Advanced Methods for Analyzing in-Situ Observations of Magnetic Reconnection.

There is ample evidence for magnetic reconnection in the solar system, but it is a nontrivial task to visualize, to determine the proper approaches and frames to study, and in turn to elucidate the physical processes at work in reconnection regions from in-situ measurements of plasma particles and electromagnetic fields. Here an overview is given of a variety of single- and multi-spacecraft data analysis techniques that are key to revealing the context of in-situ observations of magnetic reconnection in space and for detecting and analyzing the diffusion regions where ions and/or electrons are demagnetized. We focus on recent advances in the era of the Magnetospheric Multiscale mission, which has made electron-scale, multi-point measurements of magnetic reconnection in and around Earth's magnetosphere.

Direct observations of anomalous resistivity and diffusion in collisionless plasma.

Coulomb collisions provide plasma resistivity and diffusion but in many low-density astrophysical plasmas such collisions between particles are extremely rare. Scattering of particles by electromagnetic waves can lower the plasma conductivity. Such anomalous resistivity due to wave-particle interactions could be crucial to many processes, including magnetic reconnection. It has been suggested that waves provide both diffusion and resistivity, which can support the reconnection electric field, but this requires direct observation to confirm. Here, we directly quantify anomalous resistivity, viscosity, and cross-field electron diffusion associated with lower hybrid waves using measurements from the four Magnetospheric Multiscale (MMS) spacecraft. We show that anomalous resistivity is approximately balanced by anomalous viscosity, and thus the waves do not contribute to the reconnection electric field. However, the waves do produce an anomalous electron drift and diffusion across the current layer associated with magnetic reconnection. This leads to relaxation of density gradients at timescales of order the ion cyclotron period, and hence modifies the reconnection process.

Magnetotail reconnection onset caused by electron kinetics with a strong external driver.

Magnetotail reconnection plays a crucial role in explosive energy conversion in geospace. Because of the lack of in-situ spacecraft observations, the onset mechanism of magnetotail reconnection, however, has been controversial for decades. The key question is whether magnetotail reconnection is externally driven to occur first on electron scales or spontaneously arising from an unstable configuration on ion scales. Here, we show, using spacecraft observations and particle-in-cell (PIC) simulations, that magnetotail reconnection starts from electron reconnection in the presence of a strong external driver. Our PIC simulations show that this electron reconnection then develops into ion reconnection. These results provide direct evidence for magnetotail reconnection onset caused by electron kinetics with a strong external driver.

Lower-Hybrid Drift Waves Driving Electron Nongyrotropic Heating and Vortical Flows in a Magnetic Reconnection Layer.

We report measurements of lower-hybrid drift waves driving electron heating and vortical flows in an electron-scale reconnection layer under a guide field. Electrons accelerated by the electrostatic potential of the waves exhibit perpendicular and nongyrotropic heating. The vortical flows generate magnetic field perturbations comparable to the guide field magnitude. The measurements reveal a new regime of electron-wave interaction and how this interaction modifies the electron dynamics in the reconnection layer.

The assessment of stress level, anxiety, depressive symptoms, and defense mechanisms among Polish and English medical students.

INTRODUCTION: Medical education is proven to be associated with a high degree of psychological stress. Different coping strategies used by students have been investigated on their efficacy. So far, studies on medical students have been limited to a single population. AIM OF THE STUDY: Our study aimed to identify differences in the prevalence of depressive symptoms, anxiety, stress levels, and defense mechanisms among two groups of medical students, the Polish and English-speaking divisions. MATERIALS AND METHODS: The study included two groups of first-year medical students, the Polish and English-speaking divisions, comprising 305 participants (n = 204 Polish, n = 101 English, men = 127, women = 176). It was divided into two periods: the students received author questionnaires during an exam-free academic period and then completed the same questionnaires during an exam session. The survey contained questions pertaining to demographics and studying habits among participants and included the Defense Style Questionnaire and Depression Anxiety Stress Scales. Data were analyzed using STATISTICA version 12.0, and p ≤ 0.05 was considered significant. RESULTS: Polish medical students presented with significantly increased overall stress levels (p = 0.007858) and depressive symptoms (p = 0.030420) compared to the English division students. Polish students also presented with more symptoms of stress, depression, and anxiety during the exam period compared to the exam-free period (p = 0.000625), which did not apply to the English-speaking students. The English division students reached higher scores in the mature defense mechanisms section than the Polish students (p = 0.000001). The use of mature defense mechanisms correlated negatively with the intensity of stress, anxiety, and depressive symptoms in both groups, while immature defense mechanisms promoted higher values of those variables (p = 0.000001). CONCLUSIONS: Our study showed significant and multidirectional differences between medical students of the Polish and English divisions attending the same university. Such results could suggest that strategies aimed at reducing depressive symptoms among medical students ought to be adapted towards the needs of a specific population.

