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All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Microwave and hard X-ray observations of a solar flare with a time resolution better than 100 ms

Simultaneous microwave and X-ray observations are presented for a solar flare detected on 1980 May 8 starting at 1937 UT. The X-ray observations were made with the Hard X-ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28-490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Obervatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240 ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model. Previously announced in STAR as N82-30215

Kaufmann, P.↗
NASA NTRS1974

The flash phase of solar flares - Satellite observations of electrons

Satellite observations of solar electrons bearing on flare particle acceleration and the generation of radio and X-ray emission are reviewed. The observations support a two-stage acceleration process for electrons, one stage commonly occurring at the flare flash phase and accelerating electrons up to about 100 keV, and a second stage occurring only in large proton flares and accelerating electrons up to relativistic energies. The location of the acceleration region appears to be no lower than the lower corona. The accelerated non-relativistic electrons generate type III radio burst emission as they escape from the sun. Direct spacecraft observations of the type III emission generated near 1 AU and the energetic electrons, provide quantitative information on the characteristics of the electrons exciting type III emission, the production of plasma waves, and the conversion from plasma waves to electromagnetic radiation.

Lin, R. P.↗
NASA NTRS1994

Spectral evolution of microwaves and hard X-rays in the 1989 March 18 flare and its interpretation

We analyze the time variation of microwave spectra and hard X-ray spectra of 1989 March 18, which are obtained from the Solar Array at the Owens Valley Radio Observatory (OVRO) and the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM), respectively. From this observation, it is noted that the hard X-ray spectra gradually soften over 50 - 200 keV on-and-after the maximum phase while the microwaves at 1 - 15 GHz show neither a change in spectral shape nor as rapid a decay as hard X-rays. This leads to decoupling of hard X-rays from the microwaves in the decay phase away from their good correlation seen in the initial rise phase. To interpret this observation, we adopt a view that microwave-emitting particles and hard X-ray particles are physically separated in an inhomogeneous magnetic loop, but linked via interactions with the Whistler waves generated during flares. From this viewpoint, it is argued that the observed decoupling of microwaves from hard X-rays may be due to the different ability of each source region to maintain high energy electrons in response to the Whistler waves passing through the entire loop. To demonstrate this possibility, we solve a Fokker-Planck equation that describes evolution of electrons interacting with the Whistler waves, taking into account the variation of Fokker-Planck coefficients with physical quantities of the background medium. The numerical Fokker-Planck solutions are then used to calculate microwave spectra and hard X-ray spectra for agreement with observations. Our model results are as follows: in a sronger field region, the energy loss by electron escape due to scattering by the waves is greatly enhanced resulting in steep particle distributions that reproduce the observed hard X-ray spectra. In a region with weaker fields and lower density, this loss term is reduced allowing high energy electrons to survive longer so that microwaves can be emitted there in excess of hard X-rays during the decay phase of the flare. Our results based on spectral fitting of a flare event are discussed in comparison with previous studies of microwaves and hard X-rays based on either temporal or spatial information.

Lee, Jeongwoo W.↗
NASA NTRS2006

A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Preplanetary Nebula IRAS 22036+5306

We report high angular resolution (approx.1") CO J=3-2 interferometric mapping using the Submillimeter Array (SMA) of IRAS 22036+5306 (I22036), a bipolar preplanetary nebula (PPN) with knotty jets discovered in our HST snapshot survey of young PPNs. In addition, we have obtained supporting lower resolution (approx.10") CO and 13CO J=1-0 observations with the Owens Valley Radio Observatory (OVRO) interferometer, as well as optical long-slit echelle spectra at the Palomar Observatory. The CO J=3-2 observations show the presence of a very fast (approx.220 km/s), highly collimated, massive (0.03 Solar Mass) bipolar outflow with a very large scalar momentum (about 10(exp 39) g cm/s), and the characteristic spatiokinematic structure of bow shocks at the tips of this outflow. The H(alpha) line shows an absorption feature blueshifted from the systemic velocity by approx.100 km/s, which most likely arises in neutral interface material between the fast outflow and the dense walls of the bipolar lobes at low latitudes. The fast outflow in I22036, as in most PPNs, cannot be driven by radiation pressure. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I22036, implying a very substantial mass (0.02-0.04 Solar Mass) of large (radius > or approx.1 mm), cold (< or approx.50 K) dust grains associated with I22036's toroidal waist. We also find that the C-13/C-12 ratio in I22036 is very high (0.16), close to the maximum value achieved in equilibrium CNO nucleosynthesis (0.33). The combination of the high circumstellar mass (i.e., in the extended dust shell and the torus) and the high C-13/C-12 ratio in I22036 provides strong support for this object having evolved from a massive (> or approx.4 Solar Mass) progenitor in which hot-bottom-burning has occurred.

