scholarly journals A case study of a sporadic sodium layer observed by the ALOMAR Weber Na lidar

2008 ◽  
Vol 26 (5) ◽  
pp. 1071-1081 ◽  
Author(s):  
H. Nesse ◽  
D. Heinrich ◽  
B. Williams ◽  
U.-P. Hoppe ◽  
J. Stadsnes ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Electron Bombardment ◽  
Meteor Radar ◽  
Temperature Dependent ◽  
Sodium Layer ◽  
Sporadic E Layers ◽  
Meteoric Smoke ◽  
Sporadic E ◽  
Dependent Mechanism

Abstract. Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya and near Tromsø in Norway gives us an opportunity to test the different theories applied to high latitude sporadic sodium layers. We use the ALOMAR Weber sodium lidar to monitor the appearance and characteristics of a sporadic sodium layer that was observed on 5 November 2005. We also monitor the temperature to test the hypotheses regarding a temperature dependent mechanism. The EISCAT Tromsø Dynasonde, the ALOMAR/UiO All-sky camera and the SKiYMET meteor radar on Andøya are used to test the suggested relationships of sporadic sodium layers and sporadic E-layers, electron precipitation, and meteor deposition during this event. We find that more than one candidate is eligible to explain our observation of the sporadic sodium layer.

scholarly journals Coincident extremely large sporadic sodium and sporadic E layers observed in the lower thermosphere over Colorado and Utah

2007 ◽  
Vol 25 (1) ◽  
pp. 3-8 ◽  
Author(s):  
B. P. Williams ◽  
F. T. Berkey ◽  
J. Sherman ◽  
C. Y. She
Keyword(s):  
North America ◽  
Layer Structure ◽  
Lower Thermosphere ◽  
Ion Density ◽  
Bear Lake ◽  
Sodium Layer ◽  
Sporadic E Layers ◽  
Fort Collins ◽  
Sporadic E ◽  
Wind Shears

Abstract. On the night of 2 June 2002, the sodium lidar in Fort Collins, CO (40.6 N, 105 W) measured an extremely strong sporadic sodium layer lasting from 03:30 to 05:00 UT with several weaker layers later in the night at 06:00 and 09:00 UT. There is a double layer structure with peaks at 101 and 104 km. The peak sodium density was 21 000 atoms/cm3 with a column abundance of up to twice that of the normal sodium layer. The peak density was 500 times greater than the typical density at that altitude. The sporadic layer abundance and strength factor were higher than any reported in the literature. The two lidar beams, separated by 70 km at this altitude, both measured 0.6 h periodicities in the abundance, but out of phase with each other by 0.3 h. There is also evidence for strong wave activity in the lidar temperatures and winds. The NOAA ionosonde in Boulder, CO (40.0 N, 105 W) measured a critical frequency (foEs) of 14.3 MHz at 03:00 UT on this night, the highest value anytime during 2002. The high values of total ion density inferred means that Na+ fraction must have been only a few percent to explain the neutral Na layer abundances. The Bear Lake, Utah (41.9 N, 111.4 W) dynasonde also measured intense Es between 02:00 and 05:00 UT and again from 06:00 to 08:00 UT about 700 km west of the lidar, with most of the ionograms during these intervals measuring Es up to 12 MHz, the limit of the ionosonde sweep. Other ionosondes around North America on the NGDC database measured normal foEs values that night, so it was a localized event within North America. The peak of Es activity observed in Europe during the summer of 2002 occurred on 4 June. The observations are consistent with the current theories where a combination of wind shears and long period waves form and push downward a concentrated layer of ions, which then chemically react and form a narrow layer of sodium atoms.

scholarly journals Comparison of sporadic sodium layer characteristics observed at different time resolutions

2013 ◽  
Vol 31 (11) ◽  
pp. 1899-1912 ◽  
Author(s):  
Y. J. Liu ◽  
B. R. Clemesha ◽  
J. H. Wang ◽  
X. W. Cheng
Keyword(s):  
Time Resolution ◽  
Apparent Movement ◽  
Peak Height ◽  
Thin Layers ◽  
Height Range ◽  
Sodium Layer ◽  
Sporadic E Layers ◽  
Excellent Work ◽  
Sporadic E ◽  
Meteor Trails

Abstract. Sporadic sodium (Nas) layers, occurring in roughly the same height range as ionospheric sporadic-E layers, were first detected by lidar some 30 yr ago. Nas layers have a typical thickness of a few hundred meters to a few km, with peak atom concentrations several times that of the background layer. Despite a great deal of excellent work over the past decades, the source of Nas layers is still not altogether clear, partly as a result of our incomplete knowledge of Nas layer characteristics. In this paper we concentrate on some typical case studies chosen from the ~127 h of sporadic sodium layer observations made at a time resolution of 1.5 s at Yanqing (115.97° E, 40.47° N), Beijing, China. This is a much better time resolution than what has been employed in most earlier measurements. The results show that the Nas layer peak heights are dispersed at slightly different although adjacent heights. When averaged over several minutes, as has been the case with most earlier measurements, the height scatter results in an apparent layer thickness of a few km. We conclude, therefore, that these dispersed peaks at different but adjacent heights constitute the 5 min Nas layer. Similar to the observations of sporadic-E-ion (Es) layers and meteor rate, we observe quasi-periodic fluctuations on a timescale on the order of several minutes in the peak height and the peak density of sporadic layers, which is a universal feature but concealed by the lower temporal resolution previously adopted. Spatially localized multiple scatterers and multiple thin layers with similar apparent movement in Nas layers are also found. We discuss the possible formation mechanism by the direct deposition of large swarms of micrometeoroids and demonstrate a typical example of meteor trails evolving into a Nas layer, which suggests that this mechanism might indeed occur.

