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i I

FINAL TECHNICAL REPORT

/ NASA GRANT NAG 5-349

"Analysis of Atomic lhermospheric Nitrogen Density"

(NASA-Ch-176354) ANALYSIS OF ATCMIC N66-13851

THERMOSPHERIC NITICGLN DENSITY Final

Technical Report, 1 Jul. 1583 - 15 Sep. 1985

(Augsburg Lcll. , FinneaFolis, N inL. ) 14 p Uacla s

HC AU2/MF A01 CSCL 04A G3/46 04852

July 1, 1983 -- September 15, 1985

Dr. Mark J. Engebretson

Principal Investigator

Augsburg College

Minneapolis, Minnesota 55454
1

I. OVERVIEW

NASA Grant NAG 5-349 provided Dr. Mark Engebretson ar )ciates with

support for the analysis of atomic nitrogen density data obtained by the

Neutrai Atmospheric Composition Spectrometer (NACS) on board the Dynamics

Explorer-2 satellite. Initial funding was for an exploratory study of the

feasibility of obtaining ambient densities of N from source densities of NO.

Funding was continued under the Dynamics Explorer Guest Investigator Program

when initial studies indicated probable success in obtaining such ambient

densities. The .aajor scientific focus of the later work was to be to characterize the behavior of N densities at high latitudes.

As a result of this grant two presentations each were made at AGU

meetings and at NASA-sponsored workshops, one paper has been published in the

Journal of GeophYSical Research and one in a volume of conference proceedings,

and two additional papers are being readied for submission to journals.

II. PERSONNEL

Dr. Engebretson, currently Associate Professor of Physics at Augsburg

College, performed all of the preliminary analysis work associated with this

grant from July through October, 1983, and developed key elements of all the

data reduction, numerical modeling, and graphical display software used

subsequently. He is solely responsible for the application of the observed

surface chemistry to the problem of identifying the shuttle glow.

Joel Nelson and Scott Reeve were Undergraduate Assistants from November

1983 through May 1985 and from June 1985 through July 1985, respectively.

Joel was responsible for most of the operations involved in the data reduction and display effort of this project, did much of the programming for

graphics displays, and was co-author of Engebretson and Nelson (1985)•

M.
2

Joel is now a graduate student in physical chemistry at the University of

Wisconsin, ihere he is supported by a teaching assistantship. Scott Reeve,

currently a Junior at Augsburg College, was responsible for data reduction

and graphical display of data during the summer of 1985•

Jeffrey Stein, a Ph. D. candidate ', Atmospheric Physics at the University of 'innesota, wor%.ed as a Research Associate on this project from

August 1984 through July 1985. Jeff's primary contributions were (a)

development of a numerical model of the time-dependent concentration of

gases adsorbed on the surfaces of the MACS ion source, for both spinning and

despun orbits, and (b) the preparation of a paper on the response of N at

southern auroral and polar latitudes during a geomagnetic storm. Jeff completed work on the model, presented his work on the geomagnetic storm variations of N at the spring 1985 meeting of the AGU in Baltimore ( Stein and

Engebretson, 1985), and is continuing to prepare his paper for publication.

III. ANTICIPATED OUTCOMES AND CURRENT RESULTS

A. Preliminary study of DE-2 NACS atomic nitrogen data taken during

spite orbits& Over 90% of the spinning NACS passes (essentially all those

which had complete orbit and attitude data) were processed as we attempted

to check for consistency in the NACS data and conformity to known gecphysical

variations in thermospheric N densities. Ambient densities for these orbits

were determined at 1-minute intervals and written to files on private data

tapes using the DE central computer. These densities can also be easily

regenerated from MAF files of NACS ion source densities using standard software prepared by Dr. Engebretson and Joel Nelson. Data from all of these

orbits have been used as input to Alan Hedin's modeling efforts (see item

IV-B below).
M

3

B. Analysis of surface chemistry effects in the NACS ion source, with

the aim of obtainin ambient N densities usin - NACS data$ We have established that in the NACS instrument, as in earlier satellite-borne mass

spectrometers, incoming N atoms react with 0 atoms adsorbed on ion source

surfaces and desorb as N0, which becomes a quantitative measure of thermospheric N densities under certain conditions (Engebretson and Nelson, 1985)•

By restricting early studies to spinning orbits, Dr. Engebretson was

able to show that the net NO signal (forward-facing minus backward-facing)

had a scale height appropriate to a neutral species of 14 amu and a seasonal

local time variation consistent with that observed for thenaospheric N using

earlier satellite-borne mass spectrometers (Engebretson et al., 1977).

