The magnetospheric mapping of Jupiter's polar auroral emissions is highly uncertain because global Jovian field models are known to be inaccurate beyond ∼30 RJ. Furthermore, the boundary between open ...and closed flux in the ionosphere is not well defined because, unlike the Earth, the main auroral oval emissions at Jupiter are likely associated with the breakdown of plasma corotation and not the open/closed flux boundary in the polar cap. We have mapped contours of constant radial distance from the magnetic equator to the ionosphere in order to understand how auroral features relate to magnetospheric sources. Instead of following model field lines, we map equatorial regions to the ionosphere by requiring that the magnetic flux in some specified region at the equator equals the magnetic flux in the area to which it maps in the ionosphere. Equating the fluxes in this way allows us to link a given position in the magnetosphere to a position in the ionosphere. We find that the polar auroral active region maps to field lines beyond the dayside magnetopause that can be interpreted as Jupiter's polar cusp; the swirl region maps to lobe field lines on the night side and can be interpreted as Jupiter's polar cap; the dark region spans both open and closed field lines and must be explained by multiple processes. Additionally, we conclude that the flux through most of the area inside the main oval matches the magnetic flux contained in the magnetotail lobes and is probably open to the solar wind.
Wildfires devastated communities in Oregon and Washington in September 2020, burning almost as much forest west of the Cascade Mountain crest (“the westside”) in 2 weeks (~340,000 ha) as in the ...previous five decades (~406,00 ha). Unlike dry forests of the interior western United States, temperate rain forests of the Pacific Northwest have experienced limited recent fire activity, and debates surrounding what drove the 2020 fires, and management strategies to adapt to similar future events, necessitate a scientific evaluation of the fires. We evaluate five questions regarding the 2020 Labor Day fires: (1) How do the 2020 fires compare with historical fires? (2) How did the roles of weather and antecedent climate differ geographically and from the recent past (1979–2019)? (3) How do fire size and severity compare to other recent fires (1985–2019), and how did forest management and prefire forest structure influence burn severity? (4) What impact will these fires have on westside landscapes? and (5) How can we adapt to similar fires in the future? Although 5 of the 2020 fires were much larger than any others in the recent past and burned ~10 times the area in high‐severity patches >10,000 ha, the 2020 fires were remarkably consistent with historical fires. Reports from the early 1900s, along with paleo‐ and dendro‐ecological records, indicate similar and potentially even larger wildfires over the past millennium, many of which shared similar seasonality (late August/early September), weather conditions, and even geographic locations. Consistent with the largest historical fires, strong east winds and anomalously dry conditions drove the rapid spread of high‐severity wildfire in 2020. We found minimal difference in burn severity among stand structural types related to previous management in the 2020 fires. Adaptation strategies for similar fires in the future could benefit by focusing on ignition prevention, fire suppression, and community preparedness, as opposed to fuel treatments that are unlikely to mitigate fire severity during extreme weather. While scientific uncertainties remain regarding the nature of infrequent, high‐severity fires in westside forests, particularly under climate change, adapting to their future occurrence will require different strategies than those in interior, dry forests.
Background Inflammation is associated with psychological, emotional, and behavioral disturbance, known as sickness behavior. Inflammatory cytokines are implicated in coordinating this central ...motivational reorientation accompanying peripheral immunologic responses to pathogens. Studies in rodents suggest an afferent interoceptive neural mechanism, although comparable data in humans are lacking. Methods In a double-blind, randomized crossover study, 16 healthy male volunteers received typhoid vaccination or saline (placebo) injection in two experimental sessions. Profile of Mood State questionnaires were completed at baseline and at 2 and 3 hours. Two hours after injection, participants performed a high-demand color word Stroop task during functional magnetic resonance imaging. Blood samples were performed at baseline and immediately after scanning. Results Typhoid but not placebo injection produced a robust inflammatory response indexed by increased circulating interleukin-6 accompanied by a significant increase in fatigue, confusion, and impaired concentration at 3 hours. Performance of the Stroop task under inflammation activated brain regions encoding representations of internal bodily state. Spatial and temporal characteristics of this response are consistent with interoceptive information flow via afferent autonomic fibers. During performance of this task, activity within interoceptive brain regions also predicted individual differences in inflammation-associated but not placebo-associated fatigue and confusion. Maintenance of cognitive performance, despite inflammation-associated fatigue, led to recruitment of additional prefrontal cortical regions. Conclusions These findings suggest that peripheral infection selectively influences central nervous system function to generate core symptoms of sickness and reorient basic motivational states.
