The study uses satellite observations, global assimilated aerosol data sets, Atmospheric Brown Clouds (ABC) observatories, a Monte Carlo aerosol‐cloud‐radiation model and a regional chemical ...transport model (STEM‐2K) to characterize the spatial extent of brown clouds, regional and megacity ABC hot spots, chemical composition and the direct radiative forcing. It presents the first annual cycle of aerosol observations and forcing from the ABC observatories in the Indo‐Asia‐Pacific regions. East Asia, Indo‐Gangetic Plains, Indonesian region, southern Africa and the Amazon basin are the regional hot spots defined by the criteria that anthropogenic aerosol optical depths (AODs) should exceed 0.3 and absorbing AOD > 0.03. Over these hot spots, as well as in other polluted oceanic regions, the EC mass exceeds 0.5 μg m−3, the OC mass exceeds 2 μg m−3 and sulfate mass exceeds 10 μg m−3 from the surface to 3 km. The brown clouds also have strong seasonal dependence. In the tropics the seasonal dependence is driven by pollution accumulating during the dry seasons, December to February in Northern Hemisphere tropics and June to August in Southern Hemisphere tropics. In the extratropics the pollution peaks during the summer. The brown cloud problem is not restricted to the tropical regions. Over the eastern half of US and western Europe the AODs exceeds 0.2 and absorption AODs exceed 0.02. Brown clouds also extend well into the western Pacific Ocean, the Indian Ocean reaching as far south as 60°S and the eastern Atlantic Ocean. The largest total SO2 emission occurs over China and US, while SO2 emission per unit surface area is maximum over Germany and England. The largest total EC and OC emissions occur over China, but the largest OC emission per unit surface area occur over India. As a result, the maximum negative annual mean TOA direct forcing is over India and Germany. The surface annual‐diurnal mean dimming over the regional hot spots is of the order of −10 W m−2 and −20 W m−2 over megacity hotpots.
This paper summarizes the results obtained by the team “Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields” supported by the ...International Space Science Institute (ISSI) in Bern, Switzerland. We focus on the physical processes occurring in the outer heliosphere, especially at its boundary called the heliopause, and in the local interstellar medium. The importance of magnetic field, charge exchange between neutral atoms and ions, and solar cycle on the heliopause topology and observed heliocentric distances to different heliospheric discontinuities are discussed. It is shown that time-dependent, data-driven boundary conditions are necessary to describe the heliospheric asymmetries detected by the
Voyager
spacecraft. We also discuss the structure of the heliopause, especially due to its instability and magnetic reconnection. It is demonstrated that the Rayleigh–Taylor instability of the nose of the heliopause creates consecutive layers of the interstellar and heliospheric plasma which are magnetically connected to different sources. This may be a possible explanation of abrupt changes in the galactic and anomalous cosmic ray fluxes observed by
Voyager 1
when it was crossing the heliopause structure for a period of about one month in the summer of 2012. This paper also discusses the plausibility of fitting simulation results to a number of observational data sets obtained by
in situ
and remote measurements. The distribution of magnetic field in the vicinity of the heliopause is discussed in the context of
Voyager
measurements. It is argued that a classical heliospheric current sheet formed due to the Sun’s rotation is not observed by
in situ
measurements and should not be expected to exist in numerical simulations extending to the boundary of the heliosphere. Furthermore, we discuss the transport of energetic particles in the inner and outer heliosheath, concentrating on the anisotropic spatial diffusion diffusion tensor and the pitch-angle dependence of perpendicular diffusion and demonstrate that the latter can explain the observed pitch-angle anisotropies of both the anomalous and galactic cosmic rays in the outer heliosheath.
The lifetime of methane is controlled to a very large extent by the abundance of the OH radical. The tropics are a key region for methane removal, with oxidation in the lower tropical troposphere ...dominating the global methane removal budget (Bloss et al., 2005). In tropical forested environments where biogenic VOC emissions are high and NOx concentrations are low, OH concentrations are assumed to be low due to rapid reactions with sink species such as isoprene. New, simultaneous measurements of OH concentrations and OH reactivity, k'OH, in a Borneo rainforest are reported and show much higher OH than predicted, with mean peak concentrations of ~2.5×106 molecule cm−3 (10 min average) observed around solar noon. Whilst j(O1D) and humidity were high, low O3 concentrations limited the OH production from O3 photolysis. Measured OH reactivity was very high, peaking at a diurnal average of 29.1±8.5 s−1, corresponding to an OH lifetime of only 34 ms. To maintain the observed OH concentration given the measured OH reactivity requires a rate of OH production approximately 10 times greater than calculated using all measured OH sources. A test of our current understanding of the chemistry within a tropical rainforest was made using a detailed zero-dimensional model to compare with measurements. The model over-predicted the observed HO2 concentrations and significantly under-predicted OH concentrations. Inclusion of an additional OH source formed as a recycled product of OH initiated isoprene oxidation improved the modelled OH agreement but only served to worsen the HO2 model/measurement agreement. To replicate levels of both OH and HO2, a process that recycles HO2 to OH is required; equivalent to the OH recycling effect of 0.74 ppbv of NO. This recycling step increases OH concentrations by 88 % at noon and has wide implications, leading to much higher predicted OH over tropical forests, with a concomitant reduction in the CH4 lifetime and increase in the rate of VOC degradation.
