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  1. Abstract

    The radial evolution of interplanetary coronal mass ejections (ICMEs) is dependent on their interaction with the ambient medium, which causes ICME erosion and affects their geoefficiency. Here, an ICME front boundary, which separates the confined ejecta from the mixed, interacted sheath–ejecta plasma upstream, is analyzed in a multipoint study examining the ICME at 1 au on 2020 April 20. A bifurcated current sheet, highly filamented currents, and a two-sided jet were observed at the boundary. The two-sided jet, which was recorded for the first time for a magnetic shear angle <40°, implies multiple (patchy) reconnection sites associated with the ICME erosion. The reconnection exhaust exhibited fine structure, including multistep magnetic field rotation and localized structures that were measured only by separate Cluster spacecraft with the mission inter-spacecraft separation of 0.4–1.6RE. The mixed plasma upstream of the boundary with a precursor at 0.8 au lacked coherency at 1 au and exhibited substantial variations of southward magnetic fields over radial (transverse) distances of 41–237RE(114RE). This incoherence demonstrates the need for continuous (sub)second-resolution plasma and field measurements at multiple locations in the solar wind to adequately address the spatiotemporal structure of ICMEs and to produce accurate space weather predictions.

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  2. A major obstacle in cultivating a robust Heliophysics (and broader scientific) community is the lack of diversity throughout science, technology, engineering, and mathematics (STEM) fields. For many years, this has been understood as a “leaky pipeline” analogy, in which predominately minority students initially interested in STEM gradually fall (or are pushed) out of the field on their way to a scientific research position. However, this ignores critical structural and policy issues which drive even later career Ph.D.s out of a career in Heliophysics. We identify here several systemic problems that inhibit many from participating fully in the Heliophysics community, including soft money pressure, lack of accessibility and equity, power imbalances, lack of accountability, friction in collaboration, and difficulties in forming mentorship bonds. We present several recommendations to empower research-supporting organizations to help create a culture of inclusion, openness, and innovative science.

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    Free, publicly-accessible full text available August 25, 2024
  3. We present results of 131 geomagnetic storm simulations using the University of Michigan Space Weather Modeling Framework Geospace configuration. We compare the geomagnetic indices derived from the simulation with those observed, and use 2D cuts in the noon-midnight planes to compare the magnetopause locations with empirical models. We identify the location of the current sheet center and look at the plasma parameters to deduce tail dynamics. We show that the simulation produces geomagnetic index distributions similar to those observed, and that their relationship to the solar wind driver is similar to that observed. While the magnitudes of the Dst and polar cap potentials are close to those observed, the simulated AL index is consistently underestimated. Analysis of the magnetopause position reveals that the subsolar position agrees well with an empirical model, but that the tail flaring in the simulation is much smaller than that in the empirical model. The magnetotail and ring currents are closely correlated with the Dst index, and reveal a strong contribution of the tail current beyond 8 R E to the Dst index during the storm main phase. 
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  4. A large number of heliophysicists from across career levels, institution types, and job titles came together to support a poster at Heliophysics 2050 and the position papers for the 2024 Heliophysics decadal survey titled “Cultivating a Culture of Inclusivity in Heliophysics,” “The Importance of Policies: It’s not just a pipeline problem,” and “Mentorship within Heliophysics.” While writing these position papers, the number of people who privately shareddisturbing stories and experiences of bullying and harassmentwas shocking. The number of people who privately expressed howburned outthey were was staggering. The number of people who privately spoke about how theyconsidered leaving the field for their and their family’s healthwas astounding. And for as much good there is in our community, it is still atoxic environmentfor many. If we fail to do something now, our field will continue to suffer. While acknowledging the ongoing growth that we as individuals must work toward, we call on our colleagues to join us in working on organizational, group, and personal levels toward a truly inclusive culture, for the wellbeing of our colleagues and the success of our field. This work includes policies, processes, and commitments to promote:accountabilityfor bad actors;financial securitythrough removing the constant anxiety about funding;prioritizationof mental health and community through removing constant deadlines and constant last-minute requests;a collaborative culturerather than a hyper-competitive one; anda community where people can thrive as whole personsand do not have to give up a healthy or well-rounded life to succeed.

