Interpretation of3He abundance variations in the solar wind     

M. A. Coplan  K. W. Ogilvie  P. Bochsler  J. Geiss 《Solar physics》1984,93(2):415-434

The ion composition instrument (ICI) on ISEE-3 has observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km s^–1. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of³He flares occurred during this time.The long-term average⁴He⁺⁺/³He⁺⁺ flux ratio R, was 2050 ± 200, a agreement with a previously reported result obtained using part of this data set, and in very good agreement with the previous measurements made over much shorter periods of time with the foil technique. The R values for 6-month intervals show statistically significant differences. The highest of these values is 2300 and coincides with the solar maximum of cycle 21 indicating that at solar maximum there may be changes in the character and rate of occurrence of short-term variations in R. We also find that R drops under conditions of low proton flux in the solar wind, and that it is high when solar wind speeds are lowest.At solar wind speeds above 400 km s^–1 R is nearby constant at about 2000; at lower speeds it is larger and more variable, in agreement with the idea that the sources of high and low speed wind are different. At times of sector boundary current sheet crossings, identified with coronal streamers, there is a characteristic rise in the value of R indicating an encounter with a plasma with reduced³He⁺⁺ abundance. Autocorrelations have been computed for⁴He⁺⁺ and³He⁺⁺ and indicate correlation times of about 14 and 20 hr, respectively. Periods of duration of about one day whenR is less than 1000 tend to coincide with the observation of compound streams.The possibility of detectable increases in³He⁺⁺ flux in plasma which left the Sun at the time of³He flares has been investigated, but no significant increase was seen.  相似文献   

On the Spatial Distribution and Seasonal Variation of Lower-Troposphere Ozone over Europe     

H. E. Scheel  H. Areskoug  H. Geiss  B. Gomiscek  K. Granby  L. Haszpra  L. Klasinc  D. Kley  T. Laurila  A. Lindskog  M. Roemer  R. Schmitt  P. Simmonds  S. Solberg  G. Toupance 《Journal of Atmospheric Chemistry》1997,28(1-3):11-28

Surface ozone data from 25 Europeanlow-altitude sites and mountain sites located between79°N and 28°N were studied. The analysiscovered the time period March 1989–February 1993.Average summer and winter O₃ concentrations inthe boundary layer over the continent gave rise togradients that were strongest in the north-west tosouth-east direction and west-east direction, respectively. WintertimeO₃ ranged from 19 to 27 ppbover the continent, compared to about 32 ppb at thewestern border, while for summer the continentalO₃ values ranged between 39 and 56 ppb and theoceanic mixing ratios were around 37 ppb. In the lowerfree troposphere average wintertime O₃ mixingratios were around 38 ppb, with only an 8 ppbdifference between 28°N and 79°N. For summerthe average O₃ levels decreased from about 55 ppbover Central Europe to 32 ppb at 79°N. Inaddition, O₃ and O_x(= O₃ + NO₂)in polluted and clean air were compared. Theamplitudes of the seasonal ozone variations increasedin the north-west to south-east direction, while thetime of the annual maximum was shifted from spring (atthe northerly sites) to late summer (at sites inAustria and Hungary), which reflected the contributionof photochemical ozone production in the lower partsof the troposphere.  相似文献   

Nitrogen isotopes in the solar system     

Johannes Geiss  Peter Bochsler 《Geochimica et cosmochimica acta》1982,46(4):529-548

Measurements of the isotopic composition of nitrogen in the solar system are summarized. We show that the 30% change, during the last 3 to 4 billion years, of ${}^{15}\text{N}{}^{14}\text{N}$ in solar-wind-bearing lunar soils and breccias probably does not reflect changes in this ratio at the solar surface. Such changes, whether by spallation or thermonuclear reactions are ruled out by comparing the yields of ¹⁵N with those of other rare isotopes such as ⁹Be, ¹¹B, ³He or ¹³C, even if an arbitrary degree of solar mixing is introduced. Moreover, we calculate that the solar activity required for producing significant amounts of ¹⁵N by spallation at the solar surface should have resulted in a particle bombardment of the Moon of an intensity that would have produced amounts of spallation isotopes (e.g.¹⁵N, ²¹Ne, ³⁸Ar, ¹³¹Xe) several orders of magnitude in excess of what is actually found in the whole regolith.We argue that accretion of interstellar matter also does not work as a cause for a significant change of the photospheric ${}^{15}\text{N}{}^{14}\text{N}$ ratio. Evidence is presented that the mixing depth at the solar surface on a time scale of ?10⁹ years is (10^?2 ?10^?1) M_⊙ Mixing to this depth renders accretion of interstellar matter as a source of compositional changes at the solar surface inefficient, even if allowance is made for the expected large difference in the accretion rates of condensed and gaseous matter. A quantitative treatment of several alternatives of solar accretion leads to serious contradictions (e.g. with the low Ne abundances in planetary atmospheres or with the amounts of nitrogen that should have been directly accreted by the Moon), and we conclude that accretion during the main sequence life of the Sun is an unlikely source of changes in ${}^{15}\text{N}{}^{14}\text{N}$ at the solar surface.A ratio of ${}^{15}\text{N}{}^{14}\text{N}\text{= (4.0 ± 0.3) × 10}{}^{\mathrm{?3}}$ is our best estimate for average solar system material and for the Sun. We propose that a rare, very light nitrogen component (called LPN) is admixed in varying amounts to planetary matter. Undiluted LPN has not been found in meteorites or planetary atmospheres, but we show that the combined effects of LPN admixture and isotope fractionation can in principle account for the variability of ${}^{15}\text{N}{}^{14}\text{N}$ observed in the planetary system. Determination of the Jovian ${}^{15}\text{N}{}^{14}\text{N}$ ratio with an accuracy of ~10% would crucially test our interpretation of the nitrogen isotope observations.  相似文献   

