Properties of Ground Level Enhancement Events and the Associated Solar Eruptions during Solar Cycle 23

May, 2012
56 pages
Published in:
  • Space Sci.Rev. 171 (2012) 23-60
e-Print:

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Abstract: (arXiv)
We present an overview of the observed properties of the GLEs and those of the associated flares and CMEs. The solar eruptions are very intense involving X-class flares and extreme CME speeds (average ~2000 km/s). The active regions in which the GLE events originate are generally large: 1290 msh (median 1010 msh) compared to 934 msh (median: 790 msh) for SEP-producing active regions. The initial acceleration of GLE-associated CMEs is much larger (by a factor of 2) than that of ordinary CMEs (2.3 km/s2 vs.1 km/s2). The GLE particle release is delayed with respect to the onset of all electromagnetic signatures of the eruptions: type II bursts, low frequency type III bursts, soft X-ray flares and CMEs. The presence of metric type II radio bursts some 17 min (median: 16 min/ range: 3 to 48 min) before the GLE onset indicates shock formation well before the particle release. The release of GLE particles occurs when the CMEs reach an average height of ~3.09 Rs for well-connected events. For poorly connected events, the average CME height at GLE particle release is ~66% larger (mean: 5.18 Rs). The longitudinal dependence is consistent with shock accelerations because the shocks from poorly connected events need to expand more to cross the field lines connecting to an Earth observer. The CME height at metric type II burst onset is in the narrow range 1.29 to 1.8 Rs, with A mean of 1.53 Rs. The CME heights at metric type II burst onset and GLE particle release correspond to the minimum and maximum in the Alfven speed profile. The CME heights at GLE particle release are in good agreement with those obtained from the velocity dispersion analysis (Reames, 2009a,b) including the source longitude dependence. We also discuss the implications of the delay of GLE particle release with respect to complex type III bursts and hard X-ray emission.
Note:
  • 17 figures, 56 pages, based on two LWS/CDAWs on GLE events, part of Topical Issue on GLE events in Space Science Reviews
  • CME
  • Solar flare
  • GLE
  • Shock
  • Radio bursts
  • SEP
    • M. Andriopoulou
      ,
    • H. Mavromichalaki
      ,
    • C. Plainaki
      ,
    • A. Belov
      ,
    • E. Eroshenko
      • Solar Phys. 269 155
    • G.A. Bazilevskaya
      • Space Sci.Rev. 137 (2008) 149
    • G.A. Bazilevskaya
      • Adv.Space Res. 43 (2009) 530
  • Geomagnetism and Aeronomy 50 (1), 21 (2010)
    • A.V. Belov
    • M
      • J.W. Bieber
        ,
      • W. Dröge
        ,
      • P.A. Evenson
        ,
      • R. Pyle
        ,
      • D. Ruffolo
      et al.
      • Krucker
        • Rujiwarodom
          ,
        • S. T. Khumlumlert
          • Astrophys.J. 567 (2002) 622
      • T
        • J.W. Bieber
          ,
        • P. Evenson
          ,
        • W. Dröge
          ,
        • R. Pyle
          ,
        • D. Ruffolo
        et al.
        • Khumlumlert
            • Astrophys.J. 601 (2004) L103
        • Geophys. Res. Lett. (2005)
          • J.W. Bieber
            ,
          • J. Clem
            ,
          • P. Evenson
            ,
          • R. Pyle
            ,
          • D. Ruffolo
          et al.
          • in Proceedings of the 30th International Cosmic Ray Conference Vol. 1, ed
            • J.W. Bieber
            • By J. F. Valdés-Galicia
              • R. Caballero
                ,
              • J.C. D'Olivo
                ,
              • G. Medina-Tanco
                ,
              • L. Nellen
                ,
              • F.A. Sánchez
              • (Universidad Nacional Autónoma de México, Mexico City, 2008), pp. 229-232
                  • J.-L. Bougeret
                    • Geophys.Res.Lett. 25 (1998) 2513
                • Geophys. Res. Lett
                  • H.V. Cane
                    ,
                  • R.G. Stone
                    ,
                  • J. Fainberg
                    ,
                  • R.T. Stewart
                    ,
                  • J.L. Steinberg
                  et al.
                  • 8, 1285 (1981)
                      • H.V. Cane
                        ,
                      • R.G. Stone
                        • Astrophys.J. 282 (1984) 339
                      • H.V. Cane
                        ,
                      • W.C. Erickson
                        ,
                      • N.P. Prestage
                        • J.Geophys.Res. 107 (2002) 1315
                      • E.W. Cliver
                        • Astrophys.J. 639 (2006) 1206
                    • in Universal Heliophysical Processes, N. Gopalswamy, D. F. Webb (eds.)
                      • E.W. Cliver
                      • (International Astronomical Union, 2009), pp. 401-412
                          • E.W. Cliver
                            ,
                          • A.G. Ling
                            • Astrophys.J. 690 (2009) 598