Self-organization of Reconnecting Plasmas to a Marginally Collisionless State. Shinsuke Imada (Nagoya Univ., STEL)

Transcription

1 Self-organization of Reconnecting Plasmas to a Marginally Collisionless State Shinsuke Imada (Nagoya Univ., STEL)

2 Introduction The role of Magnetic reconnection Solar Flare Coronal heating, micro/nano-flare Dynamical corona is made by magnetic reconnection. Tsuneta +, 996 However, when fast RX occurs is still not clear.

3 Introduction 2 Collisionless Reconnection c/ω pi c/ω pe Current sheet thickness < ion inertia length Collisionless (Hall) RX à Fast RX η* 5 B-field Current Ion flow Electron flow Ion dissipation region Electron dissipation region Laboratory Plasma H e D 2 H 2 Simulation Relationship large & small scale? 2 c/ω pe δ SP Yamada +, 26

4 Introduction 3 Solar Corona and Earth s Magnetosphere Solar corona (flare) Earth s magnetosphere (substorm) Typical scale = ^5 km Typical scale = ^5 km almost same Macro-scale Sun: 5 km Earth: 5 km same Micro-scale Sun: -3 km Earth: 3 km 6 order Macro/Micro Sun: 8 Earth: 2 6 order Macro/Micro is largely different!

5 Hinode X-ray Observation

6 Hinode Observation X-ray Shimizu +, 29

7 Hinode Observation X-ray

8 Hinode Observation Emerging Flux: Ca IIH

9 Marginally Collisionless Plasma Uzdensky 27 proposed a self-regulating process keeping the plasma marginally collisionless in solar corona. Cassak+ 28 also discussed self-regulating process and found the observational implication from 7 flares (Sun-like star).

10 Today s Talk Basically, we discuss coronal heating problem along nano-flare heating model. Method: D Hydrodynamic calculation which is popular in the category of solar physics New points: Include the regime transition from collisional to collisionless reconnection. Aim: To understand what s happened in a large scale coronal loop with the transition and its feed back. Main difference from past studies: The plasma actively decides its heating rate.

11 D Hydrodynamic Calculation ρ t + x (ρv x)=, ( ) t (ρv x)+ ( ρv 2 x x + p ) = ρg, [( ) ] t ( p γ + 2 ρv x 2 ) + x Half loop length 26 Mm CANS D HD gravity Modified Lax- Wendroff ( ) [( γ γ p + ) Thermal conduction ] 2 ρv x 2 T V x κ x ] = ρg V x + H R, Radiative cooling Heating e.g., micro/nano-flare

12 New point:heating term by RX ***Assumption*** If current sheet thickness is less than ion inertia length, fast collisionless reconnection occurs. Current Sheets (a) (b) (c)..8 =.6 Coronal Loop f/f.4.2 CS thickness (m) Heating rate (erg cm -3 s - ) Heating rate 8 9 n (cm -3 ) Time independent (not good assumption)

13 New point:heating term by RX ***Assumption*** If current sheet thickness is less than ion inertia length, fast collisionless reconnection occurs. Current Sheets (a) (b) (c)..8 =.6 Coronal Loop f/f.4.2 CS thickness (m) Heating rate (erg cm -3 s - ) Heating rate 8 9 n (cm -3 ) Time independent (not good assumption)

14 Other heating functions H(n, T )=H (n)+h 2 (n, T )+H 3 (n, T ) H (δ i )=Ė δi Collisionless ( RX δ i fdδ = H c + λ log δ c δ c ( ( cosh δi δ c λ cosh ( δ cλ ) ))) H 2 (T )=H c2 ρ Collisional heating (Sweet-Parker RX) T ( T T c ) 3 4 ( ρ ρ c ) 4 Unknown heating to produce H 3 (ρ,t)= H ( ) 3 c3 ρ ( robust chromosphere (( ) )) T 4 ρ + tanh /λ 3 2 ρ cl

