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Response of OH, O2 and OI5577 airglow emissions to the mesospheric bore in the equatorial region of Brazil
Advances in Space Research 35 (2005) 1971–1975 www.elsevier.com/locate/asr
Response of OH, O2 and OI5577 airglow emissions to the mesospheric bore in the equatorial region of Brazil A.F. Medeiros a
a,*
, J. Fechine b, R.A. Buriti a, H. Takahashi b, C.M. Wrasse b, D. Gobbi
b
Universidade Federal de Campina Grande, Departamento de Fisica, Av. Aprigio Velozo 882, Bodocongo, 58109-790 Campina Grande, Paraiba, Brazil b Instituto Nacional de Pesquisas Espaciais (INPE), Brazil Received 1 November 2004; received in revised form 22 March 2005; accepted 23 March 2005
Abstract An all-sky CCD imager capable of measuring wave structure in the airglow OH, O2 and OI (557.7 nm) emissions was operated in the equatorial region at Sa˜o Joa˜o do Cariri (Cariri), Brazil (7S, 36W), in collaboration with the Instituto Nacional de Pesquisas Espaciais (INPE). Occurrence of mesospheric bore events was studied using the data from September 2000 to September 2002. Sixty-four bore events were detected during the observation period. Most of the bores showed the complementary effects suggested by Dewan and Picard [E.M. Dewan, R.H. Picard, Mesospheric bores. Journal of Geophysical Research 103, 6295–6305, 1998], except in a few cases where the relative variations were inconsistent with this model. 2005 Published by Elsevier Ltd on behalf of COSPAR. Keywords: Bore; Airglow; Complementary; Gravity waves; Imager
1. Introduction Over the past few decades, atmospheric bores have been observed at tropospheric heights, and only recently gravity wave-like bore events (or mesospheric fronts) have been observed in the mesosphere (Taylor et al., 1995; Medeiros et al., 2001; Smith et al., 2003; Fechine et al., 2004). During the ALOHA-93 campaign in Maui (20.8N, 156.2W), Taylor et al. (1995) observed a linear front airglow image followed by a wave train crossing the entire sky. Medeiros et al. (2001) also observed a mesospheric bore in Brazil at Cachoeira Paulista (23S) (hereafter CP). Smith et al. (2003) observed a mesospheric bore over the southwestern United States. Recently, Fechine et al. (2004) presented a climatology of mesospheric bore events for a period of two years from September 2000 to September 2002 at Cariri *
Corresponding author. Tel.: +55 83 310 1196; fax: +55 83 311 196. E-mail address: [email protected] (A.F. Medeiros).
0273-1177/$30 2005 Published by Elsevier Ltd on behalf of COSPAR. doi:10.1016/j.asr.2005.03.075
(7S, 36W). Sixty-four events were identified as mesospheric bores during this period. The first mathematical treatment of mesospheric bores was given by Dewan and Picard (1998). A simple mathematical model gave a reasonable quantitative agreement with the observations and, furthermore, could make numerous qualitative and quantitative predictions as well. Tropospheric bores normally happen when there is a reasonably strong inversion constituting a ducting condition. They postulated that a similar physical requirement must also exist for mesospheric bores. Their follow-up paper (Dewan and Picard, 2001) suggested that mesospheric bores might also be formed as a result of a gravity-wave/critical-layer interaction under a mean wind flow, so that both the resulting inversion layer and the bore should share a common origin. Munasinghe et al. (1998) suggested that a bore event could be explained by an interaction of two tidal modes within a ducting region. This explanation, however, fails to explain the sudden emission increase just
1972
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
prior to the wave train, and the emission intensity complementary feature exhibited by the nightglow emission layers during such events. Another explanation was given by Swenson et al. (1998). The event was interpreted as a leading edge of a large internal gravity wave front whose passage rendered the local medium superadiabatic, resulting in turbulence and heating. They explained an enhancement in the Na emission intensity by this assumption. In the present paper, we present the bore events observed in three airglow emissions, OH, O2b (0, 1) and OI(5577), at Cariri Airglow Observatory (7S, 36W) and discuss the airglow layer response to the bore using a schematic diagram for the four complementary effects predicted by the Dewan and Picard model (1998).
