DROPOUTS IN SOLAR ENERGETIC PARTICLES: ASSOCIATED WITH LOCAL TRAPPING BOUNDARIES OR CURRENT SHEETS?

Journal Article · Wed Mar 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/711/2/980· OSTI ID:21394329

Seripienlert, A; Ruffolo, D ^[1]; Matthaeus, W H ^[2]; Chuychai, P ^[3]

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1. Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand)
2. Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
3. ThEP Center, CHE, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

In recent observations by the Advanced Composition Explorer, the intensity of solar energetic particles exhibits sudden, large changes known as dropouts. These have been explained in terms of turbulence or a flux tube structure in the solar wind. Dropouts are believed to indicate filamentary magnetic connection to a localized particle source near the solar surface, and computer simulations of a random-phase model of magnetic turbulence have indicated a spatial association between dropout features and local trapping boundaries (LTBs) defined for a two-dimensional (2D) + slab model of turbulence. Previous observations have shown that dropout features are not well associated with sharp magnetic field changes, as might be expected in the flux tube model. Random-phase turbulence models do not properly treat sharp changes in the magnetic field, such as current sheets, and thus cannot be tested in this way. Here, we explore the properties of a more realistic magnetohydrodynamic (MHD) turbulence model (2D MHD), in which current sheets develop and the current and magnetic field have characteristic non-Gaussian statistical properties. For this model, computer simulations that trace field lines to determine magnetic connection from a localized particle source indicate that sharp particle gradients should frequently be associated with LTBs, sometimes with strong 2D magnetic fluctuations, and infrequently with current sheets. Thus, the 2D MHD + slab model of turbulent fluctuations includes some realistic features of the flux tube view and is consistent with the lack of an observed association between dropouts and intense magnetic fields or currents.

• OSTI ID: 21394329
• Journal Information: Astrophysical Journal, Vol. 711, Issue 2; Other Information: DOI: 10.1088/0004-637X/711/2/980; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
EMISSION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PARTICLE SOURCES
RANDOMNESS
SOLAR WIND
SUN
TURBULENCE
FLUID MECHANICS
HYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
RADIATION SOURCES
SIMULATION
SOLAR ACTIVITY
STARS
STELLAR ACTIVITY
STELLAR WINDS