<p dir="ltr"><br>
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"? </p>
<p dir="ltr">Consider magnetic energy density </p>
<p dir="ltr">E= B^2/ 8pi.</p>
<p dir="ltr">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.</p>
<p dir="ltr">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.</p>
<p dir="ltr">So I am very puzzled...</p>
<p dir="ltr">Philip Judge, Scientist, HAO, NCAR<br>
3037759863 <br>
</p>
<div class="gmail_quote">On Oct 30, 2014 2:49 PM, "Paola Testa" <<a href="mailto:ptesta@cfa.harvard.edu">ptesta@cfa.harvard.edu</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Dear all,<br>
<br>
you might be interested in the following paper that has just been
published on Science:<br>
"Evidence of non-thermal particles in coronal loops heated
impulsively by nanoflares"<br>
It can be downloaded from astro-ph: <a href="http://arxiv.org/abs/1410.6130" target="_blank">http://arxiv.org/abs/1410.6130</a>
or directly<br>
from the Science pages:
<a href="http://www.sciencemag.org/content/346/6207/1255724" target="_blank">http://www.sciencemag.org/content/346/6207/1255724</a><br>
The abstract is below.<br>
<br>
cheers,<br>
Paola<br>
<br>
<br>
Abstract:<br>
The physical processes causing energy exchange between the Sun’s hot
corona and its<br>
cool lower atmosphere remain poorly understood. The chromosphere and
transition region<br>
(TR) form an interface region between the surface and the corona
that is highly sensitive to<br>
the coronal heating mechanism. High-resolution observations with the
Interface Region<br>
Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60
seconds) of intensity and<br>
velocity on small spatial scales (≲500 kilometers) at the footpoints
of hot and dynamic<br>
coronal loops. The observations are consistent with numerical
simulations of heating by<br>
beams of nonthermal electrons, which are generated in small
impulsive (≲30 seconds)<br>
heating events called “coronal nanoflares.” The accelerated
electrons deposit a sizable<br>
fraction of their energy (≲10^25 erg) in the chromosphere and TR.
Our analysis provides tight<br>
constraints on the properties of such electron beams and new
diagnostics for their<br>
presence in the nonflaring corona.<br>
<br>
</div>
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<br></blockquote></div>