A statistical analysis of the relationship between solar energetic particles (SEPs) and properties of solar flares and coronal mass ejections (CMEs) is presented. SEP events during Solar Cycle 23 are ...selected that are associated with solar flares originating in the visible hemisphere of the Sun and that are at least of magnitude M1. Taking into account all flares and CMEs that occurred during this period, the probability for the occurrence of an SEP event near Earth is determined. A strong rise of this probability is observed for increasing flare intensities, more western locations, higher CME speeds, and halo CMEs. The correlations between the proton peak flux and these solar parameters are derived for a low (> 10 MeV) and high (> 60 MeV) energy range excluding any flux enhancement due to the passage of fast interplanetary shocks. The obtained correlation coefficients are 0.55±0.07 (0.63±0.06) with flare intensity, and 0.56±0.08 (0.40±0.09) with CME speed for
E
>10 MeV (
E
>60 MeV). For both energy ranges, the correlations with flare longitude and CME width are very weak or non-existent. Furthermore, the occurrence probabilities, correlation coefficients, and mean peak fluxes are derived in multi-dimensional bins combining the aforementioned solar parameters. The correlation coefficients are also determined in different proton energy channels ranging from 5 to 200 MeV. The results show that the correlation between the proton peak flux and the CME speed decreases with energy, while the correlation with the flare intensity shows the opposite behaviour. Furthermore, the correlation with the CME speed is stronger than the correlation with the flare intensity below 15 MeV and becomes weaker above 20 MeV. When the enhancements in the flux profiles due to interplanetary shocks are not excluded, only a small but not very significant change is observed in the correlation coefficients between the proton peak flux below 7 MeV and the CME speed.
Very energetic astrophysical events are required to accelerate cosmic rays to above 10(18) electronvolts. GRBs (γ-ray bursts) have been proposed as possible candidate sources. In the GRB 'fireball' ...model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and γ-rays. Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux. Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions. This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10(18) electronvolts or that the efficiency of neutrino production is much lower than has been predicted.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The capability to predict the parameters of an SEP event such as its onset, peak flux, and duration is critical to assessing any potential space weather impact. We present a new flexible modeling ...system simulating the propagation of Solar Energetic Particles (SEPs) from locations near the Sun to any given location in the heliosphere to forecast the SEP flux profiles. Solar Particle Radiation SWx (SPARX) uses an innovative methodology that allows implementation within an operational framework to overcome the time constraints of test particle modeling of SEP profiles, allowing the production of near‐real‐time SEP nowcasts and forecasts, when paired with appropriate near‐real‐time triggers. SPARX has the capability to produce SEP forecasts within minutes of being triggered by observations of a solar eruptive event. The model is based on the test particle approach and is spatially 3‐D, thus allowing for the possibility of transport in the direction perpendicular to the magnetic field. The model naturally includes the effects of perpendicular propagation due to drifts and drift‐induced deceleration. The modeling framework and the way in which parameters of relevance for Space Weather forecasting are obtained are described. The first results from the modeling system are presented. These results demonstrate that corotation and drift of SEP streams play an important role in shaping SEP flux profiles.
Key Points
A new operational modeling system simulating the propagation of SEPs
The model is based on the test particle approach including drift effects
First results show that corotation and drift shape observed SEP profiles
On 10 September 2017, a ground level enhancement (GLE) of cosmic ray intensity, identified as GLE72, was recorded by several stations of the worldwide neutron monitor network provided by the ...high‐resolution Neutron Monitor Database. The solar proton event that resulted in this GLE was associated with active region AR2673, which produced an X8.2 flare on the solar west limb. Protons were measured by the GOES satellites with energies above 10, 50, and 100 MeV, while particles at higher energies above 500 MeV were registered by ground‐based neutron monitors. This GLE event was successfully detected in real time by the GLE Alert plus System of the Athens Neutron Monitor Station (A.Ne.Mo.S.). In this work an overview of the GLE72 event is given, and a detailed analysis of the evolution of the GLE Alert signal issued by the GLE Alert plus System as well as a postevent summary are presented.
Key Points
A ground level enhancement of cosmic ray intensity, identified as GLE72, was recorded by several stations of neutron monitor network
This GLE event was successfully detected in real time by the GLE Alert plus System of the Athens Neutron Monitor Station (A.Ne.Mo.S.)
