Theory of the Jovian structure
Jupiter magnetic field shape and emission sources from analysis of radio observations
JUPITER /PLANET/↗
SEARCH · Search NASA
Results for “radiated field structure”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields
Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of <_ 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique. The same technique will be used to calculate radiation from accelerated electrons (positrons) in turbulent magnetic fields generated by Weibel instability.
Nishikawa, K.↗
SelenITA: A dual-spacecraft lunar CubeSat mission to characterize the near-surface electromagnetic plasma environment
SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package. PLAIN LANGUAGE ABSTRACT – SelenITA comes from the greek word for Moon, selene, with the addition of “ITA” as a reference to the Brazilian teammate, Instituto Tecnológico de Aeronáutica. In addition, in Portuguese "ita" is a prefix similar to "ite" in English, used in naming minerals, so Selenita could be seen as a lunar gemstone. In Spanish, “ita” is a diminutive suffix for “little” which is appropriate for this CubeSat mission which consists of twin 12U CubeSats in low lunar orbit. The primary science goal of the mission is to distinguish time varying features within the electromagnetic plasma environment near the surface of the Moon. The science objectives include investigating the origins of crustal magnetic fields, plasma interactions with these fields, plasma waves, surface potential, and interior properties. This mission is also interested in the radiation environment at the Moon and the amount of dust at the lunar poles. This is important because it helps us understand how future astronauts will live and work on the lunar surface and identify hazards.
space weather↗
SelenITA: A Dual-Spacecraft Lunar Cubesat Mission to Characterize the Near-Surface Electromagnetic Plasma Environment
SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package.
space weather↗
SelenITA: A Dual-Spacecraft Lunar CubeSat Mission to Characterize the Near-Surface Electromagnetic Plasma Environment
SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package. PLAIN LANGUAGE ABSTRACT – SelenITA comes from the greek word for Moon, selene, with the addition of “ITA” as a reference to the Brazilian teammate, Instituto Tecnológico de Aeronáutica. In addition, in Portuguese "ita" is a prefix similar to "ite" in English, used in naming minerals, so Selenita could be seen as a lunar gemstone. In Spanish, “ita” is a diminutive suffix for “little” which is appropriate for this CubeSat mission which consists of twin 12U CubeSats in low lunar orbit. The primary science goal of the mission is to distinguish time varying features within the electromagnetic plasma environment near the surface of the Moon. The science objectives include investigating the origins of crustal magnetic fields, plasma interactions with these fields, plasma waves, surface potential, and interior properties. This mission is also interested in the radiation environment at the Moon and the amount of dust at the lunar poles. This is important because it helps us understand how future astronauts will live and work on the lunar surface and identify hazards.
space weather↗
SOI N-Channel Field Effect Transistors, CHT-NMOS80, for Extreme Temperatures
Extreme temperatures, both hot and cold, are anticipated in many of NASA space exploration missions as well as in terrestrial applications. One can seldom find electronics that are capable of operation under both regimes. Even for operation under one (hot or cold) temperature extreme, some thermal controls need to be introduced to provide appropriate ambient temperatures so that spacecraft on-board or field on-site electronic systems work properly. The inclusion of these controls, which comprise of heating elements and radiators along with their associated structures, adds to the complexity in the design of the system, increases cost and weight, and affects overall reliability. Thus, it would be highly desirable and very beneficial to eliminate these thermal measures in order to simplify system's design, improve efficiency, reduce development and launch costs, and improve reliability. These requirements can only be met through the development of electronic parts that are designed for proper and efficient operation under extreme temperature conditions. Silicon-on-insulator (SOI) based devices are finding more use in harsh environments due to the benefits that their inherent design offers in terms of reduced leakage currents, less power consumption, faster switching speeds, good radiation tolerance, and extreme temperature operability. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. The objective of this work was to evaluate the performance of a new commercial-off-the-shelf (COTS) SOI parts over an extended temperature range and to determine the effects of thermal cycling on their performance. The results will establish a baseline on the suitability of such devices for use in space exploration missions under extreme temperatures, and will aid mission planners and circuit designers in the proper selection of electronic parts and circuits. The electronic part investigated in this work comprised of a CHT-NMOS80 high temperature N-channel MOSFET (metal-oxide semiconductor field-effect transistor) device that was manufactured by CISSOID. This high voltage, medium-power transistor is fabricated using SOI processes and is designed for extreme wide temperature applications such as geothermal well logging, aerospace and avionics, and automotive industry. It has a high DC current capability and is specified for operation in the temperature range of -55 C to +225 C
Patterson, Richard L.↗
Contribution of Surface Magnetic Recordings to Planetary Exploration
The transient variations of the magnetic field at the surface of a planet has a primary external source, the interaction between the environment of the planet and solar radiation, and a secondary source, the electric currents induced in the conductive planet. The continuous recording of the time variations of the magnetic fields at the surface of Mars by means of three component magnetometers installed onboard landers would therefor allow the study of both the internal structure of Mars and the dynamic of its ionized environment.
