Jorge Pérez-Peraza

ASTROPHYSICAL ASPECTS IN THE STUDIES OF SOLAR COSMIC RAYS

This review paper comprises main concepts, available observational data and recent theoretical results related to astrophysical aspects of particle acceleration at/near the Sun and extreme capacities of the solar accelerator(s). We summarize underground and ground-based observations of solar cosmic rays (SCR) accumulated since 1942, direct spacecraft measurements of solar energetic particles (SEP) near the Earths orbit, indirect information on the SCR variations in the past, and other relevant astrophysical, solar and geophysical data. The list of the problems under discussion includes: upper limit spectrum (ULS) for solar cosmic rays; maximum energy (rigidity), Em(Rm), of particles accelerated at/near the Sun; production of the flare neutrinos; energetics of SCR and solar flares; production of flare neutrons and gamma rays; charge states and elemental abundances of accelerated solar ions; coronal mass ejections (CMEs) and extended coronal structures in acceleration models; magnetic reconnection in acceleration scenarios; size (frequency) distributions of solar proton events (SPE) and stellar flares; occurrence probability of giant flares; archaeology of solar cosmic rays. The discussion allows us to outline a series of interesting conceptual and physical associations of SCR generation with the high-energy processes at other stars. The most reliable estimates of various parameters are given in each of research fields mentioned above; a set of promising lines of future studies is highlighted. A great importance of SCR data for resolving some general astrophysical problems is emphasized.

Analysis of the evolution of the Antarctic ozone hole size

[1]xa0The Antarctic ozone hole in the stratospheric layer has two basic parameters: depth and size. In this work the evolution of the ozone hole size (OHS) is analyzed using the monthly mean data for September, October, and November during 1982–2003. On the basis of the analysis of subsets of the data series we found signals of a reversal in the OHS trend during the period 1995–2003 for the months of October and November. On the other hand, the trends of the OHS subsets for the month of September show cyclical changes that approximately follow the variations of the geomagnetic Ap index and the 10.7-cm solar flux index. The detected beginning of the recovery process is a good test for models in order to match observations.

Thirty-Year Periodicity of Cosmic Rays

Cosmogenic isotopes have frequently been employed as proxies of ancient cosmic ray fluxes. On the basis of periodicities of the 10Be time series (using data from both the South and North Poles) and the 14C time series (with data from Intercal-98), we offer evidence of the existence of cosmic ray fluctuations with a periodicity of around 30 years. Results were obtained by using the wavelet transformation spectral technique, signal reconstruction by autoregressive spectral analysis (ARMA), and the Lomb-Scargle periodogram method. This 30-year periodicity seems to be significant in nature because several solar and climatic indexes exhibit the same modulation, which may indicate that the 30-year frequency of cosmic rays is probably a modulator agent for terrestrial phenomena, reflecting the control source, namely, solar activity.

Model of ionic charge states of impulsive solar energetic particles in solar flares

We have fully developed a computational model (ESCAPE) to follow the behavior of the mean charge state of ions in solar energetic particle events while the ions are accelerated. Our model combines acceleration with energy loss and charge stripping low in the corona. Therefore we have taken into account explicitly the second-order Fermi-type stochastic acceleration under a magnetohydrodynamic turbulence. We have found that the mean ionic charge states depend sensitively on plasma parameters as source temperature or density and on acceleration parameters as efficiency or the timescales for acceleration. Our model finds a systematic increase of the ionic charge states with energy for all the ions studied. This energy dependence differs between ions, and in the energy range of observations this dependence is stronger for heavy ions.

Large Ground Level events in solar cycle 22 and some peculiarities of relativistic proton acceleration.

Some of the Ground Level Enhancements of Solar Cosmic Rays (SCR) recorded by neutron monitors during solar cycle 22 are analyzed. The events appeared in series, and their occurrence rate in 1989-1991 was a factor of 4 larger than the average value (approximately equal to 1/yr) for the total observation interval (since 1942). The events of Sept. 29 and Oct. 24, 1989 proved to be the more intensive. The analyzed events show no peculiarities as to the distribution of the T1/2 parameter, whereas the shape of the profile of some events is notable for a two peak structure. The latter implies the possibility of a two component SCR ejection from two different sources in the solar atmosphere. For the event of Sep. 29 we have estimated the ejection rigidity spectrum of protons to be D solar (R) = (1-2) 10(32)R(-2.9) Gv-1 at R greater than or equal to 1 Gv. As to its proton flux, this event proved to be by 1-2 orders less intensive than the well known event of Feb. 23 1956.