stars↗
NASA NTRS1990

Modeling solar flare conduction fronts. I - Homogeneous plasmas and ion-acoustic turbulence. II - Inhomogeneous plasmas and ambipolar electric fields

A one-dimensional, electrostatic, particle-in-cell simulation is used here to model the expansion of a heated electron population in a coronal loop during a solar flare and the characteristics of the associated X-ray emissions. The hot electrons expand outward from the localized region, creating an ambipolar electric field which accelerates a return current of cooler, ambient electrons. Ion-acoustic waves are generated by the return currents as proposed by Brown et al. (1979), but they play little or no role in containing energetic electrons and the conduction front proposed by Brown et al. does not form. The X-ray emission efficiency of the electrons is too low in the corona for them to be the source of hard X-ray bursts. The particle dynamics changes dramatically if the heated plasma is at low altitudes and expands upward into the more tenuous plasma at higher altitudes. Two important applications of this finding are the radio-frequency heating of the corona and the collisional heating of the chromosphere by precipitating energetic electrons. In both cases, the overlying plasma has a density that is too low to supply a balancing return current to the expanding hot electrons. As a result, an ambipolar electric field develops that tends to confine the energetic electrons behind a front that propagate outward at about the speed of sound.

Mckean, M. E.↗
DOE OSTI2024

Magnetized Winds of M-type Stars and Star–Planet Magnetic Interactions: Uncertainties and Modeling Strategy

M-type stars are the most common stars in the Universe. They are ideal hosts for the search of exoplanets in the habitable zone (HZ), as their small size and low temperature make the HZ much closer-in than their solar twins. Harboring very deep convective layers, they also usually exhibit very intense magnetic fields. Understanding their environment, in particular their coronal and wind properties, is thus very important, as they might be very different from what is observed in the solar system. The mass-loss rate of M-type stars is poorly known observationally, and recent attempts to estimate it for some of them (e.g., TRAPPIST-1 and Proxima Centauri) can vary by an order of magnitude. In this work, we revisit the stellar wind properties of M dwarfs in the light of the latest estimates of $\dot{M}$ through Lyα absorption at the astropause and slingshot prominences. We outline a modeling strategy to estimate the mass-loss rate, radiative loss, and wind speed, with uncertainties, based on an Alfvén-wave-driven stellar wind model. We find that it is very likely that several TRAPPIST-1 planets lie within the Alfvén surface, which implies that these planets experience star–planet magnetic interactions (SPMIs). We also find that SPMIs between Proxima Cen b and its host star could be the reason for recently observed radio emissions.

M stars↗
NASA NTRS2010

Low-Frequency Type III Bursts and Solar Energetic Particle Events

We analyzed the coronal mass ejections (CMEs), flares, and type 11 radio bursts associated with a set of six low frequency (<14 MHz) extended type III bursts from active region 10588. The durations were measured at 1 and 14 MHz using high resolution data from Wind/WAVES and were within the range (>15 min) normally used to define these bursts. All but one of the type III bursts was not associated with a type 11 burst in the metric or longer wavelength domains. The burst without type 11 burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 min) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. The CMEs were of similar speeds and the flares are also of similar size and duration. This study suggests that the type III burst duration may not be a good indicator of an SEP event.

