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Results for “HOT PLASMA”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The O VII soft X-ray spectrum and its application to hot plasmas in astrophysics

The paper presents a revised theory and atomic model for the line intensities emitted by O VII, taking into account all of the processes responsible for the emission. This is used to provide a revision of the density measurements made for solar active regions and during flares, as well as an attempt to understand the spectrum of the Puppis A supernova remnant. In order to explain the strange intensity ratios observed from Puppis A, previous authors have proposed an interpretation based upon a high-temperature thermal plasma in a nonequilibrium ionization state. An alternative model is presented here, based upon the assumed presence of a proportion of fast, nonthermal electrons imbedded in an otherwise thermal plasma at a temperature below 10 to the 6th K. This can adequately explain the observations without the necessity of invoking departures from the ionization balance.

Gabriel, A. H.↗
NASA NTRS1994

Comparison between cool and hot plasma behaviors of surges

Ground-based coordinated observations with the Multichannel Subtractive Double Pass spectrograph (MSDP) allowed us to obtain chromospheric intensity and velocity field maps below coronal structures during the launch of the NIXT payload on 1991 July 11 (eclipse day). A large H-alpha ejection in AR 6713 (N38 W40) was detected during the NIXT flight. However, only a low level of X-ray emission was associated with this event. In contrast, bright X-ray emission associated with a subflare was observed in a nearby active region, but with only a weak associated ejection in H-alpha. A discussion of both of these events gives strong constraints on the triggering mechanisms of surges.

Schmieder, B.↗
NASA NTRS2004

Evidence for Hot Plasma after CME events from Remote and In Situ Observations

We present here evidence for highly ionized Fe observed both in the corona, in the aftermath of a CME, and, after propagation, {\it in situ}. The apparent source temperature is $>$6 MK. To our knowledge, this is the first time that such an unambiguous identification has been made. This detection complements studies correlating other properties of plasma observed {\it in situ} to the same properties of the same plasma remotely observed at its source in the corona.

Poletto, G.↗
DOE OSTI2019

Gamma-ray emission of hot astrophysical plasma

Very hot plasmas with ion temperature exceeding 10 10 K can be formed in certain astrophysical environments. The distinct radiation signature of such plasmas is the γ-ray emission dominated by the prompt deexcitation nuclear lines and π 0 -decay γ rays. Using a large nuclear reaction network, we compute the time evolution of the chemical composition of such hot plasmas and their γ-ray line emissivity. At higher energies, we provide simple but accurate analytical presentations for the π 0 -meson production rate and the corresponding π 0 → 2γ emissivity derived for the Maxwellian distribution of protons. Furthermore, we discuss the impact of the possible deviation of the high energy tail of the particle distribution function from the “nominal” Maxwellian distribution on the plasma γ-ray emissivity.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1978

Effect of anode-cathode geometry on performance of the HIP-1 hot ion plasma

Hot-ion hydrogen plasma experiments were conducted in the NASA Lewis HIP-1 magnetic mirror facility to determine how the ion temperature was influenced by the axial position of the cathode tips relative to the anodes. A steady-state EXB plasma was formed by applying a strong radially inward dc electric field near the throats of the magnetic mirrors. The dc electric field was created between hollow cathode rods inside hollow anode cylinders, both concentric with the magnetic axis. The highest ion temperatures, 900 eV, were attained when the tip of each cathode was in the same plane as the end of its anode. These temperatures were reached with 22 kV applied to the electrodes in a field of 1.1 tesla. Scaling relations were empirically determined for ion temperature and the product of ion density and neutral particle density as a function of cathode voltage, discharge current, and electrode positions. Plasma discharge current vs voltage (I-V) characteristics were determined.

Lauver, M. R.↗
DOE OSTI2011

ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF HOT FLARE PLASMA

We present observations of hot plasma from solar eruptions recorded by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. AIA is the first narrowband instrument capable of taking images of hot plasma in the 5-15 MK range. We find that there are hot structures above flare loops, and that they are typically more diffuse and nebulous than the well-defined flare loops. Because of the narrowband response, high sensitivity, and high spatial resolution of AIA, these supra-arcade structures are visible in exquisite detail, particularly in the 131 A and 94 A channels. In one event, a C4.9 flare observed on 2010 November 3, hot plasma is seen to outline an erupting plasmoid and possibly a current sheet. We compare hot plasma observed with AIA to structures observed with the X-Ray Telescope on the Hinode mission and find that the plasma imaged in AIA contains more fine detail. These new AIA observations show that supra-arcade flare structures and coronal mass ejections are highly structured not only in space and time, but also in temperature. This thermal structuring is expected, based on modeling efforts, but has now been imaged directly for the first time over a large range of temperatures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS2007

Cassini Observations of Saturn's Dawn-Magnetotail Region: Preliminary Results

Using Cassini thermal plasma, hot plasma and magnetic field observations for several intervals between the dawn meridian of Saturn's outer magnetosphere and Saturn's magnetotail region, we investigate the structure of the magnetotail, plasma and magnetic field properties within tail-like current sheet regions and ion flows within the dawn to magnetotail regions. We use Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) and Electron Plasma Spectrometer (ELS) observations and MIMI LEMMS ion and electron observations to characterize the plasma environment. LMS observations are used to measure plasma flow velocities from which one can infer rotation versus convective flows. IMS composition measurements are used to trace the, source of plasma from the inner magnetosphere (protons, H(2+) and water group ions) versus an external solar wind source (protons and He++ ions). A critical parameter for both models is the strength of the convection electric field with respect to the rotational electric field for the large scale magnetosphere. For example, are there significant return flows (i.e., negative radial velocities, V(sub R) < 0) and/or plasmoids (V(sub R) > 0) within the magnetotail region?

