Mesospheric oxygen atom densities inferred from night-time OH Meinel band emission rates

Planer. Spncr Ser., Vol. 36. No. 9. pp. X97-905, Printed in Great Britain.

00324633/8X $3.00+0.00 Pergamon Press plc

1988

MESOSPHERIC OXYGEN ATOM DENSITIES INFERRED FROM NIGHT-TIME OH MEINEL BAND EMISSION RATES I. C. McDADE

Institute

and E. J. LLEWELLYN

of Space and Atmospheric Studies, Department of Physics, University Saskatoon, Saskatchewan, Canada S7N OWO

of Saskatchewan,

(Received in final form 15 April 1988) Abstract-Procedures for inferring the upper mesospheric v’ = 7, v’ = 8 and u’ = 9 OH Meinel band volume emission

oxygen atom densities from observations of rates in the nightglow are described. A variety

of recently developed Meinel band excitation models, and associated parameters, are employed and it is demonstrated that although serious inadequacies exist in our understanding of the Meinel band excitation mechanism, these uncertainties have only a minor impact on the oxygen atom densities inferred between 80 and 95 km. The proposed technique for inferring oxygen atom densities is applied to the limited number of high t” OH band emission profiles which exist in the literature and the results are compared with the oxygen atom densities given by the standard atmospheric models. For one of the analyzed profiles an independent measurement of the oxygen atom densities was available and the densities inferred from the OH profile are in excellent agreement with those measured.

1. INTRODUCTION

is the major source of the vibrationally excited OH radicals. Reaction (1) is known to lead to direct production of the vibrational levels v = 7, 8 and 9 (Charters et al., 1971; Murphy, 1971; Ohoyama et al., 1985) and there is little doubt that this reaction is the only chemical source of the emission from these levels. As v = 9 is the highest level that can be populated in reaction (l), no indirect sources of v = 9 exist. However, the vibrational levels below v = 9 may also be excited indirectly from the higher vibrational levels by radiative cascade,

The OH Meinel Bands, which originate from vibration-rotation transitions within the ground electronic state of the hydroxyl radical, dominate the spectrum of the terrestrial nightglow. Numerous rocket measurements of Meinel band volume emission rates (Packer, 1961; Baker and Waddoups, 1967; Harrison, 1970; Evans et al., 1973; Rogers et al., 1973; Good, 1976; Witt et al., 1979; Watanabe et al., 1981 ; Thomas and Young, 1981; Makino ef al., 1983; Lopez-Moreno et al., 1985; Greer et al., 1986; McDade et al., 1987) have revealed that the Meinel band emission emanates from the 80-95 km region of the atmosphere and ground-based observations of the bands are routinely carried out to measure the atmospheric temperature at these altitudes. It has been recognized for many years that the Meinel band volume emission profiles must also contain important information about the upper mesospheric oxygen atom densities (Good, 1976), but inadequacies in our understanding of the Meinel band excitation mechanism, and the lack of reliable rate coefficients for the relevant reactions, have made it difficult to derive reliable oxygen atom densities. While many aspects of the Meinel band excitation mechanism are still actively disputed (Bates, 1982), it is now generally recognized that the reaction of ozone with atomic hydrogen, first suggested by Bates and Nicolet (1950), H+0,*OH(v)+02

OH(v’)=OH(v”)+hv and vibrational

energy transfer

OH(v’)+Q~OH(v”)+Q.

(2) processes, (3)

Understanding the role played by processes (2) and (3) in the production of the vibrational levels below v = 9 has been one of the major problems in the aeronomy of the Meinel bands. The other major difficulty is concerned with collisional processes that totally remove vibrationally excited hydroxyl radicals, OH(v’) + Q -products ““‘)

other than OH(v > 0) (4)

and how these may compete with processes (2) and (3). In some recent work McDade and Llewellyn

(1) 897

I. C.

898

MCDADE

and

(1987) have addressed these issues and, from an examination of the mean OH vibrational distribution in the nightglow, have derived vibrational level dependent kinetic parameters related to processes (2) (3) and (4). In the present work procedures for inferring the mesospheric atomic oxygen densities from specific Meinel band volume emission profiles are described and the atomic oxygen densities from a number of published Meinel band emission profiles are presented. 2. FORMULATION