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  5. Abstract

    Rapid plasma eruptions explosively release energy within Earth’s magnetosphere, at the Sun and at other planets. At Earth, these eruptions, termed plasmoids, occur in the magnetospheric nightside and are associated with sudden brightening of the aurora. The chain of events leading to the plasmoid is one of the longest-standing unresolved questions in space physics. Two competing paradigms have been proposed to explain the course of events. The first asserts that magnetic reconnection changes the magnetic topology in the tail, severing a part of the magnetosphere as plasmoid. The second employs kinetic instabilities that first disrupt the current sheet supporting the magnetotail and launch waves that trigger the topological change to eject the plasmoid. Here we numerically simulate Earth’s magnetosphere at realistic scales using a model that captures the physics underlying both paradigms. We show that both magnetic reconnection and kinetic instabilities are required to induce a global topological reconfiguration of the magnetotail, thereby combining the seemingly contradictory paradigms. Our results help to understand how plasma eruptions may take place, guide spacecraft constellation mission design to capture these ejections in observations and lead to improved understanding of space weather by improving the predictability of the plasmoids.

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  6. Coupling between the solar wind and magnetosphere can be expressed in terms of energy transfer through the separating boundary known as the magnetopause. Geospace simulation is performed using the Space Weather Modeling Framework (SWMF) of a multi-ICME impact event on February 18–20, 2014 in order to study the energy transfer through the magnetopause during storm conditions. The magnetopause boundary is identified using a modified plasma β and fully closed field line criteria to a downstream distance of −20 R e . Observations from Geotail, Themis, and Cluster are used as well as the Shue 1998 model to verify the simulation field data results and magnetopause boundary location. Once the boundary is identified, energy transfer is calculated in terms of total energy flux K , Poynting flux S , and hydrodynamic flux H . Surface motion effects are considered and the regional distribution of energy transfer on the magnetopause surface is explored in terms of dayside X > 0 , flank X < 0 , and tail cross section X = X m i n regions. It is found that total integrated energy flux over the boundary is nearly balanced between injection and escape, and flank contributions dominate the Poynting flux injection. Poynting flux dominates net energy input, while hydrodynamic flux dominates energy output. Surface fluctuations contribute significantly to net energy transfer and comparison with the Shue model reveals varying levels of cylindrical asymmetry in the magnetopause flank throughout the event. Finally existing energy coupling proxies such as the Akasofu ϵ parameter and Newell coupling function are compared with the energy transfer results. 
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  7. Abstract

    Solar wind—magnetosphere coupling drives magnetospheric dynamic phenomena by enabling energy exchange between magnetospheric and solar wind plasmas. In this study, we examine two‐dimensional noon‐midnight meridional plane simulation runs of the global hybrid‐Vlasov code Vlasiator with southward interplanetary magnetic field driving. We compute the energy flux, which consists of the Poynting flux and hydrodynamic energy flux components, through the Earth's magnetopause during flux transfer events (FTEs). The results demonstrate the spatiotemporal variations of the energy flux along the magnetopause during an FTE, associating the FTE leading (trailing) edge with an energy injection into (escape from) the magnetosphere on the dayside. Furthermore, FTEs traveling along the magnetopause transport energy to the nightside magnetosphere. We identify the tail lobes as a primary entry region for solar wind energy into the magnetosphere, consistent with results from global magnetohydrodynamic simulations and observations.

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  8. Abstract

    The transmission of a sheath region driven by an interplanetary coronal mass ejection into the Earth's magnetosheath is studied by investigating in situ magnetic field measurements upstream and downstream of the bow shock during an ICME sheath passage on 15 May 2005. We observe three distinct intervals in the immediate upstream region that included a southward magnetic field component and are traveling foreshocks. These traveling foreshocks were observed in the quasi‐parallel bow shock that hosted backstreaming ions and magnetic fluctuations at ultralow frequencies. The intervals constituting traveling foreshocks in the upstream survive transmission to the Earth's magnetosheath, where their magnetic field, and particularly the southward component, was significantly amplified. Our results further suggest that the magnetic field fluctuations embedded in an ICME sheath may survive the transmission if their frequency is below ∼0.01 Hz. Although one of the identified intervals was coherent, extending across the ICME sheath and being long‐lived, predicting ICME sheath magnetic fields that may transmit to the Earth's magnetosheath from the upstream at L1 observations has ambiguity. This can result from the strong spatial variability of the ICME sheath fields in the longitudinal direction, or alternatively from the ICME sheath fields developing substantially within the short time it takes the plasma to propagate from L1 to the bow shock. This study demonstrates the complex interplay ICME sheaths have with the Earth's magnetosphere when passing by the planet.

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