J/ApJ/757/94 Solar flares observed with GOES and AIA (Aschwanden, 2012)
The spatio-temporal evolution of solar flares observed with AIA/SDO: fractal
diffusion, sub-diffusion, or logistic growth?
Aschwanden M.J.
<Astrophys. J., 757, 94 (2012)>
=2012ApJ...757...94A 2012ApJ...757...94A
ADC_Keywords: Sun ; Stars, flare
Keywords: methods: statistical; Sun: flares; Sun: magnetic topology;
Sun: UV radiation
Abstract:
We explore the spatio-temporal evolution of solar flares by fitting a
radial expansion model r(t) that consists of an exponentially growing
acceleration phase, followed by a deceleration phase that is
parameterized by the generalized diffusion function
r(t)∝κ(t-t1)β/2, which includes the logistic
growth limit (β=0), sub-diffusion (β=0-1), classical
diffusion (β=1), super-diffusion (β=1-2), and the linear
expansion limit (β=2). We analyze all M- and X-class flares
observed with Geostationary Operational Environmental Satellite and
Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during
the first two years of the SDO mission, amounting to 155 events. We
find that most flares operate in the sub-diffusive regime
(β=0.53±0.27), which we interpret in terms of anisotropic chain
reactions of intermittent magnetic reconnection episodes in a low
plasma-β corona. We find a mean propagation speed of
v=15±12km/s, with maximum speeds of vmax=80±85km/s per flare,
which is substantially slower than the sonic speeds expected for
thermal diffusion of flare plasmas. The diffusive characteristics
established here (for the first time for solar flares) is consistent
with the fractal-diffusive self-organized criticality model, which
predicted diffusive transport merely based on cellular automaton
simulations.
Description:
We select all solar flare events detected with the Geostationary
Operational Environmental Satellite (GOES) and the Atmospheric Imaging
Assembly (AIA) on the Solar Dynamics Observatory (SDO; Lemen et al.
2012SoPh..275...17L 2012SoPh..275...17L) above a threshold of the M1.0 class level (which
includes M- and X-class events) during the first two years of the SDO
mission. The selected time era starts when the first science data from
AIA became available, 2010 May 13, and ends on 2011 March 31 when we
started the data analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 155 Catalog of analyzed M- and X-class flare events and
best-fit model parameters: length scale L(Mm),
diffusion coefficient K (km.s-β/2),
diffusion index β, and goodness of fit qfit
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See also:
J/ApJ/747/L41 : Solar flares probabilities (Bloomfield+, 2012)
J/A+A/304/563 : Cool X-ray flares of Sun with GOES (Phillips+, 1995)
http://sdo.gsfc.nasa.gov/ : Solar Dynamics Observatory home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/155] Running sequence number
5- 15 A11 "YYYY/MMM/DD" Date UT observation date
17- 21 A5 "h:m" Tst Start time
23- 27 A5 "h:m" Tpk Peak time
29- 33 A5 "h:m" Tend End time
35- 39 I5 s Dur [300/14760] Duration
41- 44 A4 --- Cl [MX0-9.] Geostationary Operational
Environmental Satellite (GOES) class of flare
46- 50 I5 --- AOR [11079/11445] NOAA AR number
52- 57 A6 --- Pos Heliographic position
59- 60 I2 Mm L [5/51] Length scale
62- 64 I3 --- k [18/139] Diffusion coefficient κ (1)
66- 67 I2 --- e_k [0/25] k uncertainty
69- 72 F4.2 --- beta [0.04/1.4] Diffusion index β (1)
74- 77 F4.2 --- e_beta [0/0.5] beta uncertainty
79- 81 F3.1 % Fit [0.8/4.2] Goodness of fit (qfit)
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Note (1): We quantified the spatio-temporal evolution with a general diffusion
equation that is quantified in terms of a diffusion coefficient
κ and a diffusion power-law index β (Equation (24)):
the radial size of the flare r(t) evolves with time as
r(t)=κtβ/2
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 21-May-2014