Coronal holes and solar magnetic fields

Since 1972, nearly continuous observations of coronal holes and their associated photospheric magnetic fields have been made using a variety of satellite and ground-based equipment. The results of comparisons of these observations are reviewed and it is demonstrated that the structure and evolution of coronal holes is basically governed by the large-scale distribution of photospheric magnetic flux. Non-polar holes form in the decaying remnants of bipolar magnetic regions in areas with a large-scale flux imbalance. There is strong indirect evidence that the magnetic field in coronal holes is always open to interplanetary space but not all open-field regions have associated coronal holes. The well-observed declining phase of the last solar cycle was characterized by stable magnetic field and coronal hole patterns which were associated with recurrent, high-speed wind streams and interplanetary magnetic field patterns at the Earth. The ascending phase of the current cycle has been characterized by transient magnetic field and coronal hole patterns which tend to occur at high solar latitudes. This shift in magnetic field and coronal hole patterns has resulted in a less obvious and more complicated association with high-speed wind streams at the Earth.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Visiting Scientist, Kitt Peak National Observatory.     

Dynamics of the preflare magnetic field

Space Science Reviews - Many theories of the solar flare process invoke storage of energy in the active region magnetic field above the solar photosphere. Observational evidence relating to such...     

Space telescope observations of the earth's upper atmosphere by stellar occultations

Stellar occultations provide a useful means of measuring the trace gas composition of the Earth's mesosphere with a sensitivity of order one part per billion. The operational details will differ from those of other astronomical observations by ST, because of the difficulties in guiding near the Earth's limb. Two specific trace gases of interest to atmospheric studies, C$\text{l}$ and C$\text{l}$O, are discussed in this paper.     

Space power systems: Producing transportation (and other chemical) fuels as an alternative to electricity generation

While most studies on space power systems target electricity generation as the energy product, industrialized nations also have a need for chemicals to support transportation and other purposes. This paper therefore describes an alternative target for the application of space power systems: the production of chemical fuels based on radiant energy beamed or reflected from orbiting platforms. If cost and efficiency targets can be achieved, Solar Thermochemical Plants—occupying a few square kilometers each—can potentially generate substantial quantities of transportation fuels, therefore enabling reductions in the consumption of petroleum and the emission of carbon dioxide. The specifics of the approach that are described in this paper include the concentration of radiant energy within ground-based systems so that high temperature heat is provided for thermochemical process networks. This scoping study includes the evaluation of various feedstock chemicals as input to the Solar Thermochemical Plant: natural gas, biomass and zero-energy chemicals (water and carbon dioxide); and the production of either hydrogen or long-chain hydrocarbons (i.e., Fischer–Tropsch fuels) as the Solar Fuel product of the plant.     

Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.     

