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1.
On the basis of solar flare forecasts, balloon flights were made from Hyderabad, India (vertical geomagnetic threshold rigidity of 16.9 GV), to detect the possible emission of high energy neutrons during solar flares. The detector comprised of a central plastic scintillator, completely surrounded by an anticoincidence plastic scintillator shield. The instrument responds to neutrons of about 15–150 MeV and gamma rays of about 5–30 MeV with about the same efficiency. The detector was flown to an atmospheric depth of 25 g cm-2 on February 26, 1969; while the balloon was at ceiling a flare of importance 2B and one of 1N occurred. No perceptible flare associated increase in the counting rate was observed. Using the observed counting rates, an upper limit of 1.2 × 10-2 neutrons cm-2 sec-1 is obtained for the first time for a flare of importance 2B for neutrons of energy 15–150 MeV. The corresponding upper limit for gamma rays of energy 5–30 MeV is found to be 10-2 photons cm-2 sec-1. The neutron flux limits are compared with the recent calculations of Lingenfelter.  相似文献   

2.
An experiment made with a baloon-borne large volume (16×16×24 cm3) omnidirectional plastic scintillator sensitive to high-energy -radiation is described. Two flights were carried out on 25 November, 1973 and 24 February, 1978 at high geomagnetic cut-off rigidities. For an omnidirectional detector and for energies greater than several MeV, most of the detected photons are secondary -rays produced through interactions of the charged cosmic rays with the atmosphere. To unfold the observed pulse height spectrum and obtain the incident -ray spectrum, the detector response function is calculated numerically. By using this response function a differential flux dJ/dE=(0.33±0.1)E –1.2±0.2 photons cm–2 s–1 MeV–1 averaged over all zenith angles, is estimated for the atmospheric -radiation, at 5 g cm–2, in the 10–100 MeV energy range. This result is compared with other observations made with different types of detectors and at different geomagnetic latitudes.Members of the Carrera del Investigador Cientifico y Tecnológico del Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) from Argentina.  相似文献   

3.
On December 15, 1978, an omnidirectional gamma-ray detector for the energy range 0.3 to 10 MeV was flown from São José dos Campos, Brazil at a latitude of about -23°. Around noon time, when the Sun was in the field of view of the detector, various solar flares of importance SN and SF occurred. The 2.2 MeV line flux was monitored during this time. A statistically significant line flux of (1.55 ± 0.50) × 10–2 photons cm–2 s–1 and (9.97 ± 4.85) × 10–3 photons cm–2 s–1 was observed within a few minutes of t maxima of the two long-duration SN flares respectively, whereas during SF flares only upper limits were obtained.  相似文献   

4.
We have analyzed the continuum emission of limb spectra acquired by the Cassini/CIRS infrared spectrometer in order to derive information on haze extinction in the 3–0.02 mbar range (∼150–350 km). We focused on the 600–1420 cm−1 spectral range and studied nine different limb observations acquired during the Cassini nominal mission at 55°S, 20°S, 5°N, 30°N, 40°N, 45°N, 55°N, 70°N and 80°N. By means of an inversion algorithm solving the radiative transfer equation, we derived the vertical profiles of haze extinction coefficients from 17 spectral ranges of 20-cm−1 wide at each of the nine latitudes. At a given latitude, all extinction vertical profiles retrieved from various spectral intervals between 600 and 1120 cm−1 display similar vertical slopes implying similar spectral characteristics of the material at all altitudes. We calculated a mean vertical extinction profile for each latitude and derived the ratio of the haze scale height (Hhaze) to the pressure scale height (Hgas) as a function of altitude. We inferred Hhaze/Hgas values varying from 0.8 to 2.4. The aerosol scale height varies with altitude and also with latitude. Overall, the haze extinction does not show strong latitudinal variations but, at 1 mbar, an increase by a factor of 1.5 is observed at the north pole compared to high southern latitudes. The vertical optical depths at 0.5 and 1.7 mbar increase from 55°S to 5°N, remain constant between 5°N and 30°N and display little variation at higher latitudes, except the presence of a slight local maximum at 45°N. The spectral dependence of the haze vertical optical depth is uniform with latitude and displays three main spectral features centered at 630 cm−1, 745 cm−1 and 1390 cm−1, the latter showing a wide tail extending down to ∼1000 cm−1. From 600 to 750 cm−1, the optical depth increases by a factor of 3 in contrast with the absorbance of laboratory tholins, which is generally constant. We derived the mass mixing ratio profiles of haze at the nine latitudes. Below the 0.4-mbar level all mass mixing ratio profiles increase with height. Above this pressure level, the profiles at 40°N, 45°N, 55°N, at the edge of the polar vortex, display a decrease-with-height whereas the other profiles increase. The global increase with height of the haze mass mixing ratio suggest a source at high altitudes and a sink at low altitudes. An enrichment of haze is observed at 0.1 mbar around the equator, which could be due to a more efficient photochemistry because of the strongest insolation there or an accumulation of haze due to a balance between sedimentation and upward vertical drag.  相似文献   

