A new method of determination of meteor flux density distribution over the celestial sphere is discussed. The flux density was derived from observations by radar together with measurements of angles of arrival of radio waves reflected from meteor trails. The role of small meteor showers over the sporadic background is shown

Andreev, V. V.

Belkovich, O. I.

Filimonova, T. K.

Sidorov, V. V.

English

NASA Technical Reports Server

DETERMINATION OF
Asteroids, Comets, Meteors 1991, pp. 17-22
Lunar and Planetary Institute, Houston, 1992
5q
N9;3- 19
METEOR FLUX DISTRIBUTION OVER THE CELESTIAL
SPHERE
V.V. Andreev, O.I.Belkovich
Engelhardt Astronomical Observatory, SU-42252b, Kazan, USSR
T. K.Fi 1imonova, V.V. Sidorov
Kazan State University, Lenin st. 18, SU-420008, Kazan, USSR
ABSTRACT
A new method of determination of meteor flux density
distribution over the celestial sphere is discussed. The flux
density was derived from observations by radar together with
measurements of angles of arrival of radio waves reflected from
meteor trails The role of small meteor showers over the sporadic
background is shown.
INTRODUCTION
Morton and Jones (1981) proposed a method of determination of
radiant distribution from observations by a single radar with a
measurement of arrival angles of signals reflecting from meteor
trails. The method was realized for shower meteors only. A new
method was worked out in Kazan to derive meteor flux density
distribution over the celestial sphere. Observations were carried
out by the radar with the aerial turning every 15 minutes
successively in four directions: North, East, South, West. So all
meteor radiants above the horizon were observed for an hour. The
radar has operated according to the GLOBMET program therefore
observations of velocities of meteor trail drifts due to winds
were carried out simultaneously.
DESCRIPTION OF THE METHOD
The celestial sphere was divided into 578 areas &_ lO°x 10 °
each in spherical frame of reference c, _, where c is the
elongation from the apex and s = 90 = , _ = 0 is the direction
relative to the Sun. If we know the direction to the reflecting
point at a meteor trail then a position of the meteor radiant must
be at the radiant line above the horizon. A radiant line is an arc
of a great circle formed by intersection of a plane normal to the
direction to the reflecting point and the celestial sphere. In
this case the radiant line intersects some number of areas _. The
probability P. that the radiant is inside the area _. is
t t
PRECEDING P,_,OE BLANK NOT F!LMED
https://ntrs.nasa.gov/search.jsp?R=19930009928 2020-03-17T07:17:21+00:00Z
18 Asteroids, Comets, Meteors 1991
Q . A¢_. AS. A1.
p. --_ t t t I,
" _ Q A_. AS. A1.
i. i. L 1.
Q. is the flux of sporadic meteor bodies inside the area _, AS
is the effective collecting area in the echo plane for the
direction to the reflecting point, AI. is the radiant line length
t
in the limits of the area. One can take Q.= 1 as the first
L
approximation and for every hour of observations and distribute
all registered meteors to the areas by parts equal to P.. So for
every hour one can count hourly rate for every area Nki. Meteor
activity of every area can be represented as a point (shower)
radiant with a flux
The flux density Q' for shower meteors can be calculated
ki
from known hour rate Nk_ and position of the radiant relative to
the radar aerial. Qki can be found from the previous formula. Then
the mean values
-i
Q. = n. _.t Qki.
(k>
is calculated for every area A_. and for the entire interval of
observation, n. is the number of hours of observation. These
values of Q. are used for a second approximation, etc. The
t
iteration process is repeated until the solution becomes stable.
RESULTS
The method permits us to obtain meteor flux density
distribution over the celestial hemisphere for a diurnal interval
of observation. An example of the distribution is given in Fig. 1.
Several picks are evident on the plot and they are apparently
small meteor showers acting for a period from several hours to
several days. In the last case one can trace them at successive
diurnal distributions.
Radar observations for 1988 year have been used to get an
averaged geocentric flux density distribution of meteor bodies
with masses greater then some value. The ionisation coefficient
was taken by V.Tokhtasjev (Andreev et aid 1976)
8.5
= _ (V/V - 0.2)
0 o
where _ and #Jo are the coeffitients for meteoroid velocities V and
y- ?
!
|
Asteroids, Comets, Meteors 1991 19
Vo respectively, Vo = 40 km s -i. The model of the velocity
distribution was taken from Andreev and Belkovich (1987). The
annual distribution of the meteor flux density is shown in Fig.2.
REFERENSES
Andreev V.V. and Belkovich O.I. (1987) Models of sporadic
body distriburtions. Handbook for MAP, 25, 298-304.
met eor
Andreev V.V., Belkovich O.I., and Tokhtasjev V.S. (197b)
heliocentric distribution of the meteor bodies at the vicinity
the Earth's orbit. Lecture Notes in Physics, ( H. Elsasser, H.
Fechtig, eds.), Springer-Verlag, 48, 383-384.
The
of
Morton J.D. and Oones J. (1981) A method for imaging radio meteor
radiant distributions. Mon. Not. Roy. Astron. Sot., 198_ 739-746.
20 Asteroids, Comets, Meteors 1991
Captions for Figures
Fig. I, The distribution of meteor
celestial sphere, October 9_ 1988.
flux density over the
Fig. 2. The annual distribution of flux density of meteoroids
with masses greater than 10-3g over the celestial sphere,
1988.
Asteroids, Comets, Meteors 1991 21
FIGURE 1.
22 Asteroids, Comets, Meteors 1991
_0
FIGURE 2.


Determination of meteor flux distribution over the celestial sphere

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