We found, however, that extensive modeling of the surface chemistry was

necessary in order to provide an absolute calibration of these N densities,

because the dominant desorption time observed for the NO signal, 30 s, was

very near the 60-s spin period of the DE-2 spacecraft. Jeff Stein ran

U extensive altitude-, temperature- and time-dependent simulations of source

density variations using this model during Fall 1984. The results of these

simulations were used in all subsequent absolute density determinations using

NACS N density observations. Determinations of absolute densities on spinning orbits are now routine; despun orbits still require extensive fitting

of individual orbits to model parameters.

C. Study of the behavior of N at high latitudes$

1. Because the simulations of source densities had been carried

out first using data from spinning orbits, which occurred infrequently

throughout the lifetime of DE-2, we chose first -to look at the set of such

passes through the low altitude cusp. These were used to test recently
4

published optical observations of a cusp-related source of N atoms. The

res, ilts of this study were first presented at a DE team meeting in summer 1984,

were later presented at the NASAiGeddard Workshop on Thermospheric Dynamics

in October 1984, and were recently published in the Journal of Geoph sy ical

Research (Engebretson and Nelson, 1985).

2. After submission of this paper, and with the cooperation of

George Carignan of the University of Michigan, it was decided to study a

series of approximately 40 consecutive orbits over the Southern pole and

auroral zone April 27-30, 1982. Although all of these passes were despun,

the consecutive nature of the orbits suggested that modeling efforts could

provide a repeatable absolute density correction. Jeff Stein presented the

results of this study at several fixed geographic latitudes and two local

times at the spring 1985 meeting of the AGU (Stein and Engebretson, 1985)•

Dr. Engebretson presented an updated version to the DE team meeting in

July 1985, and further work is being done before this paper is submitted

for publication. The results so far indicate no new phenomena. The response

of N near and above 300 km altitude at 8.4 and 20.4 hours local time is

oftr. similar to that of 0, with only occasional deviations attributable to

local chemistry or nonlinear dynamics. These results are similar to those

of Engebretson and Mauersberger (1983), who found at most times only a weak

gas dynamic response of N to auroral activity. Our DE-2 study did not cover

the local time period in which Engebretson and Mauersberger (1983) found

sharp,, temporary depletions in N densities after isolated substorm activity.

D
r 1 5

IV. UNANTICIPATED RESULTS

A. Surface chemistry studies relevant to the shuttle glows The

calculation of ambient N densities from signals of mass 30 observed in a

mass spectrometer ion source is complicated by the fact that two molecular

species, NO and NO 2 , both have mass 30 as their maior spectral peak.

F' Modeling efforts in the NACS ion source were expected to be more difficult

than in the case of the open source OSS mass spectrometers on the Atmosphere

Explorer satellites because the closed source nature of the NACS ion source

would cause increased source background effects in the NACS instrument.

The use of a gold plated .or, source appeared to alleviate this problem to

some extent, but the degree of consistency in the NACS data from orbit to

orbit was much better than had been anticipated. It was noted that there

was considerably less NO 2 present in the NACS ion source than was found in

the OSS ion source, and that ion source warmup effects were not as significant. As a result, although NO appeared to be still the most long-lasting

surface contaminant produced in space on the walls of the NACS ion source,

the ion source density of NO could be satisfactorily modeled in a manner

similar to that used with the AE-OSS ion sources (Engebretson and Mauersber

m, 1979).

