Universal Heliophysical Processes George Siscoe Boston University ●50 years exploring has led to a...
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Transcript of Universal Heliophysical Processes George Siscoe Boston University ●50 years exploring has led to a...
Universal Heliophysical ProcessesGeorge Siscoe
Boston University
● 50 years exploring has led to a watershed betweenexploration and consolidation
adolescence and maturityspace physics and heliophysics
● What heliophysics is notspace physics renamed
an historical science like geology, planetology, biology a derivative science
● A derivative science needs only the laws of physicsIt has no regularities peculiar to itIt has no synthesizing laws of its own It has no inherent principles with explanatory power
sufficient to link its own distinctive phenomena
In short, it has no paradigms
What Heliophysics Is
● Heliophysics is an environmental science:a unique hybrid between meteorology and astrophysics
● It has an applied branch: space weather started 1990s (NSWP)
● It has a pure branch: universal processes started 2007 (IHY)
● It is a discipline that comprisesa body of data and a set of paradigms (i.e., general laws—perhaps mostly still undiscovered) specific to magnetized plasmas and neutrals in the heliosphere interacting with themselves and with gravitating bodies and their atmospheres
● This conference concerns the general laws of heliophysics and programs to uncover them
Examples of Discipline-Specific General Laws or Principles
● ASTRONOMYKepler’s Laws, Hertzsprung-Russell diagram, expanding universe
● CHEMISTRYperiodic table, valence, Le Chatelier’s Principle
● BIOLOGY evolution, double helix
● GEOLOGY deep time, plate tectonics
● METEOROLOGY Hadley cell, baroclinic instability
● HELIOPHYSICS (place-holding examples)solar (stellar) windmagnetospheric convection magnetic organization of matterexplosive energy conversion (CMEs & substorms)magnetically coupled systems
Organization of the Universeby Long-Range Forces
Heliophysics
PlasmaAstrophysics
Astro
Solar
GravitationalOrganization
Solar System&
Planetology
AstronomyAstrophysics
MagneticOrganization
ContractionAngular Momentum
GalaxiesStars
Solar systemsPlanets
SatellitesPlanetary systems
Rings
CreationExpansion
AnnihilationSheets (HCS)
Tubes (Sunspots)Cells (magnetospheres)
g = -4 Gρxg = 0
Gravity hasmaterial sources
B = 0xB = μoJ
Magnetism has dynamo sources
Gravitational + Magnetic OrganizationSolar and Stellar WindsCMEs and Substorms
Cosmic raysPlanetary Ionospheres
“It cannot be emphasized too strongly that … understanding of the magnetic activity… in the astronomical universe, can be achieved only by coordinated study of the various forms of activity that are accessible to quantitative observation in the solar system.” E. Parker Cosmical Magnetic Fields
2004
Richness of heliospheric examples
Universal Heliophysical Processes
Electron cyclotron frequency waves upstream of bow shocks of planets as function of the solar wind field strength
Radiometric scaling law for low-frequency planetary magnetospheric radio emissions
Universal slope to suprathermal tail of ion distribution function
Universal dependence of heating on magnetic flux
10-13
10-11
10-9
10-7
10-5
10-3
10-1
101
103
1 10 100
tail retail 5:23:15 PM 2/7/06
*FWtail*tail+SWSW distribution1FWFW<FW>meanFWnetFWbkgsum core+tail quietFWPI upFW -26day to TS LECPFW -20day to TS LECPFW -26day to TS LECPFW -20day to TS LECPFW(Vr broadened)Tail with cutoffFW ionsFW H+f bg=(min+mean)/2
Pha
se S
pace
Den
sity
(s
3 /km
6 )
W Ion Speed/Solar Wind Speed
f(w) = fow -5
(in solar wind frame)
H+
<R> = 4.86 AU
ULEIS
1 AU
4.23 AU
94 AU
Core pickup protons
46 AUSolar Windthermal tail
Desch and Kaiser, 1984Russell and Hoppe, 1983Fisk and Gloeckler, 2006
X ray bright points
Solar active regions
G,K & M dwarfs
T Tauri stars
Convective envelope
Pevtsov et al., 2003
Heliospheric Examples of Cosmical Magnetic Forms
• Sheets (current sheets):Heliospheric current sheet (HCS)Planetary current sheetsAuroral curtains
• Tubes (flux ropes):Coronal Mass Ejections (CMEs)CMEs, HCS, and “blobs”Solar wind flux tube spaghettiFlux transfer events (FTEs)
• CellsICMEsMagnetospheresHeliospheres
Lin et al., 2005
Crooker et al., 1993
Borovsky, 2007
Russell and Elphic, 1979
Bagenal, 2008
Explosive Energy ConversionA universal process illustrated by
CME Initiation and PropagationThe issue: Is initiation a result of a microscale
instability causing a sudden burst of magnetic reconnection or a macroscale mechanical instability?
Macroscale option: Pneuman, The 'melon-seed' mechanism and coronal transients (1984)
And since then:
Mikic and Linker
Forbes, 2008
Time = 2:14 Time = 2:22 Time = 2:24
Triggered Substorm Using OpenGGCM at CCMC
Is there a universal initiation process?Diagnostic test:
Does rapid reconnection precede motion or vice versa?
Vice versa
• Rate determined by microstructure of reconnection
• Plus macroscale geometry of reconnection (consensus view)?
• Or rate determined by macro-kinetics (Axford conjecture)?
Pritchett and Coroniti, 2004
What determines rate of global reconnection?
Fuselier et al., 2007-1
-0.5
0
0.5
1
1.5
72200 72400 72600 72800 73000 73200 73400
DMSP data-model comparisona1398344.195
vDMSPRidleyRaederWeimer
time
GEM Metrics ChallengeHesse 2001
• New idea: global rate of reconnection set by minimizing rate of entropy generation between bow shock and reconnection dissipation
• Reconnection decreases the rate of entropy generation at the bow shock (?) but increases it at the reconnection site
• If the curves of decrease and increase as a function of reconnection rate cross, the rate is the value at the point of crossing
Need to move from a reductionist (microphysics) approach to a systems (macrophysics) approach
IMF = 0
IMF = -20Southward IMF
Reconnection Current SystemMagnetopause SegmentMagnetosheath Segment
Bow-Shock Segment
x
z
-y
Summary• Heliophysics is an environmental science, a unique hybrid
between meteorology and astrophysics• It comprises a body of data and a set of paradigms (general
laws—perhaps mostly still undiscovered) specific to magnetized plasmas and neutrals in the heliosphere interacting with themselves and with gravitating bodies and their atmospheres
• Magnetic organization of matter induces spatial and temporal structures on all scales (the Parker principle)
• Empirical laws (Kepler-like) reveal the presence of universal laws (Newton-like) underlying these structures
• Explosive energy conversion exemplified by CMEs and substorms can test the value of a heliophysics-universal-processes project
• Cellular forms of magnetic structure (exemplified by magnetospheres) should be treated as complex, non-locally coupled systems (a new heliophysical paradigm)