Oscillations of galactic cosmic rays and solar indices before the arrival of relativistic solar protons

Using modern wavelet analysis techniques, we have made an attempt to search for oscillations of intensity of galactic cosmic rays (GCR), sunspot numbers (SS) and magnitudes of coronal index (CI) implying that the time evolution of those oscillations may serve as a precursor of Ground Level Enhancements (GLEs) of solar cosmic rays (SCR). From total number of 70 GLEs registered in 1942–2006, the four large events — 23 February 1956, 14 July 2000, 28 October 2003, and 20 January 2005 — have been chosen for our study. By the results of our analysis, it was shown that a frequency of oscillations of GCR decreases as time approaches to the event day. We have also studied a behaviour of common periodicities of GCR and SCR within the time interval of individual GLE. The oscillations of GLE occurrence rate (OR) at different stages of the solar activity (SA) cycle is of special interest. We have found some common periodicities of SS and CI in the range of short (2.8, 5.2, 27 and 60 days), medium (0.3, 0.5, 0.7, 1.3, 1.8 and 3.2 years) and long (4.6 and 11.0 years) periods. Short and medium periodicities, in general, are rather concentrated around the maxima of solar cycles and display the complex phase relations. When comparing these results with the behaviour of OR oscillations we found that the period of 11 years is dominating (controlling); it is continuous over the entire time interval of 1942–2006, and during all this time it displays high synchronization and clear linear ratios between the phases of oscillations of η, SS and CI. It implies that SCR generation is not isolated stochastic phenomena characteristic exclusively for chromospheric and/or coronal structures. In fact, this process may have global features and involve large regions in the Sun’s atmosphere.

PROGNOSIS OF GLEs OF RELATIVISTIC SOLAR PROTONS

Ground level enhancements (GLEs) are relativistic solar particles measured at ground level by the worldwide network of cosmic ray detectors. These sporadic events are associated with solar flares and are assumed to be of a quasi-random nature. Studying them gives information about their source and propagation processes, the maximum capacity of the Sun as a particle accelerator engine, the magnetic structure of the medium traversed, etc. Space vehicles, as well as electric transformers and gas pipes at high latitudes may be damaged by this kind of radiation. As a result, their prediction has turned out to be very important, but because of their random occurrence, up to now few efforts toward this goal have been made. The results of these efforts have been limited to possible warnings in real time, just before a GLE occurrence, but no specific dates have been predicted well enough in advance to prevent possible hazards. In this study we show that, in spite of the quasi-stochastic nature of GLEs, it is possible to predict them with relative precision, even for future solar cycles. Additionally, a previous study establishing synchronization among some periodicities of several layers of solar atmosphere argues against the full randomness of the phenomenon of relativistic particle production. Therefore, by means of wavelet spectral analysis combined with fuzzy logic tools, we reproduce previous known GLE events and present results for future events. The next GLE is expected to occur in the first semester of 2016.

Solar particle acceleration by slow magnetosonic waves

Abstract Particle acceleration by slow magnetosonic waves (SMW) has been systematically disregarded. We examine the real possibility of this mode for acceleration of solar electrons on basis to a quantitative analysis. Evaluations of the times scales involved in the phenomenon allow us to determine the conditions in the solar atmosphere where resonant acceleration by the slow MHD mode may occur.

Acceleration of particles in shocked magnetic neutral sheets

Abstract We report on a study of particle acceleration in a magnetic neutral sheet which has been struck by a passing MHD shock, such as occurs in the sun when a flare occurs near a helmet streamer. Using trajectory calculations, we derive energy spectra. We propose that long-lived particle events with energies up to 10–100 MeV following solar flares may be explained by the mechanism described here.

Source Energy Spectrum of the 17 May 2012 GLE

Among the several GLE (Ground Level Enhancements) that have presumptuously occurred in the period 2012-2015 the 17th May 2012 is that which is more widely accepted to be a GLE, in view of the high number of high latitude Neutron Monitor (NM) stations that have registered it. In spite of the small amplitude, it was the more prominent of the predicted GLE´s of the present decade (Perez-Peraza & Juarez-Zuniga, 2015). However, the lack of latitude effect makes it difficult to study the characteristics of this event in the high energy extreme of the spectrum. Nevertheless, several outstanding works have been able to derive observational spectra at the top of the earth atmosphere for this peculiar GLE. Some of these works find that the flow of protons is characterized by two components. Quite a great number of works have been published in relation with observational features obtained with different instrumentation, but the source phenomena, regarding the generation processes and source physical parameters have not been scrutinized. The main goal of this work is to look at such aspects by means of the confrontation of the different approaches of the observational spectra with our analytical theoretical spectra based on stochastic acceleration and Electric field acceleration from reconnection processes. In this way, we derive a set of parameters which characterize the sources of these two GLE components, leading us to propose possible scenarios for the generation of particles in this particular GLE event.