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The Role of Type II Spicules in the Upper Solar AtmosphereWe examine the suggestion that most of the hot plasma in the Sun's co rona comes from type II spicule material that is heated as it is ejected from the chromosphere. This contrasts with the traditional view th at the corona is filled via chromospheric evaporation that results fr om coronal heating. We explore the observational consequences of a hy pothetical spicule dominated corona and conclude from the large discr epancy 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 spec tral lines and the ratio of lower transition region (LTR; T< or =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 temperatu res 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 pr imarily from the bulk of the spicule material that is heated to < or =0.1 MK and is visible in He II (304 ?A) as it falls back to the surf ace.
Document ID
20120015710
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Klimchuk, James A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 26, 2013
Publication Date
July 27, 2012
Subject Category
Solar Physics
Report/Patent Number
GSFC.JA.7167.2012
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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