magnetic field solar radiation Mars↗
Radiation from Accelerated Particles in Shocks and Reconnections
Plasma instabilities are responsible not only for the onset and mediation of collisionless shocks but also for the associated acceleration of particles. We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection and, more generally, relativistic acceleration behind the shock. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. Our initial results of a jet-ambient interaction with anti-parallelmagnetic fields show pile-up of magnetic fields at the colliding shock, which may lead to reconnection and associated particle acceleration. We will investigate the radiation in a transient stage as a possible generation mechanism of precursors of prompt emission. In our simulations we calculate the radiation from electrons in the shock region. The detailed properties of this radiation are important for understanding the complex time evolution and spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.
Nishikawa, K. I.↗
Absorption and Emission of EUV Radiation by the Local ISM
The Berkeley extreme ultraviolet radiation (EUV) telescope flown on the Apollo Soyuz mission in July, 1975 established the existence of a measurable flux of EUV (100 lambda or = or = 1000 A) originating from sources outside the solar system. White dwarfs, flare stars and cataclysmic variables were dicovered to be relatively intense compact sources of EUV photons. Moreover, this and other subsequent experiments have strongly suggested the presence of a truly diffuse component of the FUV radiation field possibly due to thermal emission from hot interstellar gas located in the general vicinity of the Sun. Closer to the H1, 912 A edge, the effect of a few hot O and B stars has been shown to be very important in establishing the interstellar flux density. All these results imply that the local interstellar medium (ISM) is immersed in a non-negligible EUV radiation field which, because of the strong coupling between EUV photons and matter, will play a crucial role in determining its physical structure. The available information on the local ISM derived from the limited EUV observations carried out so far is assembled and analyzed. These include measurements of the spectra of bright EUV sources that reveal clear evidence of H photo absorption at lambda 400 A and of the He ionization edge at 228 A.
Paresce, F.↗
An experimental investigation of wing tip turbulence with applications to aerosound
Wind tunnel tests were performed to measure the turbulence characteristics of flow in the wing tip region of a blunt tipped NACA 0012 airfoil at angles of attack of 16, 12 and 6 deg and flow speeds of 75, 55, and 35 m/s. Reynolds numbers based on the chord length ranged from 1.8 x 10(exp6) to 3.8 x 10(exp 6). Hot wire measurements were made at an angle of attack of 12 deg and U(infinity) = 55 ms. These indicate fluctuation velocities on the order of 0.13 U(infinity) in the tip region. Surface pressure spectra are presented for alpha = 12 deg and 16 deg; surface-pressure cross-correlations are presented for alpha = 16 deg. These suggest the presence of a well organized turbulence structure with a peak Strouhal number 0.8 to 1.1 based on the wing thickness. High frequency turbulence of lesser intensity was measured at positions near the primary tip vortex on the upper wing surface. A separation region with a spectral peak of St approximately equal to 0.4 was recorded at alpha = 16 deg for the transducer located on the low pressure side of the wing nearest the trailing edge. Surface-surface cross correlations display a double, echo like structure. Near-far field correlations indicate that the well ordered tip turbulence and the separation region on the upper surface both radiate significant levels of far field sound. The use of cross correlation techniques in the wind tunnel has permitted treatment of radiated sound levels which are 25 and more dB below tunnel background levels.