Electron Bernstein waves driven by electron crescents near the electron diffusion region.

The Magnetospheric Multiscale (MMS) spacecraft encounter an electron diffusion region (EDR) of asymmetric magnetic reconnection at Earth's magnetopause. The EDR is characterized by agyrotropic electron velocity distributions on both sides of the neutral line. Various types of plasma waves are produced by the magnetic reconnection in and near the EDR. Here we report large-amplitude electron Bernstein waves (EBWs) at the electron-scale boundary of the Hall current reversal. The finite gyroradius effect of the outflow electrons generates the crescent-shaped agyrotropic electron distributions, which drive the EBWs. The EBWs propagate toward the central EDR. The amplitude of the EBWs is sufficiently large to thermalize and diffuse electrons around the EDR. The EBWs contribute to the cross-field diffusion of the electron-scale boundary of the Hall current reversal near the EDR.

Pressure Tensor Elements Breaking the Frozen-In Law During Reconnection in Earth's Magnetotail.

Aided by fully kinetic simulations, spacecraft observations of magnetic reconnection in Earth's magnetotail are analyzed. The structure of the electron diffusion region is in quantitative agreement with the numerical model. Of special interest, the spacecraft data reveal how reconnection is mediated by off-diagonal stress in the electron pressure tensor breaking the frozen-in law of the electron fluid.

Publisher Correction: Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath.

Change history: In this Letter, the y-axis values in Fig. 3f should go from 4 to -8 (rather than from 4 to -4), the y-axis values in Fig. 3h should appear next to the major tick marks (rather than the minor ticks), and in Fig. 1b, the arrows at the top and bottom of the electron-scale current sheet were going in the wrong direction; these errors have been corrected online.

Wave Phenomena and Beam-Plasma Interactions at the Magnetopause Reconnection Region.

This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher-frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The diffusion region is bounded by crescent-shaped electron distributions and associated dissipation just upstream of the X-line and by magnetic field-aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X-line as determined by southward directed ion and electron jets. We show that electrostatic wave generation is due to magnetosheath electron beams formed by the electron jets as they interact with a cold background plasma and more energetic population of magnetospheric electrons. On the magnetosphere side of the X-line the electron beams are accompanied by a strong perpendicular electron temperature anisotropy, which is shown to be the source of an observed rising-tone whistler mode chorus event. We show that the apex of the chorus event and the onset of electrostatic waves coincide with the opening of magnetic field lines at the electron stagnation point.

Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath.

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3-5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region 6 . In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7-11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

Electron Crescent Distributions as a Manifestation of Diamagnetic Drift in an Electron-Scale Current Sheet: Magnetospheric Multiscale Observations Using New 7.5 ms Fast Plasma Investigation Moments.

We report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5 ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from E × B drift in the interval where the out-of-plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out-of-plane current is transitioning to in-plane current, the electron momentum equation is not satisfied at 7.5 ms resolution.

A micro-scale plasma spectrometer for space and plasma edge applications (invited).

A plasma spectrometer design based on advances in lithography and microchip stacking technologies is described. A series of curved plate energy analyzers, with an integrated collimator, is etched into a silicon wafer. Tests of spectrometer elements, the energy analyzer and collimator, were performed with a 5 keV electron beam. The measured collimator transmission and energy selectivity were in good agreement with design targets. A single wafer element could be used as a plasma processing or fusion first wall diagnostic.

