Lion Roars Research Articles

The LION roars

The LION roars

Waveform and packet structure of lion roars

The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5°.Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence)

First ELF wave measurements with the Equator-S magnetometer

The magnetometer onboard the Equator-S satellite is very sensitive and has a high sampling rate of up to 128 Hz. These specifications allow for the first fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for 0.2–1 sec. They are right-hand circularly polarized shear waves with typical amplitudes of 0.5–1 nT at frequencies of 15–40 Hz, i.e., around one tenth of the electron gyrofrequency.

Preliminary results from the MEMO multicomponent measurements of waves on-board INTERBALL 2

Abstract. The MEMO (MEsure Multicomposante des Ondes) experiment is a part of the INTERBALL 2 wave consortium. It is connected to a total of six electric and nine magnetic independent sensors. It provides waveforms associated with the measurement of two to five components in three frequency bands: ELF (5–1000 Hz), VLF (1–20 kHz), LF (20–250 kHz). Preliminary analyses of low and high resolution data are presented. The emphasis is put on the estimation of the propagation characteristics of the observed waves.VLF hiss emissions are shown to be mainly whistler mode emissions, but other modes are present. An accurate estimation of the local plasma frequency is proposed when the low L = 0 cutoff frequency is identified. AKR emissions observed just above source regions are studied. R-X and L-O modes are found: the first at the lowest frequencies and the second at the highest. Both propagate with wave normal directions weakly oblique or quasi-parallel to the Earth's magnetic field direction. Propagation characteristics are also determined for a (non-drifting) fine structure of AKR. There is no fundamental difference with structurless events. Nightside and dayside bursts of ELF electromagnetic emissions are presented. It is not clear whether the two emissions belong to the "lion roar" emissions or not.Key words. Magnetospheric physics (auroral phenomena; plasma waves and instabilities; instruments and techniques)

Lion roars in the magnetosheath: The Geotail observations

Lion roars in the magnetosheath are studied based on the waveform data recorded by the Geotail plasma wave instrument (PWI). It is found that about 30% (type A) of the lion roars are associated with the mirror waves or the decrease of the ambient magnetic field (B0). About 70% (type B) of the lion roars are not associated with the decrease of the B0. Both types of the lion roars cover a frequency range from 0.02Ωe to 0.75Ωe. However, the dominant frequencies are around 0.12Ωe, where Ωe is the electron cyclotron frequency. The amplitudes of the lion roars range from a few picoteslas to a few hundreds of picoteslas. Their average amplitude is about 110 pT. Most of these lion roars propagate in a slightly oblique direction (θκB ∼ ±10°) with respect to the B0. One important feature of these lion roars is that they propagate mostly in a single direction, either in the direction of or in the opposite direction to the B0. This suggests that the sources of the lion roars are very likely away from the location where they are observed. Five percent of the lion roars (only the type B lion roars) propagate in two opposite directions simultaneously. This indicates a possibility that the lion roars are generated locally in the vicinity of the spacecraft for these cases. Those highly oblique lion roars (the type B, θκB up to 87°) are usually observed near the bow shock and they are very likely the downstream propagating whistlers excited in the bow shock region. The nearly monotonic decrease of the wave normal distributions of the lion roars suggests that the Landau damping may play an important role. The relatively narrow wave normal distribution of the types A lion roars than that of the type B lion roars suggests that the type A lion roars may be closer to their sources than the type B lion roars.

Mission and Dialogue: A Paradox?