Mcinerny, S. A.↗
Radiation measurements in low Earth orbit: U.S. and Russian results
The radiation environment in low-Earth orbital flights is complex. It is strongly influenced by altitude, orbital inclination, time within a given solar cycle, flight duration, and shielding configuration. At any specified shielded location, both primary and secondary particles generated by nuclear interactions of primary particles with spacecraft structure are present. In addition, there are atmospheric secondary albedo protons and neutrons. No single detector can adequately measure this complex radiation field, and measurements of very high linear energy transfer target fragmentation products are particularly difficult. Crew radiation exposure have exclusively been measured using passive thermoluminescent detectors (TLDs). The cosmonaut exposures on the Mir station, uncorrected for the TLD inefficiency and neutron contribution, have varied from a low of 2.43 cGy to a high of 8.70 cGy. These correspond to dose rates of 144 microGy d(-1) to 468 microGy d(-1). These are consistent with rates observed by the D2 ion-chamber. Using the rates measured by the D1 chamber, dose rates under 4 cm of water vary from about 60 microGy d-1 to about 350 microGy d(-1). There is variation of about a factor of two between the dose rates at various locations in the same module. There is also a variation of dose rates of about a factor two between various modules. The highest astronaut dose for a Shuttle flight (STS-82) was 3.205 cGy with a dose rate of 3,221 microGy d(-1). Neutron contribution could be 36 +/- 15% of the astronaut charged particle dose equivalent. East-West asymmetry of dose rate is significant for spacecrafts that fly in an fixed altitude, such as the International Space Station.
NASA Center JSC↗
The influence of ground conductivity on the structure of RF radiation from return strokes
The combination of the finite conductivity of the Earth plus the propagation of the return stroke current up the channel which results in an apparent time delay between the fast field changes and RF radiation for distant observers is shown. The time delay predicted from model return strokes is on the order of 20 micro and the received signal has the characteristics of the data observed in Virginia and Florida. A piecewise linear model for the return stroke channel and a transmission line model for current propagation on each segment was used. Radiation from each segment is calculated over a flat Earth with finite conductivity using asymptotics approximations for the Sommerfeld integrals. The radiation at the observer is processed by a model AM radio receiver. The output voltage was calculated for several frequencies between HF-UHF assuming a system bandwidth (300 kHz) characteristic of the system used to collect data in Florida and Virginia. Comparison with the theoretical fast field changes indicates a time delay of 20 microns.
Levine, D. M.↗
Near-Field and Far-Field Noise Measurements for a Blowdown-Wind-Tunnel Supersonic Exhaust Jet having about 475,000 Pounds of Thrust
Near-field and far-field noise surveys were made of the supersonic The exhaust jet of the Langley 9- by 6-foot thermal structures tunnel. The jet had a thrust rating of approximately 475,000 pounds. The sound power radiated was found to be about 3.6 x 10(exp 6) watts, and on an acoustical-mechanical efficiency basis this value is in reasonable agreement with data for smaller supersonic jets and for rocket engines of other investigations. Octave-band analyses of the near-field noise show that the maximum sound pressure levels in the low-frequency bands are greatest downstream, whereas maximum sound pressure levels in the high-frequency bands were greatest near the jet exit. A comparison of near-field noise measurements is made with data previously obtained for rocket engines. Noise survey measurements of the original jet are compared with similar data obtained after the addition of a 97-foot-long exit diffuser section, and an example of the application of this facility to the problem of acoustic environmental testing of a large space capsule is cited.
Mayes, William H.↗
Investigation of the large scale coherent structure in a jet and its relevance to jet noise
A study was conducted to determine the causes of aircraft noise in large jet aircraft. It was determined that jet noise varies strongly with velocity and that significant pure tones are generated by rotor-stator interaction in the jet engines. An objective method for deducing the large eddy structure in a large jet is described. The provisions of lighthill's theory are analyzed and applied to investigating the nature of jet noise. There is considerable evidence that a large scale coherent structure exists in a jet and that this structure can play a major role in sound radiation. Mathematical models are developed to define the parameters of orthogonal decomposition, finite extent velocity field, homogeneous fields, and periodic velocity fields.
