MetFns (version 1.0)

pop.index: Calculation of population index

Description

Calculates population index of a meteor shower for a given magnitude data, specified period of days and magnitude values.

Usage

pop.index(data,year, month, day.beg, day.end=day.beg, shw, mag=-6:7)

Arguments

data

data frame consisting of visual meteor magnitude data.

year

numeric vector of length 4 specifying year.

month

numeric vector specifying month of the year.

day.beg

numeric vector specifying beginning day.

day.end

numeric vector specifying ending day.

shw

character string consisting of three capital letters which represent meteor shower code.

mag

numeric vector specifying range of magnitudes.

Value

• Data frame containing following vectors [object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Details

Cummulative summarized magnitude distribution Phi(m) is formed by summing cummulative frequencies of all observers for each magnitude class m. Using the relationship for population index r=Phi(m+1)/Phi(m) and substitutiong 0,1,...m magnitudes, equation Phi(m)=Phi(0)r^m (or ln(Phi(m))=ln(Phi(0))+r log(m) in logarithmic form) can be written. Then, population index r is calculated by the method of least squares, for chosen range of magnitude values. Standard error of population index is approximated with sigma_r= r sqrt(sum e_i^2/((n-2)sum_i m_i^2)), where i=1,2,..n, n is number of magnitude values, e_i regression residuals, i=1,2,..n.

References

Koschack R. and Rendtel J. (1990b). Determination of spatial number density and mass index from visual meteor observations (2). WGN, Journal of the IMO, 18(4), 119 - 140. Rendtel J. and Arlt R., editors (2008). IMO Handbook For Meteor Observers. IMO, Potsdam.

See Also

mag.distr,zhr

Examples

##select visual meteor data for observation of Perseids, time period 1-20th August 2007 
##and calculate population index using magnitudes m<=4
data(magn07)
magnPer<-filter(magn07,shw="PER", year=2007, month=8, day.beg=1, day.end=20)
pop.index(magnPer,year=2007, month=8, day.beg=1, day.end=20, shw="PER",mag=-6:4)