The Pali canon teaches a commitment to both and dialogue. The part, however, is tempered by a generally pessimisitic outlook about the mission. It is clear that the Buddha, although convinced of the truth of his dharma, was a respectful and accepting dialogician. As I understand the question, the theme mission and dialogue is a matter of exploring a paradox. On the one hand, anyone who is sincerely following a religious tradition or a spiritual path presumably has a notion of being on to something true, and perhaps to varying degrees feels a sense of mission-both in the sense of accomplishing the path for oneself and in the sense of wanting to share this truth with others. On the other hand, our modern world is calling for dialogue, for communication between religious traditions. Now that we are all (I hope) accepting the reality of pluralism, that there are a number of different world views existing in parallel, there is a strong expectation for a maturity of exchange that goes beyond trying to convince others of the truth of one's own tradition. The question, then, is Are these two activities really compatible? Frankly, I don't think there is an easy answer. But I found it fascinating to explore the Buddhist tradition with this theme in mind, and can perhaps point out some of the ways this paradox manifests itself in the early Buddhist perspective articulated in the Pali literature. There are many ways in which Buddhism obviously displays a sense of and even a good deal of deliberate missionary activity. It has the certainty of knowing the truth and proclaiming it to the world with a lion's roar. Yet there are also numerous examples of an apparent openness to dialogue. This openness is clearly displayed not only by the Buddha in ancient India, but even today by some of the activities of a foremost contemporary representative of Buddhism, the Dalai Lama. Furthermore, when we look closely at some of the texts of the Pali Tipitaka, we find interesting examples of Gotama seeking common ground in some of his debates with other sectarians. Perhaps these examples might well be put to good use in modern interreligious discussion. I even think there is something quite unique in the Buddhist tradition that may well serve as a solid basis for continuing dialogue: namely, a Buddhist standard of ascertaining truth and value in any teaching that lies largely outside its own dogma. Buddhist-Christian Studies 17 (1997). ? by University of Hawai'i Press. All rights reserved. 97 This content downloaded from 157.55.39.139 on Sat, 26 Nov 2016 04:17:22 UTC All use subject to http://about.jstor.org/terms

The lion's roar on the wheel-turning king: A response to Andrew Huxley's ?The Buddha and the Social Contract?

I imagine most journal articles, if not quite falling still-born from the press like Hume’s Treutise, don’t have much of a lifetime. One might say of their writers, as Samuel Beckett said of humanity, ‘They give birth astride a grave, the light gleams for an instant, then it’s night once more’. In ‘The Discourse on What is Primary’ (= DWP), published in vol. 21 pp. 301-93 of this journal, I struggled to bring forth what I thought was a reasonable argument for accepting the conventional attribution to the Aggaiikz Suttcz (= AS) of a Social Contract theory, given a specific analysis of what such a contract meant. Now Andrew Huxley plays the Beckettian midwife: ‘Astride of a grave and a difficult birth. Down in the hole, l~ge~ngly, the grave-digger puts on the forceps’. Well, I’ll let the idea die, but I want a gravestone on which is written, in flashing neon lights: No More Social Contract Talk!

Echoes from the Gorge; Percussion Quartet (1989)

In many ways, Chou Wen-chung's percussion quartet Echoes from Gorge serves as paradigm of music in latter half of twentieth century, in which element of has been elevated to position of eminence. This view of sound, revealed in Edgard Varese's use of term organized sound in preference to has been explained by Chou himself as a modern Western parallel of pervasive Chinese concept: that each single tone musical entity in itself, that musical meaning lies intrinsically in themselves, and that this concept is manifest in great emphasis placed on production and control of tones, which often involves an elaborate vocabulary of articulations, modifications in timbre, inflections in pitch, fluctuations in intensity, vibratos, and tremolos (Chou Wen-chung, Concepts and Twentieth-Century Western Composers, The Musical Quarterly 57 [1971]: 214, 216). This concern for the production and control of tones readily apparent in score to Echoes from Gorge. Seventy-two instruments are distributed evenly among four players and grouped by timbral or articulatory characteristics into families: lignophones, for example, claves, wood blocks, castanets, and temple blocks; metallophones, featuring Asian cup bells and Chinese cymbals that impart distinct oriental flavor; membranophones, such as bongos, timbales, tom-toms, and bass drums; and instruments capable of multiple articulations, such as snare and parade drums. Instruments are also categorized by characteristics of tessitura (high and low sounds), sonority, and pitch (undulating and sliding, former produced by large metal sheet and latter by lion's roar). Chou stipulates use of ten specific playing areas, from edges or rims of instruments to their centers, and twenty-five implements in addition to fingers. Fluctuations in intensity of are controlled through notation of subtle gradations in dynamic levels, at times on note-by-note basis. The coordination of multiple playing areas, number of implements, and fluctuating dynamic levels pose significant challenge for percussionist. For example, one player required to strike large gong fortissimo near its rim with hard yarn mallet in right hand, while left hand simultaneously executes mezzo-forte stroke at center with wood beater. The titles of twelve short sections of this twenty-minute work evoke an orientally inspired imagery: Raindrops on Bamboo Leaves, Shadows in Ravine, Droplets Down Rocks. Some sections are devoted to instruments of one family - metallophones in Clear Moon, membra-nophones in Drifting Clouds; others are distinguished by textural characteristics sustained, rolled sounds in Peaks and Cascades and very dense fabric in Sonorous Stones. The rhythmic structure not based on meter, but on permutations of six rhythmic modes derived from permutations of durational ratios of 3:2:1. An expressive performance of Chou's Echoes from Gorge requires consummate musicianship and ensemble playing of highest order. This literature that makes available to percussion ensemble an opportunity for musical expression previously found only in long established chamber repertory written for instruments of string, woodwind, and brass families. Wolfgang Rihm has an extensive list of works to his credit, embracing chamber music, instrumental pieces, vocal and choral works, chamber operas, pieces for music theater, and orchestral music. He has been particularly inclined to write for orchestras of Mahlerian proportions. Percussion has played prominent roles in many of these works. Rihm's Stuck for three percussionists, short theatrical event. It was written in 1988-89, product of same approximate period as his major work for musical theater, Die Eroberung von Mexico. Each of three performers in Stuck are limited to single instrument: bongo, suspended cymbal, and wood block. …