2. Mesospheric duct oscillation The aim of this section is to discuss the complementary effects in the airglow layer observed at Cariri using the Dewan and Picard model (1998). Assuming the nominal emission height of the OH emission to be 87 km, O2 to be 94 km and OI5577 to be 96 km, the model predicts that when a bore propagates in a duct between two airglow layers, separated by plane of symmetry S, it causes the following complementary effect in the three emission layers as shown in Fig. 1. The lower layer (OH layer) is pushed down adiabatically and becomes warmer, denser and presumably brighter, while the upper layer (O2 layer) is symmetrically pushed upward making the layer colder, less dense and darker. This provides an explanation for the complementary behavior of
the lower- vs. the higher-altitudes layers. Hereafter, we will use the denomination of brighter or darker to characterize the lowering or raising of the airglow layer. The model uses the same assumptions about the mesospheric duct: (i) the duct is parallel to the airglow layers and no layer is superposed on another; (ii) the bore is formed by an accelerating piston within a duct region pushing the fluid straight ahead; (iii) the bore propagates parallel to the duct. The complementary effect determined by the Dewan and Picard model (1998) for the airglow images (OH, O2 and OI5577) can be classified into four categories: (a) Brighter Brighter Brighter (BBB) effect – in this case, the duct and bore are located above the three emission layers. No complementary effect between the images can be seen. In this case, the airglow image should show a pattern of BBB; (b) Brighter Brighter Darker (BBD) effect – in this case, the bore is located below the OI5577 layer but above the OH and O2 layers. The two lower layers (OH and O2) should be lowered and become brighter, while the top layer (OI5577) will be elevated and becomes darker. The complementary effect therefore is BBD for OH, O2 and OI5577; (c) Brighter Darker Darker (BDD) effect – in this situation the bore height is below the OI5577 and O2 layers but above the OH layer. The OH layer will be lowered and become brighter, whereas the top layers will be pushed upward and become darker; (d) Darker Darker Darker (DDD) effect – the bore is localized below the three layers (OH, O2 and OI5577), thus the three layers will be elevated and become darker. The complementary effect between the three images will be a pattern of DDD. Fig. 2 summarizes the four effects expected by Dewan and Picard (1998).
Fig. 1. Schematic diagram of the oscillating duct and respective complementary effects observed in airglow images based on the Dewan and Picard (1998) model. The arrows indicate the bore propagation direction.
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
BBD After-bore level
BDD After-bore level
Bore 17-20010223
BBB
Pre-bore level
After-bore level
1973
Bore 40 - 20011022 Pre-bore level
OI 5577 (dark)
OI 5577 (bright)
O2 (bright)
O2 (bright)
OH (bright)
OH (bright)
DDD
Bore 18-20010223 Pre-bore level
Bore 14 - 20010122
After-bore level
Pre-bore level
OI 5577 (dark)
OI 5577 (dark)
O2 (dark)
O2 (dark)
OH (bright)
OH (dark)
Fig. 2. Schematic diagram for the four complementary effects predicted by the Dewan and Picard (1998) model for OH, O2 and OI5577 airglow layers.
The airglow observations were carried out at Sa˜o Joa˜o do Cariri (7S, 36W), from September 2000 to September 2002, by an all-sky airglow imager (produced by KEO consultants) under collaboration with the Instituto Nacional de Pesquisas Espaciais (INPE). A fish-eye 180 wide-angle lens followed by a telecentric lens system with interference filters produces a narrow band monochromatic image on the CCD camera. For the present study, five interference filters to measure OI 557.7 nm, OI 630 nm, O2b (0,1) at 865 nm, OHNIR (715–930 nm), and background continuum at 570 nm emissions were used. A large area (6.45 cm2) CCD camera, with 1024 · 1024 pixels, thermoelectrically cooled to 36 C, was used. The imager system operation program and image data processing algorithm were developed and described elsewhere (Medeiros et al., 2001).