Swenson et al. (1985) suggested on the basis of optical spectroscopic

data that excited NO2 might be the source of the red continuum glow observed

on ramming surfaces of the space shuttle. A recent paper by Yee et al. (1985)

gives additional support to this mechanism from AE-C optical measurements.

The study of Swenson et al. (1985) and subsequent communications led Dr.

Engebretson to look again at the surface reactions inferred from observations

on both the AE and DE satellite mass spectrometers.
6

Preliminary observations, presented at NASA/Marshall Space Flight Center

in May 1985 (Engebretson, 1985), supported the NO2 hypothesis by showing

that NO2 is preferentially produced by ramming 0 atoms impinging on adsorbed

NO or other odd nitrogen adsorbates. It was noted that the AE-D OSS mass

spectrometer also used a gold plated surface, but exhibited large amounts

of NO2 relative to NO than either the AE-C OSS or the DE-2 NACS instruments.

The difference between the NACS data and the AE data was apparently caused by

the absence of hot, ramming 0 atoms in the NACS ion source because of its

closed ion source design.

Because one of the weak points in the NO 2 model (brought out at the

May 1985 Workshop on Spacecraft Glow) was the lack of laboratory support for

the chemistry inferred from optical and mass spectrometric studies in space,

Dr. Engebretson and Scott Reeve worked during the summer of 1985 to analyze

the changes in surface chemistry observed during the first few orbits of

operation of the DE NACS instrument. These changes are caused by the first

exposure of ion source surfaces to large fluxes of reactive thermospheric

gases (0 and N). These results, presented at the July 1985 DE team meeting,

are consistent with earlier results from AE-C and AE-D first exposures:

They show a marked change in surface recombination properties as a result

of a buildup of adsorbed atomic oxygen and atomic nitrogen and a rapid depletion of carbon, largely by reaction to form CO and CO2 . Both sets of results

support the NO2 glow hypothesis, and are included in a paper being readied

for submission to Geophysical Research Letters and presentation at the fall

1985 meeting of the AGU.

B. MSIS modeling: As part of Alan Hedin's efforts to update his MSIS

model of thermospheric composition, an attempt is being made to include

11^
7

atomic nitrogen densities and variations. Dr. Engebretson published the

first global model of atomic nitrogen at 375 km altitude (Engebretson et al.,

1977), and has during 1985 assisted Dr. Hedin in obtaining all the available

N data from the AE and DE data bases. Joel Nelson provided Dr. Hedin with

software to retrieve N densities from all spinning orbits of DE-2. Nearly

all of the data has been accessed at this time, and will be included in the

global model. It is anticipated that this work will provide an easily

accessible source of information on the global variations of N, and thus

will provide an extremely useful dissemination of the results determined

with the help of this grant.

V. COMPUTER GRAPHICS EQUIPMENT

In the first supplement to this grant NASA provided funds for a color

graphics terminal for the display of thermospheric densities. The device

chosen, a SEIKO GR-1104, has extremely good resolution (1024 x 780 pixels)

at a cost of under $5000, and is upward compatible with Tektronix 4014 terminals. Dr. Engebretson, with the help of George Fleming of the DE Sigma 9

programming team, •developed color graphics extensions for the DI-3000 graphics

package in early 19x4. Since that time we have used the DI-3000 package on

the DE computer to produce several different graphical displays used in

presentations at DE team meetings, AGU meetings, and other conferences. The

SEIKO terminal has also been used to prepare black and white images for use

in publications.

Because Dr. Engebretson expects to continue his involvement in DE

data analysis, both in cooperation with DE-NACS personnel and with Dr. Laurence

J. Cahill, Co-Investigator on the DE-1 and DE-2 magnetometers and in other

NASA-funded programs, it is requested that this terminal, purchased by

Augsburg College with funds provided by this grant, be allowed to remain

at Augsburg College.
8

VI. UNFINISHED BUSINESS

A. The paper on N observations relevant to the shuttle glow will be

submitted for publication shortly. Comments on a draft version are being

contributed by Alan Hedin and George Carignan as well as others.

B. The paper by Jeff Stein on the response of N densities during

geomagnetic storm periods at high latitudes has not been submitted for

publication.

