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  • 1995-1999  (179)
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  • 1
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    The polar ozone and aerosol measurements (POAM III) instrument and early validation results (1999)
    In:  EPIC3Journal of geophysical researchD15, 104, pp. 18785-18799
    Details
    Publication Date: 2019-07-17
    Description: Polar Ozone and Aerosol Measurement (POAM) III,a follow-on to the successful POAM II, is a spaceborne experiment designedto measure the vertical profiles of ozone, water vapor, nitrogen dioxide,and aerosol extinction in the polar stratosphere and upper troposphere witha vertical resolution of 1-2 km. Measurements are made by the solaroccultation technique. POAM III, now in polar orbit aboard the SPOT 4 satellite,is providing data on north- and south-polar ozone phenomena, including the south-polar ozone hole, and on the spatial and temporal variability of stratosphericaerosols, polar stratospheric clouds, and polar mesospheric clouds.Differences between POAM III and POAM II instruments are described.First validation of POAM III products by comparison with HalogenOccultation Experiment and ozonesonde data are presented.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Electronic Resource
    Electronic Resource
    Real-Space Differentiation of IgG and IgM Antibodies Deposited on Microtiter Wells by Scanning Force Microscopy (1995)
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 1822-1826 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00005a063
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  • 3
    Electronic Resource
    Electronic Resource
    The relationship between electric fields, conductances and currents in the high-latitude ionosphere: a statistical study using EISCAT data (1998)
    Springer
    Annales geophysicae 17 (1998), S. 43-52 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; electric fields and currents)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The relationship between electric fields, height-integrated conductivities and electric currents in the high-latitude nightside electrojet region is known to be complex. The tristatic nature of the EISCAT UHF radar facility provides an excellent means of exploring this interrelationship as it enables simultaneous estimates to be made of the full electric field vector and the ionospheric Hall and Pedersen conductances, further allowing the determination of both field-perpendicular electric current components. Over 1300 h of common programme observations by the UHF radar system provide the basis of a statistical study of electric fields, conductances and currents in the high-latitude ionosphere, from which preliminary results are presented. Times at which there is significant solar contribution to the ionospheric conductances have been excluded by limiting the observations according to solar zenith angle. Initial results indicate that, in general, the times of peak conductance, identified from the entire set of EISCAT observations, do not correspond to the times of the largest electric field values; the relative contribution of ionospheric conductance and electric field to the electrojet currents therefore depends critically on local time, a conclusion which corroborates work by previous authors. Simultaneous measurements confirm a tendency for a decrease in both Hall and Pedersen conductances to be accompanied by an increase in the electric field, at least for moderate and large electric field value, a tendency which is also identified to some extent in the ratio of the conductances, which acts as an indicator of the energy of precipitating particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0043-3
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  • 4
    Electronic Resource
    Electronic Resource
    Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1392-1399 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (ionosphere - atmosphere interactions) ; Meteorology and atmospheric dynamics (thermospheric dynamics) ; Radio science (ionospheric propagations)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1392-z
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of veloCity measurements from the CUTLASS Finland radar and the EISCAT UHF system (1999)
    Springer
    Annales geophysicae 17 (1999), S. 892-902 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (ionospheric irregularities; plasma convection)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of-view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar commenced operation, in February 1995, the mainland EISCAT UHF radar has been run in common programme 1 and 2 modes for a total duration exceeding 1000 h. Simultaneous and spatially coincident returns from these two radars over this period provide the basis for a comparison of irregularity drift veloCity and F-region ion veloCity. Initial comparison is limited to velocities from four intervals of simultaneous radar returns; intervals are selected such that they exhibit a variety of veloCity signatures including that characteristic of the convection reversal and a rapidly fluctuating veloCity feature. Subsequent comparison is on a statistical basis. The velocities measured by the two systems demonstrate reasonable correspondence over the veloCity regime encountered during the simultaneous occurrence of coherent and incoherent scatter; differences between the EISCAT UHF measurements of F-region ion drift and the irregularity drift velocities from the Finland radar are explained in terms of a number of contributing factors including contamination of the latter by E-region echoes, a factor which is investigated further, and the potentially deleterious effect of discrepant volume and time sampling intervals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0892-9