4. Results From a total of 64 bore events observed at Cariri, 68% of the cases showed the complementary effects predicted by Dewan and Picard (1998). They are divided into four different groups: BBB accounting for 9% of events, BBD for 8%, BDD for 28% and DDD for 23%. Fig. 3 shows the statistics of the patterns observed. The patterns BDD and DDD have higher frequency of occurrence, suggesting a higher incidence of duct formation at around 87 km (the nominal altitude of the OH layer). It should be noted that seven bores (11% of the total) showed complementary effects of DBB and DDB, which are not predicted by Dewan and Picard (1998). One of the cases (DBB) on the night of June
N˚ of Bores
3. Observations
20 18 16 14 12 10 8 6 4 2 0
28% 23% 20%
9%
BB B
11% Not predicted
8%
BBD
BDD
DDD
DBB
DDB
others
Fig. 3. Frequency of occurrence of the complementary effects observed at Cariri.
15, 2001 is shown in Fig. 4. Note that in the OH image the front is dark while O2 and OI5577 images are bright. The arrows indicate the bore propagation direction. In Fig. 5, the cases of DBB and DDB are tentatively illustrated. The ducting condition was assumed to be in between the OH and O2 layers in the case of DBB and between O2 and OI5577 for DDB. However, the pressure wave modeled by Dewan and Picard (1998) cannot explain these cases. The opposite sense of oscillation pattern, OH/Dark and O2/Bright for example, could be caused by a vertical structure of the duct. The Dewan and Picard (1998) model assumes that the duct has less than 10 km vertical extent between the two emission layers. But, it could be larger than 10 km, overlapping the two emission layers. In this case, the response of the emission layers must be different and not in a simple way. Another possibility could be a different temperature response to the pressure wave. Both the OH and O2 emission rates are very sensitive to temperature variation. When the temperature increases, both the emissions increase their emission rates. If the temperature decreases in the lower layer
1974
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
Fig. 4. OH, O2 and OI5577 images showing the case DBB on the night of June 15 2001. Note that in the OH image the front is dark while for the O2 and OI5577 images the front is bright. The arrows indicate the bore propagation direction.
DBB After-bore level
Bore 02 - 20000928 Pre-bore level
DDB After-bore level
Bore 37 - 20010921 Pre-bore level
OI 5577 (bright)
OI 5577 (bright)
O2 (bright)
O2 (dark)
OH (dark)
OH (dark)
Fig. 5. Schematic diagram of two complementary effects not predicted by Dewan and Picard (1998) model.
(OH) and increases in the upper layer (O2), then, it could introduce the complementary effect of DBB. Takahashi et al. (2004) reported that in the OH and O2 emission layers, variations of atmospheric density and temperature are in the opposite sense. Therefore, the pressure wave could produce such an opposite complementary effect compared to the Dewan and Picard (1998) case. Of course, it is too early to conclude any mechanism to explain all of the complementary effects. Further observational results together with other measurements such as the temperature profile and wind profile would be necessary to further our present studies.
5. Conclusion Mesospheric airglow imaging observations were carried out at Sa˜o Joa˜o do Cariri (7.4S, 36.5W) during the period from September 2000 to September 2002. A total of 64 mesospheric bore events were observed. The response of the OH, O2 and OI5577 airglow layers was analyzed when the bores crossed the imager field of view. Most of the bores showed the complementary effects suggested by Dewan and Picard (1998). We also observed that airglow layers showed OH(Dark), O2(Bright) and OI5577(Bright) sequences, and also OH(Dark), O2(Dark) and OI5577(Bright), which cannot be explained by Dewan and PicardÕs model.
Acknowledgments The Cariri imager was financed by CNPq/PRONEX Grant No. 76.97.1079.00. This work has also been supported by the Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´gico and the Sa˜o Joa˜o do Cariri municipal council.
