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Wayne G. Roberge & Raymond L. Menzel NY Center for Astrobiology (NYCA)

Electrodynamic Heating in Protoplanetary Disks. Wayne G. Roberge & Raymond L. Menzel NY Center for Astrobiology (NYCA) Rensselaer Polytechnic Institute. Motivation. Chondritic meteorites deliver amino acids to Earth. Chondrites are fragments of C-type asteroids.

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Wayne G. Roberge & Raymond L. Menzel NY Center for Astrobiology (NYCA)

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  1. Electrodynamic Heating in Protoplanetary Disks Wayne G. Roberge & Raymond L. Menzel NY Center for Astrobiology (NYCA) Rensselaer Polytechnic Institute

  2. Motivation • Chondritic meteorites deliver amino acids to Earth. • Chondrites are fragments of C-type asteroids. • Were prebiotics synthesized on C asteroids? • They were warm and wet! But why? What heated asteroids and how prevalent is this process in protoplanetary disks?

  3. Asteroid Composition Types Igneous (SME) - melting; partially or completely exposed metallic cores. Metamorphic (CBGF) - aqueous alteration at 25-150 oC; hydrated minerals. Primitive (PD) – no heating; primitive solar system materials (?). Image: NASA/Hubble Space Science Institute (STScI). W.B. McKinnon, Nature, 340, 343 (1989)

  4. Radioactive Heating of Asteroids Urey 1955 • 26Al 26Mg + energy • Half life t1/2 = 0.7 Myr • 26Mg in meteorite Allende implies live 26Al was present. • 26Al/27Al = 6 x 10-5 in Allende, enough to melt asteroids. • But how did 26Al arrive at the party live? • Unknown but 26Al DID get here! • Why did heating decrease with heliocentric distance? • Only ~10-3 -10-2 of Sun-like stars receive live SLR (Ouellette et al. 2010).

  5. “Induction” Heating of Asteroids Sonnet et al. 1970 Ionized T Tauri Wind v0 =400 km/s E’ Plasma Frame: E=0, B=B0 Body frame: E’= -v0/c x B0 asteroid • Sonnet et al: Electric field E’ in asteroid frame. • Currents in plasma (yellow) flow from + to - . • Currents inside asteroid (green) close circuit. • Heating rate: P = J E = sE2 ~ 10-8 W/kg.

  6. Induction Heating Reexamined V0 here! What’s wrong with E’=-v0/c x B?

  7. Our Calculation

  8. Electric Field at Asteroid Surface In weakly inonized disks e << 1 and E ~ EH ~ v0B0/c!!!

  9. Conclusions • Classical induction heating invalid. • Found new “electrodynamic” mechanism. • Operates in weakly ionized disks! • Also operates in ionized disks. • At least as efficient as induction heating.

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