solar-b science objectives - overview of the mission - kazunari shibata (kyoto univ.)
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Solar-B Science Objectives- Overview of the Mission -
Kazunari Shibata(Kyoto Univ.)
Science Objectives of Solar-B Mission
Kosugi (1999)– coronal heating
– coronal dynamics and structure
– elementary processes such as reconnection
- emerging flux and dynamo
chromospheric heating, spicules, …
jets, prominence, CME, solar wind, waves/shocks,…
reconnection jet, inflow, slow/fast shocks,…
flux tubes, sunspots, convection, …
These Objectives are also important for astrophysics and space weather
• To explore solar MHD as a laboratory of astrophysical MHD
• To explore solar activity as a basis of space weather research
Plan of this talk
• Introduction – Main Instruments• Main Objectives
– Coronal and Chromospheric Heating Nanoflares, Alfven Waves, Spicules
– Coronal Dynamics and Structure Jets, CMEs, Coronal Waves/Shocks
– Reconnection – Emerging Flux
• Summary
Solar-B Mission
• Solar Optical Telescope (SOT)• X-Ray Telescope (XRT)• EUV Imaging Spectrometer (EIS)
• Launch Date: 2005 J-fiscal year• Mission Lifetime: > 3 years• Orbit: Polar, Sun Synchronous
Solar Optical Telescope (SOT)
• 50 cm Aplanatic Gregorian – Japan• Focal Plane Package – US(LMATC) (Filtergram+Spectro-polarimeter)• => 0.2 arsec resolution; 380-700 km vector magnetic field
measurements
X-Ray Telescope (XRT)
• Grazing-Incidence Optics – US(SAO)
• CCD Camera – Japan• => 1 arcsec resolution; 1 – 30 MK
EUV Imaging Spectrometer (EIS)
• 15 cm Offset Parabolic Mirror, Slit/Slot & Multilayer Grating – US (NRL, GSFC)
• Camera – UK(MSSL,RAL,Birmingham)• Controller – Japan• 20 km/s nonthermal motion• 2 arcsec spatial resolution• Temperature coverage
0.1 – 20 MK
太陽活動の11年周期
黒点数
2005 - 2007
Yohkoh HXT Flares in 1991-1998
Predicted Solar Corona in 2005-2007
2007Sep(minimum)
2005 Nov
1994 Nov2005 Nov ?
1996 Sep (minimum) 2007 Sep ?
Coronal HeatingAlfven wave vs Nanoflare
• Alfven Wave heating
• Nanoflare heating
BVVfF A 2
22 4/ BVfBF
Nanoflare Heating ?
• Shimizu (1995) Ph. D. Thesis
active region corona is filled
with microflare/nanoflare => nanoflare
heating ? • Kano (1997) Ph. D. Thesis
loop top heating ?
• Priest et al. (1998) nanoflare heating ?
Microflare/Nanoflare Occurrence Frequency
α = 1.6-1.7 <2Shimizu, Shimojo, Aschwanden,
…. => insufficient for coronal heating
)(2
1 2min
2max
max
min
EE
EdEdE
dNE
EdE
dN
E
E
total
α >2Krucker & Benz
Alfven Wave Heating ?
• Yashiro (2000) Ph. D. Thesis
Lx( active region ∝ ) B^1.07
F ∝ B => Alfven wave heating ? 78.0Bp
07.1xL
Alfven wave theory of Spiculesand Coronal Heating
(Hollweg et al. 1982, Kudoh-Shibata 1999)
Hα (Hida DST)
Alfven wave model of spicules:numerical simulation (Kudoh-Shibata 1999)
Energy Flux Carried by Alfven Waves into Corona (Saitoh, Kudoh, Shibata 2001)
Nonthermal Line Width(Kudoh & Shibata 1999)
Coronal Heating(Kudoh &Shibata 1999)
Question on Coronal Heating
• What is the true occurrence frequency of nanoflare ?
• What is the heating rate and its dependence upon magnetic field ?
• What is the energy flux carried by Alfven waves into the corona ?
• What is the origin of Alfven waves ? Photospheric turbulence or reconnection ?
Coronal Dynamics and Structure: X-ray Jet
Yokoyama & Shibata (1995)
Zoo of Solar Jets
• H alpha jets (surges)
• EUV macrospicules
• EIT jets
• LASCO jets
CDS spinning jet (Pike&Mason)
H alpha spinning jet (Kurokawa)
EIT-LASCO jet (Wang, Y. M.)
Cosmic jet (HST)
Polar plume
Evaporation flow produced by reconnection heating ?(Wang, Y.M. 1999)
Moreton Wave(Hα : Hida FMT, Eto et al. 2001)
Moreton wave
= Fast mode
MHD shock
(Uchida 1968)
Wave front of Moreton wave
5 : 55
Propagation speed ~ 720km/s
① ②
③ ④
5:40 - 5:31 5:58 - 5:40
6:14 - 5:58 6:31 - 6:14
Moreton wave and EIT wave
Moreton wave
EIT waveEIT wave(Thompson et al. 1998)
Photospheric flare wave(SOHO/MDI, Kosovichev)
Question on Coronal Dynamics and Structure (Jets and Waves)
• What is the true velocity of X-ray jets ?
• What is the acceleration mechanism of X-ray jets ? ( => Shimojo’s talk)
• What is the relation to coronal heating and acceleration of high speed solar wind ?
• What is EIT wave ?
• What is the origin of Moreton wave ?
Reconnection
• Yohkoh found plenty of evidence of reconnection in flares.
• But we have not seen reconnection jet and inflow in SXT images.
(but see Yokoyama et al. 2000 ApJ Let.)
Reconnection Rate of a Cusp-Shaped Flare on
May 12, 1997 (Isobe et al. => poster)
Reconnection rate is high even in a very late decay phase V_inflow/V_A=
0.001 – 0.01
Question on Reconnection
• Are there really high speed reconnection jets with 1000 km/s ?
• What is the reconnection rate (inflow speed) in solar flares, jets, and coronal mass ejections ?
• What determines the reconnection rate ?
=> Yokoyama’s talk
Emerging Flux RegionEmerging Flux
Region (EFR) is important for
(1) Dynamic Phenomena
(2) Dynamo(3) Coronal
Heating
TRACE Observation of Emerging Flux
Dark : ChromosphereBright : Corona
Wavelength ~171 A Time cadence ~1 minSpatial Resolution ~ 2 arcsec
Comparison with SXT(Yashiro-Shibata)
TRACE
SXT
Emergence of twisted flux tube - most fundamental driver of solar
activity ? -
(Matsumoto et al. 1998)
Question on Emerging Flux
• How and when are kG intense flux tubes created in emerging flux ?
• How and why are twisted emeging flux tubes generated ?
• Will we observe flare-like explosive reconnection (with jets and shocks) in photospheric reconnection associated with emerging flux ?
Summary
• More, smaller, and faster jets, plasmoids, waves, and shocks would be found by Solar-B.
• High time cadence velocity field observations (with EIS and SOT) with good coordination with XRT is extremely important.