In this work, we present methods for using human-robot dialog to improve language understanding for a mobile robot agent. The agent parses natural language to underlying semantic meanings and uses ...robotic sensors to create multi-modal models of perceptual concepts like red and heavy. The agent can be used for showing navigation routes, delivering objects to people, and relocating objects from one location to another. We use dialog clari_cation questions both to understand commands and to generate additional parsing training data. The agent employs opportunistic active learning to select questions about how words relate to objects, improving its understanding of perceptual concepts. We evaluated this agent on Amazon Mechanical Turk. After training on data induced from conversations, the agent reduced the number of dialog questions it asked while receiving higher usability ratings. Additionally, we demonstrated the agent on a robotic platform, where it learned new perceptual concepts on the y while completing a real-world task.
The lack of global field models accurate beyond the inner magnetosphere (<30 RJ) makes it difficult to relate Jupiter's polar auroral features to magnetospheric source regions. We recently developed ...a model that maps Jupiter's equatorial magnetosphere to the ionosphere using a flux equivalence calculation that requires equal flux at the equatorial and ionospheric ends of flux tubes. This approach is more accurate than tracing field lines in a global field model but only if it is based on an accurate model of Jupiter's internal field. At present there are three widely used internal field models—Voyager Io Pioneer 4 (VIP4), the Grodent Anomaly Model (GAM), and VIP Anomaly Longitude (VIPAL). The purpose of this study is to quantify how the choice of an internal field model affects the mapping of various auroral features using the flux equivalence calculation. We find that different internal field models can shift the ionospheric mapping of points in the equatorial plane by several degrees and shift the magnetospheric mapping to the equator by ~30 RJ radially and by less than 1 h in local time. These shifts are consistent with differences in how well each model maps the Ganymede footprint, underscoring the need for more accurate Jovian internal field models. We discuss differences in the mapping of specific auroral features and the size and location of the open/closed field line boundary. Understanding these differences is important for the continued analysis of Hubble Space Telescope images and in planning for Juno's arrival at Jupiter in 2016.
Key Points
There are three widely used internal Jovian magnetic field models
We compare auroral mapping results using different field models
Mapping results can be shifted by several degrees or tens of Jovian radii
Oxygen acceleration in magnetotail reconnection Liang, Haoming; Lapenta, Giovanni; Walker, Raymond J. ...
Journal of geophysical research. Space physics,
January 2017, 2017-01-00, 20170101, Letnik:
122, Številka:
1
Journal Article
Recenzirano
Motivated by the observed high concentration of oxygen ions in the magnetotail during enhanced geomagnetic activity, we investigated the oxygen acceleration in magnetotail reconnection by using 2.5‐D ...implicit particle‐in‐cell simulations. We found that lobe oxygen ions can enter the downstream outflow region, i.e., the outflow region downstream of the dipolarization fronts (DFs) or the reconnection jet fronts. Without entering the reconnection exhaust, they are accelerated by the Hall electric field. They can populate the downstream outflow region before the DFs arrive there. This acceleration is in addition to acceleration in the exhaust by the Hall and reconnection electric fields. Oxygen ions in the preexisting current sheet are reflected by the propagating DF creating a reflected beam with a hook shape in phase space. This feature can be applied to deduce a history of the DF speed. However, it is difficult to observe for protons because their typical thermal velocity in the plasma sheet is comparable those of the DF and the reflection speed. The oxygen ions from the lobes and the preexisting current sheet form multiple beams in the distribution function in front of the DF. By comparing oxygen concentrations of 50%, 5%, and 0% with the same current sheet thickness, we found that the DF thickness is proportional to the oxygen concentration in the preexisting current sheet. All the simulation results can be used to compare with the observations from the Magnetospheric Multiscale mission.
Key Points
Lobe oxygen can be accelerated by the Hall electric field downstream of dipolarization fronts
Oxygen ions in the preexisting current sheet show hook‐shaped reflected beams in phase space
The resultant oxygen distribution function in front of the dipolarization front has multiple peaks
Summary
The Yellow Stripe‐Like (YSL) family of proteins has been identified based on sequence similarity to maize Yellow Stripe1 (YS1), the transporter responsible for the primary uptake of iron from ...the soil. YS1 transports iron that is complexed by specific plant‐derived Fe(III) chelators called phytosiderophores (PS). Non‐grass species of plants neither make nor use PS, yet YSL family members are found in non‐grass species (monocot, dicot, gymnosperm, and moss species) including Arabidopsis thaliana. YSLs in non‐grasses have been hypothesized to transport metals complexed by nicotianamine (NA), an iron chelator that is structurally similar to PS and which is found in all higher plants. Here we show that Arabidopsis YSL2 (At5g24380) transports iron and copper when these metals are chelated by NA. YSL2 is expressed in many cell types in both roots and shoots, suggesting that diverse cell types obtain metals as metal–NA complexes. YSL2 transcription is regulated by the levels of iron and copper in the growth medium. Based on its expression pattern, a major function of the YSL2 appears to be in the lateral movement of metals in the vasculature.