Gopalswamy, Nat↗
NASA NTRS1994

Transition to turbulence in solar surges

Transition to turbulence in magnetohydrodynamic (MHD) tearing jets has been invoked as a mechanism underlying some of the complex behavior observed in solar surges, including deceleration of the upflowing plasma and temporal correlations with types I and III radio bursts. In this paper we investigate a possible mechanism for this transition: three-dimensional secondary instabilities on two-dimensional saturated states. We find through linear analysis that these MHD configurations -- in particular, the tearing jet -- are secondarily unstable, with the dominant energy transfer from the one-dimensional field into the 3-dimensional fields. Using nonlinear simulations, we also investigate the system evolution after the secondary modes attain finite amplitude. When the tearing jet transitions to turbulence, the total kinetic energy drops rapidly corresponding to the deceleration of the jet. The electric field grows rapidly as the primary mode saturates and the three-dimensional secondary mode develops, and then decays quickly as the tearing jet becomes turbulent, providing a possible explanation for the finite duration of the associated meter-wave bursts. The electric field decays as the magnetic and velocity fields both decay. The system is dominated at late times by spanwise modes, which strongly resemble the magnetic field-aligned filamentary flows characteristic of many surges.

Dahlburg, Russell B.↗
NASA NTRS1989

On the source conditions for herringbone structure in type II solar radio bursts

An investigation is made of the correlation of the occurrence of the herringbone phenomenon in type II solar radio bursts with various flare properties. It is shown that herringbone is strongly correlated with the intensity of the type II burst: whereas about 21 percent of all type II bursts show herringbone, about 60 percent of the most intense bursts contain herringbone. This fact can explain most of the correlations between herringbone and other properties such as intense type III bursts, type IV emission, and high type II starting frequencies. It is also shown that when this is taken into account, there is no need to postulate two classes of type II burst in order to explain why there appears to be a difference in herringbone occurrence between the set of type II bursts associated with the leading edges of coronal mass ejections, and those not so associated. It is argued that the data are consistent with the idea that all coronal type II bursts are due to blast waves from flares.

Cane, H. V.↗
NASA NTRS1999

The Plasmasphere as "Seen" by the IMAGE Mission

The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) is the first mission designed exclusively to remotely measure the magnetosphere. As such, it will reveal the ring current, plasmasphere, polar cusp, and magnetopause as whole extended, interacting systems. For the first time, our impressions of the global magnetosphere, synthesized through many years of whistler and in situ measurement, will be replaced by images. The overall morphology of each system of plasma and the correspondence of changes between them in response to the sun and solar wind will become available. The Extreme Ultraviolet Imager (EUV) and the Radio Plasma Imager (RPI) are the two IMAGE instruments which will remotely measure and image the plasmasphere. What we expect to "see" from these instruments and how it may be interpreted is the subject of this presentation. The EUV instrument includes three optical cameras, with an almost 90 degree field of view, transverse to the spin axis. EUV is designed to see He+ ions in resonantly scatter solar light at 30.4rim. The IMAGE spacecraft will spin with a period of about 2 minutes, with its spin axis parallel to the orbit normal. The IMAGE orbit will be highly inclined, with a high latitude apogee at a geocentric distance of 8RE and perigee of about 1.2RE. The normal observing integration time of 10 minutes will easily see to the outer edge of the plasmasphere. The RPI instrument makes use of three orthoganal dipole antennas: two in the spin plane with a tip-to-tip length of 500m and one along the spin axis with a length of 20 meters. Using coded pulse transmissions, the RPI instrument will broadcast from 3kHz to 3MHz. With one minute resolution, plasma densities from about 0.1 cm(exp -3) to 100,000 cm(exp -3), along with line-of-sight bulk velocities and locations, will be obtained from all returned radio wave signals. When transmitting from the high latitude magnetospheric cavity, RPI will measure density profiles for the major plasma structures in the magnetosphere, including the magnetopause, polar cusp, and plasmasphere. RPI should also see isolated density irregularities and possibly the plasma sheet. Observations The EUV instrument will return line-of-sight integrated images through the optically thin helium medium of the plasmasphere and magnetosphere. A variety of techniques have been suggested for the translation of the images into physically useful data, such as plasmapause location and three dimensional density distribution. The RPI instrument will return quantitative density values and line-of-sight velocity as a function of position along reflecting wave propagation paths. How they may be used individually and together to study plasmaspheric dynamics and global structure will be discussed. Attention will also be given to the data products and how access to IMAGE data will be provided by the IMAGE team and the NSSDC.