5.
The Cassini Composite Infrared Spectrometer (CIRS) has been used to derive the vertical and meridional variation of temperature and phosphine (PH3) abundance in Saturn's upper troposphere. PH3 has a significant effect on the measured radiances in the thermal infrared and between May 2004 and September 2005 CIRS recorded thousands of spectra in both the far (10-600 cm−1) and mid (600-1400 cm−1) infrared, at a variety of latitudes covering the southern hemisphere. Low spectral resolution (15 cm−1) data has been used to constrain the temperature structure of the troposphere between 100 and 500 mbar. The vertical distributions of phosphine and ammonia were retrieved from far-infrared spectra at the highest spectral resolution (0.5 cm−1), and lower resolution (2.5 cm−1) mid-infrared data were used to map the meridional variation in the abundance of phosphine in the 250-500 mbar range. Temperature variations at the 250 mbar level are shown to occur on the same scale as the prograde and retrograde jets in Saturn's atmosphere [Porco, C.C., and 34 colleagues, 2005. Science 307, 1243-1247]. The PH3 abundance at 250 mbar is found to be enhanced at the equator when compared with mid-latitudes. At mid latitudes we see anti-correlation between temperature and PH3 abundance at 250 mbar, phosphine being enhanced at 45° S and depleted at 25 and 55° S. The vertical distribution is markedly different polewards of 60-65° S, with depleted PH3 at 500 mbar but a slower decline in abundance with altitude when compared with the mid-latitudes. This variation is similar to the variations of cloud and aerosol parameters observed in the visible and near infrared, and may indicate the subsidence of tropospheric air at polar latitudes, coupled with a diminished sunlight penetration depth reducing the rate of PH3 photolysis in the polar region.  相似文献   

6.
Gamma-ray astronomy is devoted to study nuclear and elementary particle astrophysics and astronomical objects under extreme conditions of gravitational and electromagnetic forces, and temperature. Because signals from gamma rays below 1 TeV cannot be recorded on ground, observations from space are required. The photoelectric effect is dominant <100 keV, Compton scattering between 100 keV and 10 MeV, and electron–positron pair production at energies above 10 MeV. The sun and some gamma ray burst sources are the strongest gamma ray sources in the sky. For other sources, directionality is obtained by shielding / masks at low energies, by using the directional properties of the Compton effect, or of pair production at high energies. The power of angular resolution is low (fractions of a degree, depending on energy), but the gamma sky is not crowded and sometimes identification of sources is possible by time variation. The gamma ray astronomy time line lists Explorer XI in 1961, and the first discovery of gamma rays from the galactic plane with its successor OSO-3 in 1968. The first solar flare gamma ray lines were seen with OSO-7 in 1972. In the 1980’s, the Solar Maximum Mission observed a multitude of solar gamma ray phenomena for 9 years. Quite unexpectedly, gamma ray bursts were detected by the Vela-satellites in 1967. It was 30 years later, that the extragalactic nature of the gamma ray burst phenomenon was finally established by the Beppo–Sax satellite. Better telescopes were becoming available, by using spark chambers to record pair production at photon energies >30 MeV, and later by Compton telescopes for the 1–10 MeV range. In 1972, SAS-2 began to observe the Milky Way in high energy gamma rays, but, unfortunately, for a very brief observation time only due to a failure of tape recorders. COS-B from 1975 until 1982 with its wire spark chamber, and energy measurement by a total absorption counter, produced the first sky map, recording galactic continuum emission, mainly from interactions of cosmic rays with interstellar matter, and point sources (pulsars and unidentified objects). An integrated attempt at observing the gamma ray sky was launched with the Compton Observatory in 1991 which stayed in orbit for 9 years. This large shuttle-launched satellite carried a wire spark chamber “Energetic Gamma Ray Experiment Telescope” EGRET for energies >30 MeV which included a large Cesium Iodide crystal spectrometer, a “Compton Telescope” COMPTEL for the energy range 1–30 MeV, the gamma ray “Burst and Transient Source Experiment” BATSE, and the “Oriented Scintillation-Spectrometer Experiment” OSSE. The results from the “Compton Observatory” were further enlarged by the SIGMA mission, launched in 1989 with the aim to closely observe the galactic center in gamma rays, and INTEGRAL, launched in 2002. From these missions and their results, the major features of gamma ray astronomy are:
  • Diffuse emission, i.e. interactions of cosmic rays with matter, and matter–antimatter annihilation; it is found, “...that a matter–antimatter symmetric universe is empirically excluded....”
  • Nuclear lines, i.e. solar gamma rays, or lines from radioactive decay (nucleosynthesis), like the 1.809 MeV line of radioactive 26Al;
  • Localized sources, i.e. pulsars, active galactic nuclei, gamma ray burst sources (compact relativistic sources), and unidentified sources.
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    7.
    An additional electron flux at an energy above 100 MeV was observed in the experiments carried out with high-altitude balloons flown at geomagnetic latitudes 46° and 49°, in the upper layers of the atmosphere, on the days following magnetic perturbations.Its intensity, equal to 6 × 10–2 cm–2s–1 sr–1, decreased over 20–30 hours. The effect observed confirms the presence of high-energy electrons in the regions of the trapped radiation.  相似文献   

