[Loops] new paper on IRIS diagnostics for coronal heating and accelerated particles

[Philip Judge]

If the sun releases 10^25 erg in 30s in the chromosphere,  as needed by
these data, cannot this be just local magnetic heating?  A "chromospheric
flare"?

Consider magnetic energy density

E= B^2/ 8pi.

In plage let B be say 300G, then E=3e3.  Then for total energy of 10^25 erg
we need  3e21 cm3 and d^3=V gives length  d of 10^7 cm, or 0.1 Mm.  If I
use rho= 1e-10 g for mid chromosphere, then the alfven speed v_a is 80 kms
and d/v_a is 1.2 sec. Fast.

So I am really puzzled why you appeal to beams at all.  There is certainly
nothing in the iris data that I can see could ever be used to give direct
evidence for e- beams...  all I can glean from these data is that there is
a sudden release of energy under the place where Si IV is formed.

So I am very puzzled...

Philip Judge, Scientist, HAO, NCAR
3037759863

On Oct 30, 2014 2:49 PM, "Paola Testa" <ptesta at cfa.harvard.edu> wrote:

>  Dear all,
>
> you might be interested in the following paper that has just been
> published on Science:
> "Evidence of non-thermal particles in coronal loops heated impulsively by
> nanoflares"
> It can be downloaded from astro-ph: http://arxiv.org/abs/1410.6130 or
> directly
> from the Science pages: http://www.sciencemag.org/content/346/6207/1255724
> The abstract is below.
>
> cheers,
> Paola
>
>
> Abstract:
> The physical processes causing energy exchange between the Sun’s hot
> corona and its
> cool lower atmosphere remain poorly understood. The chromosphere and
> transition region
> (TR) form an interface region between the surface and the corona that is
> highly sensitive to
> the coronal heating mechanism. High-resolution observations with the
> Interface Region
> Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds)
> of intensity and
> velocity on small spatial scales (≲500 kilometers) at the footpoints of
> hot and dynamic
> coronal loops. The observations are consistent with numerical simulations
> of heating by
> beams of nonthermal electrons, which are generated in small impulsive (≲30
> seconds)
> heating events called “coronal nanoflares.” The accelerated electrons
> deposit a sizable
> fraction of their energy (≲10^25 erg) in the chromosphere and TR. Our
> analysis provides tight
> constraints on the properties of such electron beams and new diagnostics
> for their
> presence in the nonflaring corona.
>
>
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>
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