We investigate spatial and temporal scales at which wave‐particle interaction of Alfvén waves occurs in Jupiter's magnetosphere. We consider electrons, protons, and oxygen ions and study the regions ...along magnetic flux tubes where the plasma is the densest, that is, the equatorial plasma sheet, and where the plasma is the most dilute, that is, above the ionosphere, where auroral particle acceleration is expected to occur. We find that within a dipole L‐shell of roughly 30, the electron inertial length scale in the auroral region is the dominating scale, suggesting that electron Landau damping of kinetic Alfvén waves can play an important role in converting field energy into auroral particle acceleration. This mechanism is consistent with the broadband bidirectional electron distributions frequently observed by Juno. Due to interchange‐driven mass transport in Jupiter's magnetosphere, its magnetosphere‐ionosphere coupling is expected to be mostly not in local force balance. This might be a key reason for the dominant role of Alfvénically driven stochastic acceleration compared to the less frequently occurring, locally forced‐balanced, and thus static mono‐energetic unidirectional acceleration. Outside of approximately L = 30, the ion gyroperiod is the dominating scale suggesting that ion cyclotron damping of heavy ions plays a major role in heating magnetospheric plasma. We also present properties of the dispersion relationship and the polarization relationships of kinetic Alfvén waves including the important effects from the relativistic correction due to the displacement current in Ampère's law.
Key Points
Kinetic Alfvén waves in Jupiter's magnetosphere generate broadband bidirectional auroral electron beams
In Jupiter's middle and outer magnetosphere, ion cyclotron damping causes ion heating in plasma sheet
Stochastic acceleration due to Alfvén waves can have its root cause in magnetosphere‐ionosphere coupling locally not in stress balance
The Juno mission flew through the plasma disk near the equator in Jupiter's magnetosphere frequently. We identify 274 plasma disk crossings of Juno between 10 and 40 RJ from PJ5 to PJ44. Using a ...forward modeling method that combines the JADE‐I time‐of‐flight and SPECIES data sets, we perform a survey of ion properties in the plasma disk. Ions are heated from 1.5 to 6 keV between 15 and 30 RJ. Density and temperature are locally anti‐correlated. Assumed to be related to centrifugal instabilities, cold, dense plasma are commonly observed near midnight. Plasma corotates around Jupiter and the rigid corotation breaks down outside 15–20 RJ. The plasma bulk velocity increases from the post‐dusk sector to the pre‐dawn sector featuring injection flows in the pre‐dawn sector, which is consistent with the Vasyliunas cycle. Strong outflows (>100 km/s) are commonly observed outside 20 RJ and the average radial velocity increases with radial distance. The ion abundance changes between 10 and 18 RJ and that might indicate plasma sources and/or sinks near Europa and Ganymede. The vertical distribution of ions is controlled by the balance between centrifugal, pressure gradient, and ambipolar electric field forces. An example near the M‐shell of 13.5 shows that average plasma temperature increases by a factor of 10 from the disk center to edge, because cold ions are more confined near the equator. Lighter ions with higher charge states have more mobility along the field line and have larger scale heights. The observations are compared with multi‐species diffusive equilibrium model.
Key Points
The ion properties of the plasma disk are investigated based on 274 plasma disk crossings of Juno on Jupiter's nightside
Strong outflows are observed frequently outside 25 RJ and corotational velocity increases from the post‐dusk sector to the pre‐dawn sector
Colder (hotter) and heavier (lighter) ions with lower (higher) charge states are more (less) confined near the equator
We examine the East‐West asymmetry of the peak intensity in energetic storm particle (ESP) events using the improved Particle Acceleration and Transport in the Heliosphere model. We find that ...injection efficiency peaks east of the nose of coronal mass ejection shock where the shock exhibits a quasi‐parallel geometry. We show that the peak intensity at the eastern flank is generally larger than that at the western flank and it positively correlates with the injection efficiency. We also examine this asymmetry for heavy ions, which depends sensitively on the ion energy. Comparison between the modeling results with the measurements of ESP events at 1 au shows a reasonable agreement. We suggest that the injection efficiency can be a primary factor leading to the East‐West asymmetry of the peak intensity in ESP events. Additionally, the charge‐to‐mass (Q/A) dependence of the maximum particle energy affects this asymmetry for heavy ions.
Plain Language Summary
Energetic storm particle (ESP) events occur when coronal mass ejection‐driven shocks pass a spacecraft, leading to abrupt increases in particle intensity and posing severe radiation hazards to astronauts and spacecraft. These enhancements are usually interpreted as the result of a local particle acceleration process. Therefore, in‐situ measurements of ESP events provide a great opportunity to investigate the shock acceleration mechanism. Recent observations from multiple spacecraft show an East‐West asymmetry in the peak intensity of ESP events, with significantly different intensities observed on the eastern and the western shock flank. In this study, we use the 2D improved Particle Acceleration and Transport in the Heliosphere model to investigate the East‐West asymmetry of particle intensity in ESP events. We find that the injection efficiency, which depends on the shock geometry, is the key parameter responsible for this East‐West asymmetry.
