209 research outputs found
Journeying Toward Liberation: Creating Civic Utopias through Restorative Literacies
In this article, we forward three narratives from educators whose lived experiences moving from underrepresented youth to queer educators support the necessity of furthering representation for historically marginalized youth across classroom spaces. We begin with situating our argument in response to current policies that would seek to silence historically marginalized voices, histories, literacies, and thereby inhibit a more just social and civic future. Our narratives provide three varied perspectives of lived experiences as youth moving toward our current status as queer educators. Finally, we seek to call in other educators to engage advocacy and resources to support this work in challenging times
Investigating the Effect of IMF Path Length on Pitch- angle Scattering Strahl within 1 au
Strahl is the strongly field-aligned, beam-like population of electrons in the solar wind. Strahl width is observed to
increase with distance from the Sun, and hence strahl electrons must be subject to in-transit scattering effects.
Different energy relations have been both observed and modeled for both strahl width and the width increase with
radial distance. Thus, there is much debate regarding what mechanism(s) scatter strahl. In this study, we use a
novel method to investigate strahl evolution within 1 au by estimating the distance traveled by the strahl along the
interplanetary magnetic field (IMF). We do this by implementing methods developed in previous studies, which
make use of the onset of solar energetic particles at ∼1 au. Thus, we are able to obtain average strahl broadening in
relation to electron energy and distance, while also taking into account the general effect of IMF topology and
adiabatic focusing experienced by strahl. We find that average strahl width broadens with distance traveled along
the IMF, which suggests that strahl width is related to the path length taken by the strahl from the Sun to 1 au. We
also find that strahl pitch-angle width broadening per au along the IMF length increased with strahl energy, which
suggests that the dominant strahl pitch-angle scattering mechanism likely has an inherent energy relation. Our
pitch-angle broadening results provide a testable energy relation for the upcoming Parker Solar Probe and Solar
Orbiter missions, which are both set to provide unprecedented new observations within 1 au
Statistical azimuthal structuring of the substorm onset arc: Implications for the onset mechanism
The onset of an auroral substorm is generally thought to occur on a quiet, homogeneous auroral arc. We present a statistical study of independently selected substorm onset arcs and find that over 90% of the arcs studied have resolvable characteristic spatial scales in the form of auroral beads. We find that the vast majority (~88%) of auroral beads have small amplitudes relative to the background, making them invisible without quantitative analysis. This confirms that auroral beads are highly likely to be ubiquitous to all onset arcs, rather than a special case phenomena as previously thought. Moreover, as these auroral beads grow exponentially through onset, we conclude that a magnetospheric plasma instability is fundamental to substorm onset itself
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Statistical characterisation of the growth and spatial scales of the substorm onset arc
We present the first multi-event study of the spatial and temporal structuring of the aurora to provide statistical evidence of the near-Earth plasma instability which causes the substorm onset arc. Using data from ground-based auroral imagers, we study repeatable signatures of along-arc auroral beads, which are thought to represent the ionospheric projection of magnetospheric instability in the near-Earth plasma sheet. We show that the growth and spatial scales of these wave-like fluctuations are similar across multiple events, indicating that each sudden auroral brightening has a common explanation. We find statistically that growth rates for auroral beads peak at low wavenumber with the most unstable spatial scales mapping to an azimuthal wavelength λ≈1700 − 2500 km in the equatorial magnetosphere at around 9-12 RE. We compare growth rates and spatial scales with a range of theoretical predictions of magnetotail instabilities, including the cross-field current instability and the shear-flow ballooning instability. We conclude that, although the cross-field current instability can generate similar magnitude of growth rates, the range of unstable wavenumbers indicates that the shear-flow ballooning instability is the most likely explanation for our observations
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Statistical azimuthal structuring of the substorm onset arc: implications for the onset mechanism
The onset of an auroral substorm is generally thought to occur on a quiet, homogeneous auroral arc. We present a statistical study of independently-selected substorm onset arcs and find that over 90% of the arcs studied have resolvable characteristic spatial scales in the form of auroral beads. We find that the vast majority (~88%) of auroral beads have small amplitudes relative to the background, making them invisible without quantitative analysis. This confirms that auroral beads are highly likely to be ubiquitous to all onset arcs, rather than a special case phenomena as previously thought. Moreover, as these auroral beads grow exponentially through onset, we conclude that a magnetospheric plasma instability is fundamental to substorm onset itself
Meteorological characteristics and assessment of the effect of local emissions during high PM10 concentration in the Seoul Metropolitan Area
