Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo...
-
Upload
darcy-hunter -
Category
Documents
-
view
216 -
download
0
description
Transcript of Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo...
![Page 1: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/1.jpg)
Turbulence and Magnetic Field Amplification in the Supernova Remnants
Tsuyoshi Inoue (NAOJ)
Ryo Yamazaki (Hiroshima Univ.)Shu-ichiro Inutsuka (Kyoto Univ.)
TI, Yamasaki & Inutsuka (2009) in preparation
![Page 2: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/2.jpg)
Introduction Supernova remunants (SNRs): The site of CR acceleration SNRs emit radiations with various wavelengths (radio to TeV g)
Uchiyama+07, Uchiyama & Aharonian 08 discovered thatThere are bright X-ray hot spots in SNR RXJ1713 and CasA.The hot spots decrease its luminosity with the timescale of a few years.
Synchrotron cooling time : tsynch years
--> B ~ 1 mG (~ 200 × BISM ) is necessary!€
≈1.5 BmG ⎛ ⎝ ⎜
⎞ ⎠ ⎟−1.5 ε
keV ⎛ ⎝ ⎜
⎞ ⎠ ⎟−0.5
--> Physical conditions of SNRs are very important to understand them.
![Page 3: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/3.jpg)
Motivation of This Work A possible mechanism of B amplification in SNRs (Balsara+01, Giacalone & Jokipii 07) Density fluctuations of preshock medium cause magnetic field amplification in the post shock medium (SNR).
However, the realistic strength of turbulence cannot amplify B to the order of 1mG (Balsara+01).
They assumed the caused by turbulence of ISM.
Large amplitude r fluctuations are ubiquitously exist in ISM: Small-scale HI clouds generated by thermal instability
HI clouds have density n ~ 10-100 cm-3 >> diffuse medium n ~ 1 cm-3
--> Stronger amplification than the case of turbulent medium can be expected, if we consider complex (and realistic) ISM!
--> In order to make hot spot (1mG level of B), larger r fluctuations are needed.
![Page 4: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/4.jpg)
Interstellar Medium ISM is an open system in which radiative cooling/heating are effective ( Field+ 69, Wofire+95, 03 ) Heating source : photoelectric heating by dust grains (PAHs) Cooling sources : line emissions (T>103 K: Ly-a, T<103 K: CII/OI fine structure)
--> Diffuse warm gas and HI clouds can coexist under pressure equilibrium.
Thermal equilibrium curve
Diffu
se ga
s
HI clou
d
Diffuse warm gas
HI clouds
T ~ 8000 K, n ~ 0.1-1 cm-3
T ~ 100 K, n ~ 10-100 cm-3
Thermal instability: the equilibrium that connects warm/cold phase is unstable.
unstable
--> Unstable gas evolves into diffuse gas and HI clouds (Field 65, Balbus 95).
Heating region
Cooling region
Number density
Pres
sure
![Page 5: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/5.jpg)
Evolution of Thermally Bistable ISM
ISM is affected by (late-stage) supernova shock waves once/several Myr.
1. Shock compression
2. Cooling
3. Development of thermal instability
Cooling region
Heating region•Timescale of this evolution is a few Myr ( timesacle of cooling/heating ) .
Recent high-resolution MHD simulations have shown that ISM evolves as follows:
T.I. & Inutsuka 08, Hennebelle & Audit 07
--> In general, ISM is two-phase medium composed of warm gas and HI clouds.
(McKee & Ostriker 77)
Number density
Pres
sure
![Page 6: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/6.jpg)
Generation of Two-phase Medium To generate two-phase medium as a consequence of thermal instability, we performed MHD simulation. basic equations:
Result (density structure) Initial condition: thermally unstable equilibrium + B filed (Bx=6mG, By=0)
Results:Red region: diffuse warm gas (n~1 cm-3, T ~ 5000 K)Blue region: HI clouds (n~30 cm-3, T ~ 100 K)
*Scale of HI clouds are determined by scale of thermal instability (~ 0.1 pc)
*Small scale HI clouds are ubiquitously observed in ISM (Heiles & Troland 2003)
Thermal conduction Heating/cooling fuction
![Page 7: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/7.jpg)
Early-stage Supernova Shock wave
Set the hot plasma (n=0.1 cm-3) at one of the boundary.