In the night-time upper mesosphere reaction (1) is the major ozone removal process between 80 and 95 km (Moreels et al., 1977; Allen et al., 1984) so that, under steady-state conditions, the rate of vibrationally excited hydroxyl production from reaction (1) may be related to the total rate of ozone formation by the expression

k, WI[O,l= ~Ol~0,1~~~2~O~1+~Nz~[N~1~ (5) where /&‘2and ky2 are the termolecular rate coefficients for ozone formation with O2 and N, as the third bodies. The various v’ = 9 Meinel band emission rates, which are given by I’(9, v”) = A(9, u”)[OH(9)], may then be expressed

as

E. J. LLEWELLYN

Unfortunately, some controversy surrounds the absolute Meinel band transition probabilities as the radiative lifetime of v = 9 measured by Potter et al. (1971) is substantially longer than the lifetimes calculated by Mies (1974) and Langhoff et al. (1986). This discrepancy has in the past led to serious problems in attempts to model the Meinel band emission (Bates, 1982). To overcome this difficulty McDade and Llewellyn (1987) have recently analyzed the Meinel band emission rates in terms of reduced kinetic parameters where the rate coefficients for the the collisional processes, and the radiative transition probabilities, are expressed relative to the inverse lifetime of the u = 9 level, A(9). This approach should lead to an improved understanding of the Meinel band excitation mechanism since the relevant kinetic quantities may be obtained without assuming an OH radiative lifetime. Equation (6) may be expressed in terms of similar reduced quantities and becomes

4% ~“)f(~)~Ol~O~li~~2~021+kl;]2N1} v(97 “‘) = a(9) + I@(9)[02] + I@(9)[NZ] +e(9)[0] (7) where the K?(v) parameters correspond to kg(v)/A(9), the a(u’, v”) correspond to A(u’, v//)/A(9) and the a(v) correspond to A(v)/A(9). Equation (7) is a linear equation in [0] and a simple re-arrangement yields PI =

I,(9 v,,) = A(9, ~“)f(~)~Ol~0,1~~~2~O~1 +kE;‘W,I}

(6)

A(9)+ &%%‘)[Ql

V(9,u”)[1+{~~(9)+K~~(9)~R}[0*11

49, ~“)f(9)[021{k~~[021 + kP;W,I} - V(9, u”)K,O(9)

Q

where f(9) is the fractional yield of OH(v = 9) in reaction (I), A(9) is the inverse radiative lifetime of the v = 9 level and kf1(9) represents the total rate coefficient for collisional removal of OH(9) by species “Q” in processes (3) and (4) combined.

(8) where “R” represents the [NJ : [0,] ratio. For Meinel bands with v’ < 9 the equations relating the atomic oxygen densities to the band emission rates are somewhat more complicated as processes (2) and (3) may also contribute to the total production rate of the emitting u’ level. For any (v’, 0”) Meinel band the volume emission rate is given by

r W,

9

1

0”) ~~Ol~0,11~~2~O~l+~:2~~~l~f(~‘)+ .=$+, [OH(v)l{4~

V(v’,0”) =

A(d)+ k:2(v’)[OJ + k:$v’)[N,]

If atomic oxygen is considered not to participate with v’ = 8 may be expressed as

in process

48, ~“)~~1~~~1~~~2~~~1+~~2~~~1~ f(8)+ V(8,v”) =

Equation (10) is a quadratic are known.

[

f(9){@,

(9)

+ k?(v’)[Ol

(3) then the emission

rates of the various bands

8)+{Z@(9,8)+R*@(9,8)}[021I

49)+{~2(9)+R~@(9)}[021+~(9)[01

a(8)+{~2(8)+~*@(8)}P21+k~(8)[01 equation

u’)+ ;kf(~> v’)IQlI]

in [0] and may, therefore,

I,

(10)

be readily solved if all of the other quantities

O-atom densities from Meinel band emission rates Similarly,

for bands

with v’ = 7 the appropriate

form of equation

Equation (1 l), although somewhat cumbersome, is a cubic equation in [0] which is also readily solvable. As all of the rate coefficients and kinetic parameters appearing in equations (8), (10) and (11) have either been measured in the laboratory (see Table 1) or correspond to quantities derived from models described by McDade and Llewellyn (1987), these equations may be solved to derive the atomic oxygen densities from the emission profiles of any OH Meinel band with v’ = 7, 8 or 9. McDade and Llewellyn (1987) have derived values for the kinetic parameters appearing in equations (8), (10) and (11) from the mean OH vibrational distribution observed in the nightglow using two basic Meinel band excitation models. These two basic models differed from each other in the extent to which processes (3) and (4) were assumed to control the observed distribution and represent possible limiting cases that should bracket the actual mechanism. In one of the models of McDade and Llewellyn, referred to as the “sudden death” model, process (4) was assumed to dominate the collisional removal of all