Mutual Transformation: An Answer to a Religious Question

I want to share my life's koan with you: What is the sound of liberating truth? Perhaps one might answer, The rumble of the stone rolled from Jesus' tomb as God's Anointed One is resurrected from the dead. Or another might say, It is the formal, but celebrative, announcement by priest or minister, This is the body of Christ given for you for the remission of sin. Or it is the repetition of a carefully intoned mantra, like Gate, gate, pdragata, p2rasatmgate, bodhi svaha. Or it is a joyful, reverential murmur of thanksgiving, Namu Amida Butsu. Or the Lion's roar of silence!

On the generation of magnetosheath lion roars

A theoretical model is proposed to discuss the electron dynamics associated with the mirror waves and their effects on the generation of the observed lion roars in the magnetosheath. It is pointed out that the usual double‐adiabatic theory of hydromagnetics is not applicable to the electrons in mirror waves. Although the electron magnetic moment is conserved, the energy of each electron in the mirror waves is expected to be constant (because of the high electron speed along the magnetic field). Assuming an initial electron temperature anisotropy, we can show that in the low field region the electron temperature and thermal anisotropy are higher than the initial values, whereas in the high field region the electron temperature and anisotropy are lower. This point can lead to a theoretical explanation of the important features of the observed lion roars. The present discussion complements the existing theories in the literature.

FILM REVIEWS

Sherpa. 1984. Produced and directed by Robert Godfrey.The Lion's Roar. 1985. Produced by Kenneth H. Green and directed by Mark R. Elliott.

Magnetosheath whistler turbulence

Magnetic field short‐period fluctuations δB are observed throughout the earth's magnetosheath. We report a study of these fluctuations with frequencies 20 < f < 1000 Hz in which the turbulence has a broadband spectrum δB²(f) varying approximately as f−α, where α ∼ 4±0.5, or consists of a narrowband intermediate frequency peak superimposed on the broadband spectrum. The spectrum is interpreted as due to whistler turbulence in both cases. The broadband fluctuations may arise from the cascade of spectral power from lower‐frequency (∼0.01 Hz) magnetohydrodynamic modes, while the narrowband peak corresponds to short‐period lion roar bursts. The usual whistler cutoff as f approaches fge, the electron gyrofrequency, is observed, as well as the polarization of the wave amplitudes perpendicular to the static magnetic field. The frequency of occurrence of whistler turbulence maximizes in the inner regions of the sunward magnetosheath, apparently associated with compressional modes in MHD fluctuations which tend to occur preferentially in the same region. The distribution of fluctuation amplitudes at 200 Hz suggests a tendency for the greatest whistler mode intensities to occur near the magnetopause, a result which contrasts with the intensity distribution of 1‐kHz electrostatic waves, which tends to maximize at the bow shock. These two intensity distributions are thus indicative of the different wave‐particle interactions occurring at the inner and outer boundaries of the magnetosheath. The mapping of the magnetosheath in space by the occurrence of whistler turbulence indicates whistlers are at least quasi‐trapped in the magnetosheath.