Gallagher, D. L.↗
NASA NTRS1977

Plasma wave electric fields in the solar wind - Initial results from Helios 1

Plasma-wave measurements by Helios 1 show that the electric-field intensities in the solar wind are usually very low, much lower than those for comparable measurements near earth, where particles moving upstream from the bow shock often cause large disturbances in the solar wind. The most commonly occurring plasma wave detected by Helios is a sporadic emission at frequencies from about 1 to 10 kHz, between the electron and ion plasma frequencies. These waves are thought to be ion acoustic waves Doppler-shifted upward in frequency from below the ion plasma frequency. The maximum electric-field intensity of these waves is a few hundred microvolts per meter. At higher frequencies, from about 20 to 100 kHz, electron plasma oscillations are detected at frequencies near the local electron plasma frequency. These electron plasma oscillations are more intense, with field strengths sometimes as large as a few millivolts per meter, but occur very infrequently. Both the ion acoustic waves and the electron plasma oscillations show a tendency to occur at higher frequencies closer to the sun but no pronounced variation in intensity with radial distance from the sun. In four cases, electron plasma oscillations have been found in association with type III radio bursts.

Gurnett, D. A.↗
NASA NTRS1989

A search for five month solar induced periodicity in the stratosphere

Recent studies of solar UV spectra and various indices of solar activity indicate a strong period at about 5 months. In the 10.7 cm solar radio flux (F10.7), a conventional index for the solar EUV and UV variabilities, the spectral power of the 5 month period is comparable to the well known 27 day solar period. However, in the solar UV flux at 205 nm, directly measured from the Nimbus-7 SBUV spectrometer, the (spectral) power of the 5 month period is about half that of the 27 day period. This paper examines the possible impact of the 5 month solar period on ozone and temperature at various pressure levels in the stratosphere and discusses the implications of differences in solar forcing at the 27 day and 5 month periods. It is shown that ozone, both in the lower and the upper stratosphere, has a measurable response to solar UV forcing at 27 days. Such a solar response is not observed at 5 month period because of a relatively weaker 5 month solar UV component in the solar signal and a strong interference from dynamical signals associated with planetary wave activity.

Chandra, S.↗
NASA NTRS1990

CO aperture synthesis of NGC 4038/9 (ARP 244)

Researchers present high-resolution (approx. 6 seconds) CO observations of the merging galaxies NGC 4038/9 made with the Owens Valley Radio Observatory (OVRO) Millimeter Wave Interferometer. The CO observations of Arp 244 were obtained between April and June 1988 using the OVRO Millimeter Wave Interferometer. Two fields with phase centers near the NGC 4039 nucleus and near the NGC 4038 nucleus were observed. The size of the synthesized beam is approximately 6.5 x 7 seconds at PA=72 degrees. The rms in a single cleaned channel map is 0.06 Jy beam(exp -1), corresponding to a brightness temperature of 0.12 K over the synthesized beam. Contour maps of the integrated CO intensity for both interferometer fields are shown. Three CO concentrations are evident. Two are centered near the nuclei of NGC 4038 and NGC 4039, closely correlated with H alpha and radio continuum maxima. A third CO emission region lies about 25 seconds northeast of the NGC 4039 nucleus. A number of radio continuum, H alpha, and 10 micron emission knots appear in this region. The total integrated intensity at the northern nuclear source, 302 K km/s, leads to a molecular mass of 8.3 by 10 to the 8th power solar mass assuming a Galactic CO to H2 conversion factor of 3.0 x 10 to the 20th power H2 cm(-2) (K km/s)(-1). The integrated CO intensity of the southern nuclear source leads to a molecular mass of 2.4 x 10 to the 8th solar mass. The extranuclear CO concentration contains 1.2 x 10 to the 9th power solar mass of molecular gas, extending over 170 km/s, and is resolved in a number of channels. Its large size, mass, and morphology strongly suggest that it is an agglomeration of several clumps.