    8.
    The upper limit on the solar neutron flux from 1–20 MeV has been measured, by a neutron detector on the OGO-6 satellite, to be less than 5 × 10–2 n cm–2 s–1 at the 95% confidence level for several flares including two flares of importance 3B and a solar proton event of importance 3B. The measurements are consistent with the models proposed by Lingenfelter (1969) and by Lingenfelter and Ramaty (1967) for solar neutron production during solar flares. The implied upper limit on the flux of 2.2 MeV solar gamma rays is about the same as the 2.2 MeV flux observed by Chupp et al. (1973).  相似文献   

    9.
    A 3×3 NaI(T1) crystal-photomultiplier assembly with a 4 charged particle anticoincidence shield is used to determine the gamma ray spectrum in the energy region of about 100 keV to 8.5 MeV at a balloon altitude of 4.7 g cm–2 over Hyderabad, India (geomagnetic latitude 8°N). The atmospheric growth curves are used to obtain the contribution of the diffuse cosmic gamma ray flux in the above energy range. The cosmic photon flux thus deduced up to about 8.5 MeV is consistent with a continuation of the power law spectrum observed at energies between 20 and 200 keV with an index of –2.3, and hence contradicts the flattening trend observed in ERS-18 at an energy of a few MeV.Results presented at the IAU/COSPAR symposium No. 55 on X-and Gamma-Ray Astronomy Madrid, 11–13th May, 1972.  相似文献   

    10.
    The COS-B satellite for gamma-ray astronomy, launched on 7 August, 1975, features as part of the main instrument a 1.1 m2, 10 mm thick, plastic scintillator for the vetoing of charged particle events. This detector which has an average effective area of 360 cm2 for gamma rays in the interval 0.1 to 1 MeV has been instrumented to detect and record the temporal structure of cosmic gamma ray bursts.The instrument will be sensitive to gamma bursts down to 3% of the typical intensities measured by the Vela satellite system. The best time resolution achievable is 1.6 ms.The satellite will be placed in a 100 000 km eccentric orbit and with absolute timing accuracies of fractions of a millisecond achievable, a long base line is available for the triangulation of the source position, given comparable data from other satellites.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.  相似文献   

    11.
    In July 1994, the Shoemaker-Levy 9 (SL9) impacts introduced hydrogen cyanide (HCN) to Jupiter at a well confined latitude band around −44°, over a range of specific longitudes corresponding to each of the 21 fragments (Bézard et al. 1997, Icarus 125, 94-120). This newcomer to Jupiter's stratosphere traces jovian dynamics. HCN rapidly mixed with longitude, so that observations recorded later than several months after impact witnessed primarily the meridional transport of HCN north and south of the impact latitude band. We report spatially resolved spectroscopy of HCN emission 10 months and 6 years following the impacts. We detect a total mass of HCN in Jupiter's stratosphere of 1.5±0.7×1013 g in 1995 and 1.7±0.4×1013 g in 2000, comparable to that observed several days following the impacts (Bézard et al. 1997, Icarus 125, 94-120). In 1995, 10 months after impact, HCN spread to −30° and −65° latitude (half column masses), consistent with a horizontal eddy diffusion coefficient of Kyy=2-3×1010 cm2 s−1. Six years following impact HCN is observed in the northern hemisphere, while still being concentrated at 44° south latitude. Our meridional distribution of HCN suggests that mixing occurred rapidly north of the equator, with Kyy=2-5×1011 cm2 s−1, consistent with the findings of Moreno et al. (2003, Planet. Space Sci. 51, 591-611) and Lellouch et al. (2002, Icarus 159, 112-131). These inferred eddy diffusion coefficients for Jupiter's stratosphere at 0.1-0.5 mbar generally exceed those that characterize transport on Earth. The low abundance of HCN detected at high latitudes suggests that, like on Earth, polar regions are dynamically isolated from lower latitudes.  相似文献   

