Coronal Loop Models and Those Annoying Observations (!) James A. - - PowerPoint PPT Presentation

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Coronal Loop Models and Those Annoying Observations (!) James A. - - PowerPoint PPT Presentation

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Coronal Loop Models and Those Annoying Observations (!) James A. Klimchuk NASA / GSFC Pieces of the Coronal Loops Puzzle Thermal Lifetime Density Structure* Intensity Flows Profile** * Over cross section ** Along axis The Good Ol

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SLIDE 1

Coronal Loop Models and Those Annoying Observations (!)

James A. Klimchuk NASA / GSFC

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SLIDE 2

Pieces of the Coronal Loops Puzzle

Lifetime Density Thermal Structure*

Flows Intensity Profile** * Over cross section ** Along axis

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SLIDE 3

The Good Ol’ Days (pre SOHO)

Soft X-Ray Loops:

  • Hot (T > 2 MK)
  • Long-lived (τlife >> τcool)
  • Obey static equilibrium scaling laws
  • Consistent with steady heating

Rosner, Peres, Tsuneta, Antiochos, Golub, ….

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SLIDE 4

Then came SOHO and TRACE, and the trouble started….

EUV Loops:

  • Warm (T ~ 1 MK)
  • Over dense relative to static equilibrium
  • Super hydrostatic scale heights
  • Flat temperature profiles

Aschwanden, Warren, Winebarger, Reale, ….

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SLIDE 5

Over dense?

Solutions to the Loops Puzzle

Consider a loop.

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SLIDE 6

Over dense? Steady heating OK *

Solutions to the Loops Puzzle

No * Steady heating not required (not unique solution)

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SLIDE 7

Cooling Time Ratio vs. Temperature

TRACE Yohkoh/SXT Static Equilibrium Klimchuk (2003, 06) Under-dense Over-dense

τrad/τcond = T4 / (nL)2

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SLIDE 8

Over dense? Steady heating OK

Solutions to the Loops Puzzle

No Yes Thermal Nonequil.

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SLIDE 9

Over dense? Steady heating OK

Solutions to the Loops Puzzle

No Yes Impulsive heating Thermal Nonequil.

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SLIDE 10

Cooling Time Ratio vs. Temperature

TRACE Yohkoh Klimchuk (2006) Thermal cond. dominates Radiation dominates

Cooling track

τrad/τcond = T4 / (nL)2

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SLIDE 11

Over dense? τlife = τcool? Steady heating OK

Solutions to the Loops Puzzle

No Yes Impulsive heating Thermal Nonequil.

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SLIDE 12

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal)

Solutions to the Loops Puzzle

No Yes Yes Impulsive heating Thermal Nonequil.

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SLIDE 13

Loop Light Curves

GOES / SXI Lopez Fuentes, Klimchuk, & Mandrini (2006) Can be modeled as a self organized critical (SOC) system driven by footpoint shuffling and magnetic field tangling.

τlife >> τcool τlife >> τcool

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SLIDE 14

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal) Multi-stranded

Solutions to the Loops Puzzle

No Yes Yes Impulsive heating Thermal Nonequil. No (τlife >> τcool)

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SLIDE 15

Multi-Stranded Loop

Warren, Winebarger, & Mariska (2003) Single nanoflare Nanoflare “storm”

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SLIDE 16

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal) No (τlife >> τcool) Multi-stranded

Solutions to the Loops Puzzle

No Yes Yes Impulsive heating Multi-thermal? Thermal Nonequil.

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SLIDE 17

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal) No (τlife >> τcool) Multi-stranded Consistency

Solutions to the Loops Puzzle

No Yes Yes Yes Impulsive heating Multi-thermal? Thermal Nonequil.

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SLIDE 18

The Isothermal / Multi-thermal “Debate”

ISOTHERMAL Aschwanden Nightingale Landi Nagata Del Zanna Mason Schmeider etc. MULTI-THERMAL Schmelz Martens Cirtain Noglik Walsh Patsourakos etc.

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SLIDE 19

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal) No (τlife >> τcool) Multi-stranded Consistency Screwed! (?)

Solutions to the Loops Puzzle

No Yes No Yes Yes Impulsive heating Multi-thermal? Thermal Nonequil.

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SLIDE 20

Ugarte-Urra, Winebarger, & Warren (2006)

Yohkoh / SXT TRACE

Nanoflare storms do not last forever. Light curve overlap depends on storm duration.

