Evidence for short cooling time in the Io plasma torus

We present empirical evidence for a radiative cooling time for the Io plasma torus that is about a factor of ten less than presently accepted values. We show that brightness fluctuations of the torus in the extreme ultraviolet (EUV) at one ansa are uncorrelated with the brightness at the other ansa displaced in time by five hours, either later or earlier. Because the time for a volume of plasma to move from one ansa to the other is only five hours, the cooling time must be less than this transport time in order to wipe out memory of the temperatures between ansae. Most (∼80–85%) of the EUV emission comes from a narrow (presumably ribbon‐like) feature within the torus. The short cooling time we observe is compatible with theoretical estimates if the electron density in the ribbon is ∼10^4/cm^3. The cooling time for the rest of the torus (which radiates the remaining 15–20% of the power) is presumably consistent with the previously derived 20‐hour values. A nearly‐continuous heating in both longitude and time is needed to maintain the EUV visibility of the torus ribbon—a requirement not satisfied by presently available theories

Superthermal electron processes in the upper atmosphere of Uranus: Aurora and electroglow

Strong ultraviolet emissions from the upper atmosphere of Uranus suggest that both auroral and electroglow phenomena are of significant aeronomical consequences in the structure of the upper atmosphere. Combined modeling and data analysis were performed to determine the effect of electroglow and auroral phenomena on the global heat and atomic hydrogen budgets in the Uranus upper atmosphere. The results indicate that the auroral and electroglow heat sources are not adequate to explain the high exospheric temperature observed at Uranus, but that the atomic hydrogen supplied by these processes is more than sufficient to explain the observations. The various superthermal electron distributions modeled have significantly different efficiencies for the various processes such as UV emission, heating, ionization, and atomic hydrogen production, and produce quite different H2 band spectra. However, additional information on the UV spectra and global parameters is needed before modeling can be used to distinguish between the possible mechanisms for electroglow

On the causes of plasmaspheric rotation variability: IMAGE EUV observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95534/1/jgra20000.pd

Quantifying the azimuthal plasmaspheric density structure and dynamics inferred from IMAGE EUV

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95221/1/jgra22185.pd

NG7538 IRS1 N: modeling a circumstellar maser disk

We present an edge-on Keplerian disk model to explain the main component of the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N. The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disk. The bend seen in the position-velocity diagram is a characteristic signature of differentially rotating disks. For a central mass of 30 solar masses, suggested by other observations, our model fixes the masing disk to have inner and outer radii of about 270 AU and 750 AU.Comment: To appear in The Proceedings of the 2004 European Workshop: "Dense Molecular Gas around Protostars and in Galatic Nuclei", Eds. Y. Hagiwara, W.A. Baan, H.J. van Langevelde, 2004, a special issue of ApSS, Kluwe

The Jovian hydrogen bulge: Evidence for co-rotating magnetospheric convection

The hydrogen bulge is a feature in Jupiter's upper atmosphere that co-rotates with the planetary magnetic field (i.e. the hydrogen bulge is fixed in System III coordinates). It is located approximately 180[deg] removed in System III longitude from the active sector, which has been identified as the source region for Jovian decametric radio emission and for release of energetic electrons into interplanetary space. According to the magnetic-anomaly model, the active sector is produced by the effect of the large magnetic anomaly in Jupiter's northern hemisphere. On the basis of the magnetic-anomaly model, it has been theoretically expected for some time that a two-cell magnetospheric convection pattern exists within the Jovian magnetosphere. Because the convection pattern is established by magnetic-anomaly effects of the active sector, the pattern co-rotates with Jupiter. (This is in contrast to the Earth's two-cell convection pattern that is fixed relative to the Sun with the Earth rotating beneath it.) The sense of the convection is to bring hot magnetospheric plasma into the upper atmosphere in the longitude region of the hydrogen bulge. This hot plasma contains electrons with energies of the order of 100keV that dissociate atmospheric molecules to produce the atomic hydrogen that creates the observed longitudinal asymmetry in hydrogen Lyman alpha emission. We regard the existence of the hydrogen bulge as the best evidence available thus far for the reality of the expected co-rotating magnetospheric convection pattern.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24466/1/0000741.pd