Key Points
East‐West Asymmetry of particle intensity is often found in energetic storm particle events. We propose continuous shock acceleration can lead to this asymmetry
Continuous acceleration depends on shock geometry and through this, the injection efficiency plays a central role for this asymmetry
We simulate this asymmetry using the improved Particle Acceleration and Transport in the Heliosphere model and compared our simulation results with observations
Chronic pain is a disabling disease with limited treatment options. While animal models have revealed important aspects of pain neurobiology, therapeutic translation of this knowledge requires our ...understanding of these cells and networks of pain in humans. We propose a multi-institutional collaboration to rigorously and ethically address this challenge.
The Jovian Auroral Distributions Experiment ion sensor (JADE‐I) on board the National Aeronautics and Space Administration's Juno mission measured solar wind ions for ≈40 days prior to the ...spacecraft's arrival at Jupiter, simultaneous with numerous telescope observations of the Jovian aurora. JADE‐I is a thermal plasma time‐of‐flight instrument designed to measure Jovian auroral and magnetospheric ions. This study provides a solar wind parameter data set for the approach phase that may be used in coordinated studies with remote measurements of the Jovian aurora, to compare with models that propagate solar wind conditions from Earth and to apply to Jovian bow shock or magnetopause models. While multiple bow shock crossings were predicted during Juno's approach, there was only one observed suggesting a compressed magnetosphere that was shrinking as Juno approached. However, the calculated ram pressure at the bow shock was near the median value of those 40 days, rather than being in an upper percentile.
Key Points
A technique to extract solar wind flow and density from coarse energy and field of view particle measurements is developed
Solar wind parameters for Juno's approach to the Jovian system are derived
On approach Juno made a single bow shock crossing, rather than predicted multiple crossings
Regulation of erythropoiesis is achieved by the integration of distinct signals. Among them, macrophages are emerging as erythropoietin-complementary regulators of erythroid development, particularly ...under stress conditions. We investigated the contribution of macrophages to physiological and pathological conditions of enhanced erythropoiesis. We used mouse models of induced anemia, polycythemia vera and β-thalassemia in which macrophages were chemically depleted. Our data indicate that macrophages contribute decisively to recovery from induced anemia, as well as the pathological progression of polycythemia vera and β-thalassemia, by modulating erythroid proliferation and differentiation. We validated these observations in primary human cultures, showing a direct impact of macrophages on the proliferation and enucleation of erythroblasts from healthy individuals and patients with polycythemia vera or β-thalassemia. The contribution of macrophages to stress and pathological erythropoiesis, which we have termed stress erythropoiesis macrophage-supporting activity, may have therapeutic implications.
It has been noted that in large solar energetic particle (SEP) events, the peak intensities show an East-West asymmetry with respect to the source flare locations. Using the 2D improved Particle ...Acceleration and Transport in the Heliosphere (iPATH) model, we investigate the origin of this longitudinal trend. We consider multiple cases with different solar wind speeds and eruption speeds of the coronal mass ejections (CMEs) and fit the longitudinal distributions of time-averaged fluence by symmetric/asymmetric Gaussian functions with three time intervals of 8, 24 and 48 hr after the flare onset time respectively. The simulation results are compared with a statistical study of three-spacecraft events. We suggest that the East-West asymmetry of SEP fluence and peak intensity can be primarily caused the combined effect of an extended shock acceleration process and the evolution of magnetic field connection to the shock front. Our simulations show that the solar wind speed and the CME speed are important factors determining the East-West fluence asymmetry.
We investigate the structure of Jupiter's dawnside magnetopause using observations obtained by particle and fields instrumentation on the Juno spacecraft. Characterization of Jupiter's magnetopause ...is critical for the understanding of mass and energy transport between the solar wind and the magnetosphere. We find an extended magnetopause boundary layer (MPBL) during a magnetopause crossing on 14 July 2016. This thick MPBL, in combination with a large magnetic field component normal to the magnetopause boundary, suggests that strong magnetospheric compression enhances mass transport across the magnetopause via magnetic reconnection. We further identify ~2 h increases in the total magnetospheric pressure adjacent to the magnetopause on 14 July 2016 and 1 August 2016. These large‐scale structures provide evidence of focused energy transport into the magnetosphere via magnetohydrodynamic structures.
Key Points
Jupiter's dawnside magnetosphere is highly compressible and subject to strong Alfvén‐magnetosonic mode coupling
Magnetospheric compressions may enhance reconnection rates and increase mass transport across the magnetopause
Total pressure increases inside the magnetopause with durations of hours are indicative of strong solar wind‐magnetosphere energy transport
Magnetic reconnection is a fundamental mechanism for the transport of mass and energy in planetary magnetospheres and astrospheres. While the process of reconnection is itself ubiquitous across a ...multitude of systems, the techniques used for its analysis can vary across scientific disciplines. Here we frame the latest understanding of reconnection theory by missions such as NASA’s Magnetospheric Multiscale (MMS) mission for use throughout the solar system and beyond. We discuss how reconnection can couple magnetized obstacles to both sub- and super-magnetosonic upstream flows. In addition, we address the need to model sheath plasmas and field-line draping around an obstacle to accurately parameterize the possibility for reconnection to occur. We conclude with a discussion of how reconnection energy conversion rates scale throughout the solar system. The results presented are not only applicable to within our solar system but also to astrospheres and exoplanets, such as the first recently detected exoplanet magnetosphere of HAT-11-1b.
PDF
