A new approach to solar flare prediction

Frontiers of Physics - Graphene oxide (GO), the functionalized graphene with oxygenated groups (mainly epoxy and hydroxyl), has attracted resurgent interests in the past decade owing to its large...     

Study of the solar flare of December 16, 1988 on the basis of the 2.223-MeV γ line and initial characteristics of flare neutrons

The third burst of the solar flare of December 16, 1988 was investigated on the assumption of both Bessel and power spectra of the initial charged particles. Refined data on the flare-neutron-production cross sections were used and two different neutron source altitudes were considered. An increase in the solar plasma density under the flare region up 2 × 10¹⁷ cm^?3 has been found throughout the photosphere; in some cases, the plasma density increased to (3–6) × 10¹⁷ cm^?3 in the initial flare stages. The dynamics of the increase in the plasma density during γ emission has been traced. It is found that the particle spectrum changes from moderately hard to soft and then to hard during γ emission in both spectral representations.     

New approach to the problem of solar wind formation

A hypothesis is discussed according to which the variation of the solar activity in 11-year intervals stems from the need for convective heat transfer regularization. It is not improbable that such regularization is disturbed during the Mounder minimum of solar activity, when heat transfer is most likely chaotic. The obstacles resulting from a sharp decrease in the density of the medium in going to the uppermost strata of the convective zone are considered. The hypothesis for solar wind formation in these strata seems to be the only valid one.     

Diagnostics of the region of nuclear interactions of neutrons in the solar flare of January 20, 2005 by gamma-ray lines

Based on an analysis of the time history of the count rate in the 2.223 MeV neutron-capture line from the extreme solar event of January 20, 2005, we investigate the density of the surrounding medium and the 3He content in the area of the 2.223 MeV gamma-line production. The analysis uses data on count rates in the 2.223 MeV gamma-ray line, as well as in lines ranging from 4 to 7 MeV, which were acquired with the AVS-F apparatus from the SONG-D detector onboard the CORONAS-F satellite. It is shown that simulation of the time history of the 2.223 MeV gamma-ray line from the flare event would require an assumption of the elevated abundance of 3He. It is found that in the area of the 2.223 MeV gamma-line production the ratio n(³He)/n(¹H) is (1.4 ± 0.15) × 10^?4, although, based on the data from different flares, on average it is approximately 2 × 10^?5. The elevated abundance of ³He may be considered as an additional indirect argument for the possible presence of reaction products of neutron radiative absorption by the 3He isotope within a small increase in gamma emission in the 15?C21 MeV range over the background level (which was detected previously from the CORONAS-F/AVS-F data).     

Universality in solar flare and earthquake occurrence

Earthquakes and solar flares are phenomena involving huge and rapid releases of energy characterized by complex temporal occurrence. By analyzing available experimental catalogs, we show that the stochastic processes underlying these apparently different phenomena have universal properties. Namely, both problems exhibit the same distributions of sizes, interoccurrence times, and the same temporal clustering: We find after flare sequences with power law temporal correlations as the Omori law for seismic sequences. The observed universality suggests a common approach to the interpretation of both phenomena in terms of the same driving physical mechanism.     

Influences of misprediction costs on solar flare prediction

Science China Physics, Mechanics & Astronomy - The mispredictive costs of flaring and non-flaring samples are different for different applications of solar flare prediction. Hence, solar flare...     

Detection of solar neutrons by ground-based neutron monitors

Summary The analysis of the Rome NM-64 data, performed on the occasion of 8 solar flares accompanied by gamma-bursts and 10 solar flares accompanied by large X-ray fluxes, shows that the solar energetic neutron events could be detected by ground-based stations particularly when they are located at mountain altitude and middle-low latitudes. Suggestions for improving the neutron monitor efficiency for detecting solar neutron events are given. Paper presented at the 2^o Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May-2 June 1984.     

Cyclotron resonance maser as a solar flare trigger

We propose a new mechanism of solar flaring, which is based on explosive phenomena in magnetic traps in the presence of a two-component plasma composed of fast electrons with anisotropic velocity distribution and a dense cold background plasma with high ionization. It is assumed that such a plasma is generated in a coronal magnetic trap in a preflare stage. This system, which is essentially a cyclotron resonance maser, becomes unstable under certain conditions and gives rise to an explosive cyclotron instability, which develops at first in a very small local area and is accompanied by intense heating of the background plasma and release of fast electrons at the trap ends. The energy of fast particles is collected from the entire volume of the magnetic trap and is localized in the form of heat in the explosion area from which thermal and shock waves are propagated. The model makes it possible to explain the main solar flare effects.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 6, pp. 699–712, June, 1996.     

Proton spectrum of the 2005 January 20 solar flare

An extreme solar cosmic ray event broke out on 2005 January 20.Not only is it the most intensive solar energetic particle (SEP) event,with＞100 MeV particles measured by GOES satellite since 1986,but it has been the largest ground level enhancement (GLE) event recorded by the ground-based neutron monitors since 1956.This work presents the solar proton spectra for this event with data obtained by GOES in multiple energy cbannels.These spectra are well fitted by a modified power-law function.The spectral index of around -1 indicates that the January 20 event has a hard energy spectrum.Possible mechanisms for the acceleration of relativistic protons are discussed.     

