- [ : ( ) ] 1 (contact) (interaction) 1 2 19 MTI c Mesosphere Thermosphere Ionosphere (MTI) Research Group, Japan 1 2 (1) : (2 ) (2) : (3 ) (3) : (2, 3 ) (4) : - (4 ) 2 3 3 X 1
; 200 µs 0 1 ms 4 exponential 80 km 5 4 10 7 m/s 10 km 1 ms 5 E k N = e z/h n 6 ; N, H n :, z: ( ) 1 0 7 t ρ + (σe) = 0 E σ 1 σ σ σ e e (1/H e+1/h n )z 4 (5) E H (1 1) + O(ε) (1) z3 ; H σ 1 O(ε) ; 6 E k0 /N 0 ; 100 km N 2:O 2 = 8 : 2 (Nσ) 1 7 X 2
E altitude, km 90 80 breakdown 70 60 50 40 30 20 10 0 10 0 10 1 10 2 10 3 10 4 10 5 10 6 electric field, V/m 1: E T 1 8 ε 0 /σ T T ε 0 /σ H H E > E k 2 T ε 0 /σ e (1/H e+1/h n )z, H E k e z/h n 8 T H (He+Hn)/He (2) H e, H n (H e + H n )/H e 2 3 ; T em, T el T ε 0 /σ(z cr ) T th T em T el 9 T th z cr 9 90 km T el ε 0 /σ X 3
z ii i. field relaxation t r (z) < T iii Electric field E E k 2: H T ε 0 /σ(z) < T (i) T ii H (iii) (70 90 km) H H discharge time T, s 10-2 10-3 10-4 10-5 No sprite Halo electrostatic limit 100 1000 charge moment H, C km Streamer 3: H T (2) ; T 100 µs H 4 (e.g. Cummer and Lyons, 2005) 400-600 C km Hiraki and Fukunishi, 2006, 3 H 100 C km 10 (2) T H 2 T T ; (detect) H : H T return stroke (1 ms ) 10 X 4
continuing current (up to 100 ms) ( M-component ) Ohkubo et al. (2005) 3 11 e.g. Pasko et al., 2000; Hayakawa 11 et al., 2007 12-1ms CCD (Moudry et al., 2003; Cummer et al., 2006, 4 ) main branch tendril main branch tendril ; bead second branch 90 km leaf 5 ms main branch (i) main branch & second branch, (ii) tendril (i), (ii) 12 X 5
4: CCD (Cummer et al., 2006)main branch tendril main branch, tendril second branch, bead ; 13 main branch 13 ( H/z 3 ) ( exp( z/h n )) main branch ; 10 km km (1) z 3 14 14 X 6
( ) VHF (van der Velde et al., 2006) main branch main branch second branch tendril 15 main branch-tendril 15 10 km 16 main branch 4 17 3 5 16 17 X 7
T electron field E T c No sprite critical point Halo Structured H H c 5: (No sprite) (Halo); (Structured) T T cr n e 0 Halo (critical point) m (i) m = 0 (ii) (iii) m 0 m H T 18 (T cr, H cr ) (T > T cr, H > H cr ) T T cr m T 18 m H T m z 1,2 r 1 ; 6 z 1 z 2 T 19 (r, z) E = H 1 + 3 cos 2 θ 2πε 0 (z 2 + r 2 ) 3/2 = H 4z 2 + r 2 2πε 0 (z 2 + r 2 ) 2 (3) r = 0 E k = E 0 e z/hn H πε 0 z1 3 = E 0 e z 1/H n ( H ) z 1 H n ln πε 0 z1,0 3 E 0 z 1 ln H H n + const (4) 19 X 8
