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.Comment: 9 pages, 13 figure

Was the GLE on May 17, 2012 linked with the M5.1-class flare the first in the 24th solar cycle?

On May 17, 2012 an M5.1-class flare exploded from the sun. An O-type coronal mass ejection (CME) was also associated with this flare. There was an instant increase in proton flux with peak at $\geq 100$ MeV, leading to S2 solar radiation storm level. In about 20 minutes after the X-ray emission, the solar particles reached the Earth.It was the source of the first (since December 2006) ground level enhancement (GLE) of the current solar cycle 24. The GLE was detected by neutron monitors (NM) and other ground based detectors. Here we present an observation by the Tupi muon telescopes (Niteroi, Brazil, $22^{0}.9 S$, $43^{0}.2 W$, 3 m above sea level) of the enhancement of muons at ground level associated with this M5.1-class solar flare. The Tupi telescopes registered a muon excess over background $\sim 20\%$ in the 5-min binning time profile. The Tupi signal is studied in correlation with data obtained by space-borne detectors (GOES, ACE), ground based neutron monitors (Oulu) and air shower detectors (the IceTop surface component of the IceCube neutrino observatory). We also report the observation of the muon signal possibly associated with the CME/sheath striking the Earth magnetosphere on May 20, 2012. We show that the observed temporal correlation of the muon excess observed by the Tupi muon telescopes with solar transient events suggests a real physical connection between them. Our observation indicates that combination of two factors, the low energy threshold of the Tupi muon telescopes and the location of the Tupi experiment in the South Atlantic Anomaly region, can be favorable in the study and detection of the solar transient events. Our experiment provides new data complementary to other techniques (space and ground based) in the study of solar physics.Comment: 9 pages, 10 figure

Observation of a muon excess following a gamma-ray burst event detected at the International Space Station

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)On April 24, 2012, at 16: 47: 14 UT, the Gas Slit Camera (GSC) of the Japanese Monitor of All-sky X-ray Image (MAXI) instrument on the International Space Station detected a short x-ray transient lasting about 34 seconds. The MAXI/GSC transient was most likely a gamma-ray burst (GRB), because of the high Galactic latitude, spectral hardness ratio, and the absence of known bright x-ray sources at the detected position. In addition, the MAXI/GSC transient GRB 120424A coordinates were in the field of view of the inclined Tupi muon telescope located at ground level (3 m above sea level) at (22.9 degrees W, 43.2 degrees S) in the South Atlantic Anomaly region. We report here that the Tupi telescope registered a muon excess with a signal significance 6.2 sigma within the MAXI/GSC transient time period. Assuming a power law function with a spectral index of gamma = -1.54 in the tail of the primary gamma-ray energy spectrum, we can conclude that the fluence obtained from the muon excess detected by the Tupi telescope is consistent with the preliminary value obtained by the MAXI team. This result agrees with an assumption that the muons were produced in photonuclear reactions in the Earth's atmosphere. In addition, we show also that the South Atlantic Anomaly region can be a favorable place at ground for the detection of the tail of the energy spectrum (the GeV counterpart) of some GRBs.8710Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [306605/2009-0, 01300.077189/2008-6]Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ) [08458.009577/2011-81, E-26/101.649/2011

Relativistic proton levels from region AR 12673 (GLE #72) and the heliospheric current sheet as a Sun-earth magnetic connection

