DERIVING THE PROPERTIES OF CORONAL PRESSURE FRONTS IN 3D: APPLICATION TO THE 2012 MAY 17 GROUND LEVEL ENHANCEMENT
- Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse III (UPS) (France)
- LESIA-UMR 8109—Observatoire de Paris, CNRS, Univ. Paris 6 and 7, F-92190, Meudon (France)
- University of Turku, Turku (Finland)
- Emeritus, NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)
- Johns Hopkins Applied Physics Laboratory, Laurel, Maryland (United States)
- Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, California (United States)
- Predictive Sciences Inc., San Diego, California (United States)
- Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam (Germany)
We study the link between an expanding coronal shock and the energetic particles measured near Earth during the ground level enhancement of 2012 May 17. We developed a new technique based on multipoint imaging to triangulate the three-dimensional (3D) expansion of the shock forming in the corona. It uses images from three vantage points by mapping the outermost extent of the coronal region perturbed by the pressure front. We derive for the first time the 3D velocity vector and the distribution of Mach numbers, M {sub FM}, of the entire front as a function of time. Our approach uses magnetic field reconstructions of the coronal field, full magnetohydrodynamic simulations and imaging inversion techniques. We find that the highest M {sub FM} values appear near the coronal neutral line within a few minutes of the coronal mass ejection onset; this neutral line is usually associated with the source of the heliospheric current and plasma sheet. We illustrate the variability of the shock speed, shock geometry, and Mach number along different modeled magnetic field lines. Despite the level of uncertainty in deriving the shock Mach numbers, all employed reconstruction techniques show that the release time of GeV particles occurs when the coronal shock becomes super-critical ( M {sub FM} > 3). Combining in situ measurements with heliospheric imagery, we also demonstrate that magnetic connectivity between the accelerator (the coronal shock of 2012 May 17) and the near-Earth environment is established via a magnetic cloud that erupted from the same active region roughly five days earlier.
- OSTI ID:
- 22660941
- Journal Information:
- Astrophysical Journal, Vol. 833, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
On the Link between the Release of Solar Energetic Particles Measured at Widespread Heliolongitudes and the Properties of the Associated Coronal Shocks
SUN-TO-EARTH CHARACTERISTICS OF TWO CORONAL MASS EJECTIONS INTERACTING NEAR 1 AU: FORMATION OF A COMPLEX EJECTA AND GENERATION OF A TWO-STEP GEOMAGNETIC STORM