TABLE 1. REACTIONS AND

Reaction

(8)is

vibrational levels in the atmosphere. In the alternate model, stepwise vibrational “collisional cascade” deactivation, process (3), was assumed to dominate and to proceed via single quantum steps. Within both models the collisional removal of vibrationally excited OH by atomic oxygen was presumed to occur entirely via process (4). However, little is known about the 0+ OH(v) reaction so that McDade and Llewellyn assessed its possible impact with further limiting case assumptions. In the “no O-atom quenching” case of the “collisional cascade” model the oxygen atom removal process was assumed to be negligible and the vibrational parameters, {Z@(v) v - 1) + R .e$v, deactivation v- l)}, were derived assuming that e(v) was zero for all vibrational levels. In the other limiting collisional cascade case, the collisional cascade “with O-atom quenching” model, an upper limit for ~(v)[O]/[O,] of -6x lo-l5 cm3 molecule-’ at the mean peak of the OH layer was first deduced and an alternate set of {F$(v, v- l)+ R *Z@(v, v- l)} parameters then derived. This procedure does not of

ADOPTED COEFFICIENTS

Coefficient

Reference

f(9) = 0.32 f(8) = 0.29 f(7) = 0.19 f(6) = 0.06 f(5) = 0.06 f(4) = 0.06

H+O,=OH(v)+0,

k? = 5.70 x 10-94(T/300)~2.62 !@ = 5.96 x iO-34(T/300)~2-37

OH(v’)=OH(v”)+hv

a(u’, U”) = A(U’, v”)/A(9)

Ohoyama Ohoyama Ohoyama Ohoyama Ohoyama Ohoyama

et et et et et et

al. al. al. al. al. al.

(1985)* (1985): (1985): (1985)* (1985)* (1985)*

Lin and Leu (1982) Lin and Leu (1982) Murphy

(1971)

OH(v’) + Q kp’v”v”)bOH(v”) + Q

Q=N,,O,

See text and Table 2

OH(v) + Q

Q=Nz,OS,O

See text and Table 2

@J) ball products

*Adjusted using the relative transition cm, set units.

probabilities

of Murphy

(1971). All coefficients

are in molecule,

900

I. C. MCDA~E and E. J. LLEWELLYN

course provide an upper limit for e(u) itself, but as most experimental observations and model atmospheres indicate that the [OJ : IO] ratio is typicahy 100 : 1 near the peak of the layer, and rarely in excess of 300: 1, an upper limit for e(v) may be estimated. Under the sudden death model McDade and Llewellyn did not attempt to distinguish between the O-atom and the 02, or NZ, losses, but if oxygen atom removal is insignificant, i.e. e(v) = 0, then the sudden death parameters derived by McDade and Llewellyn must represent the {I@(u)+ R *f@(u)] parameters for a “sudden death with no O-atom quenching” case. Alternatively, if O-atom removal is in fact significant but not strongly vibration level dependent, then the analysis of McDade and Llewellyn suggests an upper limit for K&)[O]/[O,] at the peak of the OH layer of N 1.5 x lW1’ cm3 molecule-’ and a set of “sudden death with maximum O-atom quenching” (Z@(u)+ R* @(t))j parameters may also be deduced. McDade and Llewellyn, therefore, have essentially provided four sets of kinetic parameters which may be employed together with equations (8), (10) and (11) to derive oxygen atom densities from Meinel band

emission profiles for four different limiting case assumptions about the excitation mechanism. In the present work these are referred to as (a) the “‘sudden death with no O-atom quenching” model, (b) the “sudden death with maximum O-atom quenching” model, (c) the “collisional cascade with no O-atom quenching” model and (d) the “collisional cascade with maximum O-atom quenching” model. The kinetic parameters obtained from the work of McDade and Llewellyn (1987) for each of these models are listed in Table 2. 3. ANALYSIS

Although many OH Meinel band emission profiles have been reported, the foregoing procedures for deriving the atomic oxygen densities may only be applied to single band measurements involving D’ levels above z’= 6. Only a limited number of such