M stars as targets for terrestrial exoplanet searches and biosignature detection

The changing view of planets orbiting low mass stars, M stars, as potentially hospitable worlds for life and its remote detection was motivated by several factors, including the demonstration of viable atmospheres and oceans on tidally locked planets, normal incidence of dust disks, including debris disks, detection of planets with masses in the 5-20 M() range, and predictions of unusually strong spectral biosignatures. We present a critical discussion of M star properties that are relevant for the long- and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets, and the advantages and disadvantages of M stars as targets in searches for terrestrial HZ planets using various detection techniques. Biological viability seems supported by unmatched very long-term stability conferred by tidal locking, small HZ size, an apparent short-fall of gas giant planet perturbers, immunity to large astrosphere compressions, and several other factors, assuming incidence and evolutionary rate of life benefit from lack of variability. Tectonic regulation of climate and dynamo generation of a protective magnetic field, especially for a planet in synchronous rotation, are important unresolved questions that must await improved geodynamic models, though they both probably impose constraints on the planet mass. M star HZ terrestrial planets must survive a number of early trials in order to enjoy their many Gyr of stability. Their formation may be jeopardized by an insufficient initial disk supply of solids, resulting in the formation of objects too small and/or dry for habitability. The small empirical gas giant fraction for M stars reduces the risk of formation suppression or orbit disruption from either migrating or nonmigrating giant planets, but effects of perturbations from lower mass planets in these systems are uncertain. During the first approximately 1 Gyr, atmospheric retention is at peril because of intense and frequent stellar flares and sporadic energetic particle events, and impact erosion, both enhanced, the former dramatically, for M star HZ semimajor axes. Loss of atmosphere by interactions with energetic particles is likely unless the planetary magnetic moment is sufficiently large. For the smallest stellar masses a period of high planetary surface temperature, while the parent star approaches the main sequence, must be endured. The formation and retention of a thick atmosphere and a strong magnetic field as buffers for a sufficiently massive planet emerge as prerequisites for an M star planet to enter a long period of stability with its habitability intact. However, the star will then be subjected to short-term fluctuations with consequences including frequent unpredictable variation in atmospheric chemistry and surficial radiation field. After a review of evidence concerning disks and planets associated with M stars, we evaluate M stars as targets for future HZ planet search programs. Strong advantages of M stars for most approaches to HZ detection are offset by their faintness, leading to severe constraints due to accessible sample size, stellar crowding (transits), or angular size of the HZ (direct imaging). Gravitational lensing is unlikely to detect HZ M star planets because the HZ size decreases with mass faster than the Einstein ring size to which the method is sensitive. M star Earth-twin planets are predicted to exhibit surprisingly strong bands of nitrous oxide, methyl chloride, and methane, and work on signatures for other climate categories is summarized. The rest of the paper is devoted to an examination of evidence and implications of the unusual radiation and particle environments for atmospheric chemistry and surface radiation doses, and is summarized in the Synopsis. We conclude that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations. A detection or repeated nondetections could provide a unique opportunity to partially answer a fundamental and recurrent question about the relation between stability and complexity, one that is not addressed by remote detection from a planet orbiting a solar-like star, and can only be studied on Earth using restricted microbial systems in serial evolution experiments or in artificial life simulations. This proposal requires a planet that has retained its atmosphere and a water supply. The discussion given here suggests that observations of M star exoplanets can decide this latter question with only slight modifications to plans already in place for direct imaging terrestrial exoplanet missions.     

Biomarker response to galactic cosmic ray-induced NOx and the methane greenhouse effect in the atmosphere of an Earth-like planet orbiting an M dwarf star

Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NOx) in Earth-like atmospheres. We investigate to what extent these NO(Mx) species may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NOx effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth.     

Advantages of using subsurface flow constructed wetlands for wastewater treatment in space applications: ground-based Mars Base prototype.

Research and design of subsurface flow wetland wastewater treatment systems for a ground-based experimental prototype Mars Base facility has been carried out, using a subsurface flow approach. These systems have distinct advantages in planetary exploration scenarios: they are odorless, relatively low-labor and low-energy, assist in purification of water and recycling of atmospheric CO2, and will support some food crops. An area of 6-8 m2 may be sufficient for integration of wetland wastewater treatment with a prototype Mars Base supporting 4-5 people. Discharge water from the wetland system will be used as irrigation water for the agricultural crop area, thus ensuring complete recycling and utilization of nutrients. Since the primary requirements for wetland treatment systems are warm temperatures and lighting, such bioregenerative systems may be integrated into early Mars base habitats, since waste heat from the lights may be used for temperature maintenance in the human living environment. "Wastewater gardens (TM)" can be modified for space habitats to lower space and mass requirements. Many of its construction requirements can eventually be met with use of in-situ materials, such as gravel from the Mars surface. Because the technology requires little machinery and no chemicals, and relies more on natural ecological mechanisms (microbial and plant metabolism), maintenance requirements are minimized, and systems can be expected to have long operating lifetimes. Research needs include suitability of Martian soil and gravel for wetland systems, system sealing and liner options in a Mars Base, and wetland water quality efficiency under varying temperature and light regimes.