444 research outputs found
Plasma physics abstracts, 1 January 1966 through 31 December 1967
Bibliography containing 26 references with abstracts on plasma physics research, 1966-196
High resolution measurements of density structures in the Jovian plasma sheet
A recent effort to digitize the plasma density by using the low frequency cutoff of trapped continuum radiation in the vicinity of the Jovian plasma sheet has revealed the existence of sharply defined density structures in the plasma sheet. These structures typically have a plasma density which is relatively constant but of order 50 percent greater or less than in the surrounding plasma. At the boundaries of these structures, the transitions from low to high density occur on time scales of about ten seconds, which correspond to spatial dimensions on the order of a few ion Larmor radii. The structures themselves last for intervals from less than a minute to more than five minutes, corresponding to size scales from a fraction of a Jovian radius to more than a Jovian radius, depending of the velocity of the structure relative to the spacecraft. In view of the importance of near corotation plasma flows, these structures are likely to be limited in both the longitudinal and radial dimensions and, therefore, could represent flux tubes with greatly varying plasma content. These observations are presented as among the first to directly address the theoretically proposed interchange instability
Laboratory observation of a nonlinear interaction between shear Alfv\'{e}n waves
An experimental investigation of nonlinear interactions between shear
Alfv\'{e}n waves in a laboratory plasma is presented. Two Alfv\'{e}n waves,
generated by a resonant cavity, are observed to beat together, driving a low
frequency nonlinear psuedo-mode at the beat frequency. The psuedo-mode then
scatters the Alfv\'{e}n waves, generating a series of sidebands. The observed
interaction is very strong, with the normalized amplitude of the driven
psuedo-mode comparable to the normalized magnetic field amplitude () of the interacting Alfv\'{e}n waves.Comment: 10 pages, 4 figures, submitted to Phys. Rev. Let
The return of the Heliospheric 2-3 kHz radio emission during solar cycle 23
In this paper we report the detection of a new
heliospheric 2–3 kHz radio emission event by the
Voyager 1 spacecraft, the first to be observed during solar
cycle 23. The new event started on Nov. 1, 2002, and is
believed to be associated with a strong interplanetary shock
that originated from a period of intense solar activity in
early April 2001. Following previous interpretations of
events of this type, we assume that the radio emission is
produced when the interplanetary shock interacted with the
heliopause, which is the boundary between the solar wind
and the interplanetary medium. From the onset time of the
radio emission and a simple model for the propagation
speed of the interplanetary shock, the heliocentric radial
distance to the nose of the heliopause can be calculated, and
is about 153 to 158 AU, depending on the parameters used.
From computer simulations that give the ratio of the radial
distance to the termination shock to the radial distance to
the heliopause, the distance to the termination shock can
also be calculated and is estimated to be about 101 to
108 AU
Data compression for the Cassini radio and plasma wave instrument
The Cassini Radio and Plasma Wave Science experiment will employ data compression to make effective use of the available data telemetry bandwidth. Some compression will be achieved by use of a lossless data compression chip and some by software in a dedicated 80C85 processor. A description of the instrument and data compression system are included in this report. Also, the selection of data compression systems and acceptability of data degradation is addressed
The spherical probe electric field and wave experiment
The experiment is designed to measure the electric field and density fluctuations with sampling rates up to 40,000 samples/sec. The description includes Langmuir sweeps that can be made to determine the electron density and temperature, the study of nonlinear processes that result in acceleration of plasma, and the analysis of large scale phenomena where all four spacecraft are needed
Explorer 45 (S 3-A) observations of the magnetosphere and magnetopause during the 4-5 August 1972, magnetic storm period
The Explorer 45 satellite performed extensive field and particle measurements in the heart of the magnetosphere during the double magnetic storm period of August 4-5, 1972. Both ground level magnetic records and the magnetic field deformations measured along the orbit by the satellite indicated the existence of only a moderate ring current. This was confirmed by the measurements of the total proton energy density less than those observed during the December 1971 and June 1972 magnetic storms. The plasmapause in the noon quadrant was eroded continuously from the onset of the first storm at the beginning of August 4 to an altitude below L = 2.07 at about 18 hours on August 5. During the orbit containing the second sudden commencement a large amount of low frequency electric and magnetic field noise was encountered throughout the entire orbit. A noteworthy observation during this orbit was the contraction of the magnetopause to distances inside the satellite at L = 5.2
Caregiver perspectives on the continued impact of the COVID-19 pandemic on children with intellectual/developmental disabilities
The COVID-19 pandemic has significantly impacted caregivers, especially those raising a child with an intellectual/developmental disability (IDD). While research has shown substantial disruption to the family, school, and occupational lives of the IDD community, little is known about the long-term impacts of COVID-19. To address this question, 249 caregivers were surveyed via an online questionnaire, between April and August of 2022 (more than 2 years into the pandemic) about potential impacts of the COVID-19 pandemic on their child\u27s access to health- and school-based therapeutic services, caregiver mental health, and family life. The majority of caregivers reported disruptions in access to and quality of school-based therapeutic services for their child as well as a reduction in educational accommodations in the 2021-2022 academic year. Nearly half of caregivers reported feeling anxious and almost a quarter reported feeling depressed for the majority of their days. More than half of respondents reported decreased social support, and one-fifth reported employment disruptions and decreased access to food. These findings suggest that families of children with IDD are still experiencing ongoing negative impacts of the pandemic, emphasizing the critical need for continued support in the wake of the initial and more obvious disruptions caused by the COVID-19 outbreak
Enhanced ionization of the Martian nightside ionosphere during solar energetic particle events
Electron densities in the Martian nightside ionosphere are more than 90% of time too low to be detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board the Mars Express spacecraft. However, the relative number of ionograms with peak electron density high enough to be detected represents a good statistical proxy of the ionospheric density. We focus on solar energetic particle (SEP) events, and we analyze their effects on ionospheric formation. SEP time intervals were identified in situ using the background counts recorded by the ion sensor of the ASPERA-3 instrument on board Mars Express. We show that peak electron densities during the SEP events are large enough to be detected in more than 30% of measurements, and, moreover, the reflections of the sounding signal from the ground almost entirely disappear. Nightside electron densities during SEP events are thus substantially increased as compared to normal nightside conditions
Overview of Saturn lightning observations
The lightning activity in Saturn's atmosphere has been monitored by Cassini
for more than six years. The continuous observations of the radio signatures
called SEDs (Saturn Electrostatic Discharges) combine favorably with imaging
observations of related cloud features as well as direct observations of
flash-illuminated cloud tops. The Cassini RPWS (Radio and Plasma Wave Science)
instrument and ISS (Imaging Science Subsystem) in orbit around Saturn also
received ground-based support: The intense SED radio waves were also detected
by the giant UTR-2 radio telescope, and committed amateurs observed SED-related
white spots with their backyard optical telescopes. Furthermore, the Cassini
VIMS (Visual and Infrared Mapping Spectrometer) and CIRS (Composite Infrared
Spectrometer) instruments have provided some information on chemical
constituents possibly created by the lightning discharges and transported
upward to Saturn's upper atmosphere by vertical convection. In this paper we
summarize the main results on Saturn lightning provided by this
multi-instrumental approach and compare Saturn lightning to lightning on
Jupiter and Earth.Comment: 10 pages, 6 figures, 2 tables; Proc. PRE VII conference Graz Sept.
201
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