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![Page 1: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/1.jpg)
Generation of Magnetic Fields in Gravitationally
Forming Structures in the Early Universe
Russell M. Kulsrud
Princeton Plasma Physics Laboratory
![Page 2: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/2.jpg)
OUTLINE
• PROPERTIES OF OUR GALACTIC MAGNETIC FIELD
• STANDARD — DISC DYNAMO THEORY
• PROTOGALACTIC ORIGIN
![Page 3: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/3.jpg)
OUR GALACTIC MAGNETIC FIELD
• The field is toroidal.
• Its strength is 2 microgauss.
• It varies in radius possibly changing every spiral arm or about one kiloparsec.
• It does not change in the direction perpendicular to the disc.
Figure 1: The galactic magnetic field
![Page 4: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/4.jpg)
THE ALPHA-OMEGA DISC DYNAMO THEORY
• THE THEORY CONSERVES FLUX, SO TO WORK IT HAS TO EXPEL NEGATIVE FLUX
• THIS IS VERY DIFFICULT BECAUSE THE GALACTIC DISC IS IN A DEEP POTENTIAL WELL AND THE FLUX MUST CARRY MATTER OUT WITH IT
Figure 2: The escape of negative flux in the Alpha-Omega dynamo.
![Page 5: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/5.jpg)
OTHER ORIGINS
• The Galaxy was originally a plasma in the form of a protogalaxy » 100kpc with a mass of 1011 solar masses.
• It resulted from a gravitational collapse and smaller parts also suffered gravitational collapse creating many small shocks.
![Page 6: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/6.jpg)
Shocks Creating Turbulence
These shocks produced vorticity, turbulence, weak magnetic fields (Biermann) and heating that led to the support of the protogalaxy against gravity.
![Page 7: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/7.jpg)
![Page 8: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/8.jpg)
k
![Page 9: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/9.jpg)
The Magnetic Differential Equation
![Page 10: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/10.jpg)
The Solution
![Page 11: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/11.jpg)
B0=6£10-6 gauss
lnB/B0
lnk/k0
![Page 12: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/12.jpg)
![Page 13: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/13.jpg)
![Page 14: Generation of Magnetic Fields in Gravitationally Forming Structures in the Early Universe Russell M. Kulsrud Princeton Plasma Physics Laboratory.](https://reader036.fdocuments.net/reader036/viewer/2022062619/55151844550346c77d8b4e39/html5/thumbnails/14.jpg)
CONCLUSION
• Magnetic Fields may have already been generated before our galaxy was fully formed due to plasma processes in the preceding protogalaxy.
• This may be a common phenomenon.