Sittler, Edward C.↗
NASA NTRS2007

Cassini Observations of Saturn's Magnetotail Region: Preliminary Results

Using Cassini thermal plasma, hot plasma and magnetic field observations for several intervals between the dawn meridian of Saturn's outer magnetosphere and Saturn's magnetotail region, we investigate the structure of the magnetotail, plasma and magnetic field properties within tail-like current sheet regions and ion flows within the magnetotail regions. We use Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS), Electron Plasma Spectrometer (ELS) observations, MIMI LEMMS ion and electron observations and Cassini magnetometer data (MAG) to characterize the plasma environment. IMS observations are used to measure plasma flow velocities from which one can infer rotation versus convective flows. IMS composition measurements are used to trace the source of plasma from the inner magnetosphere (protons, H2+ and water group ions) versus an external solar wind source (protons and ~ e +i+on s). A critical parameter for both models is the strength of the convection electric field with respect to the rotational electric field for the large scale magnetosphere. For example, are there significant return flows (i.e., negative radial velocities, VR < 0) and/or plasmoids (V(sub R) > 0) within the magnetotail region? Initial preliminary evidence of such out flows and return flows was presented by Sittler et al. This talk complements the more global analysis by McAndrews et al.

Sittler, E. C.↗
DOE OSTI2018

Generation of Terahertz Waves under Laser Action on Hot Dense Plasma

Generation of terahertz waves by hot dense plasma under the action of a femtosecond laser pulse in the regime of anomalous skin effect is considered. The spectral, angular, and energy characteristics of terahertz waves are studied as functions of the plasma and laser parameters. It is shown that, under the conditions of anomalous skin effect, which takes place in ultradense hot plasma, the total energy of the terahertz signal is independent of the electron density, proportional to the square of the electron temperature, and maximal at tight focusing of the laser pulse.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

Studies on equatorial shock formation during plasmaspheric refilling

During the grant period starting August 1, 1992, our major effort has been on examining the presence of equatorially trapped hot plasma on plasmaspheric refilling. We performed one-dimensional PIC simulations of cold plasmas expanding into a hot plasma, consisting of hot anisotropic ions and warm isotropic electrons, trapped in a region of minimum magnetic field. Simulations showed that the electric potential barrier built up by the anisotropy of the hot ion population facilitates in the formation of electrostatic shocks when the cold ion beams begin to come into contact with the hot plasma. The shock formation occurs even when the cold ion beams are highly supersonic with respect to the ion-acoustic speed. This finding is interesting because equatorial shock formation during the early stage of plasmaspheric refilling has been debated over about two decades. In the past ion-ion instability has been invoked as the main mechanism for the coupling between the cold ion beams approaching the equator from the conjugate ionspheres. This coupling occurs when the beams are sufficiently slow; the beam velocity being less than three times the ion-acoustic speed. In the presence of hot plasma, the beams slow down by the potential barrier. The slowing down and the reflection process lead to the formation of the electrostatic shock even for highly supersonic ion beams. The mixing of hot and cold plasma was also studied.

Singh, Nagendra↗
DOE OSTI2024

Massive, long-lived electrostatic potentials in a rotating mirror plasma

Abstract Hot plasma is highly conductive in the direction parallel to a magnetic field. This often means that the electrical potential will be nearly constant along any given field line. When this is the case, the cross-field voltage drops in open-field-line magnetic confinement devices are limited by the tolerances of the solid materials wherever the field lines impinge on the plasma-facing components. To circumvent this voltage limitation, it is proposed to arrange large voltage drops in the interior of a device, but coexist with much smaller drops on the boundaries. To avoid prohibitively large dissipation requires both preventing substantial drift-flow shear within flux surfaces and preventing large parallel electric fields from driving large parallel currents. It is demonstrated here that both requirements can be met simultaneously, which opens up the possibility for magnetized plasma tolerating steady-state voltage drops far larger than what might be tolerated in material media.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Return current instability driven by a temperature gradient in ICF plasmas

Here, hot plasmas with strong temperature gradients in inertial confinement fusion (ICF) experiments are examined for ion acoustic instabilities produced by electron heat flow. The return current instability (RCI) due to a neutralizing current of cold electrons arising in response to a large electron heat flux has been considered. First, the linear threshold and growth rates are derived in the nonlocal regime of thermal transport. They are compared with the results of Vlasov-Fokker-Planck (VFP) simulations in one spatial dimension. Very good agreement has been found between kinetic VFP simulations and the linear theory of the RCI. A quasi-stationary state of ion acoustic turbulence produced by the RCI is achieved in the VFP simulations. Saturation of the RCI involves heating of ions in the tail of the ion distribution function and convection of the enhanced ion acoustic fluctuations from the unstable region of the plasma. Further evolution of the ion acoustic turbulence and its effects on absorption and transport are also discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