Seven neutron monitor stations contributed to the GLE Alert plus System due to the functionality of this system and the data availability
We report the first detailed comparisons of the rates and spectra of neutral-current neutrino interactions at two widely separated locations. A depletion in the rate at the far site would indicate ...mixing between nu(mu) and a sterile particle. No anomalous depletion in the reconstructed energy spectrum is observed. Assuming oscillations occur at a single mass-squared splitting, a fit to the neutral- and charged-current energy spectra limits the fraction of nu(mu) oscillating to a sterile neutrino to be below 0.68 at 90% confidence level. A less stringent limit due to a possible contribution to the measured neutral-current event rate at the far site from nu(e) appearance at the current experimental limit is also presented.
The rate of high energy cosmic ray muons as measured underground is shown to be strongly correlated with upper‐air temperatures during short‐term atmospheric (10‐day) events. The effects are seen by ...correlating data from the MINOS underground detector and temperatures from the European Centre for Medium Range Weather Forecasts during the winter periods from 2003–2007. This effect provides an independent technique for the measurement of meteorological conditions and presents a unique opportunity to measure both short and long‐term changes in this important part of the atmosphere.
The Double Chooz Experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. A ratio of 0.944 ± 0.016 (stat) ± 0.040 (syst) observed to ...predicted events was obtained in 101 days of running at the Chooz Nuclear Power Plant in France, with two 4.25 GWth reactors. The results were obtained from a single 10 m3 fiducial volume detector located 1050 m from the two reactor cores. The reactor antineutrino flux prediction used the Bugey4 measurement as an anchor point. The deficit can be interpreted as an indication of a non-zero value of the still unmeasured neutrino mixing parameter sin 22θ13. Analyzing both the rate of the prompt positrons and their energy spectrum we find sin 22θ13 = 0.086 ± 0.041 (stat) ± 0.030 (syst), or, at 90% CL, 0.015 < sin 22θ13 < 0.16.
SN 2008D, a core collapse supernova at a distance of 27 Mpc, was serendipitously discovered by the Swift satellite through an associated X-ray flash. Core collapse supernovae have been observed in ...association with long gamma-ray bursts and X-ray flashes and a physical connection is widely assumed. This connection could imply that some core collapse supernovae possess mildly relativistic jets in which high-energy neutrinos are produced through proton-proton collisions. The predicted neutrino spectra would be detectable by Cherenkov neutrino detectors like IceCube. A search for a neutrino signal in temporal and spatial correlation with the observed X-ray flash of SN 2008D was conducted using data taken in 2007–2008 with 22 strings of the IceCube detector. Events were selected based on a boosted decision tree classifier trained with simulated signal and experimental background data. The classifier was optimized to the position and a “soft jet” neutrino spectrum assumed for SN 2008D. Using three search windows placed around the X-ray peak, emission time scales from 100–10 000 s were probed. No events passing the cuts were observed in agreement with the signal expectation of 0.13 events. Upper limits on the muon neutrino flux from core collapse supernovae were derived for different emission time scales and the principal model parameters were constrained. While no meaningful limits can be given in the case of an isotropic neutrino emission, the parameter space for a jetted emission can be constrained. Future analyses with the full 86 string IceCube detector could detect up to ~100 events for a core-collapse supernova at 10 Mpc according to the soft jet model.
The Heliophysics Integrated Observatory (HELIO) is a software infrastructure involving a collection of web services, heliospheric data sources (
e.g.
, solar, planetary,
etc.
), and event catalogues ...– all of which are accessible through a unified front end. In this paper we use the HELIO infrastructure to perform three case studies based on solar events that propagate through the heliosphere. These include a coronal mass ejection that intersects both Earth and Mars, a solar energetic particle event that crosses the orbit of Earth, and a high-speed solar wind stream, produced by a coronal hole, that is observed
in situ
at Earth (L1). A ballistic propagation model is run as one of the HELIO services and used to model these events, predicting if they will interact with a spacecraft or planet and determining the associated time of arrival. The HELIO infrastructure streamlines the method used to perform these kinds of case study by centralising the process of searching for and visualising data, indicating interesting features on the solar disk, and finally connecting remotely observed solar features with those detected by
in situ
solar wind and energetic particle instruments. HELIO represents an important leap forward in European heliophysics infrastructure by bridging the boundaries of traditional scientific domains.
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