C. There has been no time to analyze other DE-2 data in the polar

regions. Such additional sets of data, covering different local times and

seasons, are necessary in order to obtain a complete picture of the behavior

of N at high latitudes. Because the necessary ion source model and graphical

display software are now in place, new analyses could now be accomplished

with considerably less effort. This work must await further project support,

however, as Dr. Engebretson is currently on a year's sabbatical leave at the

Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland,

working on geomagnetic micropulsations, his other principal area of

scientific interest.

I
9

VII. REFERENCES

Engebretson, M. J., AE and DE mass spectrometer observations relevant to

the shuttle glow, in Second Workshop on Spacecraft Glow, NASA Conference

Publication 2391, edited by J. H. Waite, Jr. and T. W. Moorehead,

pp. 46-54, 1985.

Engebretson, M. J., and K. Mauersberger, The impa^t of gas-surface reactions

on mass spectrometric measurements of atomic nitrogen, J. Geophys.

Res., 84, 839, 1979•

Engebretson, M. J., and K. Mauersberger, The response of thermospheric

atomic nitrogen to magnetic storms, J. Geophys. Res., 88, 6331, 1983-

Engebretson, M. J., and J. T. Nelson, Atomic nitrogen densities near the

polar cusp, J. Geophys. Res., 90, 8407, 1985.

Engebretson, M. J., K. Mauersberger, D. C. Kayser, W. E. Potter, and A. 0.

Nier, Empirical model of atomic nitrogen in the upper thermosphere,

J. Geophys. Res., 82, 461, 1977-

Stein, J. W., and M. J. Engebretson, The response of thermospheric atomic

nitrogen at south polar latitudes to a geomagnetic storm (abstract,

Eos Trans. AGU, 66, 321, 1985•

Swenson, G. R., S. B. Mende, and K. S. Clifton, Ram vehicle glow spectrum;

implications of NO 2 recombination continuum, Geophys. Res. Lett.,

12, 97, 1985•

Yee, J. H., V. J. Abreu, and A. Dalgarno, The Atmosphere Explorer optical

glow near perigee altitudes, Geophys. Res. Lett., 12, 651, 1985.
10

VIII. PUBLICATIONS AND PRESENTATIONS 2UPPORTED BY THIS GRANT

A. Publications

Engebretson, M. J., AE and DE mass ,spectrometer observations relevant to

the shuttle glow, in Second Workshop on Spacecraft Glow, NASA Conference

Publication 2391, edited by J. H. Waite, Jr. and T. W. Moorehead,

pp. 46-54, 1985.

Engebretson, M. J., and J. T. Nelson, Atomic nitrogen densities near the

polar cusp, J. Geophys. Res., 20, 8407, 1985•

B. Presentations

Engebretson, M. J., Atomic nitrogen densities near the polar cusp, NASA

Goddard Workshop on Thermospheric Dynamics, Calverton, MD, October

3-4, 1984.

Engebretson, M. J., AE and DE mass spectrometer observations relevant to

the shuttle glow, Second Workshop on Spacecraft Glow, NASA Marshall

Space Flight Center, Huntsville, AL, May 6-7, 1985.

Stein, J. W., and M. J. Engebretson, The response of thermospheric atomic

nitrogen at south polar latitudes to a geomagnetic storm, Spring Meeting

of the American Geophysical pinion, May 27-31, 1985• (Abstract in

Eos Trans. ACU, 66, 321, 1985.)

Engebretson, M. J., DE mass spectrometer observations relevant to the shuttle

glow, Fall Meeting of the American Geophysical Union, December 9-13, 1985-

San Francisco, CA.
11

A —py of the paper submitted for publication in the Proceedings of

the Second Conference on Spacecraft Glow was included in the June 30, 1985

status report. Copies of the abstracts for the Spring and Fall 1985 AGU

meetings are appended to this report, as is a reprint of the paper published

in the Journal of Geophysical Research. i7 f'

6.