We present a laser-ionized, beam-driven, passive thin plasma lens that operates in the nonlinear blowout regime. This thin plasma lens provides axisymmetric focusing for relativistic electron beams ...at strengths unobtainable by magnetic devices. It is tunable, compact, and it imparts little to no spherical aberrations. The combination of these features make it more attractive than other types of plasma lenses for highly divergent beams. A case study is built on beam matching into a plasma wakefield accelerator at SLAC National Accelerator Laboratory’s FACET-II facility. Detailed simulations show that a thin plasma lens formed by laser ionization of a gas jet reduces the electron beam’s waist beta function to half of the minimum value achievable by the FACET-II final focus magnets alone.
Swallowing and voice complaints after a whiplash injury have been observed and reported in several studies; however, variability in study design complicates current understanding of whether dysphagia ...and dysphonia should be recognised as potential adverse outcomes. A scoping review was conducted across six databases from 1950 to March 2019. A total of 18 studies were included for review. Data regarding study purpose, design, outcome measures, participant characteristics and outcomes reported were extracted. Level of evidence (LOE) was assessed by the American Speech-Language Language Association (ASHA)’s LOE system. All studies were exploratory, with 68% rated as poor (< 3) on quality ratings. Nearly half (
n
= 6) were single case reports. Only three studies investigated some type of swallow-related outcome specifically within the study aim/s. Incidence of swallow-related problems ranged from 2 to 29%, with unspecified complaints of “swallowing difficulty”, “dysphagia” and fatigue and pain whilst chewing reported. Neither swallowing biomechanics nor the underlying pathophysiology of swallow or voice complaints was investigated in any study. Four case studies presented post-whiplash voice complaints; two of which described loss of pitch range. Others described hoarseness, loss of control and weak phonation. Most studies only mentioned swallow- or voice-related deficits when reporting a wider set of post-injury symptomatology and six did not describe the outcome measure used to identify the swallow and voice-related problems reported. The existing literature is limited and of low quality, contributing to an unclear picture of the true incidence and underlying mechanisms of whiplash-related dysphagia and dysphonia.
The Integrated Science Investigation of the Sun (IS IS) instrument suite on the Parker Solar Probe (PSP) spacecraft is making in situ observations of energetic ions and electrons closer to the Sun ...than any previous mission. Using data collected during its first two orbits, which reached perihelion distances of 0.17 au, we have searched for -rich solar energetic particle (SEP) events under very quiet solar minimum conditions. On 2019-110-111 (April 20-21), -rich SEPs were observed at energies near 1 MeV nucleon-1 in association with energetic protons, heavy ions, and electrons. This activity was also detected by the Ultra-Low-Energy Isotope Spectrometer and the Electron, Proton, and Alpha Monitor instruments on the Advanced Composition Explorer (ACE) spacecraft located near Earth, 0.99 au from the Sun. At that time, PSP and ACE were both magnetically connected to locations near the west limb of the Sun. Remote sensing measurements showed the presence of type III radio bursts and also helical jets from this region of the Sun. This combination of observations is commonly associated with -rich SEP acceleration on the Sun. AR 12738, which was located at Carrington coordinates from which numerous X-ray flares were observed over a period of more than 6 months, was identified as the source of the -rich events. This region was also the source of several other SEP events detected at PSP or ACE. Aside from the period in 2019 April, IS IS did not observe any other -rich SEPs during orbits 1 and 2.