Arndt, R. E. A.↗
Study of the solar corona using radio and space observations
The physics of coronal transients, the characteristics of radiation and accelerated particles at the time of flares, and the density/temperature structure of the transition region and corona and the coronal magnetic field are investigated.
Dulk, G. A.↗
Interactions between the Space Station and the environment: A preliminary assessment of EMI
A review of the interactions between proposed Space Station systems/payloads and the environment that contribute to electromagnetic interference was performed. Seven prime sources of interference have been identified. These are: The Space Station power system; active experiments such as beam injection; ASTROMAG; ram and wake density gradients; pick up ions produced by vented or offgassed clouds; waves produced by current loops that include the plasma and structure; arcing from high voltage solar arrays (or possible ESD in polar orbit). This review indicates that: minimizing leakage current from the 20 kHz power system to the structure; keeping the surfaces of the Space Station structure, arrays, and radiators nonconducting; minimizing venting of payloads or systems to non-operational periods; careful placement of payloads sensitive to magnetic field perturbations or wake noise; and designing an operational timeline compatible with experiment requirement are the most effective means of minimizing the effects of this interference. High degrees of uncertainty exist in the estimates of magnitudes of gas emission induced EMI, radiation of 20 kHz and harmonics, ASTROMAG induced interference, and arc threshold/frequency of the solar array. These processes demand further attention so that mitigation efforts are properly calibrated.
Murphy, G. B.↗
Nonlinear acoustics and the thermal expansivity of glass
The paper shows the intrinsic relationship between acoustical nonlinearity and the thermal expansivity of crystalline solids (a thermal measure of anharmonicity) from consideration of the 'static' radiation field generated by the vibrating lattice (atomic) sources of the crystal. A modification of the theory to account for long-range structural disorder in glass is proposed and applied to an explanation of the zero thermal expansivity at the cross-over temperature in silicate and titanium silicate glasses. Experimental evidence which validates the essential features of the theory is presented. An application of nonlinearity measurement, based on these results, to the processing of ULE glass, where the addition of titanium in various amounts is used to establish the temperature at which the zero thermal expansivity occurs, is suggested.
Cantrell, John H.↗
A Model Simulation of Pinatubo Volcanic Aerosols in the Stratosphere
A one-dimensional, time-dependent model is used to study the chemical, microphysical, and radiative properties of volcanic aerosols produced by the Mount Pinatubo eruption on June 15, 1991. Our model treats gas-phase sulfur photochemistry, gas-to-particle conversion of sulfur, and the microphysics of sulfate aerosols and ash particles under stratospheric conditions. The dilution and diffusion of the volcanic eruption clouds are also accounted for in these conditions. Heteromolecular homogeneous and heterogeneous binary H2SO4/H2O nucleation, acid and water condensational growth, coagulation, and gravitational sedimentation are treated in detail in the model. Simulations suggested that after several weeks, the volcanic cloud was composed mainly of sulfuric acid/water droplets produced in situ from the SO2 emissions. The large amounts of SO2 (around 20 Mt) injected into the stratosphere by the Pinatubo eruption initiated homogeneous nucleation which generated a high concentration of small H2SO4/H2O droplets. These newly formed particles grew rapidly by condensation and coagulation in the first few months and then reach their stabilized sizes with effective radii in a range between 0.3 and 0.5 micron approximately one-half year after the eruption. The predicted volcanic cloud parameters reasonably agree with measurements in term of the vertical distribution and lifetime of the volcanic aerosols, their basic microphysical structures (e.g., size distribution, concentration, mass ratio, and surface area) and radiative properties. The persistent volcanic aerosols can produce significant anomalies in the radiation field, which have important climatic consequences. The large enhancement in aerosol surface area can result in measurable global stratospheric ozone depletion.
Zhao , Jing-xia↗