In addition to the examination of clinical signs, several laboratory markers have been measured for diagnostics and monitoring of pediatric septic bone and joint infections. Traditionally erythrocyte ...sedimentation rate (ESR) and leukocyte cell count have been used, whereas C-reactive protein (CRP) has gained in popularity. We monitored 265 children at ages 3 months to 15 years with culture-positive osteoarticular infections with a predetermined series of ESR, CRP, and leukocyte count measurements. On admission, ESR exceeded 20 mm/hour in 94% and CRP exceeded 20 mg/L in 95% of the cases, the mean (± standard error of the mean) being 51 ± 2 mm/hour and 87 ± 4 mg/L, respectively. ESR normalized in 24 days and CRP in 10 days. Elevated CRP gave a slightly better sensitivity in diagnostics than ESR, but best sensitivity was gained with the combined use of ESR and CRP (98%). Elevated ESR or CRP was seen in all cases during the first 3 days. Measuring ESR and CRP on admission can help the clinician rule out an acute osteoarticular infection. CRP normalizes faster than ESR, providing a clear advantage in monitoring recovery.
Level of Evidence:
Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
We study the solar wind interaction with Mars in a global three‐dimensional hybrid model. A well‐developed, vast ion foreshock forms under a strongly flow‐aligned interplanetary magnetic field (IMF) ...configuration but otherwise nominal solar wind and solar minimum photon flux conditions. Large‐scale ultra‐low frequency (ULF) waves are excited in the foreshock by backstreaming ions. The foreshock ULF waves constitute two distinct regions in the analyzed solar wind and IMF situation: the near region where the wave period is 71–83 s and the far region where the wave period is 25–28 s. The near foreshock region waves transmit downstream through the bow shock and affect dynamics of the solar wind and planetary ion populations. Especially, ion precipitation rate into the exobase and planetary ion escape rates fluctuate at the ULF wave period corresponding to the near foreshock region. The peak‐to‐peak amplitude of the modulation is few percent or less. Interestingly, ionospheric oxygen ion escape fluxes show more than two orders of magnitude local modulations in the heavy plume at the same period. Finally, the escape rates of the ionospheric oxygen ion populations are enhanced by 60–70% under flow‐aligned IMF compared to nominal upstream conditions.
Key Points
Two distinct foreshock ultra‐low frequency (ULF) wave regions form in a global Mars‐solar wind interaction hybrid simulation
The ULF waves modulate ion precipitation and escape at Mars
Ionospheric oxygen ion escape is enhanced by 60%–70% under radial interplanetary magnetic field
We study the Venus‐solar wind interaction and the hemispheric asymmetries of the Venus plasma environment in the global HYB‐Venus hybrid simulation. We concentrate especially on the role of the ...flow‐aligned interplanetary magnetic field (IMF) component (i.e., the Parker spiral angle or the IMF cone angle) and analyze the dawn‐dusk and Esw asymmetries between four magnetic quadrants around Venus. Using the simulation model, we study two upstream condition cases in detail: the perpendicular IMF to the solar wind flow case and the nominal Parker spiral case (dominant flow‐aligned IMF component). Several differences and similarities were found in these two simulation runs. Common features of the Venus plasma environment between the two cases include asymmetric magnetic barrier and tail lobes and asymmetric planetary ion escape in the direction of the solar wind convection electric field. Further, protons of planetary origin and of solar wind origin were found to follow similar velocity patterns in the Venus plasma wake in both cases. The differences when the IMF flow‐aligned component is dominating compared to the perpendicular IMF case, the so‐called (magnetic) dawn‐dusk asymmetries, include the parallel bow shock and the foreshock region, the asymmetric magnetic barrier, the asymmetric tail current system, and the asymmetric central tail current sheet. Further, the escaping planetary H+ and O+ ion fluxes are concentrated more on the hemisphere of the parallel bow shock. When interpreting in situ plasma and magnetic observations from Venus, the features of at least these two basic IMF configurations should be considered.
