THE IMPACT OF MICROSCOPIC MAGNETIC RECONNECTION ON PRE-FLARE ENERGY STORAGE

Journal Article · Sun Dec 20 00:00:00 EST 2009 · Astrophysical Journal (Online)

DOI:https://doi.org/10.1088/0004-637X/707/2/L158· OSTI ID:21392569

Cassak, P A ^[1]

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1. Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

It is widely accepted that magnetic reconnection releases a large amount of energy during solar flares. Studies of reconnection usually assume that the length scale over which the global (macroscopic) magnetic field reverses is identical to the thickness of the reconnection site. However, in spatially extended high-Lundquist number plasmas such as the solar corona, this scenario is untenable; the reconnection site is microscopic and embedded inside the macroscopic current set up by global fields. We use numerical simulations and scaling arguments to show that embedded effects on reconnection could have a profound influence on energy storage before a flare. From large-scale high-Lundquist number resistive magnetohydrodynamics simulations of reconnection with a diffusion region on a much smaller scale than the macroscopic current sheet, we find that the generation of secondary islands is governed by the local magnetic field immediately upstream of the diffusion region rather than the (potentially much larger) global field. This diminishes the production of secondary islands and leads to a thicker diffusion region than those predicted using the global field strength. Such considerations are crucial for understanding the onset of solar eruptions and how energy accumulates before such eruptions. We argue that if reconnection with secondary islands is fast, the energy storage times before an eruption are too small to explain observations. If reconnection with secondary islands remains slow, embedded effects cause the diffusion region to begin far wider than kinetic scales, so energy storage before a flare can occur while collisional (Sweet-Parker) reconnection with secondary islands proceeds.

• OSTI ID: 21392569
• Journal Information: Astrophysical Journal (Online), Vol. 707, Issue 2; Other Information: DOI: 10.1088/0004-637X/707/2/L158; ISSN 1538-4357
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CHROMOSPHERE
COMPUTERIZED SIMULATION
ENERGY STORAGE
ERUPTION
MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
SOLAR CORONA
SOLAR FLARES
SUN
ATMOSPHERES
FLUID MECHANICS
HYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
SIMULATION
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR FLARES
STORAGE