Long duration lion roars associated with quasi‐perpendicular bow shocks

A statistical study of the plasma waves known as lion roars shows that long duration lion roars (≳5 min) are often detected immediately behind or in the nearby downstream region of subsolar quasi‐perpendicular bow shocks. The long duration lion roars (LDLR) are associated with relatively ordered magnetosheath conditions as indicated by lower‐than‐normal magnetic field variances and higher‐than‐normal magnetic field intensities. These statistical results suggest that the relatively ordered downstream conditions associated with quasi‐perpendicular bow shocks are conducive to nearly continuous lion roar emissions. The LDLR exhibit field‐aligned propagation, as indicated by wave fluctuation amplitudes that minimize in directions parallel to the magnetic field. The distribution of LDLR frequencies f with respect to the electron gyrofrequency fge peaks at f/fge ≃ 0.25. The propagation direction and frequency ratio is consistent with previous identification of lion roars as whistler waves. By using the whistler dispersion relation and assuming field‐aligned propagation, magnetosheath plasma densities during the occurrence of LDLR can be calculated. The distribution of densities thus determined is consistent with the enhanced plasma densities of the flow downstream of quasi‐perpendicular bow shocks. The source of LDLR has not been determined; however, instabilities related to temperature anisotropy in thermal or beam electrons are possible candidates.

Stability analysis of magnetosheath lion roars

Whistler mode wave emissions in the magnetosheath, known as lion roars, are thought to be generated by an electron cyclotron instability. Using reported satellite data we model a magnetosheath medium where lion roars emissions occurred and we study the character, absolute or convective, of the associated electron cyclotron instability. We use a linear hot plasma dispersion equation for parallel and oblique propagation to the static magnetic field and apply Derfler's frequency cusp criterion to discriminate between absolute and convective instability. Our results show that an absolute instability is compatible with experimental data. From the linear temporal growth rate we extrapolate the saturated wave magnetic field and find a good agreement with the measurements.

Lion roars and nonoscillatory drift mirror waves in the magnetosheath

A complete set of ISEE plasma wave, plasma, and field data are used to identify the plasma instability responsible for the generation of extremely low frequency (ELF) electromagnetic lion roars. Lion roars detected close to the magnetopause are generated by the cyclotron instability of anisotropic (T⊥−/T∥− ≃ 1.2) thermal electrons when the local plasma critical energy, EM = B²/8πN, falls to values (EM ∼ 10–30 eV) close to or below the electron thermal energy, 25 eV, as a result of decreases in B. A companion theoretical paper, Thorne and Tsurutani (1981), demonstrates that the convective growth rates of lion roars under these conditions is greater than 100 dB RE−1. The lion roars are terminated by increases in the ambient magnetic field magnitude and consequential increases in EM to values greater than 100 eV. Because there are few resonant particles at these high energies, the growth rate decreases by 3 orders of magnitude and measurable growth ceases. The value of the absolute upper limit of the frequency of unstable waves predicted by theory, ωmax = A−Ω−/(A− + 1), is compared with observations. The predictions and observations are found to be in general, but not exact, agreement. Several possible explanations are explored. The quasi‐periodic, ∼20‐s magnetic and plasma oscillations which cause the variations in EM and hence alternately drive the cyclotron waves unstable and then stable are also investigated. The plasma and field pressures are shown to be out of phase, while the total pressure (electron + ion + field) remains relatively constant. Most of the pressure is associated with the particle thermal motion. The large 2∶1 variations in field strength cause large oscillations in β (8πP/B²), from β = 1–2 at field maximum to β = 10–25 at field minimum. Analysis of the high‐resolution magnetic fields at the two closely separated spacecraft, ISEE 1 and 2, rule out the possibility that these field and plasma oscillations could be due to magnetopause motion. Cross‐correlation analyses of the magnetic fields at the two spacecraft and the time delays for maximum correlation are shown to be consistent with the magnetic structures being quasi‐static in nature. The temporal variations of the plasma and fields are due to spatial structures convecting past the spacecraft at the magnetosheath flow speed. The quasi‐periodic structures are ∼20 proton gyroradii in scale in the plasma rest frame. Magnetic structures with similar scale lengths are also shown to exist in the magnetosheaths of Jupiter and Saturn (Pioneer 11 data). The results are consistent with the interpretation that these magnetohydrodynamic structures are nonoscillatory ‘waves’ generated by the drift mirror instability. The condition for instability, β⊥/β∥> 1 + (1/β⊥), is met for the cases studied in this paper. The electron and ion instabilities are intimately coupled. The generation of high β (>10), low critical energy (EM = 10–30 eV) regions by the drift mirror instability leads to the electrons becoming cyclotron unstable. The consequential whistler mode lion roars can then be ducted by the enhanced‐density, low‐field regions. Thus lion roar durations may not represent the propagation time for an electromagnetic wave packet travelling at the group velocity, but may correspond to the convection of a magnetosheath duct (drift mirror wave) past the spacecraft. The cyclotron and drift mirror instabilities occurring in the magnetosheath are natural relaxation processes that reduce the plasma pressure anisotropies created by preferential heating of the solar wind plasma as it passes through the bow shock and the further compression that takes place as the plasma and fields approach the near‐subsolar magnetopause. One consequence of the onset of the instabilities and isotropization of the plasma is the enhanced expulsion of the plasma along field lines toward the flanks of the magnetosheath. It remains to be determined if this mechanism is a general process of ‘plasma removal’ from planetary magnetosheaths. Furthermore, the presence of nonoscillatory drift mirror waves and the convection of these structures to the magnetopause may have important consequences for magnetic merging. The alternating high and low β regions and the (T⊥ > T∥) plasma temperature anisotropies may lead to patchy, sporadic reconnection.