Sediment magnetic properties reveal holocene climate change along the Minnesota prairie-forest ecotone     

Christoph E. Geiss  Charles E. Umbanhowar  Phil Camill  Subir K. Banerjee 《Journal of Paleolimnology》2003,30(2):151-166

We propose a model that explains variations in magnetic parameters of lake sediments as a record of Holocene climate change. Our model is based on records from 4 lakes and incorporates the effects of erosion, dust deposition, and the authigenesis and diagenesis of the magnetic component of the sediment. Once checked against high resolution multi proxy climate records, which are currently being established for some of our study sites, it will allow us to use magnetic proxies to establish high-resolution climate reconstructions on a regional scale.Our model utilizes a combination of concentration-dependent parameters (magnetic susceptibility, IRM) and grain-size-dependent parameters (ARM/IRM, hysteresis parameters). Magnetic mineralogy is characterized by a combination of low-temperature measurements and S-ratios, and our magnetic measurements are complemented by XRD, LOI and smearslide analyses.During periods of forest growth within the watershed, deposition of terrigenous material is low and the sediment magnetic properties are characterized by low concentrations of mainly authigenic minerals (low values of IRM, high ratios of ARM/IRM). During the early to mid-Holocene dry period, deposition of terrigenous material increased due to intensified dust deposition and the erosion of lake margins caused by lowered water levels. Concentration of magnetic minerals increases (high IRM, ) and so does the grain-size of the magnetic fraction (low ARM/IRM). During the late-Holocene, sediment magnetic properties depend on the varied position of the site with respect to the prairie–forest ecotone.  相似文献   

Noble gas investigations of lunar rocks 10017 and 10071     

P. Eberhardt  J. Geiss  H. Graf  N. Grögler  U. Krähenbühl  H. Schwaller  A. Stettler 《Geochimica et cosmochimica acta》1974,38(1):97-120

The noble gases He, Ne, Ar, Kr and Xe and also K and Ba were measured in the Apollo 11 igneous rocks 10017 and 10071, and in an ilmenite and two feldspar concentrates separated from rock 10071. Whole rock K/Ar ages of rocks 10017 and 10071 are (2350 ± 60) × 10⁶ yr and (2880 ± 60) × 10⁶ yr, respectively. The two feldspar concentrates of rock 10071 have distinctly higher ages: (3260 ± 60) × 10⁶ yr and (3350 ± 70) × 10⁶ yr. These ages are still 10 per cent lower than the Rb/Sr age obtained by Papanastassiouet al. (1970) and some Ar⁴⁰ diffusion loss must have occurred even in the relatively coarse-grained feldspar.The relative abundance patterns of spallation Ne, Ar, Kr and Xe are in agreement with the ratios predicted from meteoritic production rates. However, diffusion loss of spallation He³ is evident in the whole rock samples, and even more in the feldspar concentrates. The ilmenite shows little or no diffusion loss. The isotopic composition of spallation Kr and Xe is similar to the one observed in meteorites. Small, systematic differences in the spallation Kr spectra of rocks 10017 and 10071 are due to variations in the irradiation hardness (shielding). The Kr spallation spectra in the mineral concentrates are different from the whole rock spectra and also show individual variations, reflecting the differences in target element composition. The relative abundance of cosmic ray produced Xe¹³¹ differs by nearly 50 per cent in the two rocks. The other Xe isotopes show no variations of similar magnitude. The origin of the Xe¹³¹ yield variability is discussed.Kr⁸¹ was measured in all the samples investigated. The Kr⁸¹/Kr exposure ages of rocks 10017 and 10071 are (480 ± 25) × 10⁶ yr and (350 ± 15) × 10⁶ yr, respectively. Exposure ages derived from spallation Ne²¹, Ar³⁸, Kr⁸³ and Xe¹²⁶ are essentially in agreement with the Kr⁸¹/Kr ages. The age of rock 10071 might be somewhat low because of a possible recent exposure of our sample to solar flare particles.  相似文献   

