Solar cosmic rays

Summary This report is a brief overview of the energetic-particle phenomena related to solar activity discussed at the XXIV International Cosmic-Ray Conference. In the rapporteur's opinion, the most significant results to be highlighted are: 1) the new higher-energy measurements of the solar energetic ion charge state which seem to be consistent with the older measurements at ∼1 MeV/nucleon, and 2) the many reports of extended gamma-ray production during solar flares with multiple episodes of emission implying multiple episodes of particle acceleration. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Prompt-muon production in cosmic rays

Summary We discuss here the results obtained calculating the contribution of prompt muons in the vertical atmospheric muon flux, computed taking into account the up-to-date data from experiments at accelerators and the most recent theoretical achievements on charm generation in nucleon-air nucleus interactions. Our results are compared with the experimental data obtained with underground detectors.

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Riassunto Si discutono in questo lavoro i risultati ottenuti sul contributo di muoni pronti al flusso atmosferico verticale dei muoni, calcolato utilizzando i dati piú recenti di esperimenti degli acceleratori ed i risultati teorici sulla produzione di particelle charmate in interazioni nucleoni-nuclei atmosferici. I risultati ottenuti sono confrontati con i dati sperimentali forniti da esperimenti sotterranei.

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Резюме Мы обсуждаем результаты вычислений вклада мгновенных мюонов в вертикальный роток атмосферных мюонов. Вычисления учитывают данные из зкспериментов на ускорителях и недавние теоретические предсказания по рождению очарованных частиц при, взаимодействиях нуклонов с ядрами воздуха. Наши результаты сравниваются с зкспериментальными данными, полученными с помощью подземных детекторов.

     

Ultra-high energy cosmic rays and prompt TeV gamma rays from gamma ray bursts

Gamma ray bursts (GRBs) have been proposed as one possible class of sources of the ultrahigh energy cosmic ray (UHECR) events observed up to energies ≳ 10²⁰ eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV γ-rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.     

Spectral index of primary cosmic rays. A QCD-admissible derivation

Summary Considering p-p collisions in terms of Drell-Yan and other related processes, where the interaction at the quark level is represented by a dimensionaless interaction potential, we derive an analytical formula for predicting the spectral index of primary cosmic rays. Adjusting a single free parameter of this formula, we find excellent agreement with experimental data over a wide energy range.

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Riassunto Considerando le collisioni p-p in termini del processo di Drell-Yan e di altri processi ad esse collegati, in cui l'interazione al livello dei quark è rappresentata da un potenziale d'interazione senza dimensioni, si deduce una formula analitica per prevedere l'indice spettrale dei raggi cosmici primari. Adattando un parametro libero singolo di questa formula si trova un eccellente accordo con i dati sperimentali su un ampio intervallo d'energia.

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Резюме Рассматривая p-p соударения в терминах процессов Дрелла-Яна и других связанных процессов, где взаимодействие на кварковом уровне представляется с помощью потенциала безразмерного взаимодействия, мы выводим аналитическое выражение для определения спектрального показателя первичных космических лучей. Подгоняя единственный свободный параметр в этой формуле, мы получаем хорошее согласие с экспериментальными данными в широкой области енергий.

     

On the biological effects of cosmic rays: Epidemiological studies

Summary Determining the biological effects of cosmic rays and other natural ionizing radiations, could possibly help us in shedding light on the more general problem of low-dose ionizing-radiation effects. In this work we provide a survey of the most recent studies available on epidemiological methods: we discuss the main difficulties in using these methods, as well as the discrepancies in their results. Work presented as a poster at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Ultra-high-energy cosmic rays and inflation relics

There are two processes of matter creation after inflation that may be relevant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable particles, and 2) non-thermal phase transitions leading to the formation of topological defects. We review both possibilities.     

