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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Measurements on a shock wave generated by a solar flare

Shock waves generated by intense solar flares may be driven by a large amount of ejected mass, about 5 x 10 to the 16th g, and the total energy involved may be of the order of 10 to the 32nd erg. The shocks may have initial velocities of the order of 2,000 km/s and, in their exodus through the corona, may be accompanied by fast-moving optical transients, the emission of highly characteristic radio signatures and the acceleration of particles to quasi-relativistic velocities. Here, a review is presented of data on a high-velocity shock generated by a flare on 18 August 1979, 1400 UT, and comments are provided on some previously deduced velocities for the shock. Attention is given to a model, based on current computer programs to account for the overall characteristics of the shock as it propagated through the corona and the interplanetary plasma.

Maxwell, A.↗
NASA NTRS1989

Inception length to a fully-developed fin-generated shock wave boundary-layer interaction

An experimental study of fin-generated shock wave turbulent boundary-layer interactions confirmed previous observations that, sufficiently far from the fin apex, such interactions become conical. The inception length to conical symmetry was found to increase weakly with Mach number for Mach numbers from 2.5 to 4 and fin angles from 4 to 22 deg. For the range of interactions examined, the inception length was found to depend primarily upon the inviscid shock angle, this angle ranging from 21 to 40 deg. The behavior of the inception length with shock angle can be broadly divided into two categories. For 'weak' interactions with shock angles less than about 35 deg, the inception length decreased as the shock angle increased. For 'strong' interactions with shock angles greater than about 35 deg, the inception region was small and was approximately constant at three boundary-layer thicknesses in length. In the latter, strong interaction case, the inception length was an order of magnitude smaller than that found in the weakest interactions examined, to the extent that strong interactions were practically fully-developed from the apex.

Lu, Frank K.↗
NASA NTRS1978

On the observation of a flare-generated shock wave at 9.7 AU by Pioneer 10

An apparent solar-flare-generated shock wave detected by Pioneer-10 at 9.7 AU on April 9, 1976 is discussed. The shock wave may be correlated with a radio emission burst from Jupiter not associated with Io (March 30). The fact that solar flares observed on March 20 were at the central meridian with respect to Jupiter and Pioneer-10 and the fact that solar activity was very low before March 20 contribute to the argument that a shock wave had propagated to the region of the spacecraft.

Dryer, M.↗
NASA NTRS1983

Measurements on a shock wave generated by a solar flare

It is shown that path-integrated radio-scattering measurements of the solar wind velocity yield higher estimates than those of point measurements. The post-shock speed is determined from radio scattering measurements by selection of the maximum of the radio-scattering deduced from the velocity-time curve, whereas velocity points on the rising edge of the shock underestimate the post-shock gas velocity, and therefore the shock speed. However, it is suggested that large uncertainties reside in using radio techniques for measurements of parameters of the shock wave, and the uncertainties may be large enough to encompass the lower velocity values calculated by a point method of measurement.

Woo, R.↗
NASA NTRS1974

Shock waves generated by the intense solar flare of 1972, August 7, 15:00 UT

The dynamic radio spectrum of the class 3B solar flare of 1972, August 7, 15:00 UT, over the band 10 to 2000 MHz is examined. Type II and type IV bursts in the spectrum are interpreted in terms of a piston-driven shock, which appeared to be traveling at a velocity of about 1500 km per sec and which generated pulsations in the band 100 to 200 MHz as it passed through the corona. The progress of the shock through the interplanetary plasma was subsequently monitored by Malitson et al. with radio equipment covering the band 0.03 to 2.6 MHz on the IMP-6 satellite.

Maxwell, A.↗
NASA NTRS1981

Measurements of a solar flare-generated shock wave at 13.1 R/0/

The first measurements of the structure of wind speed, electron density, and electron density fluctuations are reported for a shock wave propagating through the acceleration region of the solar wind. Radio scattering observations, consisting of spectral broadening, mean phase and amplitude scintillations, were made on August 18, 1979, 13.1 solar radii east of the sun near the ecliptic plane, using the 2.3 and 8.4 GHz radio signals of Voyager 1. The results show a shock wave speed of about 3,500 km/sec; which, when compared with average transit time speed to 1 AU, shows that substantial deceleration took place with outward propagation from the sun. This result is consistent with a blast wave.

Woo, R.↗
NASA NTRS1990

Upstream-influence scaling of fin-generated shock wave boundary-layer interactions

An upstream-influence scaling law, previously formulated through analysis of Mach 3 data, has been extended to Mach numbers from 2.5 through 4. For adiabatic, equilibrium, turbulent boundary layers, there is no Mach number effect on the constants in the Reynolds number parameters of this law. In addition, based on local similarity, a new Mach number parameter, namely, the Mach number component of the incoming stream normal to the farfield upstream influence, is proposed. Scaling by either the incoming Mach number normal to the inviscid shock or by the incoming Mach number normal to the farfield upstream influence is equivalent to scaling by the hypersonic similarity parameter.

