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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for electron excitation of type III radio burst emission (1972)
    Springer
    Solar physics 26 (1972), S. 468-473 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Type III radio bursts observed at kilometric wavelengths (≲ 0.35 MHz) by the OGO-5 spacecraft are compared with 〉 45 keV solar electron events observed near 1 AU by the IMP-5 and Explorer 35 spacecraft for the period March 1968–November 1969. Fifty-six distinct type III bursts extending to ≲ 0.35 MHz (≳ 50 R ⊙ equivalent height above the photosphere) were observed above the threshold of the OGO-5 detector; all but two were associated with solar flares. Twenty-six of the bursts were followed ≲ 40 min later by 〉 45 keV solar electron events observed at 1 AU. All of these 26 bursts were identified with flares located west of W 09 solar longitude. Of the bursts not associated with electron events only three were identified with flares west of W 09, 18 were located east of W 09 and 7 occurred during times when electron events would be obscured by high background particle fluxes. Thus almost all type III bursts from the western half of the solar disk observed by OGO-5 above a detection flux density threshold of the order of 10−13 Wm−2 Hz−1 at 0.35 MHz are followed by 〉 45 keV electrons at 1 AU with a maximum flux of ≳ 10 cm−2 s−1 ster−1. If particle propagation effects are taken into account it is possible to account for lack of electron events with the type III bursts from flares east of the central meridian. We conclude that streams of ≈ 10–100 keV electrons are the exciting agent for type III bursts and that these same electrons escape into the interplanetary medium where they are observed at 1 AU. The total number of 〉 45 keV electrons emitted in association with a strong kilometer wavelength type III burst is estimated to be ⩾ 5 × 1032.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165288
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  • 2
    Electronic Resource
    Electronic Resource
    The emission and propagation of ∼40keV solar flare electrons (1970)
    Springer
    Solar physics 15 (1970), S. 453-478 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electrons of ~ 40 keV energy observed at 1 AU are used as tracers to map the emission structure of a large active region, McMath plage 8905, which crossed the visible disk in July–August, 1967. The acceleration of 10–100 keV electrons is found to be a property of active regions with a certain stage of development, and is signaled by the emission of ≳ 20 keV X-rays. The emission of electrons into the interplanetary medium may be separate from the acceleration of the electrons. Type III radio emission at long wavelengths appears to indicate the escape of the electrons into the interplanetary medium. The subsequent electron propagation in the interplanetary medium is essentially scatter-free, and the profile of the electron appears to be determined predominantly by transport/storage processes in the solar corona. The emission structure for active region McMath plage 8905 consists of (1) an open cone of ~ 70° extent in solar longitude where electrons have direct access to interplanetary field lines; (2) a cone of propagation of 100° width in solar longitude, surrounding and including the open cone in which impulsive electron events are observed; and (3) an overall ~ 200° extent of solar longitude over which low, non-impulsive fluxes from the active region are observed. A model is presented to account for the observed structure. This type of emission structure may be present in other electron-active regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151852
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  • 3
    Electronic Resource
    Electronic Resource
    Location of the electron acceleration region in solar flares (1972)
    Springer
    Solar physics 23 (1972), S. 457-466 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of impulsive solar flare X-rays ≳ 10 keV by the OGO-5 satellite and the measurements of energetic solar electrons made with the Explorer-35 and Explorer-41 (IMP-5) satellites during the period March 1968–September 1969 have been analyzed in order to determine the ion density in the X-ray source region as well as the location of the electron acceleration region in the solar atmosphere. If we assume that the efficiency of escape of the accelerated electrons into interplanetary space is ∼ 10−3, the observations are found to be consistent with the following interpretation: (i) the ion density in the X-ray source region varies from event to event and lies between 109 and 1011 ions cm−3 for those events in which the impulsive X-ray emission could be detected; (ii) for those events in which no impulsive emission was detected above threshold, the ion density in the X-ray source was 〈 109 ions cm−3; (iii) at least in some small solar flares the region where the electrons are accelerated during the flash phase is located in the lower corona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148108
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  • 4
    Electronic Resource
    Electronic Resource
    10–100 keV electron acceleration and emission from solar flares (1971)
    Springer
    Solar physics 17 (1971), S. 412-435 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present an analysis of spacecraft observations of non-thermal X-rays and escaping electrons for 5 selected small solar flares in 1967. OSO-3 multi-channel energetic X-ray measurements during the non-thermal component of the solar flare X-ray bursts are used to derive the parent electron spectrum and emission measure. IMP-4 and Explorer-35 observations of 〉 22 keV and 〉 45 keV electrons in the interplanetary medium after the flares provide a measure of the total number and spectrum of the escaping particles. The ratio of electron energy loss due to collisions with the ambient solar flare gas to the energy loss due to bremsstrahlung is derived. The total energy loss due to collisions is then computed from the integrated bremsstrahlung energy loss during the non-thermal X-ray burst. For 〉 22 keV flare electrons the total energy loss due to collisions is found to be ∼ 104 times greater than the bremsstrahlung energy loss and ∼ 102 times greater than the energy loss due to escaping electrons. Therefore the escape of electrons into the interplanetary medium is a negligible energetic electron loss mechanism and cannot be a substantial factor in the observed decay of the non-thermal X-ray burst for these solar flares. We present a picture of electron acceleration, energy loss and escape consistent with previous observations of an inverse relationship between rise and decay times of the non-thermal X-ray burst and X-ray energy. In this picture the acceleration of electrons occurs throughout the 10–100 sec duration of the non-thermal X-ray burst and determines the time profile of the burst. The average energy of the accelerated electrons first rises and then falls through the burst. Collisions with the ambient gas provide the dominant energetic electron loss mechanism with a loss time of ≲ 1 sec. This picture is consistent with the ratio of the total number of energetic electrons accelerated in the flare to the maximum instantaneous number of electrons in the flare region. Typical values for the parameters derived from the X-ray and electron observations are: total energy in 〉 22 keV electrons ≈ total energy lost by collisions = ∼ 1028–29 erg, total number of electrons accelerated above 22 keV = ∼ 1036, total energy lost by non-thermal bremsstrahlung = ∼ 1024erg, total energy lost in escaping 〉 22 keV electrons = ∼ 1026erg, total number of 〉 22 keV electrons escaping = ∼ 1033–34. The total energy in electrons accelerated above 22 keV is comparable to the energy in the optical or quasi-thermal flare, implying a flare mechanism with particle acceleration as one of the dominant modes of energy dissipation. The overall efficiency for electron escape into the interplanetary medium is ∼ 0.1–1% for these flares, and the spectrum of escaping electrons is found to be substantially harder than the X-ray producing electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150045