References Dewan, E.M., Picard, R.H. Mesospheric bores. Journal of Geophysical Research 103, 6295–6305, 1998. Dewan, E.M., Picard, R.H. On the origin of mesospheric bores. Journal of Geophysical Research 106, 2921–2927, 2001. Fechine, J., Medeiros, A.F., Buriti, R.A., Takahashi, H., Gobbi, D. Mesospheric bore events in the equatorial middle atmosphere, Journal of Atmospheric and Solar-Physics Terrestrial (submitted). Medeiros, A.F., Taylor, M.J., Takahashi, H., Batista, P.P., Gobbi, D. A unusual airglow wave event observed at Cachoeira Paulista 23S. Advances in Space Research 27, 1749–1754, 2001. Munasinghe, G., Hur, H., Huang, T.Y., Bhattachryya, A., Tuan, T.F. Application of the dispersion formula to long- and short-period gravity waves: comparisons with ALOHA-93 data and an analytical model. Journal of Geophysical Research 103, 6467– 6481, 1998. Smith, S.M., Taylor, M.J., Swenson, G.R., She, C., Hocking, W., Baumgardner, J., Mendillo, M. A multidiagnostic investigation of the mesospheric bore phenomenom. Journal of Geophysical Research 108, 13–20, 2003.
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975 Swenson, G.R., Qian, J., Plane, J.M.C., Espy, P.J., Taylor, M.J., Turnbull, D.N., Lowe, R.P. Dynamical and chemical aspects of the mesospheric Na ‘‘wall’’ event on October 9, 1993, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA) campaign. Journal of Geophysical Research 103, 6361, 1998. Takahashi, H., Nakamura, T., Shiokawa, K., Tsuda, T., Lima, L.M., Gobbi, D. Atmospheric density and pressure inferred
1975
from the meteor diffusion coefficient and airglow O2b temperature in the MLT region. Earth Planets Space 56, 249–258, 2004. Taylor, M.J., Turnbull, D.N., Lowe, R.P. Spectrometric and imaging measurements of a spectacular gravity wave event observed during the ALOHA-93 campaign. Geophysical Research Letters 20, 2849– 2852, 1995.
Response of OH, O2 and OI5577 airglow emissions to the mesospheric bore in the equatorial region of Brazil A.F. Medeiros a
a,*
, J. Fechine b, R.A. Buriti a, H. Takahashi b, C.M. Wrasse b, D. Gobbi
b
Universidade Federal de Campina Grande, Departamento de Fisica, Av. Aprigio Velozo 882, Bodocongo, 58109-790 Campina Grande, Paraiba, Brazil b Instituto Nacional de Pesquisas Espaciais (INPE), Brazil Received 1 November 2004; received in revised form 22 March 2005; accepted 23 March 2005
Abstract An all-sky CCD imager capable of measuring wave structure in the airglow OH, O2 and OI (557.7 nm) emissions was operated in the equatorial region at Sa˜o Joa˜o do Cariri (Cariri), Brazil (7S, 36W), in collaboration with the Instituto Nacional de Pesquisas Espaciais (INPE). Occurrence of mesospheric bore events was studied using the data from September 2000 to September 2002. Sixty-four bore events were detected during the observation period. Most of the bores showed the complementary effects suggested by Dewan and Picard [E.M. Dewan, R.H. Picard, Mesospheric bores. Journal of Geophysical Research 103, 6295–6305, 1998], except in a few cases where the relative variations were inconsistent with this model. 2005 Published by Elsevier Ltd on behalf of COSPAR. Keywords: Bore; Airglow; Complementary; Gravity waves; Imager
1. Introduction Over the past few decades, atmospheric bores have been observed at tropospheric heights, and only recently gravity wave-like bore events (or mesospheric fronts) have been observed in the mesosphere (Taylor et al., 1995; Medeiros et al., 2001; Smith et al., 2003; Fechine et al., 2004). During the ALOHA-93 campaign in Maui (20.8N, 156.2W), Taylor et al. (1995) observed a linear front airglow image followed by a wave train crossing the entire sky. Medeiros et al. (2001) also observed a mesospheric bore in Brazil at Cachoeira Paulista (23S) (hereafter CP). Smith et al. (2003) observed a mesospheric bore over the southwestern United States. Recently, Fechine et al. (2004) presented a climatology of mesospheric bore events for a period of two years from September 2000 to September 2002 at Cariri *
Corresponding author. Tel.: +55 83 310 1196; fax: +55 83 311 196. E-mail address: [email protected] (A.F. Medeiros).