Stanford, S. A.↗
NASA NTRS1984

Electron-cyclotron maser emission - Relative growth and damping rates for different modes and harmonics

The temporal growth rate and the number of e-folding growths are calculated and compared for the following wave modes due to a loss-cone-driven cyclotron maser: fundamental x, o, and z modes and second harmonic x and o modes. The dominant mode of the maser should be the fastest growing mode for a saturated maser and should be the mode with the greatest number of e-folding growths for an unsaturated maser; this mode is the fundamental x mode) for a plasma frequency to cyclotron frequency ratio of less than about 0.3; it is the z mode (or perhaps the fundamental o mode) for ratios between 0.3 and 1.0, and the z mode (or perhaps the second harmonic x mode) for ratios between 1.0 and 1.3. Two main points are made: the dominance of the z mode over the range of ratios considered and the very weak effect of cyclotron damping. Electron-cyclotron maser emission is seen as responsible for auroral kilometric radiation, decametric radio emission from Jupiter and Saturn, solar microwave spike bursts, and microwave emission from some flare stars.

Melrose, D. B.↗
NASA NTRS2023

ICARUS: in-Situ Studies of the Solar Corona Beyond Parker Solar Probe and Solar Orbiter

The primary scientific goal of ICARUS (Investigation of Coronal AcceleRation and heating of solar wind Up to the Sun), a mother-daughter satellite mission, proposed in response to the ESA “Voyage 2050” Call, will be to determine how the magnetic field and plasma dynamics in the outer solar atmosphere give rise to the corona, the solar wind, and the entire heliosphere. Reaching this goal will be a Rosetta Stone step, with results that are broadly applicable within the fields of space plasma physics and astrophysics. Within ESA’s Cosmic Vision roadmap, these science goals address Theme 2: “How does the Solar System work?” by investigating basic processes occurring “From the Sun to the edge of the Solar System”. ICARUS will not only advance our understanding of the plasma environment around our Sun, but also of the numerous magnetically active stars with hot plasma coronae. ICARUS I will perform the first direct in situ measurements of electromagnetic fields, particle acceleration, wave activity, energy distribution, and flows directly in the regions in which the solar wind emerges from the coronal plasma. ICARUS I will have a perihelion altitude of 1 solar radius and will cross the region where the major energy deposition occurs. The polar orbit of ICARUS I will enable crossing the regions where both the fast and slow winds are generated. It will probe the local characteristics of the plasma and provide unique information about the physical processes involved in the creation of the solar wind. ICARUS II will observe this region using remote-sensing instruments, providing simultaneous, contextual information about regions crossed by ICARUS I and the solar atmosphere below as observed by solar telescopes. It will thus provide bridges for understanding the magnetic links between the heliosphere and the solar atmosphere. Such information is crucial to our understanding of the plasma physics and electrodynamics of the solar atmosphere. ICARUS II will also play a very important relay role, enabling the radio-link with ICARUS I. It will receive, collect, and store information transmitted from ICARUS I during its closest approach to the Sun. It will also perform preliminary data processing before transmitting it to Earth. Performing such unique in situ observations in the area where presumably hazardous solar energetic particles are energized, ICARUS will provide fundamental advances in our capabilities to monitor and forecast the space radiation environment. Therefore, the results from the ICARUS mission will be extremely crucial for future space explorations, especially for long-term crewed space missions.

Solar wind↗
NASA NTRS2007

SN 1987A after 18 Years: Mid-Infrared GEMINI and SPITZER Observations of the Remnant