Nanoflare Storm Duration

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SLIDE 21

Ugarte-Urra, Warren, Brooks (2008)

Fe XVI 2.5 MK Mg VI 0.4 MK

Hinode / EIS

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Lifetime and Thermal Width

500 s Storm 195 Intensity Log EM (cm-5) 2500 s Storm 5000 s Storm Time (s) Log T (K)

EM(T) at time of max. 195 intensity

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SLIDE 23

Over dense? τlife = τcool? Steady heating OK Monolithic (isothermal) No (τlife >> τcool) Multi-stranded Long storm Short storm

Solutions to the Loops Puzzle

No Yes Minimally Yes Very Impulsive heating How multi-thermal? Thermal Nonequil. Need lifetime / thermal width consistency check

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SLIDE 24

Enthalpy Based Thermal Evolution of Loops (EBTEL)

“0D” hydro code Easy to use, runs in IDL Any heating function, H(t) DEM(T,t) in transition region Heat flux saturation Non-thermal electron beam 104 time faster than 1D codes

EBTEL “Exact” 1D

T n P 500 s nanoflare Klimchuk, Patsourakos, & Cargill (2008)

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SLIDE 25

(Super) Hot Plasma

Hot plasma predicted to be very faint: EM (cm-5) = T x DEM reduced by 1-1.5 orders magnitude DEM (cm-5 K-1) reduced by 1.5-2 orders magnitude Seen by CORONAS-F (Zhitnik et al. 2006), RHESSI (McTiernan 2008), XRT (Siarkowski et al. 2008; Reale et al. 2008); EIS (Patsourakos & K 2008)

Footpoint Weak Nanoflare Strong Nanoflare

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SLIDE 26

Patsourakos & Klimchuk (2008)

Hinode/EIS: Fe XII – XVII Ca IV – VI Ni XVII

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SLIDE 27

Fe XII, Fe XV, Ni XVII, Fe XVII See also Ko et al. (2008), Ca XVII

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SLIDE 28

Hinode / XRT

Be_m Image Be_m/Al_m T map

EM (cm-3) Log T Reale et al. (2008)

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Simulated Line Profiles

Mg X (625) 1.3MK

Patsourakos & Klimchuk (2006)

Fe XVII (254) 5.1MK Fe XVII (254) 5.1MK Fe XVII (254) 5.1MK Footpoint

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SLIDE 30

Observed Fe XVII Profile

See also Hara et al. (2008) EIS sit and stare

  • bservations
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THERMAL NONEQUILIBRIUM

  • Dynamic behavior with steady heating!
  • No equilibrium exists if the heating is concentrated

close to the loop footpoints

  • Cool condensations form and fall in cyclical pattern

Serio et al. (1981), Antiochos & Klimchuk (1991), Karpen et al. (2001-2008), Mueller et al. (2003-2005), Mok et al. (2008)

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SLIDE 32

Monolithic Loop

171 Light Curve

(averaged over corona)

171 Intensity Profile

(5000 s)

Intensity profile not like observed (uniform)

With Judy Karpen

condensation knot

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SLIDE 33

Multi-Strand Bundle

171 Intensity Profile

(time average)

Temperature Profile

(time average)

“Uniform” intensity profile Flat temperature profile Over dense in TRACE: n/neq = 23

SXT actual TRACE

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SLIDE 34

Conclusions

  • Need to examine all pieces of the puzzle for individual loops

– Lifetime, thermal distribution, density (flows, intensity profile)

  • Strong evidence that many EUV loops result from nanoflare storms
  • Are there different classes of loops?

– EUV loops without SXR counterparts (e.g., fan loops)? – SXR loops without EUV counterparts?

  • Diffuse component of active regions is important

– Background brighter than most loops – Preliminary indications of impulsive heating

  • All coronal heating mechanisms produce impulsive energy release on

individual magnetic flux surfaces (field lines) – but rapid repetition gives quasi-equilibrium conditions

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SLIDE 35

t = 2950, 4500, 4850, 5750 s Heating scale height = 5 Mm = L/15 Imbalanced heating (right leg = 75% left leg) With Judy Karpen

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SLIDE 36

Consistency

ΔTFWHM ~ 0.8 MK (EIS; Warren et al. 2008) Implies τ195~ 1 hour, as observed (TRACE; Ugarte-Urra et al. 2006)

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Issues with Thermal Nonequilibrium

  • Condensations repeat on timescale > 2 hr
  • Observed 171 loop lifetimes ~ 1 hr
  • Strands must be sufficiently out of phase to produce “uniform” intensity

profiles but not so much as to produce long-lived loops

  • Plausible? Even if phasing correct for one cycle, not likely to be

maintained for subsequent cycles.

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SLIDE 38

Fe XVII (254)

Patsourakos & Klimchuk (2006)