TABLE2. ADOPTEDMWEL PLATERS Sudden death with no O-atom quenching all K$+‘, v”) = 0 all G(u) = 5 ~~~~~~~

~~~~)~

4:5,2.1x lo-l4 5.1+1.Sxio-‘4 1.1&0.4X lo-l4 0.1 kO.1 x lo-l4

0.15+0.1 x 10-14 0.15+0.05x IO-l4 0.25+0.05x lo-l4 0.1o_rto.o5x lo-l4 Collisional cascade with no O-atom quenching all I@(U) = K&v, u - 1) illi G(zJ) = 0

Sudden death with maximum O-atom quenching all KY(u’,v”) = 0 all K?(a) = lSk5x lo-“, see text {GW + R * @(o)j 5.3&2.6x IO-“’ 4.3*2.1x 1o-‘4 4.9f 1.x x lo-l4 1.0&0.4X IQ-r4 0 0 0 0 0 Collisional cascade with maximum O-atom quenching all K&z+ = K$(u, v- 1) all K&) = (6 + 2) x IO.-13,see text

(Kp(u, 0 - I)+ R * Kyqu, u- I)]

5.3 t2.6 x 8.9k4.3 x 13.4* 5.9 x 9.814.0 x 5.9k2.6 x 4.1 i_ 1.8 x 3.3+1.4x 2.5+1.0x 1.4&0.4x

lo-l4 lo-r4 to- I4 IO-r4 HP4 Io-‘4 lo-‘J lo-l4 lo-l4

S.Sk4.3 x 12.9+5.8x 9oi:3,sx 4.Sk2.3 x 2.9* I.5 x l.Stl.Ox 0.9*0.4x 0

lo-r4 lo-” lo-l4 lo-r4 1o-‘4 lo-l4 lo-‘4

All coefficients are in units of cm3 molec.-‘. The uncertainties in the parameters correspond to those arising from possible errors in the N(v) adopted by McDade and Llewellyn (1987) and the estimated f 50% uncertainty in their model input parameter @(9)/A(9) [see Table 2 and Appendix B of McDade and Llewellyn (i987)].

901

O-atom densities from Meinel band emission rates measurements have been reported in the literature and in the present analysis the atomic oxygen densities derived from these measurements are presented for each of the four limiting case models described above. Greer et al. (1986) have recently reported a rocket measurement of the OH@, 3) band altitude profile which was made at mid-latitude during a period of medium solar activity. These observations are particularly valuable as they were made in coordination with an in situ determination of the oxygen atom densities which used the 01 resonance lamp technique and, therefore, they provide a means for truthing the presently proposed indirect technique for measuring the densities. The atomic oxygen density profiles derived from the OH@, 3) band volume emission profile of Greer et al. (1986) by solving equation (10) for its real positive roots using the sudden death kinetic parameters of Table 2 are shown in Fig. 1(a). For this calculation the adopted [O,], [N2] and temperature profiles were those of the MSIS-83 model atmosphere (Hedin, 1983) extrapolated below 85 km. For the

“maximum O-atom quenching” case of the sudden death model, the densities are shown for two different values of G(U). One of these values, 1.5 x IO-l3 cm3 moleculec’, is considered to be the best estimate of the upper limit for e(u), and is based on the upper limit for k~(v)[O]/[O,] of 1.5 x lo-” cm3 molecule-’ at the mean peak of the OH layer and a typical [O,] : [0] ratio of 100 : 1 as discussed above. The densities obtained with the larger value for e(v), 3 x IO-” cm3 molecule-‘, are shown to illustrate the sensitivity of the derived densities to any error in the best estimate value. The oxygen atom densities derived from the OH(8,3) band volume emission profile of Greer et al. (1986) by solving equation (10) with the collisional cascade kinetic parameters of Table 2 are shown in Fig. l(b). Here again, the densities derived for the “maximum O-atom quenching” case are shown for two different values of e(v). One oxygen atom profile represents the densities obtained with the best estimate of the collisional cascade e(v) upper limit, 6 x lo-l3

\ SUDDEN DEA TH

\

CULL ISIONAL

OXYGEN A TOM DENSITY FIG. 1. (a) THE OXYGEN

CASCADE

b.

\

~c,,? >

ATOM DENSITIESDERIVED FROM THE OH@, 3) BAND EMISSION PROFILE OF GREER et al. (1986) ASSUMING THE“SUDDEN DEATH" MEINEL BAND EXCITATION MODEL. The densities obtained for the “no O-atom quenching” case are shown bv the solid squares. The densities obtained with the “maximum O-atom quenching” case are shown by the open squares for e(v) = 1.5 x lo-l3 cm3 moleculec’, and by open triangles for K?(v) = 3 x lo-” cm3 moleculec’. The error bars represent the uncertainties arising from those in the meas&d’volume emission rates. The solid curve shows the densities measured by the 01 resonance technique (Greer et al., 1986). (b) SAMEAS PANEL (a) BUT ASSUMING THE “COLLISION CASCADE” MEINEL BAND EXCITATIONMODEL. For the “maximum O-atom quenching ” case the open squares show the densities obtained with e(v) = 6 x lo-l3 cm3 molecule-’ and the open triangles represent those obtained with e(v) = 1.2 x lo-l2 cm3 molecule-‘.