We present high resolution 11.7 and 18.3 micron mid-IR images of SN 1987A obtained on day 6526 since the explosion with the Thermal-Region Camera and Spectrograph (T-ReCS) attached to the Gemini South 8m telescope. The 11.7 micron flux has increased significantly since our last observations on day 6067. The images clearly show that all the emission arises from the equatorial ring (ER). Nearly contemporaneous spectra obtained on day 6184 with the MIPS at 24 micron, on day 6130 with the IRAC in 3.6- 8 micron region, and on day 6190 with the IRS in the 12-37 micron instruments on board the Spitzer Space Telescope's show that the emission consists of thermal emission from silicate dust that condensed out in the red giant wind of the progenitor star. The dust temperature is 1662(sup +18) (sub -12) K, and the emitting dust mass is (2.6(sup +2.0 (sub -1.4)) x 10 (exp -6) M(solar). Lines of [Ne II] 12.82 micron and [Ne III] 15.56 pm are clearly present in the Spitzer spectrum, as well as a weak [Si II] 3 34.8 micron line. We also detect two lines near 26 micron which we tentatively ascribe to [Fe II] 25.99 pm and [0 IV] 25.91 micron. Comparison of the mid-IR Gemini 11.7 micron image with X-ray images obtained by Chandra, UV-optical images obtained by HST, and radio synchrotron images obtained by the ATCA show generally good correlation of the images across all wavelengths. Because of the limited resolution of the mid-IR images we cannot uniquely determine the location. or heating mechanism of the dust giving rise to the emission. The dust could be collisionally heated by the X-ray emitting plasma, providing a unique diagnostic of plasma conditions. Alternatively, the dust could be radiatively heated in the dense UV-optical knots that are overrun by the advancing supernova blast wave. In either case the dust-to-gas mass ratio in the circumstellar medium around the supernova is significantly lower than that in the general interstellar medium of the LMC, suggesting either a low condensation efficiency in the wind of the progenitor star, or the efficient destruction of the dust by the SN blast wave. Overall, we are witnessing the interaction of the SN blast wave with its surrounding medium, creating an environment that is rapidly evolving at all wavelengths. Continuous multiwavelength observations of SN 1987A such as these provide unique snapshots of the very early evolution of supernova remnants.

Bouchet, Patrice↗
NASA NTRS2019

The NANOGrav 11 yr Data Set: Solar Wind Sounding through Pulsar Timing

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has observed dozens ofmillisecond pulsars for over a decade. We have accrued a large collection of dispersion measure (DM)measurements sensitive to the total electron content between Earth and the pulsars at each observation. All lines ofsight cross through the solar wind (SW), which produces correlated DM fluctuations in all pulsars. We develop andapply techniques for extracting the imprint of the SW from the full collection of DM measurements in the recentlyreleased NANOGrav 11 yr data set. We filter out long-timescale DM fluctuations attributable to structure in theinterstellar medium and carry out a simultaneous analysis of all pulsars in our sample that can differentiate thecorrelated signature of the wind from signals unique to individual lines of sight. When treating the SW asspherically symmetric and constant in time, we find the electron number density at 1au to be 7.9 ± 0.2 cm(exp -3). Wefind our data to be insensitive to long-term variation in the density of the wind. We argue that our techniques pairedwith a high-cadence, low-radio-frequency observing campaign of near-ecliptic pulsars would be capable ofmapping out large-scale latitudinal structure in the wind.

Madison, D.R.↗
NASA NTRS1995

Toward a theory of interstellar turbulence. 2: Strong alfvenic turbulence

We continue to investigate the possibility that interstellar turbulence is caused by nonlinear interactions among shear Alfven waves. Here, we restrict attention to the symmetric case where the oppositely directed waves carry equal energy fluxes. This precludes application to the solar wind in which the outward flux significantly exceeds the ingoing one. All our detailed calculations are carried out for an incompressible magnetized fluid. In incompressible magnetohydrodynamics (MHD), nonlinear interactions only occur between oppositely direct waves. We present a theory for the strong turbulence of shear Alfven waves. It has the following main characteristics. (1) The inertial-stage energy spectrum exhibits a critical balance between linear wave periods and nonlinear turnover timescales. (2) The 'eddies' are elongated in the direction of the field on small spatial scales; the parallel and perpendicular components of the wave vector, k(sub z) and k(perpendicular) are related by k(sub z) approximately equals k(sub perpendicular to)(exp 2/3) L(exp -1/3), where L is the outer scale of the turbulence. (3) The 'one-dimensional' energy spectrum is proportional to k(sub perpendicular)(exp -5/3)-an anisotropic Kolmogorov energy spectrum. Shear Alfvenic turbulence mixes specific entropy as a passive contaminant. This gives rise to an electron density power spectrum whose form mimics the energy spectrum of the turbulence. Radio wave scattering by these electron density fluctuations produces anisotropic scatter-broadened images. Damping by ion-neutral collisions restricts Alfvenic turbulence to highly ionized regions of the interstellar medium.

Goldreich, P.↗