    12.
    During February, 1981 and June, 1982 the gamma-ray and the hard X-ray spectrometers on the Hinotori satellite observed four gamma-ray bursts on 28 February, 21 July, 1981, 26 February and 13 March, 1982. These gamma-ray bursts were simultaneously observed by other satellites. The time histories and energy spectra are shown for these gamma-ray bursts, and the burst sizes (erg cm–2) are estimated. Two possible source locations for the burst of 21 July, 1981 are roughly determined from arrival time delays between two pairs of satellites, PVO-Hinotori and ISEE-3-Hinotori. The weak gamma-ray line peak structure around 1.8 MeV was observed for the burst of 13 March, 1982. The line could be interpreted in terms of gravitationally redshifted neutron capture line at 2.22 MeV.  相似文献   

    13.
    Using the Hubble Space Telescope's Space Telescope Imaging Spectrograph we have obtained for the first time spatially resolved 2000-3000 Å spectra of Io's Prometheus plume and adjoining regions on Io's anti-jovian hemisphere in the latitude range 60° N-60° S, using a 0.1″ slit centered on Prometheus and tilted roughly 45° to the spin axis. The SO2 column density peaked at 1.25×1017 cm−2 near the equator, with an additional 5×1016 cm−2 enhancement over Prometheus corresponding to a model volcanic SO2 output of 105 kg s−1. Apart from the Prometheus peak, the SO2 column density dropped fairly smoothly away from the subsolar point, even over regions that included potential volcanic sources. At latitudes less than ±30°, the dropoff rate was consistent with control by vapor pressure equilibrium with surface frost with subsolar temperature 117.3±0.6 K, though SO2 abundance was higher than predicted by vapor pressure control at mid-latitudes, especially in the northern hemisphere. We conclude that, at least at low latitudes on the anti-jovian hemisphere where there are extensive deposits of optically-thick SO2 frost, the atmosphere is probably primarily supported by sublimation of surface frost. Although the 45° tilt of our slit prevents us from separating the dependence of atmospheric density on solar zenith angle from its dependence on latitude, the pattern is consistent with a sublimation atmosphere regardless of which parameter is the dominant control. The observed drop in gas abundance towards higher latitudes is consistent with the interpretation of previous Lyman alpha images of Io as indicating an atmosphere concentrated at low latitudes. Comparison with previous disk-resolved UV spectroscopy, Lyman-alpha images, and mid-infrared spectroscopy suggests that Io's atmosphere is denser and more widespread on the anti-jovian hemisphere than at other longitudes. SO2 gas temperatures were in the range of 150-250 K over the majority of the anti-jovian hemisphere, consistent with previous observations. SO was not definitively detected in our spectra, with upper limits to the SO/SO2 ratio in the range 1-10%, roughly consistent with previous observations. S2 gas was not seen anywhere, with an upper limit of 7.5×1014 cm−2 for the Prometheus plume, confirming that this plume is significantly poorer in S2 than the Pele plume (S2 /SO2<0.005, compared to 0.08-0.3 at Pele). In addition to the gas absorption signatures, we have observed continuum emission in the near ultraviolet (near 2800 Å) for the first time. The brightness of the observed emission was directly correlated with the SO2 abundance, strongly peaking in the equatorial region over Prometheus. Emission brightness was modestly anti-correlated with the jovian magnetic latitude, decreasing when Io intersected the torus centrifugal equator.  相似文献   