Relevance of multiple muons detected underground to the mass composition of primary cosmic rays

Summary Calculations have been made of the expected frequencies of multiple muons for the situation of the Soudan underground proton decay detector. Comparisons are made with the observations and it is concluded that with our model for high-energy collisions the flux of heavy nuclei (A>20, principally iron) in the range (10¹⁵÷10¹⁶ eV)/nucleus is at most 25% of the total particle flux in the same range.

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Riassunto Sono stati effettuati i calcoli delle frequenze attese di muoni multipli per situare il rivelatore di decadimento di protoni sotterraneo di Soudan. Si eseguono confronti con le osservazioni e si conclude che con il nostro modello per le collisioni ad alta energia il flusso di nuclei pesanti (A>20, specialmente ferro) nell'intervallo (10¹⁵÷10¹⁶) eV/nucleo è al massimo il 25% del flusso totale di particelle nello stesso intervallo.

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Резюме Вычисляются ожидаемые частоты появления множественных мюонов в суданском подземном детекторе распадов протонов. Проводится сравнение с результатами наблюдений. Делается вывод, что в рамках предложенной модели для соударений при высоких энергиях поток тяжелых ядер (A>20, в основном, ядра железа) в области энерий (10¹⁵÷10¹⁶) эВ составляет, в лучшем случае, 25% от полного потока частиц в этой области энергий.

     

Origin of cosmic rays

Cosmic rays were discovered in 1911 but it is only now that some ideas are beginning to emerge as to their origin. This paper will examine the present evidence concerning the origin question over the whole energy range, from 10⁹ eV to 10²⁰ eV. At the lowest energies, (10⁹–10¹⁰ eV), the new subject of gamma ray astronomy plays a crucial role and a galactic origin is favoured. At higher energies (10¹²–10¹⁷ eV) recent measurements of the anisotropies in arrival directions also suggest a galactic origin, although the evidence is not as strong. At the very highest energies it seems likely that some, at least, of the particles come from outside the galaxy although the non-existence of the cut-off at about 6 × 10¹⁹ eV arising from interactions with the cosmological relict radiation provides a paradox. The likely future areas of advance in this fascinating subject will be indicated. Based on the B. B. Roy memorial lectures delivered at Calcutta University, February 1–3, 1978.     

Cosmic rays in the heliosphere

Summary This is a rapporteur paper for the XXIV International Cosmic-Ray Conference covering topics of anomalous cosmic rays, shock acceleration, modulation and transport theory, cosmic-ray gradients, corotating interaction regions, coronal-mass ejections, and solar neutrinos. Among the highlights of the meeting are —conclusive proof that most anomalous cosmic rays are singly charged,—undisputed detection of anomalous cosmic-ray hydrogen,—discovery of unexpectedly large anisotropies of pickup ions,—observation of pronounced solar rotational modulation of cosmic-ray fluxes to the highest heliolatitudes (∼80°) probed by the Ulysses spacecraft, and—new measurements of modulation effects sensitive to particle charge sign. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

A search for high-energy cosmic gamma-ray bursts

Summary A search has been made for excesses of cosmic-ray counting rates at primary energiesE ₀₁>5 GeV andE ₀₄>2·10⁴ GeV over the time scalet=(1÷100) ms. The measurement was performed by means of a small extensive air shower array operating at mountain altitude (3500 m a.s.l.). During the running time 111 cosmic gamma-ray bursts were detected by satellites; 10 of them certainly (55 probably) above the horizon of the detector. No significant counting rate excess has been recorded out of the statistical fluctuations. Also the search for correlations with satellite events has given a negative result. The upper limit for high-energy cosmic gamma-ray flux in bursts isϕ ₁(E>E ₀₁)<4·10⁻⁵ (t = time scale in ms),ϕ ₄(E>E ₀₄)<1.6·10⁻⁵erg/cm². Paper presented at the 2^o Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

The distribution of atomic hydrogen and diffuse gas in the galaxy

Summary We review the distribution of diffuse gas, both neutral and ionized, in the Galaxy and the galactic halo. Paper presented at the Congress ?Galactic and Extragalactic Dark Matter?, Roma, 28 to 30 June 1983.     

