Shock Waves in Interstellar Space

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ShockShock WavesWaves inin InterstellarInterstellar SpaceSpace Prof. Wayne G. Roberge A Passion for Physics Oct. 2, 2008 Outline • A Famous Example • Anatomy of a Shock Wave • Shock Waves on Earth • Shock Waves in Space • What I do Nuclear Explosion shock front What’s going on? Undisturbed Gas Shock Swept-Up Gas Disturbance (cold) Front (hot) (supersonic) (low pressure) (high pressure) F/A 18 in Transonic Flight Prandtl-Glauert Condensation (makes shock visible) Rifle Bullet in Air spherical shock cone-shaped shock Supersonic Object in Air object “bow shock” Battleship Firing Big Guns shock front Shock Wave in Traffic v v v v L L undisturbed fluid shock disturbance front • Initially: uniform speed v and separation, L. • Next: driver on right touches brakes. • Next: a traffic pileup (“shock”) ensues. WHY? Velocity of Information L • Left driver sees light and reacts. • News travels left with speed c relative to traffic. c = L Δt Δt ≅ human reaction time Signal Velocity Rel. to Ground u = v-c • Shock (pileup) if u>0 or v>c. • Now put in some numbers! V = 70 mph = 100 ft/s L = (N+1)h h = 15 ft (one car length) Δt = 1.5 s* FOR HOW MANY CAR LENGTHS (N) does v=c? *Marc Green, ”How Long Does it Take to Stop?”, Transportation Human Factors, vol. 2, p. 195. Earth’s Bow Shock solar wind Protostars Have Jets! v v HH47: 3 trillion Mile Jet A Theoretical Model HH30: Disk Detected! Georg Friedrich Bernhard Riemann 1826 - 1866 The Riemann Problem (fluid dynamics) LEFT GAS RIGHT GAS VL = VELOCITY VR = VELOCITY NL = DENSITY NR = DENSITY PL = PRESSURE PR = PRESSURE x THE RIEMANN PROBLEM (MULTIFLUID MHD) MOLECULAR JET CLOUD V = 0 VBL = 20 KM/S BR 0 4 - 0 4 -3 NL = 4 X 10 CM NR = 4 X 10 CM 3 TR= 10 K TL= 10 K BR= 50 µG BL= 50 µG x *MNRAS, IN PRESS (ARXIV:0708.4260). Summary • Shock waves = hydrodynamical surprises. • Caused by supersonic disturbances. • Found almost everywhere in space. • Light up and heat cold interstellar gas. • Allow us to see, study star-forming material..

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Radio Emissions Associated with Shock Waves and a Brief Model of Type Ii Solar Radio Bursts
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LA-2000 PHYSICS AND MATHEMATICS (TID-4500, 13th ed., Supp,.) LOS ALAMOS SCIENTIFIC LABORATORY OF THE UNIVERSITY OF CALIFORNIA LOS ALAMOS NEW MEXICO REPORT WRITTEN: August 1947 REPORT DISTRIBUTED: March 27, 1956 BLAST WAVE’ Hans A. Bethe Klaus Fuchs Joseph 0. Hirxhfelder John L. Magee Rudolph E. Peierls John van Neumann *This report supersedes LA-1020 and part of LA-1021 =- -l- g$g? ;-E Contract W-7405-ENG. 36 with the U. S. Atomic Energy Commission m 2-0 This report is a compilation of the dedassifid chapters of reports LA.-IO2O and LA-1021, which 11.a.sbeen published becWL’3eof the demnd for the hfcmmatimo with the exception d? CaM@mr 3, which was revised in MN& it reports early work in the field of blast phencmma. Ini$smw’$has the authors had h?ft the b$ Ala.mos kb(mktm’y Wkll this z%po~ was compiled, -they have not had ‘the Oppxrtl.mity to review their [email protected] and make mx.m%xtti.cms to reflect later tiitii~e ., CONTENTS Page Chapter I INTRODUCTION, by Hans A. Bethe 11 1.1 Areas of Discussion 11 1.2 Comparison of Nuclear and Ordinary Explosion 11 1.3 The Sequence of Events in a Blast Wave Produced by a Nuclear Explosion 13 1.4 Radiation 16 1.5 Reflection of Blast Wave, Altitude Effect, etc. 21 1.6 Damage 24 1.7 Measurements of Blast 26 Chapter 2 THE POINT SOURCE SOLUTION, by John von Neumann 27 2.1 Introduction 27 2.2 Analytical Solution of the Problem 30 2.3 Evaluation and Interpretation of the Results 46 Chapter 3 THERMAL RADIATION PHENOMENA, by John L.
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