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Sprite Light in a Bottle URSI Meeting Boulder, CO January 5, 2004

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Presentation on theme: "Sprite Light in a Bottle URSI Meeting Boulder, CO January 5, 2004"— Presentation transcript:

1 Sprite Light in a Bottle URSI Meeting Boulder, CO January 5, 2004
Earle Williams, MIT, Cambridge, MA Michael Valente, East Coast Induction, Brockton, MA Robert Golka, Golka Associates, Brockton, MA 1 1

2 A Small Tube

3 Current Density in Glow Discharge Tubes
Investigator Current Density J (Amperes/m2) DC Current Herz (1895) Wilson (1902) Townsend (1915) Günther-Schulze (1924) Günther-Schulze (1927) Found and Langmuir (1931) Capacitive Discharge Naudé (1932) x 104 Elmore (1974) x 104 Goto et al (2003) x 103 This study to 40

4 The Large Discharge Tube

5 Replacement of Lower Electrode

6 Air Pressure vs. Altitude

7 Absolute Spectral Units
PR-650 Colorimeter provides spectral radiance L in absolute units (watts/m2/sr/nm) Rayleighs (megaphotons/cm2/sec) = 4 (sr/unit sphere) BW (nm) L(watts/m2/sr/nm) hc/ (joule/photon) (104 cm2/m2)(106photons/megaphoton) = (2.39 x 1011) L

8 Spectral Comparison

9 Radiance vs. Input Power

10 Striations in Positive Column
(P = 70 mT) (J = 0.12 A/m2)

11 Constricted Discharge at Higher Pressure
(1.2 TORR) (6.6 A/m2)

12 Radiance vs. Current Density

13 Conductivity vs. Radiance

14 Column Sprites J (A/m2) 10-2 A/m2 3 x 10-3 A/m2 10-3 A/m2
Elizabeth Gerken

15 Carrot Sprite J (A/m2) 10-2 A/m2 3 x 10-3 A/m2 10-3 A/m2
Elizabeth Gerken

16 Large and Energetic Sprite
Elizabeth Gerken

17 Sub-Structure of Sprite
J (A/m2) 10-2 A/m2 3 x 10-3 A/m2 10-3 A/m2 Elizabeth Gerken

18 Langmuir’s Plasma Frequency

19 Conclusions Sprite spectra are reasonably well replicated in an air-filled glow discharge tube, with dominant N21PG emission (red light) The power dissipation per unit volume for a 1 Megarayleigh sprite is inferred to be ~1 watt/m3 The current density in a 1 Megarayleigh sprite streamer is inferred to be ~10-2 A/m2, with radiance proportional to current density The electrical conductivity of a 1 Megarayleigh sprite at km altitude is inferred to be ~3 x 10-5 mho/m, with conductivity proportional to radiance


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