902

1. C. MCDADE and E. J. LLEWELLYN

cm3 moleculee’, and the other profile shows the densities obtained with this quantity increased by a factor of two. It is evident from Fig. 1 that the oxygen atom densities derived under the collisional cascade and sudden death models with “no O-atom quenching” are remarkably similar to each other and only differ significantly from those obtained under the “maximum O-atom quenching” cases at altitudes above 95 km. It is also evident from Fig. I that throughout the 80-95 km region, the densities derived from the OH Meinel band emission are in excellent agreement with the oxygen atom densities measured 27 min later on another rocket using the more direct 01 resonance technique (Greer et al., 1986). Above 95 km the OH inferred densities are generally larger than those measured with the resonance technique but in this altitude region some of the ass~ptions imphcit in the OH formulation start to break down. For example, above 95 km the reaction of atomic oxygen with ozone begins to contribute significantly to the total ozone loss rate (Moreels et al., 1977 ; Allen et af., 1984) and there is some evidence to suggest that another source of ozone may exist in addition to the three-body association process assumed here (Allen, 1986). Neglecting this ozone removal process should lead to an underestimate of the oxygen atom densities, but the presence of an unrecognized source of ozone could lead to the densities being seriously overestimated. Consequently, the densities derived above 95 km should be considered unreliable. As the oxygen atom densities shown in Fig. 1 have been obtained for four quite extreme limiting case Meinel band excitation models, the range of values obtained, at a given altitude, should reflect the uncertainties arising from the inadequacies in our understanding of the Meinel band excitation mechanism. It is found that, for any one altitude, the minimum and maximum derived oxygen atom densities are obtained with the “sudden death with no O-atom quenching” and “collisional cascade with maximum O-atom quenching” parameters, respectively. These minimum and maximum derived densities are replotted in Fig. 2 for comparison with the densities given by the MSIS83 model (Hedin, 1983) and the CIRA 1972 Mean Reference Atmosphere (CIRA, 1972). The other Meinel band emission profites which may be used to derive atomic oxygen densities have been reported by Baker and Waddoups (1967, 1968), Witt et al. (1979) and Watanabe et ai. (1981). Baker and Waddoups (1967, 1968) reported an early rocket measurement of the OH (83) band made at low latitude and close to solar minimum. The published (83) band profile was not corrected for the airglow con-

Grew

eC

al.

(1986)

\

60 IO0

10’0 OXYGEN

IO” ATOM

DENSXTY

1d2 hani-‘~

RIG.2.TXiEOPTIMUM ATOM

(~LID~U~S)AND~A~~MOXYG~N DENSITIES(OPEN SQUARES)DERIVED FROM THEOH@, BAND PROFILEOFGREER etal. (1986).

3)

densities encompassed by K@) = 0 and the best estimates for the G(V) upper limit are shown. The

Only the range of

solid curve shows the oxygen atom densities given by the CIRA 1972 Mean Reference Atmosphere and the broken curve shows those of the MSIS-83 model for the conditions of the rocket flight. The plain error bars represent the uncertainties arising from the uncertainties in the measured volume emission rates. The ticked error bars represent the uncertainties arising from those of the parameter shown in Table 2.