z 2 Halo z 2 z 1 z 1 r 1 E E k 6: Halo-No sprite E E k z 1 z 2 ln z 1 z 2 ε 0 σ = T en e(z 2 )µ e (z 2 ) = ε 0 T z 2 = H eh n H e + H n ln σ ( ε0 σ 0 T z 2 = ln T H ehn He+Hn + const (5) ) = en e µ e ; n e (z) = n e0 e z/h e, µ e (z) = µ e0 e z/h n 20 Z = z 2 z 1 Z = H n ln HT He He+Hn H n ln HT 1 2 + const + const ; H e /(H e + H n ) 1/2 Z 0 r 1 z 2 E(z 2, r) = E k r 1 r 2 1 z2 2 4z2 2 20 2 µ e N e z/hn µ e N 1 H 4z2 (T ) 2 + r1 2 2πε 0 (z 2 (T ) 2 + r1 2 = b(t ) )2 b(t ) = E 0 e z 2(T )/H n r1 2 H z 2 (T ) = πε 0 b(t ) z 2(T ) 2 (6) m(t, H) m(t, H) = z2 (T ) z 1 (H) k(e/n)n e Ndz πr 2 1 z2 = const r 1 (T, H) 2 (T ) e cz νattt dz z 1 (H) c = 1 H e 1 H n = const r 1 (T, H) 2 e cz(t,h) νattt (7) k(e/n) e ν attt ; T 0 o(ε) 21 21 (5) z 2 X 9
m(t, H) (T cr, H cr ) H T T > T cr T > 0 22 z 2 H n ln T 1/2 T 0 e cz H e z 2/H n z 2 2 r2 1 m(t, H) m H r 2 1 ; Tasaki, 2007 σ 0 E σ0 = (J z=2d i=1 σ i +µ 0 H)σ 0 = (zjψ+µ 0 H)σ 0 d: µ 0 H: J σ 0 ψ ψ = tanh(βzjψ+βµ 0 H) β = β mf = 1/zJ m(β, H) 22 T T cr m T cr T cr T 0 Ψ = N i=1 σ i N ; f LR (β, H) = min 1 ψ 1 { f(β, H) µ 0 Hψ} (ψ = Ψ/N) {} m(t, H) F F m 5 X 10
van der Velde, O. A., A. Mika, S. Soula, C. Haldoupis, T. Neubert, and U. S. Inan, Observations of the relationship between sprite morphology and in-cloud lightning processes, J. Geophys. Res., 111, D15203, doi:10.1029/2005jd006879, 2006.,, http://www.gakushuin.ac. jp/ 881791/d/, 2007. Cummer, S. A., and W. A. Lyons, Implications of lightning charge moment changes for sprite initiation, J. Geophys. Res., 110, A04304, doi:10.1029/2004ja010812, 2005. Cummer, S. A., N. Jaugey, J. Li, W. A. Lyons, T. E. Nelson, and E. A. Gerken, Submillisecond imaging of sprite development and structure, Geophys. Res. Lett., 33, L04104, doi:10.1029/2005gl024969, 2006. Hayakawa, M., D. I. Iudin, E. A. Mareev, and V. Y. Trakhtengerts, Cellular automaton modeling of mesospheric optical emissions: Sprites, Phys. Plasmas, 14, 042902, 2007. Hiraki, Y., and H. Fukunishi, Theoretical criterion of charge moment change by lightning for initiation of sprites, J. Geophys. Res., 111, A11305, doi:10.1029/2006ja011729, 2006. Moudry, D., H. Stenbaek-Nielsen, D. D. Sentman, E. Wescott, Imaging of elves, halos and sprite initiation at 1ms time resolution, J. Atmos. Solar-Terr. Phys., 65, 509 518, 2003. Ohkubo, A., H. Fukunishi, Y. Takahashi, and T. Adachi, VLF/ELF sferic evidence for in-cloud discharge activity producing sprites, Geophys. Res. Lett., 32, L04812, doi:10.1029/2004gl021943, 2005. Pasko, V. P., U. S. Inan, and T. F. Bell, Fractal structure of sprites, Geophys. Res. Lett., 27, 497 500, 2000. Pasko, V. P., U. S. Inan, T. F. Bell, and Y. N. Taranenko, Sprites produced by quasielectrostatic heating and ionization in the lower ionosphere, J. Geophys. Res., 102, 4529 4561, 1997. Raizer, Y. P., Gas Discharge Physics, 1st ed., Springer-Verlag, New York, 1991. X 11