Are there two types of pulsars? (The Aristotelian current sheet) - - PowerPoint PPT Presentation

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Are there two types of pulsars? (The Aristotelian current sheet) - - PowerPoint PPT Presentation

Feb 13, 2024 187 likes •582 views

Are there two types of pulsars? (The Aristotelian current sheet) Ioannis Contopoulos RCAAM, Academy of Athens NRNU MEPhI Currently, we have (a) good understanding of (the) overall electromagnetic structure of (the) pulsar magnetosphere

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Are there two types of pulsars?

(The “Aristotelian” current sheet)

Ioannis Contopoulos

RCAAM, Academy of Athens NRNU MEPhI

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Currently, we have (a) good understanding of (the) overall electromagnetic structure of (the) pulsar magnetosphere and Large scale kinetic modeling of the magnetosphere is required Maxim Lyutikov 2016

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Ideal Magnetospheres

1969

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Ideal Magnetospheres

1999, 2005, 2006

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Ideal Magnetospheres

2006, 2009, 2016

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Ideal Magnetospheres with particle tracing

(Athens)-Goddard Group 2014 Princeton Group 2010

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Dissipative Magnetospheres with finite conductivity σ

Goddard Group 2012, 2014

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“Ab initio” Magnetospheres

Princeton Group 2014, 2015, 2016… PIC with radiation reaction + pair formation!

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Dissipative Magnetospheres in Aristotelian Electrodynamics

Gruzinov 2015, 2016

FFE AE J B

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Are there `weak’ and `strong’ pulsars?

Ioannis Contopoulos

RCAAM, Academy of Athens NRNU MEPhI

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Limitations of numerical simulations

  • Lego tiles:

– Light cylinder resolution:

  • 2D: 10,000
  • 3D: 100
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Limitations of numerical simulations

  • Lego tiles:

– Light cylinder resolution:

  • 2D: 10,000
  • 3D: 100
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Limitations of numerical simulations

  • Lego tiles:

– Light cylinder position:

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Cerutti et al. 2015 Contopoulos 2016

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Limitations of numerical simulations

  • Lego tiles:

– Light cylinder position:

Cerutti et al. 2015 Contopoulos 2016

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Limitations of numerical simulations

  • Death stars:

– ρGJ , JGJ = ρGJ c – JCKF is a global quantity (nothing to do with JGJ )

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Limitations of numerical simulations

  • Death stars:

– ρGJ , JGJ = ρGJ c – JCKF is a global quantity (nothing to do with JGJ )

  • Density floors
  • PIC simulations: “billiard balls”
  • Numerical treatment of CS: “trade secrets”
  • I needed to return to the drawing board

and reconsider the global picture

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What drives dissipation?

1999, 2005; 2006

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What drives dissipation?

2007, 2014

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What drives dissipation?

EꞱ Eǁ =xBz

=xBr

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What drives dissipation?

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What drives dissipation?

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Spontaneous dissipation?

Cowley 1985 Sironi, Spitkovsky, Arons 2013

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The Y-point

EꞱ= xBp

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The Y-point

  • Bp, Ep, σ, all three vanish right outside the Y-point
  • It becomes problematic to support a current sheet

through the Y-point, unless Bφ also vanishes there

  • There is no current sheet that returns to the star
  • CKF “proved” that the solution that is dissipationless

everywhere is unique and it does contain a separatrix current sheet

  • The CKF-type solution cannot be valid anymore, and

the magnetosphere must find a new very different global equilibrium that is strongly dissipative

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2015

The “New Pulsar Magnetosphere”

Electrostatic Current Sheet

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The “New Pulsar Magnetosphere”

Cerutti et al. 2012; 2015

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It is very hard to support an electric current sheet through the Y-point unless there is pair production at the Y-point

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The “Aristotelian” current sheet

Contopoulos 2016 “Aristotelian” Electrodynamics Force-Free Electrodynamics

E Ʇ B everywhere + zero multiplicity in “AE”

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The “Aristotelian” current sheet

Contopoulos 2016 FFE FFE+”AE”: the `Device’

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The “Aristotelian” current sheet

Contopoulos 2016 submitted FFE+”AE”

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`Weak’ pulsars?

  • No pair production at the Y-point

– All particles are provided by the star

  • No electric current through the Y-point
  • Strongly dissipative

Cerutti et al. 2015 Contopoulos 2016

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`Strong’ pulsars?

  • `Free’ pair production everywhere

– In particular at the Y-point

  • CKF-type ideal solution

– Electric current sheet through Y-point

  • Weakly dissipative (FFE)

Philippov & Spitkovsky 2014 CKF 1999 and others

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Final remarks

  • It is early for global “ab initio” PIC simulations
  • Our proposal:

Combine ideal MHD/FFE global simulations with focused PIC simulations of the equatorial current sheet and the Y-point