C. E. Navia

Muon excess at sea level from solar flares in association with the Fermi GBM spacecraft detector

This paper presents results of an ongoing survey on the associations between muon excesses at ground level registered by the Tupi telescopes and transient solar events, two solar flares whose gamma-ray and X-ray emissions were reported by, respectively, the Fermi GBM and the GOES 14. We show that solar flares of small scale, those with prompt X-ray emission classified by GOES as C-Class (power 10 to 10 W m at 1 AU) may give rise to muon excess probably associated with solar protons and ions emitted by the flare and arriving at the Earth as a coherent particle pulse. The Tupi telescopes are within the central region of the South Atlantic Anomaly (SAA), which allows particle detectors to achieve a low rigidity of response to primary and secondary charged particles (≥ 0.1 GV). Here we argue for the possibility of a “scale-free” energy distribution of particles accelerated by solar flares. Large and small scale flares have the same energy spectrum up to energies exceeding the pion production, the difference between them is only the intensity. If this hypothesis is correct, the Tupi telescope is registering muons produced by protons (ions)

Is there an enhancement of muons at sea level from transient events

In a recent study of a search for enhancements from the Galactic center with muons at sea level using the TUPI muon telescope, we have found several ground-level enhancements (GLEs) as very sharp peaks above the count rate background. This paper reports a consistent analysis of two GLEs observed in 2003 December and detected after an upgrade of the data acquisition system, which includes a noise filter and allows us to verify that the GLEs are not mere background fluctuations. The main target of this study is a search for the origin of the GLEs. The results show that one of them has a strong correlation with a solar flare, while the other has an unknown origin, because there is no satellite report of a solar flare, no prompt X-ray emission, and no excess of nuclei during the raster scan in which the GLE was observed. Even so, two possibilities are analyzed: the solar flare hypothesis and the gamma-ray burst (GRB) hypothesis. We show, by using the FLUKA Monte Carlo results for photoproduction, that under certain conditions there is the possibility of an enhancement of muons at sea level from GeV GRBs.

Tokamak equilibria with non field-aligned axisymmetric divergence-free rotational flows

Rotational ideal divergence-free magnetohydrodynamic (MHD) equations are expressed in terms of transformed variables w→*=(μρ)1/2v→ and μp* = (μp + w*2/2), where v→, p, and ρ are plasma velocity, pressure, and mass density, respectively. With divergence-free flows, ∇·v→=0, the plasma density ρ does not appear in the MHD equations written in terms of w→* and μp*. The non field-aligned rotational Grad-Shafranov equation is represented in spherical coordinates. Tokamak-like axisymmetric equilibria with v→ ⊥∇ρ are obtained analytically by solving for torus solutions under only three source functions.

Self-similar magnetohydrodynamic model for direct current discharge fireball experiments

Ball lightning models and corresponding laboratory efforts in generating fireballs are briefly summarized to give an overview of the current status. In particular, emphasis is given to direct current discharge experiments at atmospheric pressure such as capillary discharge with a plasma plume in front of the anode opening [Emelin et al., Tech. Phys. Letters 23, 758 (1997)] and water resistor discharge with fluttering fireball overhead [Egorov and Stepanov, Tech. Phys. 47, 1584 (2002)]. These fireballs are interpreted as laboratory demonstrations of the self-similar magnetohydrodynamic (MHD) model of ball lightning [Tsui, Phys. Plasmas 13, 072102 (2006)].

Search for muon enhancement at sea level from transient solar activity

This paper presents first results of an ongoing study of a possible association between muon enhancements at ground observed by the TUPI telescope and transient events such as the Suns X-ray activity. The analysis of the observed phenomenon by using the GOES satellite archive data seems to indicate that on most cases the Ground Level Enhancements (GLEs) could potentially be associated with solar flares. We show that small-scale solar flares, those with prompt X-ray emission classified as C class (power above 10{sup -6} Watts m{sup -2} at 1 AU) may give rise to GLEs, probably associated with solar protons and ions arriving to the Earth as a coherent particle pulse. The TUPI telescopes high performance with these energetic solar particles arises mainly from: (i) its high counting rate (up to {approx}100 KHz). This value in most cases is around 100 times higher than other detectors at ground and (ii) due to its tracking system. The telescope is always looking near the direction of the IMF lines. The GLEs delay in relation of the X-ray prompt emission suggest that shock driven by corona mass ejection (CME) is an essential requirement for the particle acceleration efficiency.

