Astronaut Scientific Debriefings, 1962-1963

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Meteor ionization in the E-region
117
now the electron density. For small particles, where the number of electrons
formed per centimetre of path is small, the diffusion term is predominant, and the
train quickly decreases to the equilibrium electron density, which is thus given by
°'n2 = rate of production of electrons.
The effective recombination coefficient for the E-region is e<(O2) '.::::'. 5. 10- s
cm 3 sec-1 , when 0 2 is present, and e<(O) '.::::'. 4 X 10- 9 cm 3 sec- 1 if oxygen has been
dissociated. Thus n is approximately equal to 7 . 104 and 2 . 104 in the upper and
lower E-region, respectively.
3. Co cLusrn s
The above is app ·cable to three effects in the E-layers. First, the diurnal variation
of the E-layer is found to agree fairly well with the (cos x)t law for the variation
of the simple Ch pman region (xis -the zenith angle of the sun). The variation is
found to be alm~st symmetrical with reference to the maximum at noon (MITRA,
1952). However, with the accepted value of the recombination coefficient, the
E-layer ionization at night should fall to a very low value. The residual ionization
density as observed is much greater than it hould be. It is therefore suggested
that this night-time value results from the bombardment of micrometeorites.
Secondly, measurements of effective electron density obtained by rockets
(LIEN et al. , 1953) indicated that a bifurcation, or two maxima, in electron density
were present in the B-region. It is suggested that one maximum results from solar
radiation, the other from micrometeoric bombardment.
And finally, it is proposed that the sporadic E-clouds of ionization result from
micrometeorites. Although some correlation with meteor showers is found, the
major portion of the ionization results from micrometeorites with a fine structure
undetectable by radio probing. The cloud-like structure of the E-layer very
possibly re ults from clouds of micrometeorites. The amount of micrometeorites,
the penetration depth, the ionization efficiency, and the distribution of the micro­
meteorites are all con. istent with the conditions required for such an explanation.
Granted the laboratory evidence for the ionization process is not adequate, but
the general physical reasoning based on ionization density measurements by radio
methods of lower visual magnitude meteorites leads to an order of magnitude that•
seems very promising.
In conclusion, it may be possible also to relate the meteoric bombardment of
the upper atmosphere to the high-latitude magnetic storms and aurorae. For this
process it is necessary that sufficient photoelectric effect from solar ultraviolet
radiation be ,Present to charge the micrometeorites and thereby allow some control
by the earth's magnetic field. This investigation will be described elsewhere.
REFERENCES
ARNOT, F. L., a nd I ILLIGA , J. C. (1936) Proc. Roy. S oc. A 156, 538
BERRY, H. W. (1942) Phys. Rev. 62, 378
BERRY, H. W., VARNEY, R.H., and NEWBERRY, S. (1942) Phys. Rev. 61, 63
GREENHOW, J. S., and HAWKINS, G . S. (1952) Nature, Lond. 170, 355
HEALEA, M. and HoUTERMANS , C. (1940) Phys. Rev. 58, 608
liERLOFSON, N. (1948) Phys. oc. Rep. Prog. Phys. 11, 444
LIEN, J . R. , MARCOU, R. J., ULWICK, J. C., McMORROW, D. R., BLUNDFORD, L., and HAYCO K, 0. C.
(1953) Phys. Rev. 92, 508