Plasma waves near the magnetopause

Plasma waves associated with the magnetopause, from the magnetosheath to the outer magnetosphere, are examined with an emphasis on high time resolution data and the comparison between measurements by using different antenna systems. An early ISEE crossing of the magnetopause region, including passage through two well‐defined flux transfer events, the magnetopause current layer, and boundary layer plasma, is studied in detail. The waves in these regions are compared and contrasted with the waves in the adjoining magnetosheath and outer magnetosphere. Four types of plasma wave emissions are characteristic of the nominal magnetosheath: (1) a very low frequency continuum, (2) short wavelength spikes, (3) ‘festoon‐shaped’ emissions below about 2 kHz, and (4) ‘lion roars.’ The latter two emissions are well correlated with ultra‐low frequency magnetic field fluctuations. The dominant plasma wave features during flux transfer events are (1) an intense low‐frequency continuum, which includes a substantial electromagnetic component, (2) a dramatic increase in the frequency of occurrence of the spikes, (3) quasi‐periodic electron cyclotron harmonics correlated with ∼1‐Hz magnetic field fluctuations, and (4) enhanced electron plasma oscillations. The plasma wave characteristics in the current layer and in the boundary layer are quite similar to the features in the flux transfer events. Upon entry into the outer magnetosphere, the plasma wave spectra are dominated by intense electromagnetic chorus bursts and electrostatic (n + 1/2)fg− emissions. Wavelength determinations made by comparing the various antenna responses and polarization measurements for the different waves are also presented.

The generation mechanism for magnetosheath lion roars

The origin of lion roars, intense electromagnetic whistler-mode waves which occur throughout the magnetosheath, is investigated based on particle and field data obtained on the ISEE satellites. Analysis of the measured magnetic fields, plasma densities and plasma wave intensities during periods of lion roar emission reveals the lion roar bursts to be correlated with decreases in magnetic field intensity, while the plasma density exhibits a strong anticorrelation with the magnetic field variability during the bursts and the total plasma pressure remains essentially constant. Results indicate that the waves can originate by the cyclotron resonant instability with anisotropic magnetosheath electrons whenever the magnetic energy per particle falls to values comparable with the electron thermal energy. Variations in the magnetic energy appear to be associated with the hydromagnetic mirror instability which in turn is excited by a pressure anisotropy in the magnetosheath ion population.

Americanized Comic Braggarts

Previous articleNext article No AccessAmericanized Comic BraggartsWalter BlairWalter Blair Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Critical Inquiry Volume 4, Number 2Winter, 1977 Article DOIhttps://doi.org/10.1086/447940 Views: 5Total views on this site Copyright 1977 The University of ChicagoPDF download Crossref reports no articles citing this article.

Reply to Dina Paul's Review of "The Lion's Roar of Queen Srimala"

Reply to Dina Paul's Review of "The Lion's Roar of Queen Srimala"

The Lion's Roar of Queen Śrīmālā. Translated by Alex Wayman and Hideko Wayman. Columbia University Press: New York and London, 1974. Pp. xv, 142. No price given.

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