tinuum emission that is inevitably present in the OH photometer channel, but the contribution from the continuum can be estimated using the data from a pure continuum channel on the same rocket as explained by Witt et al. (1979). The minimum and maximum oxygen atom densities derived from this corrected OH@, 3) band profile of Baker and Waddoups, using the procedures described above and the [NJ, [OJ and temperature profiles given by the MSIS-83 model for the conditions of the flight, are shown in Fig. 3. Another rocket measurement of the OH@, 3) band, which was made at high latitude and close to solar minimum, has been reported by Witt et al. (1979). This published profile had been corrected for the airglow continuum emission and the range of oxygen atom densities obtained from the measured volume emission rates are shown in Fig. 4. The OH profiles reported by Watanabe et al. (1981) included two separate single band measurements of

O-atom

densities

from Meinel band emission

110 OH (8. 3> BakeA Waddoups

8 is ;1

Cl 968)

\ 4. DISCUSSION

100

<

90

80 IO0

lOJ0

10”

10’2

OXYGEN ATOM DENSITY

(cm?,

FIG. 3. SAME AS FIG. 2 FOR THE OH(8,3) BAND PROFILE OF BAKER AND WADDOUPS (1967, 1968).

the (7,2) band from a low-latitude station. One OH(7,2) band profile was measured in August 1971 close to solar maximum and the other was measured closer to solar minimum in January 1975. As simultaneous continuum measurements were not made.

120

\ \ \ \ \

110

\ OH c-8, 3)

witt

‘i d 8 is ;:

et

01.

0979)

\

100

<

90

loo

lO’o

10”

OXYGEN ATOM DENSITY FIG.

4.

903

the two published profiles have not been corrected for any airglow continuum contributions. The oxygen atom densities obtained by solving equation (11) for its real positive roots with these uncorrected volume emission profiles, and MSIS-83 density and temperature profiles for the condition each flight, are shown in Fig. 5.

120

2 B

rates

SAME

AS

10’2 CC&-~>

FIG. 2 FOR THE OH@, 3) BAND PROFlLE OF WITT et al.(1979).

It has been demonstrated in the previous section that the upper mesospheric atomic oxygen densities which may be derived from specific Meinel band volume emission profiles in the nightglow are not particularly sensitive to current inadequacies in our understanding of the Meinel band excitation mechanism. However, the derived densities are undoubtedly prone to systematic errors which may arise from the adoption of possibly inappropriate rate coefficients or atmospheric temperatures and densities. With the proposed technique, the absolute atomic oxygen densities are largely determined by the effective first order rate coefficient for ozone formation, [O,]{k~l[O,]+k~l[N,]}, at each altitude . The important rate coefficients, k(5)2and ky2, are very well established laboratory measured quantities but both are strongly temperature dependent. Therefore, the derived oxygen atom densities may be quite sensitive to errors in the adopted model atmosphere temperatures, not only because of the temperature dependence of kyl and ky2 but aisobecause of the associated errors in the modelled atmospheric 0, and Nz densities. All of the oxygen atom profiles presented above have been derived assuming the appropriateness of the [O,], [N2] and temperature profiles given by the extrapolated MSIS-83 atmospheric model for the conditions of each rocket flight and it is important to consider how the derived oxygen atom densities may be influenced by the choice of atmospheric model. The oxygen atom densities derived from the OH(8,3) band profile of Greer et al. (1986) under the “collisional cascade with no O-atom quenching” assumption using the [O,], [N2] and temperature profiles of the CIRA 1972 Mean Reference Atmosphere are shown in Fig. 6, where they are compared with those derived in the previous section using the MSIS-83 model. Clearly the choice of background atmosphere does have an impact on the derived densities. However, as the absolute magnitudes and altitude distribution of the oxygen atom densities obtained with the MSIS-83 atmosphere are in much better agreement with the 01 resonance lamp densities it would appear, perhaps not too surprisingly, that the MSIS-83 model provides the more reliable density and temperature profiles.

904

I. C. MCDADE and E. J. LLEWELLYN 120

\ \ \

I10

OH (7, 2) llbtanabe

2 d 8

\ Aug I971 eC al.

C1991)

OH (7.2> Watanabe

\

Jan 1975 et 01. <1991.,

\

,

100

i?

2 < 90

OXYGEN ATOM DENSITY