Primary cosmic-ray composition in the energy range of 1014 eV to 1016 eV and high-energy atmospheric cosmic rays observed with emulsion chambers at Mt. Kanbala

Summary We report on the results of the measurements of energy spectra of atmospheric cosmic rays in the energy around 10 TeV measured with emulsion chambers at Mt. Kanbala (5500 m above sea-level, atmospheric depth 520 g/cm²). The power indices of the integral spectra take the values of 2.00±0.08 for gamma-rays and 1.90±0.10 for hadrons, in the energy range from 5 TeV to 20 TeV. Their intensities are compatible with those expected from the primary cosmic rays containing fewer protons than in the lower energy region. The energy spectrum of family events is also discussed with reference to the composition of primary cosmic rays. It is concluded that the portion of protons in the primary cosmic rays gradually decreases in the energy range from 10¹³ eV to 10¹⁵ eV.

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Riassunto Si riportano i risultati delle misurazioni degli spetri di energia dei raggi cosmici atmosferici all'energia di circa 10 TeV misurata con camere d'emulsione a Mt. Kambala (5500 m sul livello del mare, profondità atmosferica 520 g/cm²). Gli indici di potenza degli spettri integrali assumono i valori di 2.00±0.08 per i raggi gamma e 1.90±0.10 per gli adroni, nell'intervallo di energia da 5 TeV a 20 TeV. Le loro intensità sono compatibili con quelle attese dai raggi cosmici primari che contengono meno protoni che nella regione d'energia inferiore. Lo spettro d'energia degli eventi della famiglia è discusso anche con riferimento alla composizione dei raggi cosmici primari. Si conclude che la porzione di protoni nei raggi cosmici primari diminuisce nell'intervallo d'energia da 10¹³ eV a 10¹⁵ eV.

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Резюме Мы приводим результаты измерений энергетических спектров атмосферных космических лучей при энергиях порядка 10 TeB, определенных с помощью змульсионных камер на г. Канбала (5500 м выше уровня моря, атмосферная глубина 520 r/cm²). Степенные показатели интегральных спектров имейт значения 2.00±0.08 для гамма-лучей и 1.90±0.10 для адронов, в области энергий от 5 ТэВ до 20 ТэВ. Полученные интенсивности оказывайтся совместимыми с ожидаемыми интенсивностями от первичных космических лучей, содержащих меньшее число протонов, чем в области меньших энергий. Также обсуждается энергетнческих спектр семейства событий относительно соства первичных космических лучей. Утверждается, что доля протонов в первичных космических лучах постепенно уменьшается в области энергий от 10¹³ зВ до 10¹⁵ эВ.

     

Cosmic rays and supernova SN 1987a

Summary We discuss the possibility of obtaining information on the contribution to the galactic cosmic-ray flux by young pulsars searching for high-energy gamma-rays from SN 1987a. A small extensive air shower array operating in Chacaltaya (Bolivia, 5200 m a.s.l.) could give significant information at primary energiesE ₀∼10¹⁴ eV.     

γ射线在LSO晶体中的能量沉积

采用蒙特卡罗程序MCNP计算了γ射线在LSO晶体中的能量沉积分布并与相应的实验结果进行了对比,验证了该方法的正确性。在此基础上计算了不同能量的γ射线在LSO晶体中的能量沉积分布,分析了γ射线与物质的不同作用对晶体中能量沉积分布的影响,总结出在晶体轴向和径向的能量沉积分布规律。轴向上,不同能量γ射线在LSO晶体中的能量沉积近似为指数分布,在表面能量沉积密度较小;在径向方向,γ射线在入射轴线上能量沉积密度很高,在距入射轴较近的区域,主要是次级电子产生沉积能量,随着距离的增大,γ射线能量沉积逐渐减小;在距入射轴较远的区域,能量沉积主要是散射γ射线产生。     