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for thin-target X-ray emission in a small solar flare on 26 February 1972 (1973)
    Springer
    Solar physics 32 (1973), S. 459-468 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We compare solar X-ray observations from the UCSD experiment aboard OSO-7 with high resolution energetic electron observations from the UCAL experiment on IMP-6 for a small solar flare on 26 February 1972. A proportional counter and NaI scintillator covered the X-ray energy range 5–300 keV, while a semiconductor detector telescope covered electrons from 18 to ∼ 400 keV. A series of four non-thermal X-ray spikes were observed from 1805 to 1814 UT with average spectrum dJ/d (hv) ∼ (hv)−4.0 over the 14–64 keV range. The energetic electrons were observed at 1 AU beginning 1840 UT with a spectrum dJ/dE ∼ E −3.1. If the electrons which produce the X-ray emission and those observed at 1 AU are assumed to originate in a common source, then these observations are consistent with thin target X-ray production at the Sun and inconsistent with thick target production. Under a model consistent with the observed soft X-ray emission, we obtain quantitative estimates of the total energy, total number, escape efficiency, and energy lost in collisions for the energetic electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154958
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  • 6
    Electronic Resource
    Electronic Resource
    Non-relativistic solar electrons (1974)
    Springer
    Space science reviews 16 (1974), S. 189-256 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This review summarizes both the direct spacecraft observations of non-relativistic solar electrons, and observations of the X-ray and radio emission generated by these particles at the Sun and in the interplanetary medium. These observations bear on three physical processes basic to energetic particle phenomena: (1) the acceleration of particles in tenuous plasmas; (2) the propagation of energetic charged particles in a disordered magnetic field, and (3) the interaction of energetic charged particles with tenuous plasmas to produce electromagnetic radiation. Because these electrons are frequently accelerated and emitted by the Sun, mostly in small and relatively simple flares, it is possible to define a detailed physical picture of these processes. In many small solar flares non-relativistic electrons accelerated during flash phase constitute the bulk of the total flare energy. Thus the basic flare mechanism in these flares essentially converts the available flare energy into fast electrons. Non-relativistic electrons exhibit a wide variety of propagation modes in the interplanetary medium, ranging from diffusive to essentially scatter-free. This variability in the propagation may be explained in terms of the distribution of interplanetary magnetic field fluctuations. Type III solar radio burst emission is generated by these electrons as they travel out to 1 AU and beyond. Recent in situ observations of these electrons at 1 AU, accompanied by simultaneous observations of the low frequency radio emission generated by them at 1 AU provide quantitative information on the plasma processes involved in the generation of type III bursts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240886
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  • 7
    Electronic Resource
    Electronic Resource
    The emission and propagation of ∼ 40keV solar flare electrons (1970)
    Springer
    Solar physics 12 (1970), S. 266-303 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of prompt ∼ 40 keV solar flare electron events by the IMP series of satellites in the period August, 1966 to December, 1967 are tabulated along with prompt energetic solar proton events in the period 1964–1967. The interrelationship of the various types of energetic particle emission by the sun, including relativistic energy electrons reported by Cline and McDonald (1968) are investigated. Relativistic energy electron emission is found to occur only during proton events. The solar optical, radio and X-ray emission associated with these various energetic particle emissions as well as the propagation characteristics of each particle species are examined in order to study the particle acceleration and emission mechanisms in a solar flare. Evidence is presented for two separate particle acceleration and/or emission mechanisms, one of which produces ∼ 40 keV electrons and the other of which produces solar proton and possibly relativistic energy electrons. It is found that solar flares can be divided into three categories depending on their energetic particle emission: (1) small flares with no accompanying energetic phenomena either in particles, radio or X-ray emission; (2) small flares which produce low energy electrons and which are accompanied by type III and microwave radio bursts and energetic (∼ 20 keV) X-ray bursts; and (3) major solar flare eruptions characterized by energetic solar proton production and type II and IV radio bursts and accompanied by intense microwave and X-ray emission and relativistic energy electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227122
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  • 8
    Electronic Resource
    Electronic Resource
    Cyclic operation of reaction systems: Effects of heat and mass transfer resistance (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 818-825 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No. Abstract.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170410
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  • 9
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    Energy Loss of Low Energy Nuclei in Silicon Surface Barrier Detectors (1973)
    American Institute of Physics
    Details
    Publication Date: 1973-10-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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  • 10
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    Location of the electron acceleration region in solar flares (1972)
    Springer
    Details
    Publication Date: 1972-04-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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