Model Phot/kB position to set hot plasma( shock type) Shock speed
1 3.0 X 108 K cm-3 y=0 (perpendicular shock) 1300 km/s
2 3.0 X 108 K cm-3 x=0 (parallel shock) 1300 km/s
To investigate SNR formed by piling up the two-phase medium, we induced shock wave at a boundary of computational domain.
Basic equations: ideal MHD equations.
*Strength of induced shock wave corresponds to early-stage supernova shock of the age ~ 1,000 years.
![Page 8: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/8.jpg)
Result of Model 1 Model 1: Perpendicular shock, vshock ~ 1300 km/s )
B field is strongly amplified to the level of 1 mG in some region!
Number Density Magnetic Field Strength
T.I. et al 09 in preparation
![Page 9: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/9.jpg)
Result of Model 2 Model 1: Parallel shock, vshock ~ 1300 km/s )
B field is strongly amplified to the level of 1 mG in some regions!
Number Density Magnetic Field Strength
T.I. et al 09 in preparation
![Page 10: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/10.jpg)
Evolutions of Maximum B and b
Maximum magnetic field strength saturate at B ~ 1 mG.
|B|max plasma b at B is max
b
B [m
G]
Maximum magnetic field strength is determined by the condition b = pthermal/pmag ~ 1.
Model 1 (perp. shock)Model 2 (para. shock)
Model 1 (perp. shock)Model 2 (para. shock)
![Page 11: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/11.jpg)
Mechanism of B amplification Amplification mechanism of B
By using the eq. of continuity and induction eq., we can obtain:
--> B is amplified if velocity filed has shear along B filed line.
Strong velocity shear is generated when HI clouds are swept by the shock.
T.I. et al 09 in preparation
v B
Shock
Perp. shock case (model 1)
v
B
Shock
Para. shock case (model 2)vshock in HI cloud << vshock in warm gas
--> post shock gas flows to round HI cloud
--> velocity shear is induced most strongly at transition layer between HI cloud and surrounding diffuse gas
(scale of the transition layer l ~ ~ 0.05 pc T.I.+06)
€
rLκ T
![Page 12: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/12.jpg)
Comparison with Observation X-ray image of SNR(RXJ1713) by Uchiyama+07
Scale of hot spots ~ 0.05 pc
10 arcsec = 0.048 pc
Hot spots seem to be located far behind the shock front
![Page 13: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/13.jpg)
Comparison with Observation
Scale of the regions where magnetic field is amplified to 1 mG agrees well with the scale of the X-ray hot spots.
Result of our Simulation
0.05 pc
Regions with high B are located far behind the shock as the X-ray hot spots.
--> Regions with high B can make X-ray hot spots, if electrons are accelerated around there by secondary shock.
![Page 14: Turbulence and Magnetic Field Amplification in the Supernova Remnants Tsuyoshi Inoue (NAOJ) Ryo Yamazaki (Hiroshima Univ.) Shu-ichiro Inutsuka (Kyoto Univ.)](https://reader036.fdocument.pub/reader036/viewer/2022062523/5a4d1b097f8b9ab059989bcd/html5/thumbnails/14.jpg)
Summary
Shocked shell generated by piling up two-phase medium is turbulent.
In general, ISM has large amplitude fluctuations due to thermal instability, which generates small scale HI clouds (l~0.1 pc).
Velocity shear along B line amplifies B at transition layer between HI cloud and diffuse warm gas.
In the case Vshock ~ 1000 km/s, B strength grows to the order of 1 mG ( b ~ 1 ) . Scale of the regions where B is on the oreder of 1 mG is 0.05 pc, which agrees well with the scale of X-ray hot spots.
The scale 0.05 pc is determined by the scale of transition layer between HI cloud and surrounding diffuse gas at which velocity shear is most strongly induced.