FIG. 5. (a) SAMEAS FIG. 2 FOR THEAUGUST 1971 OH(7,2) BANDPROFILEOF WATANABEet al. (1981) (b) SAMEAS FIG. 2 FOR THEJANUARY1975 OH(7,2) BANDPROFILEOF WATANABEet al. (1981).

As the OH Meinel technique

it allows the atomic

is most useful because based

employed.

The

while

on the oxygen later

OH

dynamically

technique

important

the concentration sion rates

gradient

IO*'
FIG. 6. THE ATOMIC OXYGEN DENSITIESDERIVED FROM THE OH@, 3) BANDEMISSIONPROFILEOF G~~~~etuL(1986) UNDER THE “COLLISIONAL CASCADE WITH NO O-ATOM QUENCHING" MODELUSINGTHEBACKGROUNDATMOSPHEREFROMTHEMSIS83 MODEL (SOLID SQUARES) AND THE CIRA 1972 MEAN REFERENCEATMOSPHERE(OPEN SQUARES). The solid curve shows the densities measured by the 01 resonance technique (Greer et al., 1986) and the dashed and dot-dashed curves show the densities from MSIS-83 and CIRA 1972, respectively. The error bars represent the uncertainties arising from those in the measured volume emission rates.

to the ozone

altitudes

centrations

as low as 1 x lo9 cm-3.

number

profiles

of the proposed

it is perhaps certainly

worth

noting

suggest considerable

mesospheric

oxygen

centrations

work

atom

10” cm-‘,

conditions

to discuss

that have been

derived merely

oxygen

technique. that

Nevertheless,

the derived

variability densities

profiles

in the upper

with peak ranging

activity

1971

Watanabe

et al. (198 1).

August

as

solar

(Fig. 4), to

moderate

the

con-

from

under the high-latitude

of Witt ef al. (1979) of

atom

to demonstrate

l-2 x lOI cm3 under the low-latitude conditions

;

for con-

on the basis of the very

in the SO-95 km region

little as 1-2x

inferred

of OH band profiles

have been presented

the potential

minimum

in the present

the various

formation

[0] is very small

to be reliably

oxygen densities

analyzed-rather

in the

Meinel band emis-

where

densities

global atomic

data

the peak where

is large. Since the OH emis-

this allows

It is not intended

IO"

below

be

provide

oxygen layer,

provide

there is significant

sion even at those

1O'O

region

cannot

essentially

can

are proportional

rate, [O][O,][M],

limited

airglow

techniques

near the peak of the atomic

the

the present

to be inferred in regions where similar

techniques information

OXYGEN ATOM DENSITY

from lower alti-

features,

oxygen densities

100

bands originate

tudes than the oxygen nightglow

solar

flight

of

O-atom

densities

from Meinel band emission

5. CONCLUSION Procedures oxygen

sion rates been

for inferring

densities

from

in the nightglow

demonstrated

strongly

the

the basic

band

excitation

densities

obtained

oxvgen

number

of published densities

alies that

spheric

reliable

temperature the

those

almost

technique,

profiles

any

oxygen

between one

technique the meso-

[N2] densities. the

oxygen

of the OH

Drofiles

simultaneously, suggests

model

atmosphere

may

be usefully

where

temperature

and

neutral

anom-

a flaw in the

about and

The limited suggest

obvious

suggested

[O,]

from

made

the

of the proposed the

are not

mesospheric

agreement

inferred

measured

resonance

from

information

and

good

densities

and 01

have

A limitation

However, atom

otherwise

it requires

densities mechanism.

but do not exhibit

might

formulation. is that

in the

emisIt has

assumptions

high v’ OH band

variability

atomic

band

been described.

the derived

atomic

atom

have

Meinel

that

Meinel

considerable

mesospheric

v’ OH

upon

dependent

about

upper

high

that

using the

employed

density

have

the

MSIS-83 in cases not been

measured. Acknowledgements-This work has been supported by the Natural Sciences and Engineering Research Council of Canada. REFERENCES

