BEHAVIOR OF THE NM EMISSION IN MLT REGION DURING STRATOSPHERIC WARMING EVENTS I.V. Medvedeva, A.V. Mikhalev, M.A. Chernigovskaya Institute of Solar-Terrestrial Physics SB RAS Irkutsk, Russia Fourth UN/ESA/NASA/JAXA Workshop “First Results of IHY 2007” Sozopol, Bulgaria, June 2-6, 2008

Observation of emissions of upper atmosphere is an effective method of researching its physical and chemical properties. Airglow intensities variations are a sensitive indicator of disturbances in the middle and upper atmosphere. The atomic oxygen [OI] green line is the brightest discrete emission in the visible spectral range in night airglow of the mid-latitude upper atmosphere; it appears at heights of 85−115 km with the peak at about 96 km.

Main goal: to find out the nature of strong disturbances in behavior of the atomic oxygen nm emission observed during the winter periods in the region of Eastern Siberia in quiet geomagnetic conditions

Analyzed Data The nm airglow observational data obtained at the ISTP SB RAS Geophysical Observatory (52° N, 103° E); The vertical structures of temperature data of satellite NOAA (device TOVS) on 70 and 10 hPa levels for November 1998 through January, The TOVS data were received and processed at the receiving station of ISTP Remote Sensing Center, Irkutsk; The Berlin Meteorological University data on stratospheric warming at 10 hPa level. ( The period under analysis:

Results Daily mean nm nightglow intensity. ISTP SB RAS Geophysical observatory, 1997–2006, 645 observation nights.

In the period under analysis some significant manifestations of stratospheric warming in nm emission variations are possible to allocate: 1) Intensive local warming in late January–February, 1998, when localization of warming was practically in the place of registration of nm emission (53°N, 108°E), where the temperature reached ~250 K. Maximal temperature 267 K was registered in early February in the site with coordinates 74°N, 92°Е. Daily nm nightglow intensity grew more than by 100%, temperature growth was about 17 K. On February, 1 the maximal magnitude of intensity was registered, the intensity reached 1500 R; the time shift made about 4 days concerning temperature growth.

2) Warming in January, 2000, above Siberia – Mongolia – Manchuria which prolonged up to the early February. Maximal temperature reached ~260 K, it was registered in the center with coordinates 73°N, 120°E. Strong increase of nm emission intensity was observed from January, 17, the intensity being abnormally high till January, 22. The highest magnitude of nm nightglow intensity exceeding 2000 R was registered on January, 20.

Variations of daily mean nm nightglow intensity and atmospheric temperature at the 10 hPa and 70 hPa levels for December 1999 – January Strong intensity growth after January, 17 is well seen, the daily mean intensity grew by about 500 R whereas the temperature at the 10 hPa level grew by ~15 K.

3) Warming above Asia in the upper stratosphere in early December, The numerous centers of warm located near the observation place, the maximal temperature reaching ~270 K was registered in the center with coordinates 65°N, 93°Е. The daily mean nm nightglow intensity increased by 2.5 times for 4 days, the maximal registered intensity magnitude run up to ~650 R.

4) Warming in mid December 2001 through January 2002 over Siberia, when the temperature at the 10 hPa level grew more than by 30 K. From December, 17 a very strong increase of nm emission intensity had been observed. Daily mean nm nightglow intensity grew within 2 days from ~500 R up to ~1600 R, the maximal night intensity going up from ~900 R to ~2200 R (on December, 22).

Daily mean nm nightglow variations, 2001– 2003.

Распределение ежедневных данных областей локализации очагов стратосферных потеплений и температур в этих очагах для периода гг. Distribution of daily data for the regions of localization of stratospheric warming centers and the temperatures in these centers for the winters of 1997–2002 (December–March)

Conclusions On the basis of the experimental data obtained at the ISTP SB RAS Geophysical observatory (52°N, 103°E) in , some abnormal increases of nm airglow intensity caused by stratospheric warming were determined nm airglow variations caused by stratospheric warming are comparable by magnitude with the variations caused by seasonal variation of this emission, and sometimes exceed them essentially.

Conclusions On the basis of the experimental data obtained at the ISTP SB RAS Geophysical observatory (52°N, 103°E) in , some abnormal increases of nm airglow intensity caused by stratospheric warming were determined nm airglow variations caused by stratospheric warming are comparable by magnitude with the variations caused by seasonal variation of this emission, and sometimes exceed them essentially. The nm intensities registered during stratospheric warming in January, 2000 (more than 2000 R) and December, 2001 (more than 2200 R) can refer to extremely registered intensity variation in the middle latitudes.

Conclusions On the basis of the experimental data obtained at the ISTP SB RAS Geophysical observatory (52°N, 103°E) in , some abnormal increases of nm airglow intensity caused by stratospheric warming were determined nm airglow variations caused by stratospheric warming are comparable by magnitude with the variations caused by seasonal variation of this emission, and sometimes exceed them essentially. The nm intensities registered during stratospheric warming in January, 2000 (more than 2000 R) and December, 2001 (more than 2200 R) can refer to extremely registered intensity variation in the middle latitudes. Geographical irregularity of stratospheric warming and their high concentration in the Asian region and, in particular, over Eastern Siberia can form regional (and, probably, latitude-longitudinal) peculiarities of nm airglow variations.

Thanks for attention!

1 R = 10 6 photon*cm -2 *sec -1

The nm airglow arises as a result of 1 S  1 D forbidden transition of atomic oxygen. The Barth mechanism is now generally accepted as being responsible for the production of О( 1 S) : О( 3 Р) + О( 3 Р) + М  О 2 * + М, О 2 *+ О( 3 Р)  О 2 *+ О( 1 S) The rate of the three-body reaction should have a negative temperature coefficient of about  (300/Т) 2, and quenching should increase with temperature.

Fig. 4. Atmospheric profiles from MLS and height-temporal distribution of temperature for the region near Irkutsk during June, There is a sharp border between the stratosphere and mesosphere in summer period.

Fig. 5. Atmospheric profiles from MLS and height-temporal distribution of temperature for the region near Irkutsk during December, The different pattern of height-temporal distribution of temperature. There are several extremums in temperature profile.

Степени несогласованности с линиями регрессии: 95 км: все данные – Зима – Лето – км: Все данные – Зима – 126.4