Lu, Frank K.↗
NASA NTRS1990

Color surface-flow visualization of fin-generated shock wave boundary-layer interactions

Kerosene-lampblack mixtures with addition of a ground colored chalk were used in an experiment on visualizing surface flows of swept shock boundary-layer interactions. The results show that contrasting colors intensify the visualization of different regions of the interaction surface, and help the eye in following the fine streaks to locate the upstream influence. The study confirms observations of the separation occurring at shock strength below accepted values. The superiority of the reported technique over the previous monochrome technique is demonstrated.

Lu, F. K.↗
NASA NTRS1993

The seismic response of an aquifer to the propagation of an impact generated shock wave: A possible trigger of the Martian outflow channels?

Aquifer dilation from shock waves produced by the 8.4 magnitude Alaskan earthquake of 1964 led to water and sediment ejection from the ground up to 400 km away from the earthquake's epicenter. Groundwater disturbances were observed as far away as Perry, Florida (approximately 5500 km), where well water fluctuations with an amplitude of as much as 2.3 m were reported. The martian cratering record provides evidence that the planet has experienced numerous seismic events of a similar, and often much greater, magnitude. Given this fact, and the photogeologic evidence for abundant water in the early crust, the response of a basalt aquifer to the propagation of compressional waves (P-waves) produced by impacts in the 33-1000 km diameter size range were investigated. The resulting one-dimensional changes in effective stress and pore pressure were calculated - as a function of both distance and time - based on the following assumptions: (1) that all of the seismic energy radiated by an impact is transmitted as a single compressional wave; (2) that both the host rock and groundwater are compressible; and (3) that there is no net flow between the water-filled pores.

Leyva, Ivett A.↗
NASA NTRS2000

The Observational Consequences of Proton-Generated Waves at Shocks

In the largest solar energetic particle (SEP) events, acceleration takes place at shock waves driven out from the Sun by fast coronal mass ejections. Protons streaming away from strong shocks generate Alfven waves that trap particles in the acceleration region, limiting outflowing intensities but increasing the efficiency of acceleration to higher energies. Early in the events, with the shock still near the Sun, intensities at 1 AU are bounded and spectra are flattened at low energies. Elements with different charge-to-mass ratios, Q/A, differentially probe the wave spectra near shocks, producing abundance ratios that vary in space and time. An initial rise in He/H, while Fe/O declines, is a typical symptom of the non-Kolmogorov wave spectra in the largest events. Strong wave generation can cause cross-field scattering near the shock and unusually rapid reduction in anisotropies even far from the shock. At the highest energies, shock spectra steepen to form a "knee." For protons, this spectral knee can vary from approx. 10 MeV to approx. 1 GeV depending on shock conditions for wave growth. In one case, the location of the knee scales approximately as Q/A in the energy/nucleon spectra of other species.

Reames, Donald V.↗
NASA NTRS1975

Experimental investigation of supersonic flow past double-wedge configurations

Viscous-inviscid interactions characteristic of those which occur when the fuselage-generated shock wave interacts with the wing-generated shock wave of a shuttle orbiter were studied experimentally. Surface-pressure measurements and schlieren photographs were obtained to define the flowfield generated when a Mach 4.97 stream encounters a double-wedge configuration. The deflection angles for the two wedge surfaces were such that the shock interaction pattern was either a Type-V pattern or a Type-VI pattern, as defined by Edney. The correlation between the present data and the theoretical solution for the Type-VI solution is satisfactory. The correlation between the measured Type-V shock-interaction pattern and the theoretical solution is satisfactory up to the interaction region. Downstream of the interaction the Type-V data depend primarily on the shape of the leading-edge shock wave.

Bertin, J. J.↗
NASA NTRS1972

Effects of interplanetary magnetic field on the propagation of flare-generated interplanetary shock waves.

The effects of an interplanetary magnetic field on the propagation of flare-generated interplanetary shock waves are investigated with an approximate analytical method. It is found that the interplanetary magnetic field is relatively unimportant for strong shocks as far as the shock speed and transit time are concerned. It has more significant effects for weak shocks. However, in all the situations examined, the error committed if the magnetic field is neglected is no more than 10%. It is suggested that a model without a magnetic field gives sufficiently accurate numerical results for the propagation of flare-generated shocks.

Tam, C. K. W.↗