[Loops] type II spicule paper

Tue Jul 31 09:14:45 MDT 2012

Hi Scott,

From: loops-bounces at solar.physics.montana.edu [mailto:loops-bounces at solar.physics.montana.edu] On Behalf Of Scott W. McIntosh
Sent: Tuesday, July 31, 2012 10:46 AM
To: A mailing list for scientists involved in the observation andmodeling of solar loop structures
Cc: (Loops at solar.physics.montana.edu)
Subject: Re: [Loops] type II spicule paper

Hi Jim,

Just scanned through, will send you comments after a thorough reading, but looks like a fair discussion. Couple of points though:

Are "A" waves a viable energetic supply to the corona? They get no mention and I understand that the net effect of their dissipation would be nanoflares-like heating distribution.

***  In principle, Alfven waves could be heating the corona, at least in the quiet Sun, as your recent work suggests.  And indeed, wave heating would likely fit into the classification of nanoflares, since there would be an impulsive energy release from the perspective of an individual magnetic flux strand.  But my paper isn’t attempting to address the nature of coronal heating.  It simply means to show that there must be an energy release in the corona in order to explain the hot plasma that we observe there.  Ejecting hot material at the tips of spicules isn’t enough if you buy my analysis.

Btw, in addition to the above, discriminatory studies of quiet and coronal hole plasmas hold the key to the down-up (evaporative) vs up-down (type 2 "initiated") mass components of the mass cycle. It is a real push to expect the original energy supply for them to be different, but in one the coronal backwash is missing. The (detailed) study of the  multi-component line profiles between the two should show the relative weighting of evaporative processes (regardless of their origin - see above) in the QS. My student has done a pretty detailed study of this and is about to submit a paper on her results - I will distribute to the list once submitted.

*** I look forward to the paper.  Regarding multi-component line profiles (weakly red shifted line core with a blue wing component), I would make the following point.  The core emission likely comes from hot material that is cooling and draining, regardless of whether the hot material came from evaporation or spicules.  The blue wing emission that is seen in lines <2 MK likely comes from spicules.  Coronal nanoflares (reconnection, waves, whatever) are expected to produce blue wing emission only in very hot (>3 MK) lines, at least according to the modeling work that Spiros and I did in 2006.  So, my picture is that the corona is comprised of unresolved strands.  Most are dominated by coronal heating and some are dominated by type II spicules.

Last point: why can't type-Ii spicules be the manifestation of nanoflares in a stratified inhomogeneous plasma?

Depends on where the nanoflares occur.  Nanoflares that occur in the transition region or corona (in plasma that is originally hotter than 10^4 K) will not produce ejections of cold material.  I have a discussion of this in the paper.  Nanoflares that occur deep in the chromosphere, below the eventual spicule, can produce cold ejections.

Thanks for the comments!
Jim

Cheers, Scott

Sent from my iPhone

Dr. Scott W. McIntosh
High Altitude Observatory
NCAR/UCAR, Boulder CO
off: (303) 497-1544
mob: (720) 340-6263

On Jul 31, 2012, at 7:47, "Klimchuk, James A. (GSFC-6710)" <james.a.klimchuk at nasa.gov<mailto:james.a.klimchuk at nasa.gov>> wrote:
Dear friends,

      You might be interested in my recent paper on “The Role of Type II Spicules in the Upper Solar Atmosphere,”  which can be downloaded at   http://arxiv.org/abs/1207.7048

Cheers,
Jim

ABSTRACT:
We examine the suggestion that most of the hot plasma in the Sun's
corona comes from type II spicule material that is heated as it is
ejected from the chromosphere.  This contrasts with the traditional
view that the corona is filled via chromospheric evaporation that
results from coronal heating.  We explore the observational
consequences of a hypothetical spicule dominated corona and conclude
from the large discrepancy between predicted and actual observations
that only a small fraction of the hot plasma can be supplied by
spicules (<2% in active regions and <5% in the quiet Sun).  The
red-blue asymmetries of EUV spectral lines and the ratio of lower
transition region (LTR; T<0.1 MK) to coronal emission measures
are both predicted to be 2 orders of magnitude larger than observed.
Furthermore, hot spicule material would cool dramatically by
adiabatic expansion as it rises into the corona, so coronal heating
would be required to maintain the high temperatures that are seen at
all altitudes.  The necessity of coronal heating is inescapable.
Traditional coronal heating models predict far too little emission
from the LTR, and we suggest that this emission comes primarily from
the bulk of the spicule material that is heated to <0.1 MK and
is visible in He II (304 A) as it falls back to the surface.

********************************************************************************
James A. Klimchuk
NASA Goddard Space Flight Center
Solar Physics Lab, Code 671
Bldg. 21, Rm. 158
Greenbelt, MD  20771
USA

Phone:  1-301-286-9060
Fax:      1-301-286-7194
E-mail:  James.A.Klimchuk at nasa.gov<mailto:James.A.Klimchuk at nasa.gov>
Homepage:  https://sedupdate.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&&iPhonebookId=15844
No endorsement by NASA is implied for any correspondence related to my role as an officer of professional organizations (American Geophysical Union, International Astronomical Union, American Astronomical Society).

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