Cross-Sectional Properties of

Coronal Loops and Their Implications

Henry “Trae” Winter III with

Chester Curme

Constant Cross-Section?

•Klimchuk et al. 1992

•Studied 10 SXT loops

•Measured an Apex to Footpoint Expansion Factor of

TRACE Loops

•Watko & Klimchuk, 2000 22 Loops

•Lopéz Fuentes et al, 2006 20 Loops

DeForest, 2007

DeForest, 2007

Unresolved Structures

Lopés Fuentes et al, 2008

• Countered DeForest’s argument

• Claimed that their method could distinguish between unresolved expanding and not expanding but resolved strands

• Conversation switched to theories that predict constant cross-section loops (i.e. Constant B).

How Could Loops be of Constant Cross-

Section?

•Twist? (Klimchuk et al., 2000)

•Separators? (Plowman et al., 2009)

How Could Loops be of Constant Cross-

Section?

•Emission loops (eLoops) do not actually trace field lines (Peter & Bingert, 2012)

Apex Temperature Evolution

Apex Density Evolution

Over Pressure

Synthetic Obs.171

1.0 1.31.21.1 2.01.51.4 4.03.0 5.0

AIA Pixel Size

Hi-CPixel Size

Synthetic Obs.335

1.0 1.31.21.1 2.01.51.4 4.03.0 5.0

AIA Pixel Size

Hi-CPixel Size

zzzz

Width Measurements

Estimation of Width

AIA171

Estimation of Width

AIA 335

zzzz

Estimation of Width

“Hi-C Like”171

Estimation of Width

“Hi-C Like” 335

Summary• Loop geometry has an effect on fundamental

loop properties such as temperature and density (pressure)

• Vesecky, Antiochos, and Underwood, 1979; Mariska, 1984; Schrijver, Lemen and Mewe, 1989; Dowdy, Emslie, and Moore, 1987

• Modeled near-resolution, expanding loops can appear to be of constant cross-section just like those “pesky” observations

• Loops must be many pixels wide to make width determinations

• Is it safe to use magnetic fields to generate loop geometries for 1D models?

Extra Slides

See Anna Malanushenko’s Work at the SPD

See Anna Malanushenko’s Work

at the SPD

How Could Loops be of Constant Cross-

Section?•Twist? (Klimchuk et al., 2000)

How Could Loops be of Constant Cross-

Section?•Separators? (Plowman et al., 2009)

How Could Loops be of Constant Cross-

Section?•Maybe eLoops do not trace out magnetic

fields? (Peter & Bingert, 2012)

How Could Loops be of Constant Cross-

Section?

Peter &Bingert, 2012

What happens if loops are not of constant cross-

section?

Brooks, et al 2013

Brooks, et al 2013

Brooks, et al 2013