Non-Stationary Fast-Driven Self-Organized Criticality in Solar Flares. (arXiv:1909.08673v1 [astro-ph.SR])

Non-Stationary Fast-Driven Self-Organized Criticality in Solar Flares. (arXiv:1909.08673v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Aschwanden_M/0/1/0/all/0/1">Markus J. Aschwanden</a>

The original concept of self-organized criticality (Bak et al.~1987), applied
to solar flare statistics (Lu and Hamilton 1991), assumed a slow-driven and
stationary flaring rate, which warrants time scale separation (between flare
durations and inter-flare waiting times), it reproduces power-law distributions
for flare peak fluxes and durations, but predicts an exponential waiting time
distribution. In contrast to these classical assumptions we observe: (i)
multiple energy dissipation episodes during most flares, (ii) violation of the
principle of time scale separation, (iii) a fast-driven and non-stationary
flaring rate, (iv) a power law distribution for waiting times $Delta t$, with
a slope of $alpha_{Delta t} approx 2.0$, as predicted from the universal
reciprocality between mean flaring rates and mean waiting times; and (v) pulses
with rise times and decay times of the dissipated magnetic free energy on time
scales of $12pm6$ min, up to 13 times in long-duration ($lapprox 4$ hrs)
flares. These results are inconsistent with coronal long-term energy storage
(Rosner and Vaiana 1978), but require photospheric-chromospheric current
injections into the corona.

The original concept of self-organized criticality (Bak et al.~1987), applied
to solar flare statistics (Lu and Hamilton 1991), assumed a slow-driven and
stationary flaring rate, which warrants time scale separation (between flare
durations and inter-flare waiting times), it reproduces power-law distributions
for flare peak fluxes and durations, but predicts an exponential waiting time
distribution. In contrast to these classical assumptions we observe: (i)
multiple energy dissipation episodes during most flares, (ii) violation of the
principle of time scale separation, (iii) a fast-driven and non-stationary
flaring rate, (iv) a power law distribution for waiting times $Delta t$, with
a slope of $alpha_{Delta t} approx 2.0$, as predicted from the universal
reciprocality between mean flaring rates and mean waiting times; and (v) pulses
with rise times and decay times of the dissipated magnetic free energy on time
scales of $12pm6$ min, up to 13 times in long-duration ($lapprox 4$ hrs)
flares. These results are inconsistent with coronal long-term energy storage
(Rosner and Vaiana 1978), but require photospheric-chromospheric current
injections into the corona.

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