MAGNETIC RECONNECTION DURING THE TWO-PHASE EVOLUTION OF A SOLAR ERUPTIVE FLARE

Journal Article · Tue Dec 01 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/706/2/1438· OSTI ID:21378095

Joshi, Bhuwan; Cho, K -S; Bong, S -C; Kim, Y -H ^[1]; Veronig, Astrid ^[2]; Somov, B V ^[3]; Moon, Y -J ^[4]; Lee, Jeongwoo ^[5]

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1. Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)
2. IGAM/Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria)
3. Astronomical Institute, Moscow State University, Universitetskij Prospekt 13, Moscow 119992 (Russian Federation)
4. School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of)
5. Physics Department, New Jersey Institute of Technology, 161 Warren Street, Newark, NJ 07102 (United States)

We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 A show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for approx11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (approx15 km s{sup -1}) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Halpha flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra during the first phase are soft and indicative of hot thermal emission from flaring loops with temperatures T > 25 MK at the early stage. On the other hand, the spectra at high energies (epsilon approx> 25 keV) follow hard power laws during the second phase (gamma = 2.6-2.8). We show that the observed motion of the LT and FP sources can be understood as a consequence of three-dimensional magnetic reconnection at a separator in the corona. During the first phase of the flare, the reconnection releases an excess of magnetic energy related to the magnetic tensions generated before a flare by the shear flows in the photosphere. The relaxation of the associated magnetic shear in the corona by the reconnection process explains the descending motion of the LT source. During the second phase, the ordinary reconnection process dominates describing the energy release in terms of the standard model of large eruptive flares with increasing FP separation and upward motion of the LT source.

• OSTI ID: 21378095
• Journal Information: Astrophysical Journal, Vol. 706, Issue 2; Other Information: DOI: 10.1088/0004-637X/706/2/1438; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
FLARING
GAMMA RADIATION
HARD X RADIATION
KEV RANGE
MAGNETIC RECONNECTION
PHOTOSPHERE
SOLAR CORONA
SOLAR FLARES
SOLAR SYSTEM EVOLUTION
SPECTRA
STANDARD MODEL
SUN
ATMOSPHERES
ELECTROMAGNETIC RADIATION
ENERGY RANGE
EVOLUTION
FIELD THEORIES
GRAND UNIFIED THEORY
IONIZING RADIATIONS
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
PARTICLE MODELS
QUANTUM FIELD THEORY
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR FLARES
UNIFIED GAUGE MODELS
X RADIATION