The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe’s First Orbit
Name:
Lavraud_2020_ApJL_894_L19.pdf
Size:
1.216Mb
Format:
PDF
Description:
Final Published Version
Affiliation
Univ Arizona, Lunar & Planetary LabIssue Date
2020-05-08Keywords
Slow solar windSolar coronal streamers
Solar coronal transients
Heliosphere
Solar magnetic reconnection
Space plasmas
Plasma jets
Metadata
Show full item recordPublisher
IOP PUBLISHING LTDCitation
Lavraud, B., Fargette, N., Réville, V., Szabo, A., Huang, J., Rouillard, A. P., ... & Whittlesey, P. L. (2020). The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe’s First Orbit. The Astrophysical Journal Letters, 894(2), L19.Journal
ASTROPHYSICAL JOURNAL LETTERSRights
© 2020. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present heliospheric current sheet (HCS) and plasma sheet (HPS) observations during Parker Solar Probe's (PSP) first orbit around the Sun. We focus on the eight intervals that display a true sector boundary (TSB; based on suprathermal electron pitch angle distributions) with one or several associated current sheets. The analysis shows that (1) the main density enhancements in the vicinity of the TSB and HCS are typically associated with electron strahl dropouts, implying magnetic disconnection from the Sun, (2) the density enhancements are just about twice that in the surrounding regions, suggesting mixing of plasmas from each side of the HCS, (3) the velocity changes at the main boundaries are either correlated or anticorrelated with magnetic field changes, consistent with magnetic reconnection, (4) there often exists a layer of disconnected magnetic field just outside the high-density regions, in agreement with a reconnected topology, (5) while a few cases consist of short-lived density and velocity changes, compatible with short-duration reconnection exhausts, most events are much longer and show the presence of flux ropes interleaved with higher-beta regions. These findings are consistent with the transient release of density blobs and flux ropes through sequential magnetic reconnection at the tip of the helmet streamer. The data also demonstrate that, at least during PSP's first orbit, the only structure that may be defined as the HPS is the density structure that results from magnetic reconnection, and its byproducts, likely released near the tip of the helmet streamer.ISSN
2041-8205EISSN
2041-8213Version
Final published versionScopus Count
Collections
Related items
Showing items related by title, author, creator and subject.
-
The distribution of water in the solar nebula: Implications for solar system formationWater is important in the solar nebula both because it is extremely abundant and because it condenses out at 5 AU, allowing all three phases of H₂O to play a role in the composition and evolution of the solar system. In this work, a thorough examination of the inward radial drift of ice particles from 5 AU is undertaken. Drift model results are then linked to the outward diffusion of vapor, in one overall model which is numerically evolved over the lifetime of the nebula. Results of the model indicate that while the inner nebula is generally depleted in water vapor, there is a zone in which the vapor is enhanced by ∼40-100%, depending on the choice of ice grain growth mechanisms and rates. This enhancement peaks in the region from 0.1-2 AU and gradually drops off out to 5 AU. Conversely, ice abundance is enhanced over 3-5 AU. Representative hot (early) and cool (later) conditions during the quiescent phase of nebular evolution are examined. Additionally, the effect of the radial dependence of water depletion on nebular chemistry is quantified using a chemical equilibrium code that computes abundances of nebular elements and major molecular C, N, S, etc. species over a range of temperatures. In particular, changes in the local C/O ratio and organics abundance due to the radially dependent decrease in oxygen fugacity are tracked and plotted. Generally, the diffusion-drift model results in a more complex water distribution than previous models, with both radial and temporal variations in the C/O ratio which produce both relatively oxidizing and reducing nebular conditions across 1-5 AU. Depending on the value assumed for the solar C/O ratio, modest to significant enhancements of CH₄ and other organics abundances are produced in the inner nebula. These results coupled with the revised ice distribution may explain the radial signatures of hydration detections and darkening in asteroids, and perhaps the oxidation states of enstatite chondrites. The results also indicate that the inner nebula could have supplied organics and water to the terrestrial planets, as well as possibly to Europa and beyond, via outward mixing processes.
-
THE SOLAR VISTA: Integrating solar energy into our neighborhood parksUrban ecology emerged, in the 1970’s, as a response to the increasing reality of growing populations causing environmental and health problems of both urban and non-urban dwellers. As such, human settlements were acknowledged by ecologists as legitimate areas of ecological study. Almost 50 years later, great strides have been made to improve the ecology within our cities. This Masters Report looks to build upon past success by rethinking the implementation of sustainable practices into the urban fabric of a city. The report examines a contextually suburban park within Tucson, Arizona as an opportunity to better integrate and showcase the, increasingly popular and affordable, practice of harnessing solar energy. A review of literature and design projects was conducted to gain an understanding of ecological design principles, multi-functional solar sites, and educational features in public spaces. Site inventory and analysis revealed the existing condition of the site, as well as possible design limitations and opportunities. In response to the research and site assessment, design solutions were made to further progress the ecological practices within our public spaces.