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  • 6
    Electronic Resource
    Electronic Resource
    Solar and seasonal dependence of ion frictional heating (1999)
    Springer
    Annales geophysicae 17 (1999), S. 682-691 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions; plasma temperature and density)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ion frictional heating constitutes one of the principal mechanisms whereby energy, originating in the solar wind, is deposited into the Earth’s ionosphere and ultimately the neutral atmosphere. Common programme observations by the EISCAT UHF radar system, spanning the years 1984 to 1995, provide the basis for a comprehensive statistical study of ion frictional heating, results of which are documented in this and a previous paper by the authors. In the present work, the authors demonstrate the solar and seasonal dependence of the universal time distribution of frictional heating, and explain these results with reference to corresponding dependences of the ion velocity. Although EISCAT observes a significant increase in the occurrence of enhanced ion velocities associated with increased solar activity, the latter characterised according to the prevailing 10.7 cm solar flux, this is not reflected to such an extent in the occurrence of frictional heating. It is suggested that this is a consequence of the decreased neutral atmosphere response times associated with active solar conditions, resulting from the higher ionospheric plasma densities present. Seasonal effects on the diurnal distribution of ion frictional heating are well explained by corresponding variations in ionospheric convection, the latter principally a result of geometrical factors. It is noted that, over the entire dataset, the variations in the unperturbed F-region ion temperature, required to implement the identification criterion for ion heating, are highly correlated with model values of thermospheric temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0682-4
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  • 7
    Electronic Resource
    Electronic Resource
    Geohydrological models and earthquake effects at Yucca Mountain, Nevada (1997)
    Springer
    Environmental geology 32 (1997), S. 23-35 
    Details
    ISSN: 1432-0495
    Keywords: Key words Yucca Mountain ; Water table ; Earthquakes ; Geohydrological models ; Fractures ; Hazard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Yucca Mountain, the proposed site for the high-level nuclear waste repository, is located just south of where the present water table begins a sharp rise in elevation. This large hydraulic gradient is a regional feature that extends for over 100 km. Yucca Mountain and its vicinity are underlain by faulted and fractured tuffs with hydraulic conductivities controlled by flow through the fractures. Close to and parallel with the region of large hydraulic gradient, and surrounding the core of the Timber Mountain Caldera, there is a 10- to 20-km-wide zone containing few faults and thus, most likely, few open fractures. Consequently, this zone should have a relatively low hydraulic conductivity, and this inference is supported by the available conductivity measurements in wells near the large hydraulic gradient. Also, slug injection tests indicate significantly higher pressures for fracture opening in wells located near the large hydraulic gradient compared to the opening pressures in wells further to the south, hence implying that lower extensional stresses prevail to the north with consequently fewer open fractures there. Analytical and numerical modeling shows that such a boundary between media of high and low conductivity can produce the observed, large hydraulic gradient, with the high conductivity medium having a lower elevation than the water table. Further, as fractures can close due to tectonic activity, the conductivity of the Yucca Mountain tuffs can be reduced to a value near that for the hydraulic barrier due to strain release by a moderate earthquake. Under these conditions, simulations show that the elevation of the steady-state water table could rise between 150 and 250 m at the repository site. This elevation rise is due to the projected shift in the location of the large hydraulic gradient to the south in response to a moderate earthquake, near magnitude 6, along one of the major normal faults adjacent to Yucca Mountain. As the proposed repository would only be 200–400 m above the present water table, this predicted rise in the water table indicates a potential hazard involving water intrusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540050190
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  • 8
    Electronic Resource
    Electronic Resource
    ATP, pH and Mg2+ modulate a cation current in Beta vulgaris vacuoles: A possible shunt conductance for the vacuolar H+-ATPase (1995)
    Springer
    The journal of membrane biology 145 (1995), S. 75-86 
    Details
    ISSN: 1432-1424
