SOLAR ENERGETIC ION AND ELECTRON LIMITS FROM HIREGS OBSERVATIONS     

Feffer  P. T.  Lin  R. P.  Slassi-Sennou  S.  McBride  S.  Primbsch  J. H.  Zimmer  G.  Pelling  R. M.  Pehl  R.  Madden  N.  Malone  D.  Cork  C.  Luke  P.  Vedrenne  G.  Cotin  F. 《Solar physics》1997,171(2):419-445

The HIgh-REsolution Gamma-ray and hard X-ray Spectrometer (HIREGS) consists of an actively shielded array of twelve liquid-nitrogen-cooled germanium detectors designed to provide unprecedented spectral resolution and narrow-line sensitivity for solar gamma-ray line observations. Two long-duration, circumpolar balloon flights of HIREGS in Antarctica (10–24 January, 1992 and 31 December, 1992–10 January, 1993) provided 90.9 and 20.4 hours of solar observations, respectively. During the observations, eleven soft X-ray bursts at C levels and above (largest M1.7) occurred, and three small solar hard X-ray bursts were detected by the Compton Gamma-Ray Observatory. HIREGS detected a significant increase above 30 keV in one. No solar gamma-ray line emission was detected. Limits on the 2.223-MeV line and the hard X-ray emission are used to estimate the relative contribution of protons and electrons to the energy in flares, and to coronal heating. For the 2.223-MeV line, the upper limit fluence is 0.8 ph cm^-2 in the flares, and the upper limit flux is 1.8 × 10^-4 ph s^-1 cm^-2 in the absence of flares. These limits imply that 6 × 10³⁰ (2) protons above 30 MeV were accelerated in the flares, assuming standard photospheric abundances and a thick target model. The total energy contained in the accelerated protons >30 MeV is 4 × 10²⁶ ergs, but this limit can be more than 10³⁰ ergs if the spectrum extends down to 1 MeV. The upper limit on the total energy in accelerated electrons during the observed flares can also exceed 10³⁰ ergs if the spectrum goes down to 7 keV. Quiet-Sun observations indicate that 10²⁶erg s^-1 are deposited by energetic protons >1 MeV, well below the10²⁷ –10²⁸ erg s^-1 required for coronal heating, while <3 × 10²⁷ erg s^-1 are deposited by energetic electrons, which does not exclude the possibility of coronal heating by quiet-time accelerated electrons. The quiet-Sun observations also suggest that if protons stored in the corona are to supply the energy for flares, as suggested by Elliot (1964), the proton spectrum must extend down to at least 2 MeV. However, collisional losses at typical coronal-loop densities prevent those low-energy protons from being stored for 10⁴ s. It therefore seems unlikely that the energy for flares could come from energetic protons stored over long periods.  相似文献   

Flare fragmentation and type III productivity in the 1980 June 27 flare     

M. J. Aschwanden  A. O. Benz  R. A. Schwartz  R. P. Lin  R. M. Pelling  W. Stehling 《Solar physics》1990,130(1-2):39-55

We present observations of the solar flare on 1980 June 27, 16:14–16:33 UT, which was observed by a balloon-borne 300 cm² phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200–400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence, with a coefficient of 7.6 × 10²⁷ photons keV^–1 per type III burst at 20 keV. The occurrence of 10 type III bursts per second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile.The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.Universities Space Research Associates.ST Systems Corporation.  相似文献   

A long-duration balloon payload for hard X-ray and gamma-ray observations of the sun     

Lin  R. P.  Curtis  D. W.  Primbsch  J. H.  Harvey  P. R.  Levedahl  W. K.  Smith  D. M.  Pelling  R. M.  Duttweiler  F.  Hurley  K. 《Solar physics》1987,113(1-2):333-345

We describe a balloon payload designed to study the processes of energy release, particle acceleration, and heating of the active corona, in hard X-ray microflares and normal flares. An array of liquid nitrogen-cooled germanium detectors together with large area phoswich scintillation detectors provide the highest sensitivity (∼500 cm²) and energy resolution (≤0.7 keV) ever achieved for solar hard X-ray (∼15–600 keV) measurements. These detectors were flown in February 1987 from Australia on a long duration RAdiation COntrolled balloON (RACOON) flight (LDBF) which provided 12 days of observations before cutdown in Brazil. The payload includes solar cells for power, pointing and navigation sensors, a microprocessor controlled data system with VCR tape storage, and transmitters for GOES and ARGOS spacecraft. This successful flight illustrates the potential of LDBF's for solar flare studies.

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Understanding adaptation: What can social capital offer assessments of adaptive capacity?   总被引：7，自引：3，他引：7  

Mark Pelling  Chris High 《Global Environmental Change》2005,15(4):308-319

The burgeoning interest in social capital within the climate change community represents a welcome move towards a concern for the behavioural elements of adaptive action and capacity. In this paper the case is put forward for a critical engagement with social capital. There is need for an open debate on the conceptual and analytical traps and opportunities that social capital presents. The paper contrasts three schools of thought on social capital and uses a social capital lens to map out current and future areas for research on adaptation to climate change. It identifies opportunities for using social capital to research adaptive capacity and action within communities of place and communities of practice.  相似文献