scholarly journals Comparison of D-region Doppler drift winds measured by the SuperDARN Finland HF radar over an annual cycle using the Kiruna VHF meteor radar

2003 ◽  
Vol 21 (10) ◽  
pp. 2073-2082 ◽  
Author(s):  
N. F. Arnold ◽  
P. A. Cook ◽  
T. R. Robinson ◽  
M. Lester ◽  
P. J. Chapman ◽  
...  
Keyword(s):  
Hf Radar ◽  
Meteor Radar ◽  
Meteorology And Atmospheric Dynamics ◽  
Sporadic E Layers ◽  
D Region ◽  
Summer Echoes ◽  
Instruments And Techniques ◽  
Waves And Tides ◽  
Sporadic E ◽  
Meteor Trails

Abstract. The SuperDARN chain of oblique HF radars has provided an opportunity to generate a unique climatology of horizontal winds near the mesopause at a number of high latitude locations, via the Doppler shifted echoes from sources of ionisation in the D-region. Ablating meteor trails form the bulk of these targets, but other phenomena also contribute to the observations. Due to the poor vertical resolution of the radars, care must be taken to reduce possible biases from sporadic-E layers and Polar Mesospheric Summer echoes that can affect the effective altitude of the geophysical parameters being observed. Second, there is strong theoretical and observational evidence to suggest that the radars are picking up echoes from the backward looking direction that will tend to reduce the measured wind strengths. The effect is strongly frequency dependent, resulting in a 20% reduction at 12 MHz and a 50% reduction at 10 MHz. A comparison of the climatologies observed by the Super-DARN Finland radar between September 1999 and September 2000 and that obtained from the adjacent VHF meteor radar located at Kiruna is also presented. The agreement between the two instruments was very good. Extending the analysis to the SuperDARN Iceland East radar indicated that the principles outlined above could be applied successfully to the rest of the SuperDARN network.Key words. Ionosphere (ionosphere-atmosphere interactions; instruments and techniques) – Meteorology and atmospheric dynamics (waves and tides)

scholarly journals Sporadic sodium layer: A possible tracer for the conjunction between the upper and lower atmospheres

2020 ◽  
Author(s):  
Shican Qiu ◽  
Ning Wang ◽  
Willie Soon ◽  
Gaopeng Lu ◽  
Mingjiao Jia ◽  
...  
Keyword(s):  
Electric Field ◽  
World Wide ◽  
Atmospheric Electric Field ◽  
Fluxgate Magnetometer ◽  
Ionospheric Disturbances ◽  
Sodium Layer ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Statistical Results

Abstract. In this research, we reveal the inter-connection between lightning strokes, reversal of the electric field, ionospheric disturbances, and a trigger of sporadic sodium layer event (NaS), based on the joint observations by three lidars, an ionosonde, an atmospheric electric mill, a fluxgate magnetometer, and World Wide Lightning Location Network (WWLLN). Our results suggest that lightning strokes would probably have an influence on the ionosphere and thus give rise to the occurrence of NaS, with the overturning of electric field playing an important role. Statistical results reveal that the sporadic E layers (ES) could hardly be formed or maintained when the atmospheric electric field turns upward. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena, and the key processes could be suggested as follows: lightning strokes→overturning of electric field→different collisional frequencies for ions and electrons→depletion of ES/generation of NaS.

scholarly journals Manganese-Oxidizing Antarctic Bacteria (Mn-Oxb) Release Reactive Oxygen Species (ROS) as Secondary Mn(II) Oxidation Mechanisms to Avoid Toxicity

Biology ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1004
Author(s):  
Ignacio Jofré ◽  
Francisco Matus ◽  
Daniela Mendoza ◽  
Francisco Nájera ◽  
Carolina Merino
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Soil Formation ◽  
Ros Production ◽  
Oxygen Species ◽  
Ros Scavenging ◽  
Cell Protection ◽  
Temperature Dependent ◽  
Antarctic Soils ◽  
Dependent Mechanism

Manganese (Mn) oxidation is performed through oxidative Mn-oxidizing bacteria (MnOxb) as the main bio-weathering mechanism for Mn(III/IV) deposits during soil formation. However, with an increase in temperature, the respiration rate also increases, producing Reactive Oxygen Species (ROS) as by-products, which are harmful to microbial cells. We hypothesize that bacterial ROS oxidize Mn(II) to Mn(III/IV) as a secondary non-enzymatic temperature-dependent mechanism for cell protection. Fourteen MnOxb were isolated from Antarctic soils under the global warming effect, and peroxidase (PO) activity, ROS, and Mn(III/IV) production were evaluated for 120 h of incubation at 4 °C, 15 °C, and 30 °C. ROS contributions to Mn oxidation were evaluated in Arthrobacter oxydans under antioxidant (Trolox) and ROS-stimulated (menadione) conditions. The Mn(III/IV) concentration increased with temperature and positively correlated with ROS production. ROS scavenging with Trolox depleted the Mn oxidation, and ROS-stimulant increased the Mn precipitation in A. oxydans. Increasing the Mn(II) concentration caused a reduction in the membrane potential and bacterial viability, which resulted in Mn precipitation on the bacteria surface. In conclusion, bacterial ROS production serves as a complementary non-enzymatic temperature-dependent mechanism for Mn(II) oxidation as a response in warming environments.

scholarly journals Midnight variations of spreading of ionospheric sporadic E-layers before earthquakes

2012 ◽  
Vol 55 (1) ◽  
Author(s):  
Elena V. ◽  
Alexandra S. ◽  
Victor A. ◽  
Claudia-Veronika Meister ◽  
Dieter H.H. ◽  
...  
Keyword(s):  
Sporadic E Layers ◽  
Sporadic E
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