Abstract
The Rosetta mission provided detailed observations of the growth of a cavity in the solar wind around comet 67P/Churyumov–Gerasimenko. As the comet approached the Sun, the plasma of cometary ...origin grew enough in density and size to present an obstacle to the solar wind. Our results demonstrate how the initial slight perturbations of the solar wind prefigure the formation of a solar wind cavity, with a particular interest placed on the discontinuity (solar wind cavity boundary) passing over the spacecraft. The slowing down and heating of the solar wind can be followed and understood in terms of single particle motion. We propose a simple geometric illustration that accounts for the observations, and shows how a cometary magnetosphere is seeded from the gradual steepening of an initially slight solar wind perturbation. A perspective is given concerning the difference between the diamagnetic cavity and the solar wind cavity.
This study examined the associations of cardiorespiratory fitness (CRF) and leisure‐time physical activity (LTPA) with health‐related quality of life (HRQoL) in women at risk for gestational diabetes ...mellitus (GDM). The participants were 39 women planning pregnancy with a history of GDM and/or BMI >29 kg/m2. We assessed CRF by measuring maximal oxygen consumption (VO2max) during incremental cycle ergometer exercise until voluntary fatigue. LTPA was self‐reported, and HRQoL assessed with the SF‐36 Health Survey (SF‐36). The mean (SD) VO2max was 27 (6) mL·kg−1·min−1, and the mean LTPA was 2.6 (1.7) h/wk. After controlling for BMI, VO2max was positively associated with the SF‐36 General Health scale (β 1.27, 95% CI: 0.09, 2.44, P=.035) and the Physical Component Summary (β 0.48, 95% CI: 0.14, 0.82, P=.007). The General Health scale (P=.023) and the Physical Component Summary (P=.011) differed even between those with very poor and poor CRF. After controlling for BMI, LTPA was positively associated with the SF‐36 Physical Functioning scale (rs=.34, P=.039), the General Health scale (β 3.74, 95% CI: 0.64, 6.84, P=.020), and the Physical Component Summary (β 1.13 95% CI: 0.19, 2.06, P=.020). To conclude, CRF and LTPA were positively associated with perceived general health and physical well‐being in women planning pregnancy and at risk for GDM. Even a slightly better CRF would be beneficial for well‐being among women with low levels of CRF.
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.
Flux transfer events (FTEs) are transient magnetic flux ropes at Earth's dayside magnetopause formed due to magnetic reconnection. As they move across the magnetopause surface, they can generate ...disturbances in the ultralow frequency (ULF) range, which then propagate into the magnetosphere. This study provides evidence of ULF waves in the Pc2 wave frequency range (>0.1 Hz) caused by FTEs during dayside reconnection using a global 3D hybrid‐Vlasov simulation (Vlasiator). These waves resulted from FTE formation and propagation at the magnetopause are particularly associated with large, rapidly moving FTEs. The wave power is stronger in the morning than afternoon, showing local time asymmetry. In the pre and postnoon equatorial regions, significant poloidal and toroidal components are present alongside the compressional component. The noon sector, with fewer FTEs, has lower wave power and limited magnetospheric propagation.
Plain Language Summary
The Earth's magnetosphere is a dynamic region shaped by the interplay between the solar wind and Earth's magnetic field. This interaction occurs at the boundary of the magnetosphere (magnetopause) through a process known as magnetic reconnection, giving rise to Flux Transfer Events (FTEs), which are magnetic structures that carry flux and energy into the magnetosphere. These FTEs form either in sudden bursts, patchy patterns or in a continuous, and relatively stable way making the magnetopause surface dynamic. As the FTEs move along the boundary of the magnetosphere, they create compressed regions and lead to wave generation that can extend into the magnetosphere. The study uses an advanced 3D hybrid‐Vlasov simulation model to analyze waves originated from FTE formation and propagation at the magnetopause. We find that rapidly moving and large FTEs have a significant impact on the magnetopause, leading to the generation of ULF waves with frequency above 0.1 Hz. This shows first direct evidence supporting previous theoretical speculations regarding the ability of FTEs to generate waves near the magnetopause.
Key Points
Dayside Pc2 waves (>0.1 Hz) have been detected in a 3D hybrid‐Vlasov simulation
These waves exhibit lower intensity within the magnetosphere at noon, compared to the prenoon and postnoon sectors
Pc2 waves observed in the simulation are associated with largest and fast moving flux transfer events initiated by subsolar reconnection
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.
The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide. GDM may be prevented by improving the diets of pregnant women. The objective of this study was to evaluate the effect of ...dietary counselling on the diets of pregnant women at GDM risk.