0273-1177/$30 2005 Published by Elsevier Ltd on behalf of COSPAR. doi:10.1016/j.asr.2005.03.075
(7S, 36W). Sixty-four events were identified as mesospheric bores during this period. The first mathematical treatment of mesospheric bores was given by Dewan and Picard (1998). A simple mathematical model gave a reasonable quantitative agreement with the observations and, furthermore, could make numerous qualitative and quantitative predictions as well. Tropospheric bores normally happen when there is a reasonably strong inversion constituting a ducting condition. They postulated that a similar physical requirement must also exist for mesospheric bores. Their follow-up paper (Dewan and Picard, 2001) suggested that mesospheric bores might also be formed as a result of a gravity-wave/critical-layer interaction under a mean wind flow, so that both the resulting inversion layer and the bore should share a common origin. Munasinghe et al. (1998) suggested that a bore event could be explained by an interaction of two tidal modes within a ducting region. This explanation, however, fails to explain the sudden emission increase just
1972
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
prior to the wave train, and the emission intensity complementary feature exhibited by the nightglow emission layers during such events. Another explanation was given by Swenson et al. (1998). The event was interpreted as a leading edge of a large internal gravity wave front whose passage rendered the local medium superadiabatic, resulting in turbulence and heating. They explained an enhancement in the Na emission intensity by this assumption. In the present paper, we present the bore events observed in three airglow emissions, OH, O2b (0, 1) and OI(5577), at Cariri Airglow Observatory (7S, 36W) and discuss the airglow layer response to the bore using a schematic diagram for the four complementary effects predicted by the Dewan and Picard model (1998).
2. Mesospheric duct oscillation The aim of this section is to discuss the complementary effects in the airglow layer observed at Cariri using the Dewan and Picard model (1998). Assuming the nominal emission height of the OH emission to be 87 km, O2 to be 94 km and OI5577 to be 96 km, the model predicts that when a bore propagates in a duct between two airglow layers, separated by plane of symmetry S, it causes the following complementary effect in the three emission layers as shown in Fig. 1. The lower layer (OH layer) is pushed down adiabatically and becomes warmer, denser and presumably brighter, while the upper layer (O2 layer) is symmetrically pushed upward making the layer colder, less dense and darker. This provides an explanation for the complementary behavior of
the lower- vs. the higher-altitudes layers. Hereafter, we will use the denomination of brighter or darker to characterize the lowering or raising of the airglow layer. The model uses the same assumptions about the mesospheric duct: (i) the duct is parallel to the airglow layers and no layer is superposed on another; (ii) the bore is formed by an accelerating piston within a duct region pushing the fluid straight ahead; (iii) the bore propagates parallel to the duct. The complementary effect determined by the Dewan and Picard model (1998) for the airglow images (OH, O2 and OI5577) can be classified into four categories: (a) Brighter Brighter Brighter (BBB) effect – in this case, the duct and bore are located above the three emission layers. No complementary effect between the images can be seen. In this case, the airglow image should show a pattern of BBB; (b) Brighter Brighter Darker (BBD) effect – in this case, the bore is located below the OI5577 layer but above the OH and O2 layers. The two lower layers (OH and O2) should be lowered and become brighter, while the top layer (OI5577) will be elevated and becomes darker. The complementary effect therefore is BBD for OH, O2 and OI5577; (c) Brighter Darker Darker (BDD) effect – in this situation the bore height is below the OI5577 and O2 layers but above the OH layer. The OH layer will be lowered and become brighter, whereas the top layers will be pushed upward and become darker; (d) Darker Darker Darker (DDD) effect – the bore is localized below the three layers (OH, O2 and OI5577), thus the three layers will be elevated and become darker. The complementary effect between the three images will be a pattern of DDD. Fig. 2 summarizes the four effects expected by Dewan and Picard (1998).