Key Points
Venus plasma environment is hemispherically remarkably asymmetric
Asymmetries are due to solar wind electric field and IMF flow‐aligned component
The IMF flow‐aligned component affects interpretation of in situ observations
ABSTRACT
We study the solar wind interaction with Mercury using a global three-dimensional hybrid model. In the analysed simulation run, we find a well-developed, dynamic Hermean ion foreshock ahead ...of the quasi-parallel bow shock under upstream solar wind and interplanetary magnetic field (IMF) conditions corresponding to the orbital perihelion of the planet. A portion of the incident solar wind ion flux is scattered back upstream near the quasi-parallel bow shock including both major solar wind ion species, protons and alphas. The scattered particles form the Hermean suprathermal foreshock ion population. A significant part of the suprathermal population is backstreaming with a velocity component towards the Sun in the near-foreshock at the planetocentric distance of few planetary radii in the plane of the IMF. The ion foreshock is associated with large-scale, oblique fast magnetosonic waves in the ultra-low-frequency (ULF) range convecting downstream with the solar wind. The ULF wave period is about 5 s in the analysed upstream condition case at Mercury, which corresponds to the 30-s foreshock waves at Earth when scaled by the IMF magnitude.
The lunar surface is continuously under the impact of solar wind plasma, which breaks the chemical bonds of the surface material resulting in weathering of the surface and a modified chemical ...composition. Ion impact also sputters the surface material, affecting the composition of the lunar exosphere, and it controls the electrical properties of both the lunar surface and the near surface space.
We have studied the lunar farside-nearside (FN) hemispherical asymmetry of the solar wind proton impact on the lunar surface along the orbit of the Moon during fast solar wind conditions. The analysis is based on a 3D hybrid model where ions are accelerated by the macroscopic j × B and pressure gradient forces.
The derived proton impact surface map shows that the highest cumulative solar wind proton addition on the lunar surface is located on the farside while the most energetic protons precipitate on the nearside. The total ion impact rate was found to be smallest when the Moon is deep in the magnetotail. The total ion impact rate on the lunar surface varies while the Moon orbits the Earth and these longitudinal variations are caused by the magnetosphere and lunar tidal locking.
•Solar wind precipitation on the Moon calculated by a 3D j×B hybrid model.•Proton precipitation has a cumulative farside-nearside asymmetry: The ion flux is smaller but more energetic on nearside.•Asymmetry is a consequence of lunar tidal locking and shielding of the magnetosphere
We have developed a new fully kinetic electrostatic simulation, HYBes, to study how the lunar landscape affects the electric potential and plasma distributions near the surface and the properties of ...lifted dust. The model embodies new techniques that can be used in various types of physical environments and situations. We demonstrate the applicability of the new model in a situation involving three charged particle species, which are solar wind electrons and protons, and lunar photoelectrons. Properties of dust are studied with test particle simulations by using the electric fields derived from the HYBes model. Simulations show the high importance of the plasma and the electric potential near the surface. For comparison, the electric potential gradients near the landscapes with feature sizes of the order of the Debye length are much larger than those near a flat surface at different solar zenith angles. Furthermore, dust test particle simulations indicate that the landscape relief influences the dust location over the surface. The study suggests that the local landscape has to be taken into account when the distributions of plasma and dust above lunar surface are studied. The HYBes model can be applied not only at the Moon but also on a wide range of airless planetary objects such as Mercury, other planetary moons, asteroids, and nonactive comets.
