[Show abstract][Hide abstract] ABSTRACT: In this work, we apply an updated version of the Neutron Monitor (NM) Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model, in order to derive the characteristics of the ground-level enhancement (GLE) on 2012 May 17 (GLE71), the spectral properties of the related solar energetic particle (SEP) event, the spatial distributions of the high-energy solar cosmic ray fluxes at the top of the atmosphere, and the time evolution of the location of the GLE source. Our modeling, based uniquely on the use of ground-level NM data, leads to the following main results. The SEP spectrum related to GLE71 was rather soft during the whole duration of the event, manifesting some weak acceleration episodes only during the initial phase (at ~01:55-02:00 UT) and at ~02:30-02:35 UT and ~02:55-03:00 UT. The spectral index of the modeled SEP spectrum supports the coronal mass ejection-shock driven particle acceleration scenario, in agreement with past results based on the analysis of satellite measurements. During the initial phase of GLE71, the solar proton source at the top of the atmosphere was located above the northern hemisphere, implying that the asymptotic directions of viewing of the northern hemisphere NMs were more favorably located for registering the event than the southern ones. The spatial distribution of the solar proton fluxes at the top of the atmosphere during the main phase manifested a large variation along longitude and latitude. At the rigidity of 1 GV, the maximum primary solar proton flux resulted on the order of ~3 × 104 part. m-2 s-1 sr-1 GV-1.
The Astrophysical Journal 03/2014; 785(2). · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cosmic ray (CR) modulation is driven by both solar activity and drift
effects in the heliosphere, although their role is only qualitatively
understood as it is difficult to connect the CR variations to their
sources. In order to address this problem, the Empirical Mode
Decomposition technique has been applied to the CR intensity, recorded
by three neutron monitors at different rigidities (Climax, Rome, and
Huancayo-Haleakala (HH)), the sunspot area, as a proxy for solar
activity, the heliospheric magnetic field magnitude, directly related to
CR propagation, and the tilt angle (TA) of the heliospheric current
sheet (HCS), which characterizes drift effects on CRs. A prominent
periodicity at ~six years is detected in all the analyzed CR data sets
and it is found to be highly correlated with changes in the HCS
inclination at the same timescale. In addition, this variation is found
to be responsible for the main features of the CR modulation during
periods of low solar activity, such as the flat (peaked) maximum in even
(odd) solar cycles. The contribution of the drift effects to the global
Galactic CR modulation has been estimated to be between 30% and 35%,
depending on the CR particle energy. Nevertheless, the importance of the
drift contribution is generally reduced in periods nearing the sunspot
maximum. Finally, threshold values of ~40°, ~45°, and
>55° have been derived for the TA, critical for the CR modulation
at the Climax, Rome, and HH rigidity thresholds, respectively.
The Astrophysical Journal 02/2014; 781(2):71-. · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cosmic rays of solar and galactic origin at energies >100 MeV/n charge and induce spurious forces on free-floating test masses on board interferometers devoted to gravitational wave detection in space. LISA Pathfinder (LISA-PF), the technology testing mission for eLISA/NGO, will carry radiation monitors for on board test-mass charging monitoring. We present here the results of a simulation of radiation monitor performance during the evolution of solar energetic particle (SEP) events of different intensity. This simulation was carried out with the Fluka Monte Carlo package by taking into account for the first time both energy and spatial distributions of solar protons for the SEP events of 23 February 1956, 15 November 1960 and 7 May 1978. Input data for the Monte Carlo simulations was inferred from neutron monitor measurements. Conversely, for the SEP event of 13 December 2006 observed by the PAMELA experiment in space, we used the proton pitch angle distribution (PAD) computed from the Particle Acceleration and Transport in the Heliosphere (PATH) code. We plan to adopt this approach at the time of LISA-PF data analysis in order to optimize the correlation between radiation monitor observations and test-mass charging. The results of this work can be extended to the future space interferometers and other space missions carrying instruments for SEP detection.