15 New point:heating term by RX ***Assumption*** If current sheet thickness is less than ion inertia length, fast collisionless reconnection occurs. Current Sheets (a) (b) (c)..8 =.6 Coronal Loop f/f.4.2 CS thickness (m) Heating rate (erg cm -3 s - ) Heating rate 8 9 n (cm -3 ) Time independent (not good assumption)

16 Weak heating: Usual corona Temperature Density Velocity Heating rate Collisionless RX Radiative Loss Thermal conduction Cooling Heating

17 New point:heating term by RX ***Assumption*** If current sheet thickness is less than ion inertia length, fast collisionless reconnection occurs. Current Sheets (a) (b) (c)..8 =.6 Coronal Loop f/f.4.2 CS thickness (m) Heating rate (erg cm -3 s - ) Heating rate 8 9 n (cm -3 ) Time independent (not good assumption)

18 Middle heating: Micro/nano-flaring Temperature Temperature (MK).. t = 2 sec t = 2 sec t = 66 sec t = 92 sec t = 6 sec Density Density (cm -3 ) Velocity Velocity (km s - ) Heating rate Radiative Loss & Conduction Radiation & Conduction Heating Rate x (Mm)

19 Comparison Temperature (MK).. Density (cm -3 ) Velocity (km s - ) Heating Rate x (Mm)

20 Long term calculation Loop Top Density ( 9 cm -3 ) Loop Top Density 5 5 Loop Top Temperature (MK) Loop Top Temperature 5 Total Collisionless Heating Total Collisionless Heating (erg cm -2 s - ) Normalized Xray Emission Total Soft X-Ray emission Time ( 3 sec)

21 New point:heating term by RX ***Assumption*** If current sheet thickness is less than ion inertia length, fast collisionless reconnection occurs. Current Sheets (a) (b) (c)..8 =.6 Coronal Loop f/f.4.2 CS thickness (m) Heating rate (erg cm -3 s - ) Heating rate 8 9 n (cm -3 ) Time independent (not good assumption)

22 Strong heating: Flare Temperature Temperature (MK).. t = 2 sec t = 6 sec t = 3 sec t = 3 sec t = 46 sec Density Density (cm -3 ) Velocity Velocity (km s - ) Heating rate Radiative Loss & Conduction Radiation & Conduction Heating Rate x (Mm)

23 Comparison Temperature (MK) Density (cm ) Velocity (km s - ) Heating Rate x (Mm) 2

24 5 5 Long term calculation Loop Top Density ( 9 cm -3 ) Loop Top Density Loop Top Temperature (MK) Loop Top Temperature.5 4 Total Collisionless Heating (erg cm -2 s - ) Total Collisionless Heating Normalized Xray Emission Total Soft X-Ray emission -4 5 Oscillation 5 period 2 becomes 4 longer 5 Time ( 3 sec). 4-4

25 What s Happened? Temperature (MK) Radiative Cooling Density (cm -3 ) Velocity (km sec - ) Collisionless Heating (erg cm -3 sec - ) Thermal Conduction (erg cm -3 sec - ) Time (sec) Draining Reduce density Heating On gradp acc. Evaporation Stop heating

26 Parameter Survey Total Collisionless Heating 6 Loop Top Density Total Collisionless Heating (erg cm -2 s - ) 4 2 H c. H c.4 Loop Top Density ( cm -3 ) 9 H c.5 H c.3 Cross : max Square : mean Diamonds : min Oscilation Period ( sec ) 3 H c.25 Oscillation Period Loop Top Temperature ( MK ).3 H c.8 H c H c (erg cm -3 s - ) LT Temperature

27 Conclusion We studied coronal loop hydrodynamics including the regime transition from collisional to collisionless RX. We found two regime of behavior; small amplitude heating à steady large amplitude heating à cyclic On average the density of the loop system is close to the marginally collisionless value.

28 Future work for observation Comparison with Observation Warm loop (MK) à cooling stage of cycle Hot loop (>2MK) à steady state Before flare à faint loop à downflow (~ km/s)

29 Future Work for modeling Hall MHD Calculation gravity

30 Future Work for modeling Combination With Emerging Flux