Imaging Thermal He(+)in Geospace from the Lunar Surface

By mass, thermal plasma dominates near-earth space and strongly influences the transport of energy and mass into the earth's atmosphere. It is proposed to play an important role in modifying the strength of space weather storms by its presence in regions of magnetic reconnection in the dayside magnetopause and in the near to mid-magnetotail. Ionospheric-origin thermal plasma also represents the most significant potential loss of atmospheric mass from our planet over geological time. Knowledge of the loss of convected thermal plasma into the solar wind versus its recirculation across high latitudes and through the magnetospheric flanks into the magnetospheric tail will enable determination of the mass balance for this mass-dominant component of the Geospace system and of its influence on global magnetospheric processes that are critical to space weather prediction and hence to the impact of space processes on human technology in space and on Earth. Our proposed concept addresses this basic issue of Geospace dynamics by imaging thermal He(+) ions in extreme ultraviolet light with an instrument on the lunar surface. The concept is derived from the highly successful Extreme Ultraviolet imager (EUV) flown on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. From the lunar surface an advanced EUV imager is anticipated to have much higher sensitivity, lower background noise, and higher communication bandwidth back to Earth. From the near-magnetic equatorial location on the lunar surface, such an imager would be ideally located to follow thermal He(+) ions to high latitudes, into the magnetospheric flanks, and into the magnetotail

'A habitual disposition to the good': on reason, virtue and realism

Amidst the crisis of instrumental reason, a number of contemporary political philosophers including Jürgen Habermas have sought to rescue the project of a reasonable humanism from the twin threats of religious fundamentalism and secular naturalism. In his recent work, Habermas defends a post-metaphysical politics that aims to protect rationality against encroachment while also accommodating religious faith within the public sphere. This paper contends that Habermas’ post-metaphysical project fails to provide a robust alternative either to the double challenge of secular naturalism and religious fundamentalism or to the ruthless instrumentalism that underpins capitalism. By contrast with Habermas and also with the ‘new realism’ of contemporary political philosophers such as Raymond Geuss or Bernard Williams, realism in the tradition of Plato and Aristotle can defend reason against instrumental rationality and blind belief by integrating it with habit, feeling and even faith. Such metaphysical–political realism can help develop a politics of virtue that goes beyond communitarian thinking by emphasising plural modes of association (not merely ‘community’), substantive ties of sympathy and the importance of pursuing goodness and mutual flourishing

Fifteenth Century Problems for the Twenty-First Century Gift: Human Tissue Transactions in Ethnically Diverse Societies

The language of the ‘gift’ continues to be drawn upon in attempts to encourage altruistic organ and tissue donation. My aim here is to consider the anxieties that come into focus when this rhetoric is deployed in the context of ethnic minorities and, moreover, their donation practices are situated within universalistic discourses of charity and the gift. The article considers ideas of the body, debt, obligation, relationality, and solidarity, and how these fit within the overarching projects of society, modernity, and democracy when the market figures as an ever more prominent feature of such projects. Drawing on a variety of examples, the piece reflects on the movement of tissue across ethnically and culturally marked corporeal boundaries and highlights the tensions that arise from refusal as well as acceptance of such transactions

Mars Aeronomy Observer: Report of the Science Working Team

The Mars Aeronomy Observer (MAO) is a candidate follow-on mission to Mars Observer (MO) in the Planetary Observer Program. The four Mariner and two Viking spacecraft sent to Mars between 1965 and 1976 have provided a wealth of information concerning Martian planetology. The Mars Observer, to be launched in 1990, will build on their results by further examining the elemental and mineralogical composition of the surface, the strength and multipolar composition of the planetary magnetic field, the gravitational field and topography, and the circulation of the lower atmosphere. The Mars Aeronomy Observer is intended to address the last major aspects of Martian environment which have yet to be investigated: the upper atmosphere, the ionsphere, and the solar wind interaction region