 Wl^ u

IX. ACKNOWLEDGMENTS

Thanks are due to George Carignan for his readiness to offer support,

advice, and needed criticism, to Alan Hedin for his helpful introduction

to the NACS data and for his continued assistance, and to Robert Hoffman,

Dynamics Explorer Project Scientist, for his continual encouragement of

these efforts.

J, 
1. 1985 Spring Meeting

The Response of Thermospheric Atomic Nitrogen at South 2. 003558838

Polar latitudes to a Geomagnetic Store

3. (a) Corresponding Address

JEFFREY N. STEIN and MARK J. ENGEdRETSON (Department of

Phys Ici',—Lgs6u

College, Minneapolis. Mti 55454) Jeffrey M. Stein

Department of Physics

The Neutral Atmospheric Composition Spectrometer Augsburg College

(MACS) on the Dynamics Explorer-2 satellite measured Minneapolis, MN 5545

0. Ne and N densities during 45 consecutive orbits

Apr11 27-30. 1982. A geomagnetic storm with sharp onset (b) Telephone number:

and rapid recovery occurred early in this period.

followed by a series of isolated substorms. The perigee 612-330-1040 or 1000

of DE-2 at this time was near the south pole, and the

satellite's orbital plane traversed meridians at 8.4 4. SA (Aeronomy)

and 20.4 hours local time. N densities increased at

each high latitude sampled during the initial large 5. None

magnetic storm, and gradually returned to lower levels

in its aftermath. Atomic nitrogen densities responded 6. 0 (Oral)

in an inconsistent manner to isolated substor- activity

1-3 days after the main storm period. Although varia- 7. None

Lions in N densities were often intermediate between

those of 0 and N2, on certain occasions N density 8. (a;

increases could not be easily explained by gas dynamical

processes, suggesting the important role of odd nitrogen (b) Mark J. Engebratson

chemistry in determining N densities at high latitudes. Department of Physics

Augsburg College

Minneapolis, MN 55!!4

(c)

(d) Student rate applicabl

9. C (Contributed)

y
1. 1985 Fall Meeting

2. 000745585

°. -:. J. Ergebretson

JHU/APL

Laurel, MD 20707

953-5000 ext. 8275

4. SA (Aeronomy)

5. None

6. P (poster)

0355

7. 40% at NASA Worshop

on Spacecraft Glow

Huntsville, AL

May, 1985

8. Murrie W. Burgan

JHU/APL

Laurel, MD 20707

9. (C (Contributed)

DE-2 :Hass Spectrometer Observations Relevant To The

Shuttle Glow

MARK J. ENGEBRETSON (The Johns Hopkins University

Applied Physics Laboratory, Laurel, Maryland 20707)

Recent work by Swenson et al. [Geophys. Res. Lett.,

12, 97, 19851 has suggested that NO 2 may be

responsible 3r the observed continuum glow near

surfaces of the space shuttle. This report will

review earlier observations of thermospheric atomic

nitrogen (N) at shuttle altitudes using mass

spectrometers and of related odd nitrogen (N, NO, and

NO2 ) reactions on spacecraft surfaces, and will

present new data from the Neutral Atmospheric

Composition Spectrometer (NACS) on the Dynamics

Explorer-2 satellite, all of which are supportive of

this hypothesis. Comparison of data from the closedsource DE-2 NACS instrument and the Open-Source

Neutral Mass Spectrome,ers (OSS) on the Atmosphere

Explorer-C and -D satellites indicates similar

behavior of NO in each case but significant

differences in the behavior of NO 2

. (1) Initial

surface conditioning effects in the DE-2 NACS ion

source are found to be similar to those observed by

the AE-9 OSS instrument. In each case there is a

buildup of 02 and NO, products of surface

recombination, during the initial exposure of ion

source surfaces to thermospheric gases. (2) Although

signals of NO and NO2 are highly dependent on surface

temperature and surface composition, it appears that

direct exposure of ion source surfaces to rammed gas

is a necessary condition for the production of large

amounts of NOV Our data also indicate that elevated

surface temperatures can significantly reduce the

production of 170 21 likely by causing more rapid

desorption of NO from these surfaces.

sue. f ^,...: