234 research outputs found
U.S.-Canada High Technology Trade Issues
Canada-United States Economic Ties: The Technology Context, high technology and trad
The United States Policy toward Inward Foreign Direct Investment
This paper presents the perspective of the author, a trade and investment policy official, on the most significant aspects of the United States policy toward foreign direct investment. The summary in this section is presented to give the author\u27s policy viewpoint in order to assist the reader in evaluating the paper\u27s arguments... United States policy, at both the federal and local levels, reflects a strong positive attitude concerning the general benefits of inward foreign direct investment. While foreign ownership of United States assets is restricted in certain sectors, the general United States approach is one of national treatment --i.e., foreign investors are treated as favorably as domestic investors with respect to the application of United States laws and regulations
Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, i.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study this statistical correlation closer to the corona. As a first step, we analyze the separate correlation properties of the EPs measured by the Integrated Science Investigation of the Sun (ISâIS) instruments during the first solar encounter. The distribution of time intervals between a specific type of event, i.e., the waiting time, can indicate the nature of the underlying process. We find that the ISâIS observations show a power-law distribution of waiting times, indicating a correlated (non-Poisson) distribution. Analysis of low-energy (~15 â 200 keV/nuc) ISâIS data suggests that the results are consistent with the 1 au studies, although we find hints of some unexpected behavior. A more complete understanding of these statistical distributions will provide valuable insights into the origin and propagation of solar EPs, a picture that should become clear with future PSP orbits
Electrons in the Young Solar Wind: First Results from the Parker Solar Probe
The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar
Probe (PSP) mission measures the three-dimensional electron velocity
distribution function. We derive the parameters of the core, halo, and strahl
populations utilizing a combination of fitting to model distributions and
numerical integration for electron distributions measured near
the Sun on the first two PSP orbits, which reached heliocentric distances as
small as AU. As expected, the electron core density and temperature
increase with decreasing heliocentric distance, while the ratio of electron
thermal pressure to magnetic pressure () decreases. These quantities
have radial scaling consistent with previous observations farther from the Sun,
with superposed variations associated with different solar wind streams. The
density in the strahl also increases; however, the density of the halo plateaus
and even decreases at perihelion, leading to a large strahl/halo ratio near the
Sun. As at greater heliocentric distances, the core has a sunward drift
relative to the proton frame, which balances the current carried by the strahl,
satisfying the zero-current condition necessary to maintain quasi-neutrality.
Many characteristics of the electron distributions near perihelion have trends
with solar wind flow speed, , and/or collisional age. Near the Sun,
some trends not clearly seen at 1 AU become apparent, including
anti-correlations between wind speed and both electron temperature and heat
flux. These trends help us understand the mechanisms that shape the solar wind
electron distributions at an early stage of their evolution
Small-scale Magnetic Flux Ropes in the First two Parker Solar Probe Encounters
Small-scale magnetic flux ropes (SFRs) are a type of structures in the solar
wind that possess helical magnetic field lines. In a recent report (Chen & Hu
2020), we presented the radial variations of the properties of SFR from 0.29 to
8 au using in situ measurements from the Helios, ACE/Wind, Ulysses, and Voyager
spacecraft. With the launch of the Parker Solar Probe (PSP), we extend our
previous investigation further into the inner heliosphere. We apply a
Grad-Shafranov-based algorithm to identify SFRs during the first two PSP
encounters. We find that the number of SFRs detected near the Sun is much less
than that at larger radial distances, where magnetohydrodynamic (MHD)
turbulence may act as the local source to produce these structures. The
prevalence of Alfvenic structures significantly suppresses the detection of
SFRs at closer distances. We compare the SFR event list with other event
identification methods, yielding a dozen well-matched events. The cross-section
maps of two selected events confirm the cylindrical magnetic flux rope
configuration. The power-law relation between the SFR magnetic field and
heliocentric distances seems to hold down to 0.16 au.Comment: Accepted by ApJ on 2020 Sep 1
Plasma Double Layers at the Boundary Between Venus and the Solar Wind
The solar wind is slowed, deflected, and heated as it encounters Venusâs induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kineticâscale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated doubleâlayer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond nearâEarth space, supporting the idea that kinetic plasma processes are active in many space plasma environments.Plain Language SummaryVenus has no internally generated magnetic field, yet electric currents running through its ionized upper atmosphere create magnetic fields that push back against the flow of the solar wind. These induced fields cause the solar wind to slow and heat as the flow is deflected around Venus. This work reports observations of very small plasma structures that accelerate particles, identifiable by their characteristic electric field signatures, at the boundary where the solar wind starts to be deflected. These small plasma structures observed at Venus have been studied in nearâEarth space for decades but have never before been found near another planet. These structures are known to be important to the physics of strong electrical currents in space plasmas and the blending of dissimilar plasmas. Their identification at Venus is a strong demonstration that these small plasma structures are a universal plasma phenomena, at work in many plasma environments.Key PointsPlasma double layers are detected near the Venusian bow shockMultiple double layers are identified in a small amount of burst dataKinetic processes may help mediate interaction between the solar wind and induced magnetospheresPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163462/2/grl61354.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163462/1/grl61354_am.pd
Parker Solar Probe observations of proton beams simultaneous with ion-scale waves
Parker Solar Probe (PSP), NASA's latest and closest mission to the Sun, is on
a journey to investigate fundamental enigmas of the inner heliosphere. This
paper reports initial observations made by the Solar Probe Analyzer for Ions
(SPAN-I), one of the instruments in the Solar Wind Electrons Alphas and Protons
(SWEAP) instrument suite. We address the presence of secondary proton beams in
concert with ion-scale waves observed by FIELDS, the electromagnetic fields
instrument suite. We show two events from PSP's 2nd orbit that demonstrate
signatures consistent with wave-particle interactions. We showcase 3D velocity
distribution functions (VDFs) measured by SPAN-I during times of strong wave
power at ion-scales. From an initial instability analysis, we infer that the
VDFs departed far enough away from local thermodynamic equilibrium (LTE) to
provide sufficient free energy to locally generate waves. These events
exemplify the types of instabilities that may be present and, as such, may
guide future data analysis characterizing and distinguishing between different
wave-particle interactions.Comment: 24 pages, 9 figures, 2 table
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