摘要:

Laboratory measurements were carried out to test for the possible direct loss of ozone on ice surfaces and solid solutions of nitric acid, sulfuric acid, and sodium sulfite over the temperature range 195 to 262 K. Experiments were performed in a vertical flow tube where the reactor wall was coated with the desired surface. Results indicate that loss of ozone on an ice surface is insignificant. A discussion of the possible importance of these results in the stratosphere is given.

ISSN:0094-8276    

DOI:10.1029/91GL02092

年代:1992

数据来源: WILEY

摘要:

Simultaneous in situ measurements of stratospheric CH4,13CH4, N2O, OC18O, pressure, and temperature have been made from Palestine, Texas (32°N) in September 1988 with the JPL Balloon‐borne Laser In Situ Sensor (BLISS). Measurements of CH4and N2O in the altitude range 30–35 km agree well with other measurements, except for an anomalously high value for the N2O at 31 km. Measurements of CH4support earlier observations of a fold in the vertical profile. A ratio for stratospheric13CH4/CH4of 0.0105 ± 0.0010 implies an enrichment of δ13C = −45 ± 92 parts per thousand over the PDB value, in agreement with previous measurements in the troposphere. A large mixing ratio of 1.9 ± 0.2 ppmv for OC18O is measured, corresponding to an enrichment of δ18O = 280 ± 50 parts per thousand for the18O isotopic species over th

ISSN:0094-8276    

DOI:10.1029/91GL02782

年代:1992

数据来源: WILEY

摘要:

During 1964–91, stratospheric temperature and circulation in northern hemisphere winter varied interannually on time scales from 2 to ∼12 years. A substantial percentage of December‐February (DJF) interannual variance was correlated with the quasi‐biennial oscillation (QBO). Additional monthly variance could be accounted for by quasi‐decadal oscillation and QBO/low‐frequency modulation. The QBO was the largest and most consistent of these signals, and its decadal modulation explains an apparent correlation with the solar cycle depending on the sign of the QBO ‐ an interpretation supported by principal compo

ISSN:0094-8276    

DOI:10.1029/91GL02869

年代:1992

数据来源: WILEY

摘要:

The neutral wind and temperature of the upper mesosphere above Amundsen‐Scott Station (South Pole) have been optically determined from the emission of naturally‐occurring OH tracer molecular species. The results show that quasi‐periodic oscillations occur on these fields at near semidiurnal frequencies. In addition, the steady component of the winds indicates that the center of the polar vortex, at mesospheric heights, is displaced from the geographic pole. Examination of the data suggests that the observed oscillations are caused by the transport of lower‐latitude tidal oscillations by ducting pr

ISSN:0094-8276    

DOI:10.1029/91GL02957

年代:1992

数据来源: WILEY

摘要:

In December 1989 a Na lidar was installed at the Amundsen‐Scott South Pole Station and was used to measure aerosol, stratospheric temperature and mesospheric Na profiles through October 1990. The mesospheric Na data are used to characterize the gravity wave field in the mesopause region. These first lidar observations of Na layer dynamics at the South Pole show strong wave activity during the Antarctic winter. Data for 25 June and 19 August 1990 UT are presented here. The total wave induced variances in atmospheric density are respectively 29 and 35 (%)2. The Na layer centroid height is very low during both observation periods. On 25 June a strong 12 h oscillation is observed in the bottomside of the Na layer which extends to altitudes as low as 74 km. The vertical displacement and temperature amplitudes associated with the 12 h oscillation are respectively 1.9 km and 19 K. The characteristics of the 12 h wave are similar to the pseudotide observed at Svalbard by Walterscheid et al. [1986

ISSN:0094-8276    

DOI:10.1029/91GL02780

年代:1992

数据来源: WILEY

摘要:

Recent high‐resolution height observations of the HF‐induced plasma line have been made byDjuth et al. [1990]. The plasma line is first observed after 3 ms very close to the HF‐reflection height and not at the height expected from weak‐turbulence theory in a uniformly varying ionosphere. Natural field‐aligned ducts exist in the ionosphere. Those with a diameter of a few meters or more can trap Langmuir waves (L waves) generated by the parametric decay instability and propagating nearly parallel to the magnetic fieldB. The ponderomotive force of the trapped L waves near the highest HF interference maximum causes electrons to be expelled parallel to B and ions to be expelled perpendicular to B. The ion gyroradius is comparable to the smallest duct diameter that can trap L waves. Since it only takes a few milliseconds for the ions to move at their thermal velocity across the duct, the duct can grow in a few milliseconds to a level where L waves capable of backscattering the Arecibo radar can be trapped. Duct growth is eventually limited by Landau damping and/or escape of the ducted L waves. These control the lower‐height limit of the plasma line and terminate th

ISSN:0094-8276    

DOI:10.1029/91GL02870

年代:1992

数据来源: WILEY

摘要:

Dayside auroral pulsations (10–40 s periods) have been studied for different levels of geomagnetic disturbance with N2+427.8 nm emission data obtained at South Pole station, Antarctica (−74.2° MLAT). The occurrence distribution exhibits a single peak at magnetic noon under geomagnetically quiet conditions (0 ≤ Kp<1). With increased Kp, the distribution shifts to earlier times, the peak occurring at 1000–1030 MLT for 1 ≤, Kp<4. At these higher Kp levels a secondary occurrence peak is evident in the afternoon sector between 1400 and 1600 MLT, occurring earlier as Kp increases. These results are compared with those obtained separately for pre‐noon pulsations observed at Ny Alesund and post‐noon pulsations observed at Davis, northern and southern hemisphere sites at approximately the same magnetic latitude as South Pole. South Pole and Ny Alesund observe morning peaks at the same time and with a similar lack of Kp dependence; South Pole and Davis observe afternoon peaks with similar Kp dependence, though the peak occurs earlier at Davis. In contrast to the results from the earlier studies, the South Pole observations show larger pulsation amplitudes in the morning sector and significantly higher occurrence

ISSN:0094-8276    

DOI:10.1029/91GL02781

年代:1992

数据来源: WILEY

摘要:

The five largest magnetic storms that occurred between 1971 to 1986 are studied to determine their solar and interplanetary causes. All of the events are found to be associated with high speed solar wind streams led by collisionless shocks. The high speed streams are clearly related to identifiable solar flares. It is found that: 1) it is the extreme values of the southward interplanetary magnetic fields rather than solar wind speeds that are the primary causes of great magnetic storms, 2) shocked and draped sheath fields preceding the driver gas (magnetic cloud) are at least as effective in causing the onset of great magnetic storms (3 of 5 events) as the strong fields within the driver gas itself, and 3) precursor southward fields ahead of the high speed streams allow the shock compression mechanism (item 2) to be particularly geoeffective.

ISSN:0094-8276    

DOI:10.1029/91GL02783

年代:1992

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/91GL03150

年代:1992

数据来源: WILEY