Classical and Quantum Gravity 01/2014; 31(4). · 3.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: On 2012, May 17 the GOES satellites recorded a great and simultaneous
increase on proton flux in different energy channels thereby producing a
solar proton event (SPE). These protons had enough energy to be recorded
by the ground based worldwide network of neutron monitors thereby
producing the first ground level enhancement of solar cosmic rays
(GLE71) of the current solar cycle. In this work a combined study of the
this solar proton event, as it is recorded by GOES satellites as well as
by the ground based network of Neutron monitors is presented. On 2012,
May 17 at 02:10 UTC the GOES spacecraft recorded a fast rise in the flux
of solar protons, followed by a slower decay, which was still ongoing on
18 May 2012. Several solar proton events stronger than that of 17 May
2012 were detected by GOES in January and March 2012. This event of 17
May extended to much higher energies than those earlier ones, but was
weaker at lower energies. Through this research an attempt to understand
the reason for these differences is performed. Additionally, a first
attempt to derive the characteristics of this recent proton event, by
applying an updated version of the NMBANGLE PPOLA model, already used
for modeling past GLEs (e.g. GLE70 ) is presented. The special
characteristics of this event with respect to the result of NMBANGLE
POLLA model can provide useful information not only about the solar
source that triggered this SPE, but also its special impact at
[Show abstract][Hide abstract] ABSTRACT: The 4 April 2000 solar energetic particle (SEP) event has been selected
to investigate its spectral shape by using a distribution typical of the
Extreme Value Statistics (EVS). Data from ACE/EPAM and SOHO/ERNE have
been used. A calibration procedure has been applied in order to obtain a
reliable spectrum for the energy range ~ 0.1 - 100 MeV. Results suggest
that the EVS functional form can explain the observed spectrum, both
integrated over the whole SEP event and over an interval around the
shock arrival time. Implications for the solar particle acceleration are
[Show abstract][Hide abstract] ABSTRACT: High energy particles of galactic and solar origin crossing a spacecraft
affect experiment performance in space. At time scales of tens of
minutes, galactic cosmic-ray (GCR) energy fluxes vary of a few percent
at most. Conversely, solar energetic particle (SEP) fluxes may vary of
several orders of magnitude during the same periods of time. In order to
study accurately the effects of the incident solar particles on future
space experiments, a good knowledge of particle energy distribution
during the whole duration of SEP events is necessary. We report here the
parameterization of proton and helium energy spectra observed during SEP
events of different intensity at energies above 100 MeV/n. We benefit of
both data inferred at the top of the atmosphere from ground neutron
monitor observations and recent measurements gathered by the PAMELA
cosmic-ray experiment carrying a magnetic spectrometer in space.
Journal of Physics Conference Series 02/2013; 409(1):2159-.
[Show abstract][Hide abstract] ABSTRACT: Recently, details of modular cosmic ray detectors developed by the staff
of the SVIRCO Observatory and Terrestrial Physics Laboratory (Rome,
National Institute for Astrophysics) were published (Signoretti and
Storini, 2011). Data recorded during June 2011 by a modular mobile
neutron detector, equipped with a large helium counter (5.08 cm in
diameter, 191 cm long) and assembled with twenty-three modules, were
carefully checked and used to investigate the detector response to the
perturbations originating on the Sun and travelling through the
interplanetary medium. We show that at the Rome rigidity threshold
(about 6.3 GV) the registered intensity well accounts for the macro
perturbations in the near-Earth Space. Nevertheless, to investigate the
fine structure of the perturbations the modular detector should operate
at mountain altitudes or in polar areas.
Journal of Physics Conference Series 02/2013; 409(1):2045-.
[Show abstract][Hide abstract] ABSTRACT: The 4 April 2000 solar energetic particle (SEP) event has been selected to investigate its spectral shape by using a distribution typical of the Extreme Value Statistics (EVS). Data from ACE/EPAM and SOHO/ERNE have been used. A calibration procedure has been applied in order to obtain a reliable spectrum for the energy range ∼ 0.1 − 100 MeV. Results suggest that the EVS functional form can explain the observed spectrum, both integrated over the whole SEP event and over an interval around the shock arrival time. Implications for the solar particle acceleration are discussed.
[Show abstract][Hide abstract] ABSTRACT: An oscillating magnetic field deep within the solar radiative region can significantly alter the helioseismic g-modes. The presence of density gradients along g-modes, can excite Alfvén waves resonantly, the resulting waveforms show sharp spikes in the density profile at radii comparable with the neutrino's resonant oscillation length. This process should ex-plain the observed quasi-biennial modulation of the solar neutrino flux. If confirmed, the coupling between solar neu-trino flux and g-modes should be used as a "telescope" for the solar interior.
[Show abstract][Hide abstract] ABSTRACT: The time variability of solar activity indices such as sunspot areas (SAs) and green-line coronal emission, fluxes of solar energetic protons and galactic cosmic rays (CRs) in the period 1974–2001 has been investigated through the empirical mode decomposition (EMD). We found that the quasi-biennial periodicity is a prominent time scale of solar variability, having the energetic particle indices an amplitude comparable with the 11 years one. Moreover, we provide evidence for the quasi-biennial modulation of the solar neutrino flux, which results to be also significantly correlated with the fluxes of solar energetic protons and galactic CRs. The significance of all the correlation has been tested by applying both bootstrap and Monte Carlo methods.
