Transcript Document

Analysis of the Temperature and Emission Measure
of Solar Coronal Arcades and Test of Flare/Arcade
Loop Length
(Yamamoto, Shiota, Sakajiri, Akiyama, Isobe, and Shibata)
Presented By H.D. Winter
Outline
I.
Why I chose this paper
II.
Background needed to understand paper
III. Purpose of Paper
IV. What they said
V.
Obvious problems with Paper
VI. Implications of Paper
Why I chose this paper
•Directly parallels the work being done in PHYS 580
(HD/MHD class)
•Current research work is focusing on numerical modeling of
flaring loops
•SXT observation are used in determining relevance of the
Emission Measure to Temperature scaling “law”
•Implications for SADE
Background I
Work began as a result of an observational paper by Feldman, Laming, and
Doschek (1995) that combined SXT flare observations with the observations
of extra-solar flares observed by the Ginga satellite.
Background II
Using several assumed boundary conditions the group states that
the relationship between temperature and emission measure scales
as
17 / 2
EM  T
Using an energy balance between conductive cooling and Petschek
reconnection heating
 0T
7
2
2 L2
 B2   vA 



4

L




And a balance between gas and magnetic pressure
2 nkT
 B2 


8



Purpose of the Paper
•
The purpose of this paper was to test the modeling predictions of
previous works with physical observables (i.e. loop length and
temperature)
•
Examine a correlation between flare heating mechanism and arcade
heating mechanisms
•
Elimination of possible heating mechanisms by using the Emission
Measure/ Temperature Power law index=17/2 (Shibata &
Yokoyama, 1999)
1.
Joule heating Index =13/4 NO!
2.
Parker nanoflare heating EM is 9 orders of magnitude lower than
what is observed in the corona WHAT!!!
3.
Alfvén wave heating EM is 13 orders of magnitude larger than the
observed value if the velocity amplitude of the Alfven waves is
v  30 kms1 WHAT!!!
What they said. I
Assuming constant Loop width a result from previous work
is given (Yokoyama & Shibata, 1998), and a β=0.2 gives
Equation 6
LTheory
EM


 10 
46
3 
8

10
cm


10
3
5
2
5
8
5
T
 n0  

 8 3  
 cm
6
 10 cm   3.7  10 K 
What they said. II
Compare Ltheory to Lobs for 17 arcades for which temperature
and emission measure can be determined and for 64 flares
observed in SXT and HXT and you get
Obvious Problems of the Paper
ASSUMPTIONS!!!
How can anything be constant in flares and arcades!
3
V

2
L
• arc
• Vflare  L3
• Normalization of Equation 3
• Use of 2-D modeling
• Same heating function for arcade and flare??
• Data selection Bias?
• EM estimates for other heating mechanisms
1.
Joule heating Index =13/4 NO!
2.
Parker nanoflare heating EM is 9 orders of magnitude lower than
what is observed in the corona WHAT!!!
3.
Alfvén wave heating EM is 13 orders of magnitude larger than the
observed value if the velocity amplitude of the Alfven waves is
v  30 kms1 WHAT!!!
Implications of Paper
• For flares if you know T you know EM
• Law can be restated for different values of
Implications of Paper II