Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The Challenging Minisatellite Payload (CHAMP) satellite for example has enabled many ...observations of the perturbation, showing that it is mesoscale in size and exists statistically over solar cycle timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine‐scale Poynting fluxes are associated with the density perturbations on a case‐by‐case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically. In this study, we use nearly 8 years of the overlapping Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment datasets to generate global‐scale patterns of the high‐latitude and height‐integrated Poynting flux into the ionosphere, with a time resolution of 2 min. From these, average patterns are generated based on the interplanetary magnetic field orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Importantly, the lack of correlation between mesoscale height‐integrated Poynting fluxes and the cusp neutral mass density enhancement gives possible insight into other processes that may account for the discrepancy, such as energy deposition at finer scale sizes or at higher altitudes than captured.
Key Points
Statistical patterns of the total downward Poynting flux into the atmosphere have been derived using Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment data
Statistical patterns of neutral mass density perturbations as a percentage of the background density have been derived using Challenging Minisatellite Payload data
Mesoscale downward Poynting flux in the cusp region do not correlate very well with neutral mass density enhancements at a similar scale
Our proficiency at any skill is critically dependent on the ability to monitor our performance, correct errors and adapt subsequent movements so that errors are avoided in the future. In this study, ...we aimed to dissociate the neural substrates critical for correcting unexpected trajectory errors and learning to adapt future movements based on those errors. Twenty stroke patients with focal damage to frontal or parietal regions in the left or right brain hemispheres and 20 healthy controls performed a task in which a novel mapping between actual hand motion and its visual feedback was introduced. Only patients with frontal damage in the right hemisphere failed to correct for this discrepancy during the ongoing movement. However, these patients were able to adapt to the distortion such that their movement direction on subsequent trials improved. In contrast, only patients with parietal damage in the left hemisphere showed a clear deficit in movement adaptation, but not in online correction. Left frontal or right parietal damage did not adversely impact upon either process. Our findings thus identify, for the first time, distinct and lateralized neural substrates critical for correcting unexpected errors during ongoing movements and error-based movement adaptation.
Two missions presently under development by the United States Air Force Academy (USAFA), FalconSAT-2 and FalconSAT-3, include mission scientific objectives targeting the study of ionospheric F region ...plasma density depletions and topside bubbles associated with the so-called Equatorial Spread F (ESF) phenomena. The Miniature Electrostatic Analyzer (MESA), a USAFA-designed patch sensor that measures differential energy fluxes of electrons from 0.05 to 13
eV in six channels, is the primary experiment aboard FalconSAT-2, a 25-kg microsatellite intended for launch into an International Space Station (ISS) orbit via the Space Shuttle. Because the orbit will be approximately 360
km in altitude and of 52° inclination, FalconSAT-2 observations will complement those of low latitude missions (e.g., C/NOFS) and polar latitude, higher altitude missions (e.g., DMSP). Realistic internal magnetic field models demonstrate that field lines with apex heights of 1500
km (representing the upper altitude limit of equatorial plasma bubbles) may intersect the orbit plane at dip latitudes greater than 35°. Thus, FalconSAT-2 will be able to observe plasma depletions that have propagated poleward along the field lines and lower in altitude, depletions that may not be observed with the high altitude DMSP and the low latitude C/NOFS. Additionally, there may be opportunities for FalconSAT-2 to make simultaneous multipoint in situ measurements of large-scale plasma bubbles with other low altitude satellites, such as C/NOFS and DMSP. We will present a statistical analysis of the probability of making such measurements using nominal orbital parameters of the relevant spacecraft. Finally, a description of the FalconSAT-3 follow-on mission, including scientific objectives associated with seeking kinetic effects, is presented.
Kinematic analyses of reaching have suggested that the left hemisphere is dominant for controlling the open loop component of the movement, which is more dependent on motor programmes; and the right ...hemisphere is dominant for controlling the closed loop component, which is more dependent on sensory feedback. This open and closed loop hypothesis of hemispheric asymmetry would also predict that advance planning should be dependent on the left hemisphere, and on‐line response modification, which defines closed loop processes, should be dependent on the right hemisphere. Using kinematic analyses of reaching in patients with left or right hemisphere damage (LHD or RHD), we examined the ability: (i) to plan reaching movements in advance by examining changes in reaction time (RT) when response amplitude and visual feedback were cued prior to the response; and (ii) to modify the response during implementation when target location changed at the RT. Performance was compared between the stroke groups, using the ipsilesional arm, and age‐matched control groups using their right (RNC) or left (LNC) arm. Aiming movements to a target that moved once or twice, with the second step occurring at the RT, were performed with or without visual feedback of hand position. There were no deficits in advance planning in either stroke group, as evidenced by comparable group changes in RT with changes in amplitude and visual feedback. Response modification deficits were seen for the LHD group in secondary velocity only. In addition, LHD produced slower initial peak velocity with prolongation of the deceleration phase and faster secondary peak velocities, and the RHD group produced deficits in final error only. These differences are more consistent with the dynamic dominance hypothesis, which links left hemisphere specialization to movement trajectory control and right hemisphere specialization to position control, rather than to global deficits in open and closed loop processing.
