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.

 

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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@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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