    14.
    The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of 7% at 662 keV) every 16.38 s over the energy range 0.3–9 MeV. Higher time resolution (2 s) is available in three windows between 3.5 and 6.5 MeV to study prompt gamma ray line emission at 4.4 and 6.1 MeV. Gamma ray spectral analysis can be extended to 15 MeV on command. Photons in the energy band from 300–350 keV are recorded with a time resolution of 64 ms. A high energy configuration also gives the spectrum of photons in the energy range from 10–100 MeV and the flux of neutrons 20 MeV. Both have a time resolution of 2 s. Auxiliary X-ray detectors will provide spectra with 1-sec time resolution over the energy range of 10–140 keV. The instrument is designed to measure the intensity, energy, and Doppler shift of narrow gamma ray lines as well as the intensity of extremely broadened lines and the photon continuum. The main objective is to use this time and spectral information from both nuclear gamma ray lines and the photon continuum in a direct study of the dynamics of the solar flare/particle acceleration phenomena.  相似文献   

    15.
    The NATALYA-2M high-energy radiation spectrometer is an element of the complex of scientific equipment of the CORONAS-PHOTON satellite. The instrument intended for registering gamma radiation of solar flares in the broad energy range of 0.2–1600 MeV as well as neutrons of solar origin with energies of 20–300 MeV represents itself as a scintillation spectrometer based on CsI(Tl) crystals with a total area of 32 × 38 cm2 and the thickness of 18 cm. The spectra and time profiles of the gamma quanta count rates are measured in four subranges: R (0.2–2 MeV), L (1–18 MeV), M (7–250 MeV), and H (50–1600 MeV). Depending on the gamma radiation energy, the effective area of the instrument varies within the range from 750 to 900 cm2, and the energy resolution at the Cs-137 line (662 keV) is 10%, it being about 30% at energies higher than 50 MeV. A system of stabilization based on the signal from the generator of reference light pulses is used to provide stability and automated adjustment of the parameters of spectrometric modules. The measuring channels of the instrument are calibrated during the flight using a source of “tagged” gamma quanta on the Co-60 radioactive isotope. Polystyrene scintillation counters are used to provide protection from the background of charged particles. The “CORONAS-PHOTON” spacecraft (SC) was launched from the Plesetsk spaceport on January 30, 2009, to a low circular near-Earth orbit (the altitude is 550 km, the inclination is 82.5°). On February 27, the first scientific data were obtained from the NATALYA-2M instrument. The results of the flight calibration of the instrument detectors in different energy channels demonstrated good agreement with the ground measurements. The paper describes the instrument and observational potentials of the NATALYA-2M spectrometer, gives the results of the adjustment and calibration, and exemplifies the registration of gamma-ray bursts (GRBs)on the orbit.  相似文献   

    16.
    An analysis of the longitudinal distribution of gamma rays from SAS-II data has been carried out using the available information on the gas distribution in the Galaxy. The overall distribution of cosmic rays in the galactic plane can be represented by an exponential function in galactocentric distance with a scale length of 8 kpc upto the solar circle and 10 kpc beyond. There is no evidence for a large gradient of the cosmic ray intensity in the outer parts of the Galaxy. The local emissivities of gamma rays in the energy regionsE >100 MeV and 35 MeV<E <100 MeV are (1.73±0.27)×10–25 photon/(cm3 s nH) and (2.40±0.41)×10–25 photon/(cm3 s nH) respectively. The contribution of °-decay gamma rays is 80% forE >100 MeV and 20% at lower energies. The electron spectrum required by this analysis has a power law spectral index of about –2.7 below a few hundred MeV. The observed gas distribution towards the galactic centre would predict a gamma-ray flux larger than observed. It is suggested that the molecular gas in the central region may be in the form of dense coudlets, in which low evergy cosmic rays do not penetrate; in this case the centre should be seen as a strong source only at high energies. An analysis of the radio sky survey map of the Galaxy at 408 MHz shows thatB varies with a scale-length of 40 kpc; no significance can be attached to the apparent deviation from the equipartition of energy densities between cosmic rays and magnetic field. The derived local emissivity is (1.46±0.28)×10–40 W/((m3 Hz), which corresponds toB 5 G. The surface brightness of radio and gamma-ray emissions in the Galaxy decreases from the centre with scale-lengths 6 kpc and 7 kpc respectively. No positive correlation can be noticed with either co-rotation radius or pattern speed, when compared with external spiral galaxies.  相似文献   