Cognitive functions and mood during chronic thyrotropin-suppressive therapy with L-thyroxine in patients with differentiated thyroid carcinoma.

BACKGROUND: Subclinical thyroid dysfunctions may cause cognitive deficits and mood disorders. Chronic TSH-suppressive therapy with L-T(4) causing subclinical hyperthyroidism has been widely used in treatment of patients with thyroid differentiated carcinoma. The impact of this therapy on cognitive functions and mood have not been systematically studied. The aim of this study was to asses executive functions, working memory, attention, and depression in patients with subclinical hyperthyroidism in the course of TSH-suppressive therapy. METHODS: Thirty-one patients with subclinical hyperthyroidism in the course of suppressive treatment with L-T(4) following the total thyroidectomy and radioiodine ablative therapy were included in the study. Cognitive functioning in patients and control group were investigated using the battery of neuropsychological tests [Wisconsin Card Sorting Test (WCST), The Oral Word Association Test (OWAT), Trail Making Test, The Stroop Color-Word Interference test and Digit span]. Psychometric evaluation was performed using 17-items the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). RESULTS: The performance on tests assessed executive functions, psychomotor speed, and attention was significantly lower in patients group. There was no differences in results of Stroop test and Digit Span forward and backwards between both groups. The intensity of depressive symptoms negatively correlated with a number of completed categories on WCST and results of OWAT. Cognitive deficits were still observed when patients with concomitant general medical conditions and depression were excluded from the analysis. CONCLUSION: Our findings provide evidence of neuropsychological impairment in patients with differentiated thyroid carcinoma treated with chronic TSH-suppressive therapy.

Inflammatory cytokine inhibition with combination daclizumab and infliximab for steroid-refractory acute GVHD.

Treatment options for steroid-refractory GVHD (SR-GVHD) are unsatisfactory and prognosis is poor. Inflammatory cytokines IL-2 and TNF-α are important mediators of GVHD and may be critical targets for therapy. We retrospectively reviewed our experience using combination anti-cytokine therapy of daclizumab and infliximab. Seventeen evaluable patients had a median age of 47 years (range 35-63). The conditioning regimen was myeloablative in 13 and non-myeloablative in 4 cases. GVHD occurred at a median of 49 days after transplant in 12 patients (range 21-231 days) and at a median of 46 days (range 25-119 days) after donor lymphocyte infusion in 5 patients. All patients had persistent or progressive GVHD despite 1-2 mg/kg/day of corticosteroids for a median of 7 days (range 2-26 days). They received a combination of daclizumab and infliximab for acute GVHD IBMTR severity index B (3), C (10) or D (4). Of the 17 patients analyzed, 47% responded to treatment, 24% had complete resolution of symptoms and 24% had partial responses. Survival was limited and all the patients died a median of 6.7 months (range 1.6-26) from transplant and 35 days from initiation of daclizumab/infliximab. This retrospective analysis suggests that combination anti-cytokine therapy with daclizumab/infliximab has significant activity in SR-GVHD, but outcomes remain poor. New methods to prevent and treat GVHD are urgently needed.

Linking land cover and water quality in New York City's water supply watersheds.

The Catskill/Delaware reservoirs supply 90% of New York City's drinking water. The City has implemented a series of watershed protection measures, including land acquisition, aimed at preserving water quality in the Catskill/Delaware watersheds. The objective of this study was to examine how relationships between landscape and surface water measurements change between years. Thirty-two drainage areas delineated from surface water sample points (total nitrogen, total phosphorus, and fecal coliform bacteria concentrations) were used in step-wise regression analyses to test landscape and surface-water quality relationships. Two measurements of land use, percent agriculture and percent urban development, were positively related to water quality and consistently present in all regression models. Together these two land uses explained 25 to 75% of the regression model variation. However, the contribution of agriculture to water quality condition showed a decreasing trend with time as overall agricultural land cover decreased. Results from this study demonstrate that relationships between land cover and surface water concentrations of total nitrogen, total phosphorus, and fecal coliform bacteria counts over a large area can be evaluated using a relatively simple geographic information system method. Land managers may find this method useful for targeting resources in relation to a particular water quality concern, focusing best management efforts, and maximizing benefits to water quality with minimal costs.