Boundary Conditions of the Heliosphere

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Boundary Conditions of the Heliosphere

• Priscilla Frisch, University of Chicago
• Collaborator Jonathan Slavin, Smithsonian
  Astrophysical Observatory, CFA

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Sun in decelerating interstellar flow from Loop I
10 pc Filling factors G, AG 40, 26
Log plot (AU)
Sun
?
G Cloud 29.3 km/s
LIC 26.2 km/s
36 Oph
LISM Bulk Flow 28.1 - 4.6 km/s Obs
Direction L,B 12.4o, 11.6o ????82.4o,
-11.6o
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Heliosphere Boundary Conditions determined
by Galactic Neighborhood of Sun
GC
B
Dust Model of Spiral Arms from COBE Far infrared
240 mm
B MAGNETIC FIELD from Faraday Rotation
Drimmel 2004
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Goal Predict Interstellar Boundary Conditions
of Heliosphere
Local Bubble Void affects heliosphere boundary
conditions

• Radiation field in LIC
• Loop I -gt cloud kinematics

Local ISM

• Cloud density
• ionization

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RADIATIVE TRANSFER MODELS

• 4 input Variables to CLOUDY n(H), N(Ho), TLB, B
• Model interstellar radiation field at cloud
  surface including EUV radiation from cloud
  interface
• Properties of boundary between LIC and adjacent
  hot plasma - conductive interface regulated by
  TLB, B (use Wisconson SXRB B-band and Be-band
  data)
• Set total n(H) and N(HI) cloud density
• Run radiative transfer models
• Select results that agree with Data
• Local Interstellar Cloud towards ? CMa
• Heo inside of heliosphere
• Partially neutral ISM forming pickup ions N, O,
  Ne, Ar
• Tweak radiation field, n, N(HI), until models
  match data
• Model C, N, O, Mg, Si, S, Fe abundances
  constrained by C, No, Oo(??), Mg, Si, S, Fe
  LIC data for ? CMa
• Model Ne, Ar abundances fixed

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Slavin Frisch (2007)
Radiative Transfer Models
Model 26
Model 42
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? CMa (Gry Jenkins)
Pickup Ions (Gloeckler)
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Matter Distribution at Sun from ABOVE
600 pc
Galactic Center
Interstellar Radiation Field
Galactic Center
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Ultraviolet Radiation Hot Stars ? CMa, ? Cma
--gt LIC Ho Ionization
Hot Stars --gt Red H Balmer Emission (H?, WHAM)
X-rays
0o
270o
90o
Adhara B2II ? CMa
Hot Stars --gt 1565 A (TD-1 data)
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Conductive Interface between Local Bubble Plasma
and Local Interstellar Cloud (Slavin 1989 Slavin
Frisch 2007)
Voutflow 10-35 km/s
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Interstellar Radiation Field in LIC at Heliosphere
Ne
TD-1
e CMa
White Dwarf Stars
Slavin Frisch 2007
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Cluster of Local Interstellar Clouds Low Opacity
t1 at 504 A
t1 at 912 A
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Cluster of Local Interstellar Clouds Low Opacity
Ho/Heo Varies Continuously between Cloud Surface
and Sun
HII
Ho and Ca data
n(HI) 0.2 cm-3
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LIC is low opacity ISM, gives ionized gas
N/No H/Ho by charge exchange
26
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CLOUD IONIZATION
Electron Density in LIC
1) Ionization balance of Mg
2) Collisional ionization of C fine-structure
J3/2 and J1/2 lines
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Electron Density in LIC

Sightline 2
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Ionization Gradient across LICseen in H, He, N,
O, Ne (Ar)
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Model Selection Criteria

• In situ He density and temperature
• - Cavaet Is He filtration lt 1?
• MgI/MgII (CII/CII) to star
• Cavaet MgII--gtMgI dielectronic recombination
  strong function T
• Pickup Ion data for Ar, Ne, N, O
• Interstellar Ar, Ne abundances poorly known
• N, O filtrations depend on Heliosphere model
  IBEX will help

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• n(Ho) 0.19-0.20 cm-3
• n(e-) 0.04-0.08 cm-3
• If pressure equibrium -gt B2.5 ?G
• VSun-LIC 26.3 km/s (Ulysses)

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Slavin Frisch (2007)
Model 26
Model 42
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LIC Only (Model 26) Constraints Results
Data PUI Gloeckler Geiss 2006, PUI Cummings
Stone 2002, HeI Moebius et al. 2005 Eps CMa Gry
and Jenkins 2002, Solar-Asplund et al 2007
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Current epoch Interstellar Cloud Surrounding
Sunhas High Neutral Fraction which enters
Heliosphere

• n(Ho) 0.19-20 cm-3
• n(Heo) 0.015 cm-3
• n(e-) 0.04-0.08 cm-3
• (new MgII-gtMgI rates)
• Ulysses T 6,300340 K
• Hydrogen 22 ionized
• Helium 43 ionized
• Ionization gradient in LIC

Ne
Heo
He
Neo
Ne
LIC IONIZATION
(Slavin Frisch 2006)
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RADIATIVE TRANSFER MODELS ILLUMINATE INTERSTELLAR
DUST
Slavin Frisch 2007
Ratio of Gas mass to Dust mass in LIC
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Depletions Abundances Log(Agas) Log(Asun) ?
Depletion (?)
Cold ISM
Welty
Dust Grain Destruction in Shock
LIC
Need H
halo
warm
cold
Welty
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Same Upwind Gas and Dust inflow
Cold ISM
LIC
halo
warm
cold
Frisch et al. 1999
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Grain Destruction In Interstellar Shocks
Cold ISM
LIC
halo
warm
cold
Frisch et al. 1999
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Summary Boundary Conditions of the Heliosphere

• n(Ho) 0.19-0.20 cm-3
• n(e-) 0.04-0.08 cm-3
• If pressure equibrium -gt B2.5 ?G
• VSun-LIC 26.3 km/s (Ulysses)
• Enhanced abundances of Fe, Ca, refractories
  indicate grain destruction in shock.
• LIC is normal gas for an expanding superbubble
  shell - high abundances, warm, tenuous,
  intermediate velocity gas.

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The Local Bubble
0o
OB Associations De Zeeuw et al. 1999
CO Clouds Dame Thaddeus 1987
HII Region - Gum Nebula
Sun
Plasma T 106.1 K n 0.005 - 0.026 cm-3
Associations Form Tilted Plane
200 pc
180o
Ref Frisch, American Scientist (2000)