers the dynamics of two planets, as the planets B and C of the pulsar PSR B1257+12, near a 3/2 mean-motion resonance. A two-degrees-of-freedom model, in the framework of the general three-body planar problem, is used and the solutions are analyzed through surfaces of section and Fourier techniques in the full phase space of the system.On the possibility of existence of a fourth planet in distant orbit, see Wolszczan et al., 2000     

Afghanistan: rich resource base and existing environmental despoliation

Because of its climatically stressed dry land and high altitudes, coupled with severe human despoliation amid three decades of war and known rampant corruption, Afghanistan has long had severe environmental problems. Overgrazing, deforestation, ??deshrubification,?? soil erosion, soil salinization, ground and surface water contamination and water overuse beyond natural recharge, climate change, threats to biodiversity, and natural hazards are the background problems already causing strong environmental stress. With the advent of the newly recognized mineral resources that will be exploited, additional environmental stressors are likely. Agencies of the United Nations, in concert with new national environmental laws and programs, offer some potential for remediation of environmental problems in the face of unrelenting societal pressures to ignore them. Whether Afghanistan will rise out of its status as a failed state depends in some large way upon whether the newly recognized mineral resources are exploited in environmentally benign ways.     

The evolution of the polar coronal holes

He i 10830 Å synoptic maps, obtained at the Kitt Peak National Observatory during 1974–1979, show that the Sun's polar coronal holes have contracted significantly during 1977–1978. Prior to the accelerated increase of sunspot activity in mid-1977, the area of each polar cap was on the order of 8% of the Sun's total surface area (4R ²), whereas toward the end of 1978 these areas fell below 2% of 4R ². Synoptic polar plots show that the vestigual holes had irregular shapes and were often well removed from the poles themselves. These results are consistent with the changes that one would expect when the polar magnetic fields are weakening just prior to sunspot maximum.     

Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets

We used chemical equilibrium and chemical kinetic calculations to model chemistry of the volatiles released by heating different types of carbonaceous, ordinary and enstatite chondritic material as a function of temperature and pressure. Our results predict the composition of atmospheres formed by outgassing during accretion of the Earth and other terrestrial planets. Outgassing of CI and CM carbonaceous chondritic material produces H₂O-rich (steam) atmospheres in agreement with the results of impact experiments. However, outgassing of other types of chondritic material produces atmospheres dominated by other gases. Outgassing of ordinary (H, L, LL) and high iron enstatite (EH) chondritic material yields H₂-rich atmospheres with CO and H₂O being the second and third most abundant gases. Outgassing of low iron enstatite (EL) chondritic material gives a CO-rich atmosphere with H₂, CO₂, and H₂O being the next most abundant gases. Outgassing of CV carbonaceous chondritic material gives a CO₂-rich atmosphere with H₂O being the second most abundant gas. Our results predict that the atmospheres formed during accretion of the Earth and Mars were probably H₂-rich unless the accreted material was dominantly CI and CM carbonaceous chondritic material. We also predict significant amounts of S, P, Cl, F, Na, and K in accretionary atmospheres at high temperatures (1500-2500 K). Finally, our results may be useful for interpreting spectroscopic observations of accreting extrasolar terrestrial planets.