    Keywords: Amino acid transport ; ATP regulation ; Beta ; Mg2+ ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Macroscopic instantaneous and time-dependent currents have been measured in the vacuolar membrane of Beta vulgaris using a patch clamp configuration analogous to whole cell mode. At low cytosolic Ca2+ and in the absence of Mg2+, only an instantaneous current was observed. This current is carried predominantly by cations (PK∶PCl 7∶1, pna∶pcl 4∶1 and arginine is also conducted). The instantaneous current can be activated by ATP4− (e.g., ATP-activated mean K+ current density was −20 mA.m−2 at a membrane voltage of −20 mV) and by increasing cytosolic pH and Mg2+ (raising Mg2+ from 0 to 0.4 mm induced a mean current density increase of −7 mA.m−2 at −20 mV). Such current can be activated by simultaneous addition of putative in vivo concentrations of ATP4−/MgATP/Mg free 2+ (in the presence of bafilomycin to inhibit the vacuolar ATPase) and further modulated by cytosolic pH. With vacuolar K+ concentration greater than that of the cytosol, activation of the instantaneous current would mediate vacuolar K+ release over the range of physiological membrane voltage. It is argued that the ATP4−-activated current, in addition to acting as a K+ mobilization pathway, could provide a counter-ion (shunt) conductance, allowing the two electrogenic H+ pumps which reside in the vacuolar membrane to acidify the vacuolar lumen. A separate time-dependent current, which was not observed at low Ca2+ concentrations (less than 500 nm) could also be elicited by addition of Mg2+ at the cytoplasmic membrane face. This current was stimulated by increasing cytoplasmic pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233308
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  • 9
    Electronic Resource
    Electronic Resource
    A statistical study of ion frictional heating observed by EISCAT (1997)
    Springer
    Annales geophysicae 15 (1997), S. 1399-1411 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Results of a statistical survey of F-region ion frictional heating are presented, a survey which is based on over 4000 h of common programme observations taken by the European incoherent scatter (EISCAT) UHF radar facility. The criterion adopted in this study for the identification of ion frictional heating was that defined by McCrea et al., requiring an enhancement in the F-region field-parallel ion temperature exceeding 100 K over two consecutive integration periods, which was itself based on a selection criterion for frictional heating derived for the study of high-latitude F-region ion temperature observations from the Atmospheric Explorer-C satellite. In the present study, the diurnal distribution of ion frictional heating observed by EISCAT is established and, furthermore, its dependence on geomagnetic activity and the orientation of the interplanetary magnetic field (IMF) is investigated; results are interpreted with reference to corresponding distributions of enhanced ion velocity, again derived from the extended set of EISCAT UHF common programme observations. The radar, due to its location relative to the large-scale convection pattern, observes ion frictional heating principally during the night, although preferentially during the post-midnight hours where there is reduced coupling between the ion and neutral populations. There is an increased preponderance of frictional heating during intervals of high geomagnetic activity and for a southward z component of the IMF and, moreover, evidence of asymmetries introduced by the y component of the IMF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-1399-x
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  • 10
    Electronic Resource
    Electronic Resource
    Deriving the normalised ion-neutral collision frequency from EISCAT observations (1997)
    Springer
    Annales geophysicae 15 (1997), S. 1557-1569 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Common programme observations by the EISCAT UHF radar revealed an extended interval, post geomagnetic local noon on 03 April 1992, during which the F-region ion velocity orthogonal to the geomagnetic field was significantly enhanced, to values exceeding 2 km s−1 corresponding to a perpendicular electric field of some 100 mV m−1. Observations from this interval are used to illustrate a method by which estimates of the E-region ion-neutral collision frequency may be derived in the presence of enhanced electric field. From both the rotation of the ion velocity vector and the reduction in the ion velocity magnitude relative to that in the F-region, independent estimates of the normalised ion-neutral collision frequency are made at the UHF E-region tristatic altitudes; the derived values are, in general, lower than model predictions. Although initial calculations assume a stationary neutral atmosphere, first-order estimates of the E-region neutral wind are subsequently employed to calculate revised estimates of the normalised ion-neutral collision frequency; these neutral winds are derived by attributing the difference between predicted and observed enhancements in field-parallel ion temperature to thermospheric motion. The inclusion of neutral winds, which are themselves not inconsiderable, appears to have only a limited effect on the normalised collision frequencies derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-1557-1
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