Advances in Adaptive Data Analysis 08/2012; 04(01n02).
[Show abstract][Hide abstract] ABSTRACT: LISA (Laser Interferometer Space Antenna) and its precursor mission LISA Pathfinder (LISA-PF) will carry particle monitors for noise diagnostics. It was proposed to build and place radiation detectors on board the ASTROD missions as well. We present here a study of the solar energetic particle (SEP) events that the LISA-PF radiation monitors are able to detect above the galactic cosmic-ray (GCR) background predicted at the time of the mission data taking in 2015. In order to optimize the correlation between radiation monitor measurements and gravitational sensor test-mass charging, the energy threshold for particles traversing both detectors should be approximately the same. In LISA-PF, the radiation monitor particle energy cut-off was conservatively set at 75 MeV per nucleon (MeV/n) for protons and ion normal incidence, while the minimum energy of the same particles reaching the test masses is 100 MeV/n. We find that SEP events detectable on LISA-PF are characterized by peak fluxes and fluences at energies >75 MeV/n larger than about 45%, on average, with respect to those at energies >100 MeV/n. We conclude that for an accurate correlation between radiation monitor count rates and test-mass charging, it is mandatory to benefit from absolute flux measurements of both galactic and high-energy solar particles provided by experiments carrying magnetic spectrometers in space at the time of LISA-PF (PAMELA, AMS). On the other hand, the role of the radiation detectors on board LISA-PF is crucial allowing for SEP event onset and dynamics monitoring.
Classical and Quantum Gravity 05/2012; 29(10). · 3.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The time variability of the cosmic-ray (CR) intensity at three different rigidities has been analyzed through the empirical mode decomposition technique for the period 1964–2004. Apart from the ∼11 yr cycle, quasi-biennial oscillations (QBOs) have been detected as a prominent scale of variability in CR data, as well as in the heliomagnetic field magnitude at 1 AU and in the sunspot area. The superposition of the ∼11 yr and QBO contributions reproduces the general features of the CR modulation, such as most of the step-like decreases and the Gnevyshev Gap phenomenon. A significant correlation has also been found between QBOs of the heliospheric magnetic field and the CR intensity during even solar activity cycles, suggesting that the former are responsible for step-like decreases in CR modulation, probably dominated by the particle diffusion/convection in such periods. In contrast, during odd-numbered cycles, no significant correlation is found. This could be explained with an enhanced drift effect also during the solar maximum or a greater influence of merged interaction regions at great heliocentric distances during odd cycles. Moreover, the QBOs of CR data are delayed with respect to sunspot activity, the lag being shorter for A > 0 periods of even cycles (∼1–4 months) than for A < 0 periods of odd cycles (∼7–9 months); we suggest that solar QBOs also affect the recovery of the CR intensity after the solar activity maximum.
The Astrophysical Journal 04/2012; 749:167-11. · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A review of selected experimental results relevant for the use of cosmic ray records in Space Weather research is presented.
Interplanetary perturbations, initiated in the solar atmosphere, affect galactic cosmic rays. In some cases their influence
on the cosmic ray intensity results in data signatures that can possibly be used to predict geomagnetic storm onsets. Case
studies illustrating the complexity of the cosmic ray effects and related geomagnetic activity precursors are discussed. It
is shown that some indices for cosmic ray activity are good tools for testing the reliability of cosmic ray characteristics
for Space Weather forecasts. A brief summary of the influence of cosmic rays on the ozone layer is also given. The use of
cosmic ray data for Space Weather purposes is still in its infant stage, but suggestions for both case and statistical studies
Space Science Reviews 04/2012; 93(1):153-174. · 5.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak synoptic magnetic maps covering the period August 1976-September 2003. For each heliographic latitude the field has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition, in order to investigate the time evolution of the various characteristic oscillating frequencies at different latitudes. The quasi biennial oscillations are identified as the fundamental periodicity of the magnetic field and linked to dynamo waves which transport magnetic flux both polewards and equatorwards from latitudes of about 35°. On the other hand, the usual pattern of the Sporer law is associated with periodicities related to the high frequency fluctuating part of the magnetic field. Finally the usual ~22 yr cycle, related to the polarity inversions of the large-scale dipolar field, are consistent with alpha-omega dynamo models including meridional circulation.