This study was a secondary analysis of a randomised controlled trial the Finnish gestational diabetes prevention study (RADIEL) in which pre-pregnant and pregnant women with previous GDM or BMI ⩾30 kg/m(2) were allocated into two groups, namely the control and the intervention groups. The control group received standard antenatal dietary counselling according to the Finnish Nutrition Recommendations. The intervention group participated in one individual dietary counselling session and one group dietary counselling session in addition to the standard counselling. This study included women who were recruited during pregnancy. To assess changes in food intake, food-intake questionnaires were collected during the first and the second trimester of pregnancy. Bootstrap type analysis of covariance was used, and 242 participants were included in the final analysis to study changes in food intake.
The intakes of low-fat cheese (baseline adjusted mean 0.09 times/day; 95% confidence interval (CI) 0.07, 0.24; P=0.040) and fish (baseline adjusted mean 0.28 times per week; 95% CI 0.08, 0.49; P=0.011) showed a significant increase in the intervention group compared with the control group.
This study showed that dietary counselling in early pregnancy can lead to modest dietary improvements in pregnant women at GDM risk.
Vlasiator is a high‐performance ion‐kinetic code that is now conducting 3D hybrid‐Vlasov simulations of the global magnetosphere. We use Vlasiator to investigate the impact of a pressure pulse with ...southward‐oriented magnetic field on the Earth's magnetosphere. The simulation driving parameters are comparable to conditions that have led to geomagnetic storms. Our pressure pulse simulation reproduces many physical effects, namely the expansion of the auroral oval, the development of field‐aligned currents, enhanced particle precipitation near the open/closed field line boundary, and compression of Earth's magnetopause. This demonstrates the effectiveness of the hybrid‐Vlasov approach for moderate driving conditions. Our investigation of the time‐dependent magnetopause compression motivates a generalization of the existing theory. Specifically, we find that accounting for the finite transition time of the solar wind dynamic pressure improves the model's description of the magnetopause oscillations.
Plain Language Summary
We perform state‐of‐the‐art simulations of the interaction of near‐Earth space environment with the incoming material ejected from the Sun. The response of Earth's magnetic field to such ejecta is known as a “geomagnetic storm.” Our simulation approach captures the motion of protons more accurately than commonly used fluid models, but at the cost of making the simulations more computationally intensive. To validate this novel approach, we compare the output of our simulation with established observational signatures of the initial storm phase. We find that our simulation, of relatively moderate storm conditions, reproduces known effects that are relevant to society. Such effects include particle precipitation into the atmosphere and reconfiguration of global magnetic field. Our simulation does diverge from established models on how the magnetopause, the boundary between Earth's magnetic environment and the solar wind, moves in response to a sudden increase of incoming pressure. This inspires a modification of the theory of magnetopause motion, which better accounts for the detailed time profile of the incoming solar wind.
Key Points
Vlasiator's 3D hybrid‐kinetic model of the global magnetosphere produces expected behavior for a pressure pulse arriving at Earth
The finite transition time of the pressure pulse causes magnetopause oscillations to be weak and elongated relative to established models
The magnetopause oscillations are explained with a generalized model that accounts for the finite transition time of the pressure pulse
We study the properties of neutral hydrogen atoms precipitating onto the upper atmosphere of Mars. Energetic neutral atoms (ENAs) are produced by the charge exchange process between protons of solar ...wind (both upstream and shocked) as well as planetary origins and the Martian exospheric neutrals. Using a global hybrid plasma model for Mars‐solar wind interaction combined with an up‐to‐date exosphere model of Mars, we calculate the fluxes, spatial distributions, energy spectra, and direction distributions of hydrogen ENAs (H‐ENAs) at the Martian exobase for each source proton population. H‐ENAs originating from the upstream solar wind region and the magnetosheath dominate the precipitation. Two percent of the solar wind flux penetrates through the magnetic barrier as H‐ENAs under solar minimum conditions. The precipitating solar wind H‐ENA flux is axially symmetric about Sun‐Mars line, while the magnetosheath and planetary H‐ENAs have higher fluxes and a more‐extended precipitation area in the hemisphere where the convection electric field is pointing away from the planet, causing a significant precipitation beyond the terminator. The observed asymmetry is consistently explained by an asymmetric plasma flow in the dayside magnetosheath. The solar wind dynamic pressure increases the solar wind H‐ENA precipitation normalized by the upstream proton flux, due to a closer bow shock position and thus a higher exospheric column density for charge exchange. The spatial distribution of the magnetosheath solar wind and planetary H‐ENAs becomes more axially symmetric with increased dynamic pressure. The solar wind interaction with Mars exhibits more gas‐dynamic‐like signatures for higher dynamic pressure.
Key Points
Approximately 2% of solar wind protons precipitate as neutral hydrogen atoms (H‐ENA) during solar minimum conditions, depending on solar wind conditions
H‐ENA precipitation map reveals asymmetric shocked solar wind flow. Asymmetry reduces with increasing upstream dynamic pressure
H‐ENA precipitating to nightside exobase can contribute to nightside ionization of Mars' ionosphere
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