Proton spectrum of the 2005 January 20 solar flare

An extreme solar cosmic ray event broke out on 2005 January 20. Not only is it the most intensive solar energetic particle (SEP) event, with >100MeV particles measured by GOES satellite since 1986, but it has been the largest ground level enhancement (GLE) event recorded by the ground-based neutron monitors since 1956. This work presents the solar proton spectra for this event with data obtained by GOES in multiple energy channels. These spectra are well fitted by a modified power-law function. The spectral index of around －1 indicates that the January 20 event has a hard energy spectrum. Possible mechanisms for the acceleration of relativistic protons are discussed.     

Statistical properties and universality in earthquake and solar flare occurrence

Earthquakes are phenomena of great complexity, however some simple general laws govern the statistics of their occurrence. Some of these most important laws exhibit scale invariance, as the Gutenberg-Richter law and the Omori law. The origin of these scaling behaviours is not yet fully understood and a natural fondamental question concerns the existence of these features also in other complex phenomena. A direct inspection of experimental catalogues has shown that the stochastic processes underlying solar flare and earthquake occurrence have universal properties. Another intensively debated question is the existence of correlations between magnitudes of subsequent earthquakes. Our recent analysis of the Southern California Catalogue has shown that non-zero magnitude correlations exist. A branching model based on a dynamical scaling hypothesis, relating magnitude to time, reproduces the hierarchical organization in time and magnitude of events and the observed magnitude correlations.     

Method for registration of solar cosmic rays by detecting neutrons

We consider a method of detecting the ionizing component of solar cosmic rays (SCRs) with energy from tens of MeV to tens of GeV by measuring the energy loss of SCR protons and light nuclei in scintillators and the multiplicity of the local neutron generation in a converter. Scintillation detectors based on stilbene, lithium glass, and solid-state photomultiplier tubes are capable of detecting fast neutrons with a temporal resolution of 10 ns and rejecting the gamma-ray background in the measuring system. The method will allow investigating the nucleon components of primary SCRs in circumterrestrial space.     

Radiative capture of low-energy neutrons in the shell-model approach to nuclear reactions

The shell-model approach to photonuclear reactions is applied to the radiative capture of low-energy neutrons. The direct, compound and channel resonant contributions to the collision matrix appear in a natural way. We show that the experimental data in the vicinity of the 3s giant resonance can be quantitatively interpreted in terms of the channel resonant capture. The relationship with the R-matrix approach of Lane and Lynn is discussed.     

Repeated gamma-ray bursts from the June 15, 1991 solar flare

The results of the detection of repeated bursts of gamma rays with energies exceeding 30 MeV from the June 15, 1991 solar flare, observed with the Gamma-1 telescope, are examined. It is shown that they occur on the declining part of the temporal profile of the gamma radiation and last for ∼10 min (they occur 27 min after the optical part of the flare starts). No appreciable radiation bursts were observed during the subsequent quasiconstant part (∼20 min). It is concluded that repeated events in which particles are accelerated occur in the active stage of the powerful June 15, 1991 solar flare. It is noted that while the June 15, 1991 and March 26, 1991 gamma-ray bursts share a common character, their spectral and temporal characteristics are substantially different. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 889–893 (25 June 1996)     

Spectrum and mechanism of the acceleration of protons in a solar flare

Investigations based on neutron monitor data show that two components of relativistic cosmic rays are generated by a solar flare. The so-called prompt component comes from a flare with flight times and is characterized by an exponential spectrum with a parameter of E ₀ ≈ 0.5 Gev. Numerical simulation of the conditions in the flare current sheet of the Bastille flare demonstrated that such a spectrum is formed at a magnetic reconnection velocity of ∼10⁷ cm s⁻¹. The delayed component has a power law spectrum and is apparently formed during the diffusion of protons in the plasma of the interplanetary magnetic field.     

Identifying time-clustering structures in the sequence of solar flare hard X-ray bursts

Time-clustering behavior in the sequence of solar flare hard X-ray bursts from April 1991 to May 2000 obtained from BATSE/GRO (Burst and Transient Source Experiment aboard the Compton Gamma Ray Observatory satellite) was investigated by using the Allan Factor statistics. The presence of different timescale regimes ranging from Poissonian to rather strong long-range correlated behaviors has been revealed.     

New gravitational experiment with ultracold neutrons

The results of a new neutron gravitation experiment are reported. The change in the energy of a neutron falling to a known height in the Earth’s gravitational field is compensated by an energy quantum ?Θ transferred to the neutron as a result of the phase modulation of the neutron wave. A phase diffraction grating moving across the direction of the propagation of the neutron wave is used as a modulator. The experiment has been carried out with ultracold neutrons Interference filters, neutron analogues of Fabry-Perot interferometers, are used for the spectrometry of ultracold neutrons. The force m _g g _n acting on the neutron in the Earth’s gravitational field has been measured with an accuracy of about 0.2%.