Astronaut Scientific Debriefings, 1962-1963

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"Meteors" (A Symposium on Meteor Physics): Special Supplement (Vol. 2) toJ. Atmosph. T err. Phys. (1955)
Meteor Ionization in the E-region
MAURICE DUBIN
Air Force Cambridge Research Center, U.S.A.
ABSTRACT
The theories of meteoric interaction with the atmosphere have been reviewed to determine the total
contribution by meteors to the ionization content of the E-region.
From Herlofson's theoretical
treatment of this interaction, and Watson's distribution of the size and numbers of meteoric particles
entering the atmosphere per day, the number of electrons produced at various altitudes in the E-region
was computed. These computations indicated that most of the ionization at higher altitudes resulted
from meteors oflarge visual magnitude. Since, as Whipple has shown, the ablation process would probably
not occur in the case of micrometeorites because of heat loss by radiation, the collision processes for
ionization were reviewed; it seems that the ionization process is mainly a function of the relative energy
of the co11·'ion, and therefore ablation prior to ionization would not be required for small particles.
Using the
Jue (of GREENHOW and H AWKINS, 1952) for the efficiency of the ionization process and the
recently re ised value for the amount of meteoric material entering the atmosphere per day, the rate of
production f electrons was found to be 20 electrons/cc sec. From this value and the recombination
coefficients ·n the E-region, the equilibrium electron density in the E-region was found to be between
2 x 104 and 7 x 104 electrons/cc. It is therefore proposed that the night-time value for the electron
density in the E -region results from meteoric bombardment, and that sporadic Eis caused by the same
process on the assumption that the distribution of meteoric particles in space is non-isotropic and
contains centres of high density. P erhaps, also, the interaction of charged micrometeorites with the
earth's magnetic field, may be considered as a mechanism for the production of magnetic storms.
1. INTRODUCTION
METEORS, as commonly known, are extra-terrestrial particles of only a few milli­
grams, which enter the earth's atmosphere at relatively high velocities. In their
interaction with the air, they are vaporized by the heat generated and ~re respon­
sible for the emission of light and. production of ions along the meteor trail. The
major portion of the kinetic energy of the meteoric particles is absorbed in the
altitude region between 80 and 120 km. It is attempted below to consider whether
the integrated effects of this meteoric interaction might contribute to the structure
of the E-region.
2. THEORY
HERLOFSON (1948) has constructed a model for the interaction of meteoric particles
with the atmosphere. It is assumed that in the region of meteoric flash, the mean
free path of the molecule is much greater than the radius of the meteor. Under
such conditions, the front surface of the meteor is bombarded by single air mole­
cules and the major portion of them is trapped in the metal surface. The kinetic
energy relative to the meteor which is given up to the meteor suffices to bring the
temperature to that of ev:aporation. The meteor atoms evaporate off the meteor
(ablation) with velocities appropriate to the temperature and the relative velocity
of the meteor with respect to the air.
From consideration of the physical interaction.of the meteor with the air mass,
using the differential form ofthe conservation ofenergyand momentum, HERLOFSON
determined the equation for the rate of evaporation at any point along th!;) trail.
r
n = ¾nmax(P/Pmax) [l -
¼(P/Pmax)]2
(1)
wher.e nmax = 7 X 1023 r 00 3 = the maximum rate of evaporation.
p = the pressure at any point along the trail.
Pmax = 4 X 10- 2 r 00 = pressure along the trail where nmax occurs.
00 = the initial radius of the meteoric particle.
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