|
The bursty nature of solar flare X-ray emission
|
|
R.T.James McAteer Submitted: 2007-05-23 13:47
The complex and highly-varying temporal nature of emission from an X4.8 flare is studied across 7 X-ray energy bands. A wavelet transform modulus maxima method is used to obtain the multifractal spectra of the temporal variation of the X-ray emission. As expected from the Neupert effect, the time series of emission at low (3--6, 6--12~keV; thermal) energies is smooth. The peak Holder exponent around 1.2 for this low energy emission is indicative of a signal with a high degree of memory and suggestive of a smooth chromospheric evaporation process. The more bursty emission at higher energies (100--300, 300--800~keV; non-thermal) is described by a multifractal spectrum which peaks at a smaller Holder exponent (less than 0.5 for the largest singularities), indicative of a signal with a low degree of memory. This describes an anti-persistent walk and indicates a impulsive, incoherent driving source. We suggest this may arise from bursty reconnection, with each reconnection event producing differing and uncorrelated non-thermal particle sources. The existence of power law scaling of wavelet coefficients across timescales is in agreement with the creation of a fractal current sheet diffusion region.
Authors: R.T.James McAteer, C.Alex Young, Jack Ireland, Peter T. Gallagher
Projects: RHESSI
|
Publication Status: ApJ, 662, 691, 2007
Last Modified: 2007-06-11 07:58
|
 
 
 
 
|
|