Allen, M. (1986) A new source of ozone in the terrestrial upper atmosphere? J. geophys. Res. 91, 2844. Allen, M., Lunine, J. L. and Yung, Y. L. (1984) The vertical distribution of ozone in the mesosphere and lower thermosphere. J. geophys. Res. 89,484l. Baker, D. J. and Waddoups, R. 0. (1967) Rocket measurement of midlatitude night airglow emissions. J. geophys. Res. 72,4881. Baker, D. J. and Waddoups, R. 0. (1968) Correction to paper by D. Baker and R. Waddoups, “Rocket measurement of midlatitude night airglow emissions”. J. geophys. Res. 73, 2546. Bates, D. R. (1982) Airglow and aurora, in Applied Atomic Collision Physics, (Edited by Massey, H. S. W., Baderson, B. and McDaniel, E. W.), Vol. 1, pp. 149-224. Academic Press, New York. Bates, D. R. and Nicolet, M. (1950) The photochemistry of atmospheric water vapour. J. geophys. Res. 55, 301. Charters, P. E., MacDonald, R. G. and Polanyi, J. C. (1971) Formation of vibrationally excited OH by the reaction H+O,. Appl. Optics 10, 1747. CIRA (1972) COSPAR International Reference Atmosphere. Akademie, Berlin. Evans, W. F. J., Llewellyn, E. J. and Valiance Jones, A. (1973) Altitude distribution of hydroxyl bands of the Au = 2 sequence in the nightglow. Can. J. Phys. 51, 1288. Good, R. E. (1976) Determination of atomic oxygen density from rocket borne measurement of hydroxyl airglow. Planet. Space Sci. 24, 389. Greer, R. G. H., Murtagh, D. P., McDade, I. C., Dickinson,

rates

905

P. H. G., Thomas. L., Jenkins. D. B.. Steernan. J.. Llewellyn, E. J., Witt, d., Mackinnon, D. J:and-Williams, E. R. (1986) ETON 1: a data base pertinent to the study of energy transfer in the oxygen nightglow. Planet. Space Sci. 34, 771. Harrison, A. W. (1970) Altitude profile of airglow hydroxyl emission. Can. J. Phys. 48, 2231. Hedin, A. E. (1983) A revised thermospheric model based on mass SDectrometer and incoherent scatter data : MSIS83. J. geobhys. Rex 88, 10170 Langhoff, S. R., Werner, H.-J. and Rosmus, P. (1986) Theoretical transition probabilities for the OH Meinel system. .I. molec. Spectrosc. 118, 507. Lin, C. L. and Leu, M. T. (1982) Temperature and thirdbody dependence of the rate constant for the reaction O+O,+M --* O,+M. Int. J. Chem. Kinetics 14,417. Lopez-Moreno, J. J., Rodrigo, R. and Vidal, S. (1985) Radiative contamination in rocket-borne infrared photometric measurements. J. geophys. Res. 90,6617. Makino, T., Yamamoto, H. and Sekiguchi. H. (1983) Altitude profiles of OH and 0, near in&ared ai&ows’in the evening twilight. J. Geomqn. Geoelect. 35, 57. McDade, I. C. and Llewellyn, E. J. (1987) Kinetic parameters related to sources and sinks of vibrationally excited OH in the nightglow. J. aeouhvs. Rex 92. 7643. McDade, 1: CT, Murtagh,‘D: P., Lleweilyn, E. J. and Greer, R. G. H. (1987) ETON 5 : simultaneous rocket measurements of the OH Meinel Au = 2 sequence and (8,3) band emission profiles in the nightglow. Plunet. Space Sci. 35, 1137. Mies, F. H. (1974) Calculated vibrational transition mobabilities of OH(X’H). J. molec. Spectrosc. 53, 150. _ Moreels, G., Metie. G.. Valiance Jones. A. and Gattincer. R. L. (1977) Ai oxyg&hydrogen atmospheric model and its application to the OH emission problem. J. atmos. terr. Phys. 39, 551. Murphy, R. E. (1971) Infrared emission of OH in the fundamental and first overtone bands. J. them. Phys. 54, 4852. Ohoyama, H., Kasai, T., Yoshimura, Y., Kimura, H. and Kuwata, K. (1985) Initial distribution of vibration of the OH radicals’ produced in the H + 0, + OH(X*H) + 0, reaction. Chem. Phys. Lett. 118, 263. Packer, D. M. (1961) Altitudes of the night airglow radiations. Ann. Geophys. 17, 67. Potter, A. E., Jr., Coltharp, R. N. and Worley, S. D. (1971) Mean radiative lifetime of vibrationally excited (u = 9) hydroxyl. Rate of the reaction of vibrationally excited hydroxyl (v = 9) with ozone. J. them. Phys. 54,992. Rogers, J. W., Murphy, R. E., Stair, A. T., Jr., Ulwick, J. C., Baker, K. D. and Jensen, L. L. (1973) Rocket-borne radiometer measurements of OH in the aurora1 zone. J. geophys. Res. 78, 7023. Thomas, R. J. and Young, R. A. (1981) Measurement of atomic oxygen and related airglows in the lower thermosphere. J. geophys. Res. 86, 7389. Watanabe, T., Nakamura, M. and Opawa. T. (1981) Rocket measurements of the 0, atmospheric and OH Meinel bands in the airglow. J. geophys. Res. 86, 5768. Witt, G., Stegman, J., Solheim, B. H. and Llewellyn, E. J. (1979) A measurement of the 0, (b’x-X3x) atmospheric band and the 01(‘S) green line in the nightglow. Planet. Space Sci. 27, 341.