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| 2. |
- Abazov, V. M., et al.
(författare)
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Search for particles decaying into a Z boson and a photon in p(p)over-bar collisions at root s=1.96 TeV
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 641:6, s. 415-422
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a search for a new particle X produced in p (p) over bar collisions at root s- = 1.96 TeV and subsequently decaying to Z gamma. The search uses 0.3 fb(-1) of data collected with the DO detector at the Fermilab Tevatron Collider. We set limits on the production cross section times the branching fraction sigma(p (p) over bar -> X) x B(X -> Z gamma) that range from 0.4 to 3.5 pb at the 95% C.L. for X with invariant masses between 100 and 1000 GeV/c(2), over a wide range of X decay widths.
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| 3. |
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| 4. |
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| 5. |
- Torbert, R. B., et al.
(författare)
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Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space
- 2018
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 362:6421, s. 1391-1395
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvenic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.
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| 6. |
- Farrugia, C. J., et al.
(författare)
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MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub-Alfvénic Flow
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : Blackwell Publishing Ltd. - 2169-9380 .- 2169-9402. ; 122:10, s. 9934-9951
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Tidskriftsartikel (refereegranskat)abstract
- We present MMS observations during two dayside magnetopause crossings under hitherto unexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning to sub-Alfvénic flow and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i) a strong B (∼20 nT) pointing south and (ii) a density profile with episodic decreases to values of ∼0.3 cm−3 followed by moderate recovery. During the crossings the magnetosheath magnetic field is stronger than the magnetosphere field by a factor of ∼2.2. As a result, during the outbound crossing through the ion diffusion region, MMS observed an inversion of the relative positions of the X and stagnation (S) lines from that typically the case: the S line was closer to the magnetosheath side. The S line appears in the form of a slow expansion fan near which most of the energy dissipation is taking place. While in the magnetosphere between the crossings, MMS observed strong field and flow perturbations, which we argue to be due to kinetic Alfvén waves. During the reconnection interval, whistler mode waves generated by an electron temperature anisotropy (Te⊥>Te∥) were observed. Another aim of the paper is to distinguish bow shock-induced field and flow perturbations from reconnection-related signatures. The high-resolution MMS data together with 2-D hybrid simulations of bow shock dynamics helped us to distinguish between the two sources. We show examples of bow shock-related effects (such as heating) and reconnection effects such as accelerated flows satisfying the Walén relation.
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| 7. |
- Farrugia, C. J., et al.
(författare)
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Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:11, s. 8983-9004
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report on a sequence of large-amplitude Alfvenic fluctuations terminating in a field and flow discontinuity and their effects on electromagnetic fields and plasmas in the near-magnetopause magnetosheath. An arc-polarized structure in the magnetic field was observed by the Time History of Events and Macroscale Interactions during Substorms-C in the solar wind, indicative of nonlinear Alfven waves. It ends with a combined tangential discontinuity/vortex sheet, which is strongly inclined to the ecliptic plane and at which there is a sharp rise in the density and a drop in temperature. Several effects resulting from this structure were observed by the Magnetospheric Multiscale spacecraft in the magnetosheath close to the subsolar point (11:30 magnetic local time) and somewhat south of the geomagnetic equator (-33 degrees magnetic latitude): (i) kinetic Alfven waves; (ii) a peaking of the electric and magnetic field strengths where E . J becomes strong and negative (-1 nW/m(3)) just prior to an abrupt dropout of the fields; (iii) evolution in the pitch angle distribution of energetic (a few tens of kilo-electron-volts) ions (H+, Hen+, and On+) and electrons inside a high-density region, which we attribute to gyrosounding of the tangential discontinuity/vortex sheet structure passing by the spacecraft; (iv) field-aligned acceleration of ions and electrons that could be associated with localized magnetosheath reconnection inside the high-density region; and (v) variable and strong flow changes, which we argue to be unrelated to reconnection at partial magnetopause crossings and likely result from deflections of magnetosheath flow by a locally deformed, oscillating magnetopause.
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| 8. |
- Charman, D. J., et al.
(författare)
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Climate-related changes in peatland carbon accumulation during the last millennium
- 2013
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 10:2, s. 929-944
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declined over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands in a warmer future.
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| 9. |
- Farrugia, C. J., et al.
(författare)
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Magnetospheric Multiscale Mission observations and non-force free modeling of a flux transfer event immersed in a super-Alfvenic flow
- 2016
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 43:12, s. 6070-6077
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Tidskriftsartikel (refereegranskat)abstract
- We analyze plasma, magnetic field, and electric field data for a flux transfer event (FTE) to highlight improvements in our understanding of these transient reconnection signatures resulting from high-resolution data. The similar to 20 s long, reverse FTE, which occurred south of the geomagnetic equator near dusk, was immersed in super-Alfvenic flow. The field line twist is illustrated by the behavior of flows parallel/perpendicular to the magnetic field. Four-spacecraft timing and energetic particle pitch angle anisotropies indicate a flux rope (FR) connected to the Northern Hemisphere and moving southeast. The flow forces evidently overcame the magnetic tension. The high-speed flows inside the FR were different from those outside. The external flows were perpendicular to the field as expected for draping of the external field around the FR. Modeling the FR analytically, we adopt a non-force free approach since the current perpendicular to the field is nonzero. It reproduces many features of the observations.
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| 10. |
- Aczel, Balazs, et al.
(författare)
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Consensus-based guidance for conducting and reporting multi-analyst studies
- 2021
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Ingår i: eLIFE. - : eLife Sciences Publications. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Any large dataset can be analyzed in a number of ways, and it is possible that the use of different analysis strategies will lead to different results and conclusions. One way to assess whether the results obtained depend on the analysis strategy chosen is to employ multiple analysts and leave each of them free to follow their own approach. Here, we present consensus-based guidance for conducting and reporting such multi-analyst studies, and we discuss how broader adoption of the multi-analyst approach has the potential to strengthen the robustness of results and conclusions obtained from analyses of datasets in basic and applied research.
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