Stabilizing the carbon dioxide–induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (∼10 13 watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission–free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non–primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.

[1] We present a numerical study of the propagation of VLF whistler waves in the magnetospheric plasma. In this study the plasma is considered to be homogeneous in the direction along the ambient magnetic field and strongly inhomogeneous across it. The goal of this investigation is to understand whistler propagation in magnetic-field-aligned channels (also called ducts) with either enhanced or depleted plasma density. In particular, the paper is focused on situations where the transverse scale size of the duct is comparable to or smaller than the perpendicular wavelength of the whistler. In this case, classical analysis of the whistler dynamics based on the geometrical optic approximation becomes invalid, and numerical solutions of the full wave equations should be performed. Our simulations extend the earlier analysis based on the ray-tracing technique and analytical studies of the very low frequency wave equations. We show that high-density ducts are inherently leaky and this leakage depends on the perpendicular wavelength of the wave inside the duct. We also show that whistler trapping occurs not only at density maxima and minima but also at critical points along a density gradient. This effect can explain whistler guiding along strong transverse plasma density gradients at the plasmapause.

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Steady-state planar ablative flow in a laser produced plasma is studied. The calculations relate all steady-state fluid quantities to only three parameters, the material, absorbed irradiance, and laser wavelength. The fluid is divided into three regions; the subcritical expanding plasma, the steady-state ablation front, and the accelerated slab. Boundary conditions at the interfaces of these regions are given. If the absorbed irradiance is nonuniform, the nonuniformity in ablation pressure is calculated. Results are compared with experiment and fluid simulation for both uniform and nonuniform illumination.

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)2 The interaction of intense, femtosecond (fsec) laser pulses with a dielectric medium is examined using a numerical simulation. The simulation uses the 1-D electromagnetic wave equation to model laser pulse propagation. In addition, it includes multiphoton ionization, electron attachment, ohmic heating of free electrons, and temperature dependent collisional ionization. Laser pulses considered in this study are characterized by peak intensities -1012 to 1014 W/cm and pulse durations -10 to 100 fsec. These laser pulses, interacting with fused silica, are shown to produce abovecritical plasma densities and electron energy densities sufficient to attain experimentally measured damage thresholds. Significant transmission of laser energy is observed even in cases where the peak plasma density is above the critical density for reflection. A damage fluence based on absorbed laser energy is calculated for various pulse durations. The calculated damage fluence is found to be consistent with recent experimental results. SPONSORING I MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR / MONITOR'S ACRONYM(S) ONR SUBJECT TERMSUltra-short laser pulse; Laser-dielectric interaction; Ionization; Laser damage 16.

A detailed theory in conjunction with the results of computer simulation experiments is presented for the beam cyclotron instability. The main results are (1) After a period of exponential quasilinear development, turbulent wave-particle interactions cause cross-field diffusion of the electrons which smears out the electron gyroresonances. This occurs at a level of turbulence which scales as Σκ(| Eκ |2/4πN0Te)∼(Ωe/ωe)2(Ωe/kve), where Ωe and ωe are the electron cyclotron and plasma frequencies, and results in a transition to ordinary ion sound modes that would occur in an unmagnetized plasma. The magnetic field serves to reduce the effects of electron trapping. (2) This level of turbulence appears to have virtually no effect on long wavelength fluid modes. (3) At this level the instability stabilizes if ordinary ion sound is stable due to ion Landau damping. For cold ions it continues to develop at the slower ion acoustic growth rate until the fields become strong enough to trap the ions. After the fields saturate, further plasma heating is much slower than exponential.

This article is an editorial, which makes the case that fusion breeding (that is using fusion neutrons to breed nuclear fuel for use in conventional nuclear reactors) is the best objective for the fusion program. To make the case, it reviews a great deal of plasma physics and fusion data. Fusion breeding could potentially play a key role in delivering large-scale sustainable carbon-free commercial power by mid-century. There is almost no chance that pure fusion can do that. The leading magnetic fusion concept, the tokamak, is subject to well-known constraints, which we have called conservative design rules, and review in this paper. These constraints will very likely prevent tokamaks from ever delivering economical pure fusion. Inertial fusion, in pure fusion mode, may ultimately be able to deliver commercial power, but the failure to date of the leading inertial fusion experiment, the National Ignition Campaign, shows that there are still large gaps in our understanding of laser fusion. Fusion breeding, based on either magnetic fusion or inertial fusion, greatly relaxes the requirements on the fusion reactor. It is also a much better fit to today's and tomorrow's nuclear infrastructure than is its competitor, fission breeding. This article also shows that the proposed fusion and fission infrastructure, 'The Energy Park', reviewed here, is sustainable, economically and environmentally sound, and poses little or no proliferation risk.

include, among other things, continuous frequency tunability, very high power of operatbios asid hiigh efficiency. Vic free electron laamr ;s charmeterized by a pump field; foi example., a spatially periodic magnetic filrd, which scatters from o, relativistic electron bkatn. The scattered radiation has a wavelength much smaller thaai the pump wavelength depending on the electron (Continued) DD ASTRACT (Continued),beoz energy. We present & general self-conulsteAt non-linear theory of the free electron lawe promess. The non4invar formulation of'the temporal steady state free electron laser problem results in -st of coupled differential Oquatirns govairiiip the spatWa ovolution of the ampl itudes and wavelength lrnf the radiation~ad space charge f&r1Ida These 1!quations are readily solved numerialy since the amnpltude and wavelength vtry on a Mpatla Scale which is comparable to a growth length of the output radiation. A itunaber of nuinerical/analytical illustrations are presenetd ranging from the optical to the stibmillllmter wavelunitth regime. Our non incear formulation in the linear regime is compared with lknsar theory and agrement is found to he excellent.. Analytical expressions for the saturated of ficiency and radiation amplitude ate als Shown to be in very good agreement with our non-linear numerical soiutiana. Efficiency curves are obtained for both the optical and submindimoter FEL examples with fixed magnetic: pump parameters. We show that these intrinsic efficiencie can be greatly enhanced by appropriately contouring the magnetic pump period~ciii the case of the optical FEL, the theoretical W4nge pals efficiency can be peter than 20% by'ã ppropriately decreasing the pump period and increasing th, pump magnetic field.