Muon enhancements at sea level in association with Swift-BAT and MILAGRO triggers

Recently, triggers occurring during high background rate intervals have been reporter by the Swift-BAT gamma-ray burst detector. Among them, there were two on January 24, two on January 25, and two on February 13 and 18, all in 2008. These Swift-BAT triggers in most cases are probably noise triggers that occurred while Swift was entering the South Atlantic Anomaly (SAA). In fact, we show that they happen during a plentiful precipitation of high energy particles in the SAA, producing muons in the atmosphere detected by two directional telescopes at sea level, inside the SAA region (Tupi experiment). They look like sharp peaks in the muon counting rate. In the same category are two triggers from the MILAGRO ground-based detector, on January 25 and 31, 2008, respectively. In addition, the trigger coordinates are close to (and, in two cases, inside) the field of view of the telescopes. From an additional analysis in the behavior of the muon counting rate, it is possible to conclude that the events are produced by precipitation of high energy charged particles in the SAA region. Thus, due to its localization, the Tupi experiment constitutes a new sensor of high energy particle precipitation in the SAA, and it can be useful in the identification of some triggers of gamma-ray burst detectors.

OBSERVATION OF MUON EXCESS AT GROUND LEVEL IN RELATION TO GAMMA-RAY BURSTS DETECTED FROM SPACE

In this paper we examine the possibility of the ground observation of the gigaelectronvolt counterparts associated with the Monitor of All-sky X-ray Image transient event (trigger 58072727) and the Swift GRB140512A event. In both cases, there was a muon excess with a statistical significance above 4σ. The coordinates of the events were located in the field of view (FOV) of the Tupi muon telescopes at the time of the occurrence. Since 2013 August, the Tupi experiment has been operating a new extended array of five muon telescopes, located at ground level at (, 3 m above sea level). This location coincides with the South Atlantic Anomaly central region. We consider a hypothesis that the muon excess could be due to photonuclear reactions in the Earths atmosphere induced by gamma rays with energies above 10 GeV. We describe a data analysis for candidate events identified by internally triggered (by the Tupi experiment) as well as untriggered (dependent on external observations) modes of search. In light of the Fermi LAT () gamma-ray bursts (GRBs) catalog, we examine the possibility of the ground observation of similar transient events within the FOV of the extended Tupi array and perform a systematic analysis of the Tupi data. Using a Monte Carlo simulation, we discuss the experimental conditions that allow the detection of signals from GRBs at ground level.

Search for a simultaneous signal from small transient events in the Pierre Auger Observatory and the Tupi muon telescopes

We present results of a search for a possible signal from small scale solar transient events (such as flares and interplanetary shocks) as well as possible counterparts to Gamma-Ray Burst (GRB) observed simultaneously by the Tupi muon telescope Niteroi-Brazil, 22.90S, 43.20W, 3 m above sea level) and the Pierre Auger Observatory surface detectors (Malargue-Argentina, 69.30S, 35.30W, altitude 1400 m). Both cosmic ray experiments are located inside the South Atlantic Anomaly (SAA) region. Our analysis of several examples shows similarities in the behavior of the counting rate of low energy (above 100 MeV) particles in association with the solar activity (solar flares and interplanetary shocks). We also report an observation by the Tupi experiment of the enhancement of muons at ground level with a significance higher than 8 sigma in the 1-sec binning counting rate (raw data) in close time coincidence (T-184 sec) with the Swift-BAT GRB110928B (trigger=504307). The GRB 110928B coordinates are in the field of view of the vertical Tupi telescope, and the burst was close to the MAXI source J1836-194. The 5-min muon counting rate in the vertical Tupi telescope as well as publicly available data from Auger (15 minutes averages of the scaler rates) show small peaks above the background fluctuations at the time following the Swift-BAT GRB 110928B trigger. In accordance with the long duration trigger, this signal can possibly suggest a long GRB, with a precursor narrow peak at T-184 sec.

Self-affine properties of intensity fluctuations of muons at sea level

Abstract Using muon intensities (in the GeV energy region) observed at sea level every 20 s , we have studied the muon background characteristics. The muon intensities time series has been obtained by using a new muon telescope and analyzed applying the methods of power spectral and fractal analysis. Under certain conditions it is found that they have self-affine properties as well as they are basically equivalents. In addition, we show which fractal dimension of the muon time series reflects the interplanetary magnetic Kolmogorovs turbulence. This means that the progenitors of the muon observed are charged particles, probably galactic protons (E p >200 GeV ) and that they are modulated by the interplanetary magnetic field.

Possible GeV counterpart at the ground level associated with Fermi LAT gamma-ray bursts

From June 2014 to February 2017, the Fermi LAT detected 46 gamma-ray bursts (GRBs) with photon energies above 20 MeV, and the trigger coordinates of seven of them were within the FoV of New-Tupi detector located in the central region of the South Atlantic Anomaly (SAA). We show in this paper that two of these seven GRBs have a probable GeV counterpart observed at ground level by New-Tupi detector. The first is GRB 160609A, a short duration GRB with a bright emission of photons over a broad energy range extending up to GeV energies. The second is GRB 160625B, a very long duration GRB, for which the Fermi LAT detected more than 300 photons with energies above 100 MeV in the