Key Points
New electrostatic 1‐D/2‐D/3‐D model developed to study direct plasma‐surface interaction
The model was used to study plasma above various 2‐D lunar surfaces
Landscape shape dominates properties of plasma above the surface, electric field, and dust
Context. The ESA/Rosetta mission has been orbiting comet 67P/Churyumov-Gerasimenko since August 2014, measuring its dayside plasma environment. The ion spectrometer onboard Rosetta has detected two ...ion populations, one energetic with a solar wind origin (H+, He2+, He+), the other at lower energies with a cometary origin (water group ions such as H2O+). He+ ions arise mainly from charge-exchange between solar wind alpha particles and cometary neutrals such as H2O. Aims. The He+ and He2+ ion fluxes measured by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA) give insight into the composition of the dayside neutral coma, into the importance of charge-exchange processes between the solar wind and cometary neutrals, and into the way these evolve when the comet draws closer to the Sun. Methods. We combine observations by the ion spectrometer RPC-ICA onboard Rosetta with calculations from an analytical model based on a collisionless neutral Haser atmosphere and nearly undisturbed solar wind conditions. Results. Equivalent neutral outgassing rates Q can be derived using the observed RPC-ICA He+/He2+ particle flux ratios as input into the analytical model in inverse mode. A revised dependence of Q on heliocentric distance Rh in AU is found to be Rh-7.06 between 1.8 and 3.3 AU, suggesting that the activity in 2015 differed from that of the 2008 perihelion passage. Conversely, using an outgassing rate determined from optical remote sensing measurements from Earth, the forward analytical model results are in relatively good agreement with the measured RPC-ICA flux ratios. Modelled ratios in a 2D spherically-symmetric plane are also presented, showing that charge exchange is most efficient with solar wind protons. Detailed cometocentric profiles of these ratios are also presented. Conclusions. In conclusion, we show that, with the help of a simple analytical model of charge-exchange processes, a mass-capable ion spectrometer such as RPC-ICA can be used as a “remote-sensing” instrument for the neutral cometary atmosphere.
We study the solar wind‐induced ion escape from planetary atmospheres at different radial heliospheric distances in the solar system. We derive histograms of the gyroaveraged E×B velocities, ...energies, and Larmor radii of planetary ions in the solar wind at Mercury, Venus, Earth, and Mars. The statistical analysis is based on the interplanetary Pioneer Venus Orbiter and OMNI solar wind data sets. In addition to the energization in the undisturbed solar wind we also model how planetary heavy ions get energized in the solar wind interaction of an unmagnetized planet at different distances to the Sun. We found that due to the Parker spiral, pickup ions are expected to be found on average at lower energies and at velocities more perpendicular to the solar wind flow, the closer to the Sun a planet or a comet is. According to a global hybrid simulation, planetary heavy ion energization is influenced qualitatively in a similar way in the presence of an induced magnetosphere than in the upstream solar wind under different Parker spiral angles due to fact that the structure of an induced magnetosphere depends strongly on the interplanetary magnetic field and solar wind conditions. Finally, the energization and dynamics of the pickup ions vary considerably with the solar activity. The variation is stronger the farther away from the Sun an object is. The Larmor radii of the pickup ions are largest during a solar minimum while the pickup ion energies are highest during the declining phase of a solar cycle.
Key Points
Energization of atmospheric pickup ions varies considerably in the Solar System
Energization is weakest and most perpendicular to solar wind close to the Sun
Energization is strongest during a declining phase of a solar cycle
We study the formation of the lunar wake by a quasi‐neutral hybrid (QNH) model. In the model ions are particles while electrons form a massless change neutralizing fluid. The model is three ...dimensional enabling us to study non‐axisymmetric filling of the tail with solar wind plasma resulting from non‐axisymmetric electromagnetic forces. We find that already a not fully kinetic QNH model can reproduce some of the basic observed features, namely (1) a long (over 10 lunar radii) tail of depleted plasma density, (2) enhanced magnetic field within the optical shadow and depressed magnetic field near the edge of the optical shadow and (3) non‐Maxwellian plasma beams with high temperature anisotropy. The analysis also supports previous studies which have emphasized the role of the direction of the magnetic field and kinetic effects in the lunar wake.
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