When the interplanetary magnetic field is northward for a period of time, O+ from the high‐latitude ionosphere escapes along reconnected magnetic field lines into the dayside magnetopause boundary ...layer. Dual‐lobe reconnection closes these field lines, which traps O+ and mass loads the boundary layer. This O+ is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O+‐rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high‐shear magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the magnetopause. The high‐latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside magnetopause.
Key Points
During sustained periods of northward IMF, O+ from the dayside high‐latitude ionosphere mass loads the boundary layer adjacent to the magnetopause
For the example shown, this mass loading is substantial and does have an effect on reconnection at the magnetopause when the IMF turns southward
This mass loading causes a transient reduction in the reconnection rate but does not suppress reconnection at the magnetopause
In this study, we examine whether corrections made during an ongoing movement are differentially affected by left hemisphere damage (LHD) and right hemisphere damage (RHD). Our hypothesis of motor ...lateralization proposes that control mechanisms specialized to the right hemisphere rely largely on online processes, while the left hemisphere primarily utilizes predictive mechanisms to specify optimal coordination patterns. We therefore predict that RHD, but not LHD, should impair online correction when task goals are unexpectedly changed. Fourteen stroke subjects (7 LHD, 7 RHD) and 14 healthy controls reached to 1 of the 3 targets that unexpectedly "jumped" during movement onset. RHD subjects showed a considerable delay in initiating the corrective response relative to controls and LHD subjects. However, both stroke groups made large final position errors on the target jump trials. Position deficits following LHD were associated with poor intersegmental coordination, while RHD subjects had difficulty terminating their movements appropriately. These findings confirm that RHD, but not LHD, produces a deficit in the timing of online corrections and also indicate that both stroke groups show position deficits that are related to the specialization of their damaged hemisphere. Further research is needed to identify specific neural circuits within each hemisphere critical for these processes.
The warm plasma cloak is a source of magnetospheric plasma that contain significant O+. When the O+ density in the magnetosphere near the magnetopause is >0.2 cm‐3 and the H+ density is <1.5 cm‐3, ...then O+ dominates the magnetospheric ion mass density by more than a factor of 2. A survey is conducted of such O+‐rich warm plasma cloak intervals and their effect on reconnection at the Earth's magnetopause. The survey uses data from the Magnetospheric Multiscale mission (MMS) and the results are compared and combined with a previous survey of the warm plasma cloak. Overall, the warm plasma cloak and the O+‐rich warm plasma cloak reduce the magnetopause reconnection rate by >20% due to mass‐loading only about 2% to 4% of the time. However, during geomagnetic storms, O+ dominates the mass density of the warm plasma cloak and these mass densities are very high. Therefore, a separate study is conducted to determine the effect of the warm plasma cloak on magnetopause reconnection during geomagnetically disturbed times. This study shows that the warm plasma cloak reduces the reconnection rate significantly about 25% of the time during disturbed conditions.
Key Points
The magnetospheric warm plasma cloak is O+‐rich during geomagnetically active times
The warm plasma cloak reduces the magnetic reconnection rate at the magnetopause ~2‐4% of the time
During geomagnetic storms, the O+‐rich warm plasma cloak reduces the reconnection rate by >20% sometime during 25% of the storms
Precise timing of sensory information from multiple sensory streams is essential for many aspects of human perception and action. Animal and human research implicates the basal ganglia and cerebellar ...systems in timekeeping operations, but investigations into the role of the cerebral cortex have been limited. Individuals with focal left (LHD) or right hemisphere (RHD) lesions and control subjects performed two time perception tasks (duration perception, wherein the standard tone pair interval was 300 or 600 msec) and a frequency perception task, which controlled for deficits in time-independent processes shared by both tasks. When frequency perception deficits were controlled, only patients with RHD showed time perception deficits. Time perception competency was correlated with an independent test of switching nonspatial attention in the RHD but not the LHD patients, despite attention deficits in both groups. Lesion overlays of patients with RHD and impaired timing showed that 100% of the patients with anterior damage had lesions in premotor and prefrontal cortex (Brodmann areas 6, 8, 9, and 46), and 100% with posterior damage had lesions in the inferior parietal cortex. All LHD patients with normal timing had damage in these same regions, whereas few, if any, RHD patients with normal timing had similar lesion distributions. These results implicate a right hemisphere prefrontal-inferior parietal network in timing. Time-dependent attention and working memory functions may contribute to temporal perception deficits observed after damage to this network.
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