    17.
    Torsti  J.  Valtonen  E.  Anttila  A.  Vainio  R.  Mäkelä  P.  Riihonen  E.  Teittinen  M. 《Solar physics》1997,170(1):193-204
    The energy spectra of the anomalous components of helium, nitrogen and oxygen have been measured by the ERNE experiment on board the SOHO spacecraft. During February 28–April 30, 1996, the maximum intensity of anomalous helium was found to be 3.8 × 10-5 cm-2 sr-1 s-1 (MeV nucl-1)-1 in the energy range 10–15 MeV nucl-1. During the period January 26–April 30, 1996, the maximum oxygen intensity was 1.2 × 10-5 cm-2 sr-1 s-1 (MeV nucl-1)-1 at 4–7 MeV nucl-1, and the maximum nitrogen intensity 1.7 × 10-6 cm-2 sr-1 s-1 (MeV nucl-1)-1 at 4–9 MeV nucl-1. These peak intensities are at the same level as two solar cycles ago in 1977, but significantly higher than in 1986. This gives observational evidence for a 22-year solar modulation cycle. A noteworthy point is that the spectra of anomalous nitrogen and oxygen appear to be somewhat broader than in 1977.  相似文献   

    18.
    Retrievals of jovian tropospheric phosphine from Cassini/CIRS   总被引：1，自引：0，他引：1  
    On December 30th, 2000, the Cassini-Huygens spacecraft reached the perijove milestone on its continuing journey to the Saturnian System. During an extended six-month encounter, the Composite Infrared Spectrometer (CIRS) returned spectra of the jovian atmosphere, rings and satellites from 10-1400 cm−1 (1000-7 μm) at a programmable spectral resolution of 0.5 to 15 cm−1. The improved spectral resolution of CIRS over previous IR instrument-missions to Jupiter, the extended spectral range, and higher signal-to-noise performance provide significant advantages over previous data sets.CIRS global observations of the mid-infrared spectrum of Jupiter at medium resolution (2.5 cm−1) have been analysed both with a radiance differencing scheme and an optimal estimation retrieval model to retrieve the spatial variation of phosphine and ammonia fractional scale height in the troposphere between 60° S and 60° N at a spatial resolution of 6°. The ammonia fractional scale height appears to be high over the Equatorial Zone (EZ) but low over the North Equatorial Belt (NEB) and South Equatorial Belt (SEB) indicating rapid uplift or strong vertical mixing in the EZ. The abundance of phosphine shows a similar strong latitudinal variation which generally matches that of the ammonia fractional scale height. However while the ammonia fractional scale height distribution is to a first order symmetric in latitude, the phosphine distribution shows a North/South asymmetry at mid latitudes with higher amounts detected at 40° N than 40° S. In addition the data show that while the ammonia fractional scale height at this spatial resolution appears to be low over the Great Red Spot (GRS), indicating reduced vertical mixing above the ∼500 mb level, the abundance of phosphine at deeper levels may be enhanced at the northern edge of the GRS indicating upwelling.  相似文献   

    19.
    A Monte Carlo program has been developed in order to examine the influence of multiple Compton scattering in the atmosphere on the spectrum of cosmic diffuse gamma rays. It is shown that the corrections to the made to the measurements of the double-Compton gamma telescope at 2·5 gr cm–2 rest atmosphere by Schönfelder and Lichti (1974) are lower than 4% in the energy range between 1.5 and 10 MeV.Under support of a fellowship by the Deutscher Akademischer Austauschdienst  相似文献   

    20.
    Data accumulated by the Solar Maximum Mission Gamma Ray Spectrometer (GRS) have been searched for evidence of the 2.223 MeV neutron capture line from the Sun, outside the times of -ray-emitting solar flares. Background-corrected spectra accumulated over 3-day intervals between 1980 and 1989 show no evidence of the line. Upper limits are reported separately for periods of high and low solar activity.A conservative 3 upper limit of 5.7 × 10–5 (cm2 s)–1 is placed on the steady flux in the 2.223 MeV line during inactive periods, which is nearly two orders of magnitude lower than previously published results. After correction for limb darkening of the line emission from off-center positions, this upper limit becomes 7.1 × 10–5 (cm2s)–1. Our 3 upper limit on the steady flux in the line during periods of high solar activity is 6.9 × 10–5 (cm2 s)–1, or 8.6 × 10–5 (cm2 s)–1 after correction for limb darkening. Our results imply that the quiescent solar corona cannot be heated by ions accelerated above 1 MeV in microflares (or a continuous acceleration process), so long as the ion energy spectrum is similar to that measured in large flares. We also use our results to derive the rate of tritium production at the solar surface; our upper limit of 9 nuclei (cm2 s)–1 is about a factor of 9 below the upper limit from searches for 3H in the solar wind. We place upper limits of the order 1033 on the number of energetic (> 30 MeV) protons which can be stored in active regions prior to being released in solar flares, which imply that the strongest observed flares cannot be produced by such a mechanism.  相似文献   

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