We have carried out a series of numerical experiments designed to evaluate the sensitivity of global magnetohydrodynamic simulations to changes in ionospheric conductance. We multiplied the ...precipitating energy fluxes due to both strong pitch angle scattering and parallel currents by constant factors in the Robinson et al. (1987, https://doi.org/10.1029/JA092iA03p02565) model and used them as input to a simulated substorm interval on 14 March 2008. We also used the Kaeppler et al. (2015, https://doi.org/10.1002/2015JA021396) model. When we reduced the energy fluxes by a factor of about three (0.34), the agreement on substorm location was best. Larger conductances led to onset at later local times. For multiplication factors greater than one, the magnetotail became line tied and no flows entered the inner magnetotail region. Relatively small (<50%) differences in the conductances lead to major changes in the tail configuration. We calculated auroral indices from the simulations and compared them to observations. None of the models reproduced the DP1 system but, we obtained much better agreement with the observed DP2 system. The model with the basic Robinson formula gave the best agreement with the DP2 system. We also ran a generic simulation with constant solar wind and southward IMF using the basic Robinson et al. model. The results were very similar to those of the event simulation suggesting that the changes were due to the ionospheric boundary condition. In the simulation, the energy flux obtained by assuming strong pitch angle scattering makes a larger contribution to the conductance than the field‐aligned current energy flux.
Key Points
Relatively small differences in ionospheric conductance led to major differences in the magnetotail magnetic field and flows
For southward IMF, magnetic field and flows are more sensitive to the conductance model used then they are to changes in the IMF and solar wind
The simulated conductances result mainly from the energy fluxes assuming strong pitch angle scattering not parallel currents
The magnetosphere of Mercury is studied using an implicit full particle‐in‐cell simulation (PIC). We use a hybrid simulation where ions are full particles and electrons are considered as a fluid to ...start a PIC simulation where electrons are also particles and follow their distribution function. This approach allows us to estimate the changes introduced by the electron kinetic physics. We find that the overall macroscopic state of the magnetosphere of Mercury is little affected, but several physical processes are significantly modified in the full PIC simulation: the foreshock region is more active with more intense shock reformation, the Kelvin‐Helmholtz rippling effects on the nightside magnetopause are sharper, and the magnetotail current sheet becomes thinner than those predicted by the hybrid simulation. The greatest effect of the electron physics comes from the processes of particle energization. Both species, not just the electrons, are found to gain more energy when kinetic electron processes are included. The region with the most energetic plasma is found on the dusk side of the tail where magnetic flux ropes are formed due to reconnection. We find that the ion and electron energization is associated with the regions of reconnection and the development of kinetic instabilities caused by counter‐streaming electron populations. The resulting electron distributions are highly non Maxwellian, a process that neither MHD nor hybrid models can describe.
Key Points
We study the magnetosphere of Mercury using an implicit, three‐dimensional, full particle‐in‐cell simulation
The currents, interfaces and transition region are made thinner by the electron kinetic effects and become more active
The greatest effect of including the electron physics is particle energization for both species
Ion heating during a substorm on 15 February 2008, starting at 0348 UT, is studied with a new approach recently described in Ashour‐Abdalla et al. (2015). The general conditions of the magnetotail ...are obtained from a global magnetohydrodynamic (MHD) model and are used to drive a full kinetic particle‐in‐cell (PIC) simulation of a 3‐D region of the tail. Within the kinetic box, the ions, the electrons, and the fields evolve self‐consistently. The large scales are captured by the MHD model and the small scales by the PIC model based on the MHD state. This approach is used to study ion heating. Different heating mechanisms were analyzed by examining the velocity distributions at different locations. In the x direction heating occurs as the reconnection‐generated ion jet interacts with the environment in which it propagates. The heating is found mostly in the separatrices and increases downstream of the reconnection region. In the y direction the heating is less intense and is found near the dipolarization fronts. It occurs as ions become magnetized and gyrotropize the distribution function. In addition, ions can be heated in the y direction by the reconnection electric field near the reconnection site. In the z direction the ions are heated by the formation of beams moving along z between the separatrices.
Key Points
Coupled kinetic‐fluid simulations predict ion distributions observed by THEMIS
The localization and causes of ion heating during one substorm are found
Ions are unmagnetized with anisotropic processes of energization
PDF
