Living with a Star Robertus Erdélyi Robertus@sheffield.ac.uk SP 2 RC, School of Mathematics & Statistics, The (UK)
Living with a Star The Secrets of the Sun Robertus Erdélyi Robertus@sheffield.ac.uk SP 2 RC, School of Mathematics & Statistics, The (UK)
The Outline Dynamic solar atmosphere Linear MHD Waves Heating in the solar atmosphere Space Weather
Why Bother? Modern Physics Plasma Physics Solar and stellar interiors are composed of ionised plasma and hence are excellent conductors of electricity In fact, 99.9% matter of Universe is in plasma state! ST system is a natural plasma laboratory geo-, astro- and tokamak physics, To explore space plasmas waves, in general, are excellent diagnostic tools!!!
Dynamic solar atmosphere
Dynamic solar atmosphere
Dynamic solar atmosphere more than 100,000 pulsation modes single mode three modes many modes
UV 1600 Å 8000 K Hα 15,000 K Magnetic field 5000 K Visible 5000 K Solar Physics & Space Plasma Dynamic solar atmosphere He EUV 50,000 K Fe VIII/IX EUV 1 MK Highly inhomogeneous Ubiquitous magnetic field X rays 4-6 MK Fe XIV 3 MK Fe XI 1.5 MK
Dynamic solar atmosphere
Dynamic solar atmosphere: Photosphere Visible surface of the Sun Only 100 km thick Temperature 6000 K
Dynamic solar atmosphere: Photosphere
Dynamic solar atmosphere: Photosphere
Dynamic solar atmosphere: Photosphere
Approximate 11 year cycle Whole magnetic field reverses Solar Physics & Space Plasma Dynamic solar atmosphere: Solar Cycle
Dynamic solar atmosphere: Solar Cycle Aert van der Neer [1603/4-1677] Sports on a Frozen River, ca. 1660
Dynamic solar atmosphere: Solar Cycle Rigozo et al., 2001, Solar Physics
Hydrogen alpha filter image Thickness 2500 km Solar Physics & Space Plasma Dynamic solar atmosphere: Chromosphere
Dynamic solar atmosphere: Spicules Solar spicules are thin, hair-like jets of gas seen on the solar limb in chromospheric emission lines They occur predominantly at supergranule boundaries and appear to be guided along the intense magnetic flux tubes gathered there Typical properties are: Width Height Lifetime 200-1000km 5000-10000km 5-15mins Axial Velocity 20kms -1 Temperature 5000-15000K Density 0.5-2.5kgm -3 Hα Image from the Big Bear Solar Observatory, California Some spicules display rapid rotation about their axis, typically of the order of 25km s -1 The spicule rise is probably not ballistic, although the evidence for this is not conclusive
Dynamic solar atmosphere: Tornadoes
Dynamic solar atmosphere: Tornadoes
Dynamic solar atmosphere
Dynamic solar atmosphere: Prominences Active prominence Non-active prominence
Dynamic solar atmosphere: Coronal Loops
Dynamic solar atmosphere: Coronal Loops SOHO/TRACE examples (mainly TR and higher)
Dynamic solar atmosphere: Coronal Loops SOHO/TRACE examples (mainly TR and higher)
MHD waves in magnetic tubes and slabs (structured plasma)
MHD waves in magnetic tubes and slabs (structured plasma) Linear motions of a compressible cylindrical/slab plasma
Linear MHD waves Magnetoacoustic modes Modes of identical parity transversal structure can be distinguished as slow and fast modes.
Linear MHD waves: Dispersion Relation Original MHD theory by e.g., Edwin & Roberts (1983) modelled a coronal loop as a magnetic cylinder. It was found that there are many different types standing waves, e.g., fast/slow magneto-acoustic and Alfvén modes. Magnetically twisted cylinder (Erdélyi & Fedun 2010) r D 0 K m (m 0e r 0 ) e ' m 0e K m (m 0e r 0 ) = - A2 2 r 0 2 1- a 2 2 + D m i r 0 0 M ' (a,b,x m(1- a) + 2x 0 ) 0 M(a,b,x 0 )
m 02 >0 surface waves ) ( ) ( ) ( ) ( ) ( ) ( ' 0 2 2 2 ' 2 2 2 0 m a I m a I m v k m a K m a K m v k o n o n Ae e e n e n e A ) ( ) ( ) ( ) ( ) ( ) ( ' 0 2 2 2 ' 2 2 2 0 a n J a n J n v k m a K m a K m v k o n o n Ae e e n e n e A m 0 2 = -n 0 2 <0 body waves. Note n=0 refers to sausage, n=1 to kink modes, etc. Roberts (1981), Edwin & Roberts (1983) Dispersion relation ω(k) for tubes Linear MHD waves: Dispersion Relation
Theory of tube oscillations Solutions to DR for lower atmosphere magnetic tubes Main modes: torsional Alfvén (incompressible) fast sausage ( B, ρ) fast kink (almost incompressible) slow (acoustic) type (ρ, v) Torsional waves n=0 n=1
Dynamic solar atmosphere: Coronal Cycle
Dynamic solar atmosphere: Solar Wind
Solar Flares Solar Physics & Space Plasma Expanding corona: solar storms 1 10 20 J to 1 10 25 J (equivalent of 1 billion megatons of TNT ) ~ 5 occurring every day at present Coronal Mass Ejections (CMEs) 100 to 1000 km/s 1 to 10 billion tonnes (10 13 kg) released 2 to 3 occurring every day at present
Blackouts and burnouts Solar storm shuts down air space (4 Nov 2015)
Blackouts and burnouts
SOHO TRACE RHESSI Yohkoh IUSS 2009 16 June 2009, Sheffield
SOHO Solar Physics & Space Plasma TRACE RHESSI??? STEREO Solar-B/Hinode SDO Solar Orbiter IUSS 2009 16 June 2009, Sheffield
The end