The Astrophysical Journal 04/2012; 749(1). · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The kinetic energy spectra of solar energetic particle (SEP) events
contain information on the particle acceleration mechanisms. A novel
approach is proposed to investigate the time evolution of the spectral
shape for the 20 February 2002 SEP event. Proton differential fluxes
recorded by the ERNE instrument aboard SOHO, in the energy range
1.67-112 MeV, are analyzed. The solar source is associated with this SEP
event by studying solar and interplanetary conditions during the
considered time period. The energy spectrum evolution is studied by
evaluating the time history of Shannon's differential entropy derived
from the SEP fluxes. Our findings suggest that particle acceleration in
the considered event is produced by a perpendicular shock in the solar
corona. Moreover, dropouts in the particle flux are clearly identified
up to energies of at least ~10 MeV.
Astrophysics and Space Sciences Transactions 01/2012;
[Show abstract][Hide abstract] ABSTRACT: The time variability of the cosmic ray (CR) intensity, recorded by the Climax neutron monitor and covering the period 1953–2004, has been analyzed by the joint application of the wavelet and the empirical mode decomposition (EMD) analyses. Dominant time scales of variability are found at ~11 yr, ~22 yr, ~6 yr and in the range of the quasi-biennial oscillations (QBOs). The combination of the 11 yr cycle and QBOs explains the Gnevychev Gap (GG) phenomenon and many step-like decreases characterizing the CR modulation. The additional scales of variability at ~22 yr and ~6 yr are responsible for other features of the long-term CR trend, such as the intensity flat-topped profile, following the maxima of even-numbered cycles during positive polarity state of the heliosphere ( A > 0 ). Comparison with basic time scales of variability derived from the sunspot area (SA) allows the association of the 11 yr cycle and QBOs with solar activity variations, whereas the other two modes with the drift effects govern the CR entrance in the heliosphere.
Advances in Astronomy 01/2012; 2012. · 1.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Results from the wavelet power spectrum (WPS) analysis of the cosmic ray intensity, registered by the Calgary neutron monitor from 1969 to 1998 years, are used to discuss the characteristic behaviour of the quasi-biennial modulation of galactic cosmic rays during solar activity cycles n. 21 and n. 22. Results from the temporarily averaged global power spectra (GPS) are also shown.
[Show abstract][Hide abstract] ABSTRACT: A quasi-biennial periodicity has been recently found (Vecchio et al.,
2010) in the solar neutrino flux, as detected at the Homestake
experiment, as well as in the flux of solar energetic protons, by means
of the Empirical Modes Decomposition technique. Moreover, both fluxes
have been found to be significantly correlated at the quasi-biennial
timescale, thus supporting the hypothesis of a connection between solar
neutrinos and solar activity. The origin of this connection is
investigated, by modeling how the standard Mikheyev-Smirnov-Wolfenstein
(MSW) effect (the process for which the well-known neutrino flavor
oscillations are modified in passing through the material) could be
influenced by matter fluctuations. As proposed by Burgess et al., 2004,
by introducing a background magnetic field in the helioseismic model,
density fluctuations can be excited in the radiative zone by the
resonance between helioseismic g-modes and Alfvén waves. In
particular, with reasonable values of the background magnetic field
(10-100 kG), the distance between resonant layers could be of the same
order of neutrino oscillation length. We study the effect over this
distance of a background magnetic field which is variable with a ~2 yr
period, in agreement with typical variations of solar activity. Our
findings suggest that the quasi-biennial modulation of the neutrino flux
is theoretically possible as a consequence of the magnetic field
variations in the solar interior. A. Vecchio, M. Laurenza, V. Carbone,
M. Storini, The Astrophysical Journal Letters, 709, L1-L5 (2010). C.
Burgess, N. S. Dzhalilov, T. I. Rashba, V., B.Semikoz, J. W. F. Valle,
Mon. Not. R. Astron. Soc., 348, 609-624 (2004).
[Show abstract][Hide abstract] ABSTRACT: Fifteen solar energetic particle (SEP) events have been analyzed using proton flux data recorded by the Helios 1, Helios 2, and IMP 8 spacecraft in the energy range ∼4–40MeV during 1974–1982. For each of the events at least two of the spacecraft have their nominal magnetic footpoint within 20° in heliocentric longitude from each other. The SEP events are sub-grouped as a function of their heliocentric longitudinal separation and heliocentric radial distance from the SEP associated solar flare and several case studies are presented in this paper. Main results concerning their usage in estimating the SEP radial dependence are given. Moreover, we investigate the behavior of the third not connected spacecraft in order to study the dependence of the proton flux as a function of flare location. It is found that the contribution of the longitudinal gradient in determining variations in the SEP proton flux is particularly relevant for spacecraft having their magnetic connection footpoint separated from the flare between 30° and 50°.
Advances in Space Research 06/2011; 47(12):2127-2139. · 1.24 Impact Factor