In this study, we investigate the meteorological characteristics and the effect of local emissions during high PM10 concentrations in the Seoul Metropolitan Area (SMA) by utilizing data from a high-resolution urban meteorological observation system network (UMS-Seoul) and The Air Pollution Model (TAPM). For a detailed analysis, days with PM10 concentrations higher than 80 ??g m-3 for daily average PM10 concentration (classified as unhealthy by the Korean Ministry of Environment) in the Seoul Metropolitan Area (SMA) were classified into 3 Cases. Case I was defined as when the prevailing effect was from outside the SMA. Case II was defined as when the prevailing effect was a local effect with outside. Case III was defined as when the prevailing effect was local. Overall, high PM10 concentrations in the SMA mostly occurred under weak migratory anticyclone systems over the Korean Peninsula during warm temperatures. Prior to the PM10 concentration reaching the peak concentration, the pattern in each case was distinctive. After peak concentrations, however, the pattern for the 3 cases became less distinct. This study showed that nearly 50% of the high PM10 concentrations in the SMA occurred in spring and were governed by the conditions for Case II more than these for Cases I and III. In spring, the main sources of the high PM10 concentrations in the SMA were local emissions due to the predominance of weak winds and local circulation. The simulation showed that the non-SMA emissions were about 63 to 73% contribution to the spring high PM10 concentrations in the SMA. Specifically, local point sources including industrial combustion, electric utility, incineration and cement production facilities scattered around the SMA and could account for PM10 concentrations more than 10 ??g m-3 in the SMA
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Comprehensive ground-based and in situ observations of substorm expansion phase onset
In this paper, we present comprehensive ground-based and space-based in situ geosynchronous observations of a substorm expansion phase onset on 1 October 2005. The Double Star TC-2 and GOES-12 spacecraft were both located within the substorm current wedge during the substorm expansion phase onset, which occurred over the Canadian sector. We find that an onset of ULF waves in space was observed after onset on the ground by extending the AWESOME timing algorithm into space. Furthermore, a population of low-energy field-aligned electrons was detected by the TC-2 PEACE instrument contemporaneous with the ULF waves in space. These electrons appear to be associated with an enhancement of field-aligned Poynting flux into the ionosphere which is large enough to power visible auroral displays. The observations are most consistent with a near-Earth initiation of substorm expansion phase onset, such as the Near-Geosynchronous Onset (NGO) substorm scenario. A lack of data from further downtail, however, means other mechanisms cannot be ruled out
Overturning circulation, nutrient limitation, and warming in the Glacial North Pacific
This work was funded by NERC grant NE/N011716/1 to J.W.B.R., a NERC studentship to B.T., and NSF grant OPP 1643445 to I.E. A.R. acknowledges support from NSF grant 1736771.Although the Pacific Ocean is a major reservoir of heat and CO2, and thus an important component of the global climate system, its circulation under different climatic conditions is poorly understood. Here, we present evidence that during the Last Glacial Maximum (LGM), the North Pacific was better ventilated at intermediate depths and had surface waters with lower nutrients, higher salinity, and warmer temperatures compared to today. Modeling shows that this pattern is well explained by enhanced Pacific meridional overturning circulation (PMOC), which brings warm, salty, and nutrient-poor subtropical waters to high latitudes. Enhanced PMOC at the LGM would have lowered atmospheric CO2—in part through synergy with the Southern Ocean—and supported an equable regional climate, which may have aided human habitability in Beringia, and migration from Asia to North America.Publisher PDFPeer reviewe
A direct examination of the dynamics of dipolarization fronts using MMS
Energy conversion on the dipolarization fronts (DFs) has attracted much research attention through the suggestion that intense current densities associated with DFs can modify the more global magnetotail current system. The current structures associated with a DF are at the scale of one to a few ion gyroradii, and their duration is comparable to a spacecraft's spin period. Hence, it is crucial to understand the physical mechanisms of DFs with measurements at a timescale shorter than a spin period. We present a case study whereby we use measurements from the Magnetospheric Multiscale (MMS) Mission, which provides full 3-D particle distributions with a cadence much shorter than a spin period. We provide a cross validation amongst the current density calculations and examine the assumptions that have been adopted in previous literature using the advantages of MMS mission (i.e., small-scale tetrahedron and high temporal resolution). We also provide a cross validation on the terms in the generalized Ohm's law using these advantageous measurements. Our results clearly show that the majority of the currents on the DF are contributed by both ion and electron diamagnetic drifts. Our analysis also implies that the ion frozen-in condition does not hold on the DF, while electron frozen-in condition likely holds. The new experimental capabilities allow us to accurately calculate Joule heating within the DF, which shows that plasma energy is being converted to magnetic energy in our event
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