Abstract
NASA’s Parker Solar Probe mission continues to travel closer to the Sun than any prior human-made object, with an expected closest approach of <10 solar radii (<0.046 au) by 2024. On board, ...the Integrated Science Investigation of the Sun instrument suite makes unprecedented in situ measurements of energetic particles in the near-Sun environment. The current low level of solar activity offers a prime opportunity to measure cosmic rays closer to the Sun than ever before. We present the first observations of anomalous cosmic rays in to 36 solar radii (0.166 au), focusing specifically on helium. Our results indicate a strong radial intensity gradient of ∼25 ± 5%/au over energies of ∼4 to ∼45 MeV/nuc. These values are larger than prior observations, further out in the heliosphere, and come at a unique time in our understanding and modeling of particle transport and acceleration, particularly as both Voyagers have crossed the heliopause and IBEX has accumulated a full solar cycle of observations. Thus, continued measurements of cosmic rays by Parker Solar Probe will play a critical role in linking past observations with our present knowledge and significantly advancing our understanding of cosmic ray transport in the heliosphere.
Abstract We present an event observed by Parker Solar Probe (PSP) at ∼0.2 au on 2022 March 2 in which imaging and in situ measurements coincide. During this event, PSP passed through structures on ...the flank of a streamer blowout coronal mass ejection (CME) including an isolated flux tube in front of the CME, a turbulent sheath, and the CME itself. Imaging observations and in situ helicity and principal variance signatures consistently show the presence of flux ropes internal to the CME. In both the sheath and the CME interval, the distributions are more isotropic, the spectra are softer, and the abundance ratios of Fe/O and He/H are lower than those in the isolated flux tube, and yet elevated relative to typical plasma and solar energetic particle abundances. These signatures in the sheath and the CME indicate that both flare populations and those from the plasma are accelerated to form the observed energetic particle enhancements. In contrast, the isolated flux tube shows large streaming, hard spectra, and large Fe/O and He/H ratios, indicating flare sources. Energetic particle fluxes are most enhanced within the CME interval from suprathermal through energetic particle energies (∼keV to >10 MeV), indicating particle acceleration, as well as confinement local to the closed magnetic structure. The flux-rope morphology of the CME helps to enable local modulation and trapping of energetic particles, in particular along helicity channels and other plasma boundaries. Thus, the CME acts to build up energetic particle populations, allowing them to be fed into subsequent higher-energy particle acceleration throughout the inner heliosphere where a compression or shock forms on the CME front.
Association between rotavirus infection and pancreatic islet autoimmunity in children at risk of developing type 1 diabetes.
M C Honeyman ,
B S Coulson ,
N L Stone ,
S A Gellert ,
P N Goldwater ,
C E ...Steele ,
J J Couper ,
B D Tait ,
P G Colman and
L C Harrison
Autoimmunity and Transplantation Division, Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital,
Victoria, Australia. honeyman@wehi.edu.au
Abstract
Pancreatic islet autoimmunity leading to type 1 diabetes could be triggered by viruses in genetically susceptible individuals.
Rotavirus (RV), the most common cause of childhood gastroenteritis, contains peptide sequences highly similar to T-cell epitopes
in the islet autoantigens GAD and tyrosine phosphatase IA-2 (IA-2), suggesting T-cells to RV could trigger islet autoimmunity
by molecular mimicry. We therefore sought an association between RV infection and islet autoantibody markers in children at
risk for diabetes who were followed from birth. There was a specific and highly significant association between RV seroconversion
and increases in any of these antibodies: 86% of antibodies to IA-2, 62% to insulin, and 50% to GAD first appeared or increased
with increases in RV IgG or IgA. RV infection may therefore trigger or exacerbate islet autoimmunity in genetically susceptible
children.
Since crossing the heliopause on 2012 August 25, Voyager 1 observed reductions in galactic cosmic ray count rates caused by a time-varying depletion of particles with pitch angles near 90°, while ...intensities of particles with other pitch angles remain unchanged. Between late 2012 and mid-2017, three large-scale events occurred, lasting from ∼100 to ∼630 days. Omnidirectional and directional high-energy data from Voyager 1's Cosmic Ray Subsystem are used to report cosmic ray intensity variations. Omnidirectional ( 20 MeV) proton-dominated measurements show up to a 3.8% intensity reduction. Bidirectional ( 70 MeV) proton-dominated measurements taken from various spacecraft orientations provide insight about the depletion region's spatial properties. We characterize the anisotropy as a "notch" in an otherwise uniform pitch angle distribution of varying depth and width centered about 90° in pitch angle space. The notch averages 22° wide and 15% deep, signifying a depletion region that is broad and shallow. There are indications that the anisotropy is formed by a combination of magnetic trapping and cooling downstream of solar-induced transient disturbances in a region that is also likely influenced by the highly compressed fields near the heliopause.
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