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOOn 2017 September 10 Neutron Monitors (NMs) apparatus located at ground level and high latitudes detected an increase in the counting rate associated to solar energetic particles (SEPs) emission from X8.2-class solar flare and its associated CME. This was the second-highest flare of the current solar cycle. The origin was the active region AR 12673 when it was located at the edge of the west solar disk, magnetically poorly connected with Earth. However, there was a peculiar condition: the solar protons accelerated by the CME shocks were injected within a heliospheric current sheet (HCS) region when Earth was crossing this region. We show that often HCS and SEPs propagation are closely related. If the source locations of SEPs are within or close to HCS, the HCS play the role of a Sun-Earth magnetic connection. SEPs drift around HCS paths, and SEPs are also drift in a wide range of longitudes by the HCSs. In some cases, and especially when Earth crosses the HCS sector, a fraction of these particles can reach Earth with a harder energetic particle flux, triggering a ground-level enhancement (GLE). The blast on 2017 September 10, which triggered the GLE #72, was the second in the current solar cycle. We show that the two GLEs, including all sub-GLEs observed in the current solar cycle, comes from solar explosions that happened within an HCS structure; this behavior is also observed in the GLEs of the previous solar cycle. In general, solar explosions from active regions poorly connected with Earth can trigger GLEs, through the mechanism described above. In all cases, the SEPs drift processes by HCS structures provides an efficient particle transport, allowing the observation of these solar transient events.131996114CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO306605/2009-0308494/2015-608458.009577/2011-812011/50193-4We acknowledge the use of the NMDB database, founded under the European Unions FP7 programme (contract no. 213007). The data of the South Pole NM is provided by the University of Delaware with support from the U.S. National Science Foundation under grant ANT-0838839. We express our gratitude to the ACE Science Center; the NOAA Space Weather Prediction Center for valuable information and data used in this study; and Maximilian Teodorescu for the AR 12673 image. This work is supported by the National Council for Research (CNPq) of Brazil, under Grant 306605/2009-0 and 308494/2015-6, Rio de Janeiro Research Foundation (FAPERJ), under Grants 08458.009577/2011-81, and So Paulo Research Foundation (FAPESP), under Grant 2011/50193-4

The 2015 summer solstice storm: one of the major geomagnetic storms of solar cycle 24 observed at ground level

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOWe report on the 22 - 23 June 2015 geomagnetic storm that occurred at the summer solstice. There have been fewer intense geomagnetic storms during the current solar cycle, Solar Cycle 24, than in the previous cycle. This situation changed after mid-June 2015, when one of the largest solar active regions (AR 12371) of Solar Cycle 24 that was located close to the central meridian, produced several coronal mass ejections (CMEs) associated with M-class flares. The impact of these CMEs on the Earth's magnetosphere resulted in a moderate to severe G4-class geomagnetic storm on 22 - 23 June 2015 and a G2 (moderate) geomagnetic storm on 24 June. The G4 solstice storm was the second largest (so far) geomagnetic storm of Cycle 24. We highlight the ground-level observations made with the New-Tupi, Muonca, and the CARPET El Leoncito cosmic-ray detectors that are located within the South Atlantic Anomaly (SAA) region. These observations are studied in correlation with data obtained by space-borne detectors (ACE, GOES, SDO, and SOHO) and other ground-based experiments. The CME designations are taken from the Computer Aided CME Tracking (CACTus) automated catalog. As expected, Forbush decreases (FD) associated with the passing CMEs were recorded by these detectors. We note a peculiar feature linked to a severe geomagnetic storm event. The 21 June 2015 CME 0091 (CACTus CME catalog number) was likely associated with the 22 June summer solstice FD event. The angular width of CME 0091 was very narrow and measured degrees seen from Earth. In most cases, only CME halos and partial halos lead to severe geomagnetic storms. We perform a cross-check analysis of the FD events detected during the rise phase of Solar Cycle 24, the geomagnetic parameters, and the CACTus CME catalog. Our study suggests that narrow angular-width CMEs that erupt in a westward direction from the Sun-Earth line can lead to moderate and severe geomagnetic storms. We also report on the strong solar proton radiation storm that began on 21 June. We did not find a signal from this SEP at ground level. The details of these observations are presented.2935128CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO306605/2009-0406331/2015-4308494/2015-6312066/2016-3152050/2016-708458.009577/2011-81E-26/101.649/20112011/24117-92011/50193-