Ionization states of cosmic rays:Anuradha (IONS) experiment in Spacelab-3

The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to 6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area of about 800 cm² and determines the arrival time information of particles with active elements. Experimental methods, flight operations and preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles, oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Search for UHE cosmic sources with a large-area underground muon detector

Summary The newly discovered gamma-ray emission from Cyg-X 3 with energies up to 2·10¹⁶eV gives the first evidence that particle acceleration in galactic gamma-ray sources can reach energies of the order of 10⁴ TeV. We discuss the detectability of this type of sources by an underground muon tracking detector with area of the order of ∼1000 m² and the physical information which could be obtained in this way. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

Are the proposed cosmic H particles psionlike in Nature?

Summary The hints to explain the unusual type of cosmic cluster events (called generally the ?exotic? events) in ultrahigh-energy nuclear collisions in terms of proposed H particles have, to date, been neither substantiated nor concretised. We assort here some crucial aspects and assemble a few supportive evidences to favour our idea that the proposed H particles might be viewed as cosmic psionlike particles.     

High-energy cosmic rays: Puzzles,models, and giga-ton neutrino telescopes

The existence of cosmic rays of energies exceeding 10²⁰ eV is one of the mysteries of high-energy astrophysics. The spectrum and the high energy to which it extends rule out almost all suggested source models. The challenges posed by observations to models for the origin of high-energy cosmic rays are reviewed, and the implications of recent new experimental results are discussed. Large area high-energy cosmic ray detectors and large volume high-energy neutrino detectors currently under construction may resolve the high-energy cosmic ray puzzle, and shed light on the identity and physics of the most powerful accelerators in the Universe.     

Energetic neutrons and gamma rays measured on the Aryabhata satellite

An experiment to measure energetic neutrons and gamma rays in space was launched in the first Indian scientific satellite,Aryobhata, on April 19, 1975. From this experiment, the first measurements in space of the Earth’s albedo fiux of neutrons of energy between 20 and 500 MeV have been made; the values obtained for two mean geomagnetic vertical cut-off rigidities of 5.6 and 17.0 GV are (6.3±0.4)×10⁻² and (1.4±0.3)×10⁻² neutrons cm⁻² sec⁻¹ respectively. These measurements confirm that protons arising from cosmic ray albedo neutron decay, can adequately account for the protons in the inner radiation belt. Observations on gamma rays of energy between 0.2 and 24 MeV have enabled the determination of the total background gamma ray flux in space as a function of latitude. This in turn has permitted useful information on the diffuse cosmic gamma rays. We have also observed four events that showed sudden increases in the gamma ray counting rates between 0.2 and 4.0 MeV. Observational details of these events are given.     

On detecting diffuse ultraviolet radiation of cosmological origin

Summary The intensity of diffuse extragalactic background radiation is determined by the integrated emission of all sources along a given line of sight through the Universe and by absorption due to intervening cool gas and dust. Due to red-shift and lookback-time effects, more distant objects contribute at a given wave-length today with light emitted at earlier epochs at shorter wave-lengths. Possible sources of ultraviolet (100÷3000) ? emission include, but may not be restricted to, galaxies and quasars, a lukewarm or photoionized dense intergalactic medium and a cosmological sea of decaying massive neutrinos and photinos formed in the hot big bang. The resultant complex spatial intensity pattern and spectral distribution will appear superimposed on an intense galactic emission source whose main characteristics have yet to be clearly and satisfactorily established. Although substantial progress has been made recently in understanding galactic emission mechanisms, the remaining uncertainties substantially limit the accuracy with which a cosmologically significant signal may be disentangled from the diffuse galactic background ?noise?. On assignment from the Astrophysics Division, Space Science Department, European Space Agency.