Decomposition of Spatial Structure of Nocturnal Flow over Gentle Terrain     

Andrew Geiss  Larry Mahrt 《Boundary-Layer Meteorology》2015,156(3):337-347

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Determination of solar wind elemental abundances from M/Q observations during three periods in 1980     

S. Kunz  P. Bochsler  J. Geiss  K. W. Ogilvie  M. A. Coplan 《Solar physics》1983,88(1-2):359-376

Mass spectra in the range 2 ≦ M/Q ≦ 3 provided by a high resolution mode of the ISEE-3 Plasma Composition Experiment were evaluated for three selected periods during early 1980. The observed Ne/O ratios are compatible with estimated solar abundance ratios. In two of the three periods, the He/Ne-ratios agree with the Apollo foil results. Freezing-in temperatures for oxygen are similar to those obtained by other groups. Possible reasons for an unexpectedly high flux at M/Q = 2.4 are discussed.  相似文献   

Space-based measurements of elemental abundances and their relation to solar abundances     

M. A. Coplan  K. W. Ogilvie  P. Bochsler  J. Geiss 《Solar physics》1990,128(1):195-201

The solar wind provides a source of solar abundance data that only recently is being fully exploited. The Ion Composition Instrument (ICI) aboard the ISEE-3/ICE spacecraft was in the solar wind continuously from August 1978 to December 1982. The results have allowed us to establish long-term average solar wind abundance values for helium, oxygen, neon, silicon, and iron. The Charge-Energy-Mass (CHEM) instrument aboard the CCE spacecraft of the AMPTE mission has measured the abundance of these elements in the magnetosheath and has also added carbon, nitrogen, magnesium, and sulfur to the list. There is strong evidence that these magnetosheath abundances are representative of the solar wind. Other sources of solar wind abundances are Solar Energetic Particle (SEP) experiments and Apollo lunar foils. When comparing the abundances from all of these sources with photospheric abundances, it is clear that helium is depleted in the solar wind while silicon and iron are enhanced. Solar wind abundances for carbon, nitrogen, oxygen, and neon correlate well with the photospheric values. The incorporation of minor ions into the solar wind appears to depend upon both the ionization times for the elements and the Coulomb drag exerted by the outflowing proton flux.  相似文献   

AN EMPIRICAL STUDY OF THE ELECTRON TEMPERATURE AND HEAVY ION VELOCITIES IN THE SOUTH POLAR CORONAL HOLE     

Ko  Yuan-Kuen  Fisk  Lennard A.  Geiss  Johannes  Gloeckler  George  Guhathakurta  Madhulika 《Solar physics》1997,171(2):345-361

The solar wind ions flowing outward through the solar corona generally have their ionic fractions freeze-in within 5 solar radii. The altitude where the freeze-in occurs depends on the competition between two time scales: the time over which the wind flows through a density scale height, and the time over which the ions achieve ionization equilibrium. Therefore, electron temperature, electron density, and the velocity of the ions are the three main physical quantities which determine the freeze-in process, and thus the solar wind ionic charge states. These physical quantities are determined by the heating and acceleration of the solar wind, as well as the geometry of the expansion. In this work, we present a parametric study of the electron temperature profile and velocities of the heavy ions in the inner solar corona. We use the ionic charge composition data observed by the SWICS experiment on Ulysses during the south polar pass to derive empirically the electron temperature profile in the south polar coronal hole. We find that the electron temperature profile in the solar inner corona is well constrained by the solar wind charge composition data. The data also indicate that the electron temperature profile must have a maximum within 2 solar radii. We also find that the velocities of heavy ions in their freeze-in regions are small (<100 km s^-1) and different elements must flow at different velocities in the inner corona.  相似文献   

Trapped solar wind noble gases and exposure age of Luna 16 lunar fines     

O Eugster  N Grögler  M.D Mendia  P Eberhardt  J Geiss 《Geochimica et cosmochimica acta》1973,37(9):1991-2003

He, Ne, Ar, Kr and Xe concentrations and isotopic abundances were measured in three bulk grain size fractions prepared from sample L-16-19, No. 120 (C level, 20–22 cm depth) returned by the Luna 16 mission. The expected anticorrelation between the concentrations of trapped solar wind noble gases and grain size is observed. Elemental abundances of solar wind trapped noble gases are similar to those previously found in corresponding grain size fractions of the Apollo 11 and 12 fines. The trapped ratio ${}^4\text{He}{}^{20}\text{Ne}$ varies in the soils from different lunar maria due to diffusion losses. A rough correlation of ${}^4\text{He}{}^{20}\text{Ne}$ with the proportion of ilmenite in these samples is apparent. The elemental and isotopic ratios of the surface correlated noble gases in Luna 16 resemble those previously found in Apollo fines. Based on ²¹Ne, ⁷⁸Kr and ¹²⁶Xe a cosmic ray exposure age of 360 my was determined. This age is similar to those obtained for the soils from other lunar maria.  相似文献