Fig. 1. Schematic diagram of the oscillating duct and respective complementary effects observed in airglow images based on the Dewan and Picard (1998) model. The arrows indicate the bore propagation direction.
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
BBD After-bore level
BDD After-bore level
Bore 17-20010223
BBB
Pre-bore level
After-bore level
1973
Bore 40 - 20011022 Pre-bore level
OI 5577 (dark)
OI 5577 (bright)
O2 (bright)
O2 (bright)
OH (bright)
OH (bright)
DDD
Bore 18-20010223 Pre-bore level
Bore 14 - 20010122
After-bore level
Pre-bore level
OI 5577 (dark)
OI 5577 (dark)
O2 (dark)
O2 (dark)
OH (bright)
OH (dark)
Fig. 2. Schematic diagram for the four complementary effects predicted by the Dewan and Picard (1998) model for OH, O2 and OI5577 airglow layers.
The airglow observations were carried out at Sa˜o Joa˜o do Cariri (7S, 36W), from September 2000 to September 2002, by an all-sky airglow imager (produced by KEO consultants) under collaboration with the Instituto Nacional de Pesquisas Espaciais (INPE). A fish-eye 180 wide-angle lens followed by a telecentric lens system with interference filters produces a narrow band monochromatic image on the CCD camera. For the present study, five interference filters to measure OI 557.7 nm, OI 630 nm, O2b (0,1) at 865 nm, OHNIR (715–930 nm), and background continuum at 570 nm emissions were used. A large area (6.45 cm2) CCD camera, with 1024 · 1024 pixels, thermoelectrically cooled to 36 C, was used. The imager system operation program and image data processing algorithm were developed and described elsewhere (Medeiros et al., 2001).
4. Results From a total of 64 bore events observed at Cariri, 68% of the cases showed the complementary effects predicted by Dewan and Picard (1998). They are divided into four different groups: BBB accounting for 9% of events, BBD for 8%, BDD for 28% and DDD for 23%. Fig. 3 shows the statistics of the patterns observed. The patterns BDD and DDD have higher frequency of occurrence, suggesting a higher incidence of duct formation at around 87 km (the nominal altitude of the OH layer). It should be noted that seven bores (11% of the total) showed complementary effects of DBB and DDB, which are not predicted by Dewan and Picard (1998). One of the cases (DBB) on the night of June
N˚ of Bores
3. Observations
20 18 16 14 12 10 8 6 4 2 0
28% 23% 20%
9%
BB B
11% Not predicted
8%
BBD
BDD
DDD
DBB
DDB
others
Fig. 3. Frequency of occurrence of the complementary effects observed at Cariri.
15, 2001 is shown in Fig. 4. Note that in the OH image the front is dark while O2 and OI5577 images are bright. The arrows indicate the bore propagation direction. In Fig. 5, the cases of DBB and DDB are tentatively illustrated. The ducting condition was assumed to be in between the OH and O2 layers in the case of DBB and between O2 and OI5577 for DDB. However, the pressure wave modeled by Dewan and Picard (1998) cannot explain these cases. The opposite sense of oscillation pattern, OH/Dark and O2/Bright for example, could be caused by a vertical structure of the duct. The Dewan and Picard (1998) model assumes that the duct has less than 10 km vertical extent between the two emission layers. But, it could be larger than 10 km, overlapping the two emission layers. In this case, the response of the emission layers must be different and not in a simple way. Another possibility could be a different temperature response to the pressure wave. Both the OH and O2 emission rates are very sensitive to temperature variation. When the temperature increases, both the emissions increase their emission rates. If the temperature decreases in the lower layer
1974
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975
Fig. 4. OH, O2 and OI5577 images showing the case DBB on the night of June 15 2001. Note that in the OH image the front is dark while for the O2 and OI5577 images the front is bright. The arrows indicate the bore propagation direction.
