G. Cini Castagnoli

The EAS size spectrum and the cosmic ray energy spectrum in the region 1015–1016 eV

Abstract The cosmic ray energy spectrum in the range E 0 = 10 15 –10 16 eV (including the region of the steepening, “knee” ) is studied by means of the EAS-TOP array (Campo Imperatore, Gran Sasso Laboratories, atmospheric depth 820 g cm −2 ). Measurements of the electromagnetic size ( N e = total number of charged particles at the observation level) are performed as a function of zenith angle with statistical accuracies of a few percent. The change of slope of the spectrum is observed in each bin of zenith angle at size values decreasing with increasing atmospheric depth. Its attenuation is compatible with the one of shower particles ( Λ e = 219 ± 3 g cm −2 ). This observation provides a consistency check, supporting a normal behaviour of showers at the break, that make plausible astrophysical interpretations based on an effect on primaries occurring at a given primary energy. The break has a “sharp” shape (i.e., within experimental errors is compatible with two intersecting power laws) that represents a constraint with which any interpretation has to match. The change of slope of the power law index reproducing the size spectrum is Δγ = 0.40 ± 0.09. The derived all particle energy spectrum is in good agreement with the extrapolation of the direct measurements at low energies and with other EAS data at and above the knee. Power laws fits to the energy spectrum below and above the knee give (in units of m −2 s −1 sr −1 TeV −1 ) S ( E 0 ) = (3.48 ± 0.06) × 10 −10 ( E 0 /2300) −2.76±0.03 for 900 TeV E 0 S ( E 0 ) = (3.77 ± 0.08) × 10 −11 ( E 0 /5000) −3.19±0.06 for 5000 TeV E 0 4 TeV. The systematic uncertainties connected to the interaction model and the primary composition are discussed.

Measurement of the cosmic ray hadron spectrum up to 30-TeV at mountain altitude: The Primary proton spectrum

The flux of cosmic ray hadrons at the atmospheric depth of 820 g/cm^2 has been measured by means of the EAS-TOP hadron calorimeter (Campo Imperatore, National Gran Sasso Laboratories, 2005 m a.s.l.). The hadron spectrum is well described by a single power law : S(E_h) = (2.25 +- 0.21 +- 0.34(sys)) 10^(-7)(E_h/1000)^(-2.79 +- 0.05) m^(-2) s^(-1) sr^(-1) GeV^(-1) over the energy range 30 GeV-30 TeV. The procedure and the accuracy of the measurement are discussed. The primary proton spectrum is derived from the data by using the CORSIKA/QGSJET code to compute the local hadron flux as a function of the primary proton spectrum and to calculate and subtract the heavy nuclei contribution (basing on direct measurements). Over a wide energy range E_0 = 0.5-50 TeV its best fit is given by a single power law : S(E_0) = (9.8 +- 1.1 +- 1.6(sys)) 10^(-5) (E_0/1000)^(-2.80 +- 0.06) m^(-2) s^(-1) sr^(-1) GeV^(-1). The validity of the CORSIKA/QGSJET code for such application has been checked using the EAS-TOP and KASCADE experimental data by reproducing the ratio of the measured hadron fluxes at the two experimental depths (820 and 1030 g/cm^2 respectively) at better than 10% in the considered energy range.

The CaCO3 profiles of deep and shallow mediterranean sea cores as indicators of past solar-terrestrial relationships

SummaryWe study the total carbonate profiles of three coastal cores extracted from the continental shelf in the Ionian Sea and of two deep-sea cores extracted from the Tyrrhenian abissal plane. An overall similarity between the two deep-sea profiles and among the three coastal profiles is observed, indicating the complete reproductibility of this type of experimental measurements. In the case of the coastal cores, a constant sedimentation rates=(0.0646±0.0007) cm/y has been determined by radiometric methods and by tephroanalysis. For the deep-sea cores, the spectra of the upper and lower halves of the carbonate depth profiles display the same periodic components, suggesting that the sedimentation rate is nearly the same along the entire deep cores as well. The use of a careful tephroanalysis, the recognition of the Ignimbrite layers of Campanian origin at the expected depths and the similarity between the upper part (5000y) of the carbonate profile of the deep-sea core with that of the coastal cores provide the indication that, on the average, 1 cm of sediment is deposited in about 100 y. We show that the trend of the carbonate record in the deep-sea core is well approximated by a signal obtained by linearly superposing the obliquity and the precession parameters of the Earth rotation axis. Since these astronomical factors contribute to the temporal variations of the Earth insolation, and since the CaCO3 content of the sediment is presumably affected by climatic factors, this result supports the evidence of astronomical control on the Earths climate, as already pointed out by several authors who analysed the power spectra of δ18O, δD and CO2 temporal series from sediment and ice cores. After removal of the «astronomical» trend, the carbonate record displays a dominant periodicity at approximately 12000 y. The 12000 y wave, taken with the opposite sign, corresponds to the trend of the radiocarbon record in tree-rings. This result becomes particularly relevant in view of the existence of common periodicities of about 200 y waves (Suess wiggles) which have already been detected in the carbonate profiles of the coastal cores and in tree-ring radiocarbon data.

Solar radiation variability in the last 1400 years recorded in the carbon isotope ratio of a mediterranean sea core

Abstract We present measurements and data analysis of the carbon stable isotopes (δ 13 C) in the planktonic Globigerinoides ruber extracted from the GT90/3 shallow water Ionian sea core, dated with high precision. It is commonly accepted that δ 13 C variations in symbiontic foraminifera mainly record the effects of productivity and of photosynthetic activity, varying with the ambient light level. Therefore from this time series we can deduce information on the sea surface illumination at the time of the planktonic foraminifera growth. The profile (359 points) covers the period 590–1979 AD, with a resolution of 3.87 years and it is an extension of the time series (215 points) previously published in this journal. The spectral analysis of the longer time series confirms the presence of the 11 y signal, with amplitude ∼0.08‰ (peak-to-trough), found in the shorter time series in phase with the sunspot solar cycle; furthermore it shows the presence of two centennial cycles of 100 and 200 years, with amplitude 0.08‰ and 0.02‰ respectively. These components are identified at high significance level by Monte Carlo singular spectrum analysis (MC-SSA). A comparison between the δ 13 C profile and the historical aurorae series (600–1500 AD) shows that the long-term δ 13 C variations are at least partially generated by the solar activity modulation and in phase with the solar output, as represented by the solar wind interaction with the magnetosphere.

A limit to the rate of ultra high energy γ-rays in the primary cosmic radiation

Abstract An upper limit to the flux of Ultra High Energy (UHE) γ-rays in the primary cosmic radiation is obtained through the data of the electromagnetic and the muon detectors of the EAS-TOP Extensive Air Shower array (Campo Imperatore, National Gran Sasso Laboratories, atmospheric depth 810g cm−2). The search is performed by selecting Extensive Air Showers (EAS) with low muon content. For EAS electron sizes Ne > 6.3 · 105, no showers are observed with the core located inside a fiducial area and no muons recorded in the 140 m2 muon detector, during a live time of 8440 h. The 90% c.l. upper limit to the relative intensity of γ-ray with respect to cosmic ray (c.r.) primaries is I γ I c.r. −5 , at primary energy E0 ≥ 1015 eV: this limit is lower than reported in previous measurements.

Radiometric and tephroanalysis dating of recent Ionian Sea cores

SummaryAn accurate dating of recent Ionian Sea sediment cores has been performed by the210Pb radiometric method and by a detailed tephroanalysis. The markers of the historical volcanic eruptions which occurred in the Campanian area (Vesuvius, Phlegrean Fields, Ischia) during the last two millenia have been identified along the cores. Among the others, the famous Plinian Vesuvius eruption of 79 AD, which buried the Roman town of Pompei, has been recognized. Direct210Pb dating is limited to the last two centuries. The tephroanalysis demonstrates that the sedimentation rate estimated by the210Pb method is correct and it is constant, at least for the last 2 ky. The presence of the137Cs peak due to the intense activity of nuclear-weapon testing in the atmosphere in 1963–64 AD assures that the top of the core is present and not disturbed. The high precision of the core dating allows to transform the depth scale into a time scale with an accuracy of ∼1%. The analysis of several cores taken in the same area demonstrates that the results presented here are of general validity, at least in this region. The carbonatic mud deposited in the last millennia in the Gallipoli Terrace can be successfully utilized for investigating the environmental conditions in the recent past.

On the R z -sunspot relative number variations

The Zürich sunspot relative number Rzseries has been analysed by the cyclogram method. The amplitude and the frequency variations of the Fourier 11 yr component between 1700–1983 A.D., were determined in a continuous way.Four distinct time intervals with significantly different characteristics of the periodicities are observed and discussed.Their second harmonics are also considered. The periodicity changes are contemporary to those of the 11 yr cycles.Around the year 1903 it seems that an important event has happened in the Sun. In fact the 11.4 yr cycle periodicity, that was very stable since at least 1825 started to change gradually to smaller values and similarly it happened to the second harmonic which also stopped and abruptly changed of phase of 90°.

Measurement of cosmogenic radionuclides in meteorites with a sensitive gamma-ray spectrometer

SummaryA large-volume HPGe gamma-ray spectrometer in a NaI(Tl) well has been set up underground at 70 m.w.e. depth for whole body counting of cosmogenic radionuclides in meteorites. The detectors are housed in a 20 cm thick lead shield with a lining of cadmium and OFHC copper. The scintillator is simultaneously operated in anticoincidence as well as in coincidence in selected energy channels to achieve low background levels (in the range of counts per day) and high specificity. In this way a large number of radionuclides such as26Al,44Ti,60Co,22Na,54Mn, and shorter-lived nuclides produced in extraterrestrial materials like meteorites and lunar rocks can be analysed. Results on Bouvante and Bereba achondrites and Dhajala and Torino chondrites are presented.

700 year record of the 11 year solar cycle by planktonic foraminifera of a shallow water Mediterranean core

Abstract In this paper we present the δ 18 O and δ 13 C profiles of Globigerinoides Ruber measured in the GT90/3 shallow water Ionian sea core, dated with high precision. They are records respectively of the sea surface temperature (SST) and of the biomass amount present at the time of the planktonic forams growth. The profiles cover the period 1200–1900 AD, with a resolution of 3.87 years. The spectral analysis of the δ 18 O time series performed with different methods shows a dominant periodicity of 11.4 years with an amplitude of ∼0.07‰, in antiphase with the sunspot solar cycle, while the δ 13 C time series shows a dominant periodicity of 11.2 years with an amplitude of ∼0.04‰, in phase with the sunspot cycle. These components are identified at high significance level by Monte Carlo singular spectrum analysis (MC-SSA). These 700 year long records of δ 18 O and δ 13 C disclose the presence of a clear and statistically significant imprint of the solar cycle in a terrestrial archive.

Long term solar-terrestrial records from sediments: carbon isotopes in planktonic foraminifera during the last millennium

Abstract We show the δ13C profile of Globigerinoides ruber measured in the GT90/3 shallow-water Ionian sea core. This core is dated with high accuracy (better than 1%) using radiometric and tephroanalysis methods, for the last 2000 years. The core, extracted from the Gallipoli platform, was sampled at contiguous steps of thickness 2.5 mm, corresponding to 3.87 years. The δ13C profile covers the period 1147–1975 AD. During the first seven centuries it appears fairly flat, while it shows a steep increase between 1760 and 1950 of ∼0.3‰. The analysis of the time series performed using different methods shows a dominant decadal periodicity throughout the record. The 11-year component is identified at high significance level by Monte Carlo singular spectrum analysis (MC-SSA); the SSA-reconstructed-11-year component is in phase with the sunspot solar cycle. The average amplitude of this component is A11y=0.04‰. It is commonly accepted that δ13C variations in symbiontic foraminifera mainly record the effects of symbiont density and of photosynthetic activity, varying with ambient light level. The δ13C peak-to-trough 11-year variation (0.08‰) can be related to solar irradiance variation of 0.1% on decadal time scale, like that measured in space in the last 20 years. By supposing that the observed δ13C modern increase of ∼0.3‰ is also produced by a solar irradiance variability on a longer time scale, through the same mechanisms, we estimate a secular increase of the total solar irradiance between 1760 and 1950 of (0.3/0.08)∗0.1% ≅ 0.37%. This value is at the higher limit of the long term variability estimates (0.25%–0.35%) that are currently proposed. Finally, in the light of the available experimental evidences, we discuss possible ways in which direct solar forcing can be modified by atmospheric processes in order to give the observed δ13C signal.