author = "Augusto, C. R. A. and Navia, C. E. and Oliveira, M. N. de and 
                         Nepomuceno, A. A. and Raulin, J. P. and Tueros, E. and 
                         Mendon{\c{c}}a, Rafael Rodrigues Souza de and Fauth, A. C. and 
                         Souza, H. Vieira de and Kopenkin, V. and Sinzi, T.",
          affiliation = "{Universidade Federal Fluminense (UFF)} and {Universidade Federal 
                         Fluminense (UFF)} and {Universidade Federal Fluminense (UFF)} and 
                         {Universidade Federal Fluminense (UFF)} and {Universidade 
                         Presbiteriana Mackenzie} and {Universidade Presbiteriana 
                         Mackenzie} and {Instituto Nacional de Pesquisas Espaciais (INPE)} 
                         and {Universidade Estadual de Campinas (UNICAMP)} and 
                         {Universidade Estadual de Campinas (UNICAMP)} and {Waseda 
                         University} and {Rikkyo University}",
                title = "The 2015 summer solstice storm: one of the major geomagnetic 
                         storms of solar cycle 24 observed at ground level",
              journal = "Solar Physics",
                 year = "2018",
               volume = "293",
               number = "5",
                pages = "e84",
             keywords = "Sun: activity  Astroparticle physics  Atmospheric effects  
                         Instrumentation: detectors.",
             abstract = "We 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 Earths 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 \∼56\∘ 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 SunEarth 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.",
                  doi = "10.1007/s11207-018-1303-8",
                  url = "http://dx.doi.org/10.1007/s11207-018-1303-8",
                 issn = "0038-0938 and 1573-093X",
             language = "en",
           targetfile = "augusto_2015.pdf",
        urlaccessdate = "28 nov. 2020"