DBB After-bore level
Bore 02 - 20000928 Pre-bore level
DDB After-bore level
Bore 37 - 20010921 Pre-bore level
OI 5577 (bright)
OI 5577 (bright)
O2 (bright)
O2 (dark)
OH (dark)
OH (dark)
Fig. 5. Schematic diagram of two complementary effects not predicted by Dewan and Picard (1998) model.
(OH) and increases in the upper layer (O2), then, it could introduce the complementary effect of DBB. Takahashi et al. (2004) reported that in the OH and O2 emission layers, variations of atmospheric density and temperature are in the opposite sense. Therefore, the pressure wave could produce such an opposite complementary effect compared to the Dewan and Picard (1998) case. Of course, it is too early to conclude any mechanism to explain all of the complementary effects. Further observational results together with other measurements such as the temperature profile and wind profile would be necessary to further our present studies.
5. Conclusion Mesospheric airglow imaging observations were carried out at Sa˜o Joa˜o do Cariri (7.4S, 36.5W) during the period from September 2000 to September 2002. A total of 64 mesospheric bore events were observed. The response of the OH, O2 and OI5577 airglow layers was analyzed when the bores crossed the imager field of view. Most of the bores showed the complementary effects suggested by Dewan and Picard (1998). We also observed that airglow layers showed OH(Dark), O2(Bright) and OI5577(Bright) sequences, and also OH(Dark), O2(Dark) and OI5577(Bright), which cannot be explained by Dewan and PicardÕs model.
Acknowledgments The Cariri imager was financed by CNPq/PRONEX Grant No. 76.97.1079.00. This work has also been supported by the Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´gico and the Sa˜o Joa˜o do Cariri municipal council.
References Dewan, E.M., Picard, R.H. Mesospheric bores. Journal of Geophysical Research 103, 6295–6305, 1998. Dewan, E.M., Picard, R.H. On the origin of mesospheric bores. Journal of Geophysical Research 106, 2921–2927, 2001. Fechine, J., Medeiros, A.F., Buriti, R.A., Takahashi, H., Gobbi, D. Mesospheric bore events in the equatorial middle atmosphere, Journal of Atmospheric and Solar-Physics Terrestrial (submitted). Medeiros, A.F., Taylor, M.J., Takahashi, H., Batista, P.P., Gobbi, D. A unusual airglow wave event observed at Cachoeira Paulista 23S. Advances in Space Research 27, 1749–1754, 2001. Munasinghe, G., Hur, H., Huang, T.Y., Bhattachryya, A., Tuan, T.F. Application of the dispersion formula to long- and short-period gravity waves: comparisons with ALOHA-93 data and an analytical model. Journal of Geophysical Research 103, 6467– 6481, 1998. Smith, S.M., Taylor, M.J., Swenson, G.R., She, C., Hocking, W., Baumgardner, J., Mendillo, M. A multidiagnostic investigation of the mesospheric bore phenomenom. Journal of Geophysical Research 108, 13–20, 2003.
A.F. Medeiros et al. / Advances in Space Research 35 (2005) 1971–1975 Swenson, G.R., Qian, J., Plane, J.M.C., Espy, P.J., Taylor, M.J., Turnbull, D.N., Lowe, R.P. Dynamical and chemical aspects of the mesospheric Na ‘‘wall’’ event on October 9, 1993, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA) campaign. Journal of Geophysical Research 103, 6361, 1998. Takahashi, H., Nakamura, T., Shiokawa, K., Tsuda, T., Lima, L.M., Gobbi, D. Atmospheric density and pressure inferred
1975
from the meteor diffusion coefficient and airglow O2b temperature in the MLT region. Earth Planets Space 56, 249–258, 2004. Taylor, M.J., Turnbull, D.N., Lowe, R.P. Spectrometric and imaging measurements of a spectacular gravity wave event observed during the ALOHA-93 campaign. Geophysical Research Letters 20, 2849– 2852, 1995.