Agarwal, D C

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Electron collision frequency in Martian ionosphereBy D. C. AgarwalJ, K. Institute of Applied Physics and Technology Allahabad University, Allahabad {Received 23 May 1969, revised 5 February ]970)The roBults for F2 region (Bradbury Layer) collisinn frequency o f the Martian atmos­phere are presented. It is observed that for this layer, the collision frequency of electrons with neutral constituents are negligible in oompariaon to that with positive ions. The region collision frequency is found to be 7.6 x 10® sec“ .^I n t r o d u c t io nThe collision frequency of electrons with neutral and ionized gases of earth’s at­mosphere is well established. For the Martian atmosphere, it has neither been experimentally nor theoretically deduced. It is the purpose of the present paper to calculate these collison frequency in the Martian ionosphere.T h e o r e t ic a l  c o n s id e r a t io n sThe collision frequency of electrons with neutral gases depends on (a) the distribution of electron velocities, (b) the variation of electron collision cross- section for each gas with electron velocity and (c) the number densities of the neutral gases present Thus, collision frequency for mono-energetic electrons, vm is proportional to the electron-collision cross-section cr, the electron velocity v, and the density of each gas p, i.e.,vm^ervp ... (1)where, o* is a complex function of v.This expression can be rewritten in a simpler form according to GersonIndian J. Ph^s. 44, 336-338 (1970)(1961) :... (2)where, h is the Boltzmann’s constant, T is the absolute temperature of the region under consideration, m is the mass of the electron and N  is the number density of the gas with which the electrons collide.The argument given above is strictly true only if the electron temperature and the gas temperature are the same. Otherwise, the collision frequency at each height should bo increased by the ratio TejTg, where Te is the electron temperature and Tg is the gas temperature,336According to Nicolet (1953), the collision frequency of electrons with posi­tive ions is given hy3/2r ®Electron collision frequency in M artian ionosphere 337[ 34+8.36 log (3)where T is the absolute temperature of the region under consideration, JVg is the electron density and is the positive ion density. The expression (3) is valid only if the electron temperature Te is same as the ion tem7)erature If Te 7^  Tt, tlien one should adopt the following expression for vie (Thraue & Piggott, 1966)== [a+6  In Te{T^|Nt)^N,Te-' l^ -^ ... (4)wliero, a and h are constants.Total collision frequency of the F 2 region is the sum of and vie (Ramana & Rao, 1961) as the collision frequency of electrons with the negative ions is negligble,V =  vtn-\-VieR e su l t s  a n d  d isc u ssio n s(5)The region of the Martian ionosphere is at about 128 km high from its surface (J’jeldbo & Eshleman, 1968). Eor this region, the calculated values of the collison frequency o f electrons with neutral and ionized gases arc tabulated in table 1 In this calculation, it is asumed that Te =  Ti =  Tg and neutral particle concentrations in region ai’e taken from Fjeldbo & Eshleman’s paper (1968). The positive ion distribution has been taken from Agarwal’s paper (1970). From table 1, it is apparent that »^0 , the collision frequency ofTable 1. Collision frequency of electrons with neutrals and IonsNeutralgasCollision frequency of eleotroiiB with neutral gas at 1281^[onizedgasCollision frequency of electrons with - f  VO ions at 128 kmCOa 8.2x 10-®sec-^ CO2+ 3 X 1O“S0O-^CO 8.6 X 10-^aeo-'^ CO+ 2.4 X 10®soo” ^Oa 2.5 X lO-’ sec” ^ 1.2xl0®soo-i0 8.60 S0C“^ 0+ 1.0 X 10®flec"^electrons with oxygen atoms is larger than 0^2- However, in com-piiriaon to the collision frequency of electrons with positive ions vO is negligible and hence v =  Among i'q > O^Oa *- largest because of their largest number density in that region.338Jj'iom table 1,D. C. Agarwal''C0a++’'C0^+'’0 /+ ''0 t  7.6x10* Bee \As no exporimental values of v aro available, the calculated value could not be compared with them. It is proposed that v should be determined also by experiments as it would be useful in framing a better theoretical model.R e f e r e n c e sAganval D. 0. 1970 Ind. J  Pure and A p pl Phys (In course o f puhlication.) Fjelflbo G. c& Ewhltonian, V K 1968 Planet. Space. Sci. 16, 1035.Goraoii N. C. 1961 J Atmos Terr Phys. 23, 1.Nicolet M. 1953 J. Atmos. Terr. Phys. 3, 200Riimana IC. V. V. & Rao R. 1961 J^roc l O Y  Symp. C S IP  New Delhi 140. Thraiie E. V. & Piggott W. R. 1966 J. Atmos. Terr. Phs. 28, 721.

Electron Collision Frequency in Martian Ionosphere

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Electron Collision Frequency in Martian Ionosphere

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