scholarly journals On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region

2010 ◽  
Vol 28 (5) ◽  
pp. 1107-1120 ◽  
Author(s):  
J. K. Hargreaves ◽  
M. J. Birch ◽  
D. S. Evans
Keyword(s):  
Close Correlation ◽  
Auroral Zone ◽  
Time Of Day ◽  
Energy Electron ◽  
Small Scale ◽  
Medium Energy ◽  
Angle Scattering ◽  
D Region ◽  
Highly Correlated ◽  
Radiowave Absorption

Abstract. This study is based on measurements of trapped and precipitated electrons of energy >30 keV and >100 keV observed by polar orbiting environmental satellites during overpasses of the imaging riometer at Kilpisjärvi, Finland. The satellites are in sun-synchronous orbits of about 850 km altitude, recording the electron fluxes at 2-s time resolution. The riometer measures the radiowave absorption at 38.2 MHz, showing the spatial pattern within a 240 km field of view. The analysis has focussed on two areas. Having found a close correlation between the radiowave absorption and the medium-energy electron fluxes during satellite overpasses, empirical relationships are derived, enabling one quantity to be predicted from the other for three sectors of local time. It is shown that small-scale variations observed during a pass are essentially spatial rather than temporal. Other properties, such as the spectra and the relation between precipitated and trapped components, are also considered in the light of the theory of pitch angle scattering by VLF waves. It is found that the properties and behaviour depend strongly on the time of day. In the noon sector, the precipitated and trapped fluxes are highly correlated through a square law relationship.

scholarly journals D- and E-region effects in the auroral zone during a moderately active 24-h period in July 2005

2007 ◽  
Vol 25 (8) ◽  
pp. 1837-1849 ◽  
Author(s):  
J. K. Hargreaves ◽  
M. J. Birch ◽  
B. J. I. Bromage
Keyword(s):  
Energetic Electron ◽  
Radar Data ◽  
Early Morning ◽  
Auroral Zone ◽  
Small Scale ◽  
Absorption Region ◽  
Horizontal Structure ◽  
D Region ◽  
E Region ◽  
Eiscat Radar

Abstract. The effects of energetic electron precipitation into the auroral region at a time of enhanced solar wind have been investigated during a continuous period of 24 h, using the European Incoherent Scatter (EISCAT) radar, an imaging riometer, and particle measurements on an orbiting satellite. The relative effects in the E region (120 km) and D region (90 km) are found to vary during the day, consistent with a gradual hardening of the incoming electron spectrum from pre-midnight to morning. Whereas the night spectra are single peaked, the daytime spectra are found to be double peaked, suggesting the presence of two distinct populations. A comparison between the radiowave absorption observed with the riometer and values estimated from the radar data shows generally good agreement, but with some discrepancies suggesting the occurrence of some small-scale features. The height and thickness of the absorbing region are estimated. Two periods of enhanced precipitation and the related radio absorption, one near magnetic midnight and one in the early morning, are studied in detail, including their horizontal structure and movement of the absorption patches. A sharp reduction of electron flux recorded on a POES satellite is related to the edge of an absorption region delineated by the imaging riometer. The observed particle flux is compared with a value deduced from the radar data during the overpass, and found to be in general agreement.

scholarly journals Preferential Ribosome Loading on the Stress-Upregulated mRNA Pool Shapes the Selective Translation under Stress Conditions

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 304
Author(s):  
Yan Chen ◽  
Min Liu ◽  
Zhicheng Dong
Keyword(s):  
Enrichment Analysis ◽  
Close Correlation ◽  
Stress Conditions ◽  
Functional Categories ◽  
Molecular Pattern ◽  
Mrna Pool ◽  
Selective Translation ◽  
Stress Responsive Genes ◽  
Highly Correlated ◽  
Response To Water

The reprogramming of gene expression is one of the key responses to environmental stimuli, whereas changes in mRNA do not necessarily bring forth corresponding changes of the protein, which seems partially due to the stress-induced selective translation. To address this issue, we systematically compared the transcriptome and translatome using self-produced and publicly available datasets to decipher how and to what extent the coordination and discordance between transcription and translation came to be in response to wounding (self-produced), dark to light transition, heat, hypoxia, Pi starvation and the pathogen-associated molecular pattern (elf18) in Arabidopsis. We found that changes in total mRNAs (transcriptome) and ribosome-protected fragments (translatome) are highly correlated upon dark to light transition or heat stress. However, this close correlation was generally lost under other four stresses analyzed in this study, especially during immune response, which suggests that transcription and translation are differentially coordinated under distinct stress conditions. Moreover, Gene Ontology (GO) enrichment analysis showed that typical stress responsive genes were upregulated at both transcriptional and translational levels, while non-stress-specific responsive genes were changed solely at either level or downregulated at both levels. Taking wounding responsive genes for example, typical stress responsive genes are generally involved in functional categories related to dealing with the deleterious effects caused by the imposed wounding stress, such as response to wounding, response to water deprivation and response to jasmonic acid, whereas non-stress-specific responsive genes are often enriched in functional categories like S-glycoside biosynthetic process, photosynthesis and DNA-templated transcription. Collectively, our results revealed the differential as well as targeted coordination between transcriptome and translatome in response to diverse stresses, thus suggesting a potential model wherein preferential ribosome loading onto the stress-upregulated mRNA pool could be a pacing factor for selective translation.

scholarly journals Medium Energy Electron Flux in Earth's Outer Radiation Belt (MERLIN): A Machine Learning Model

2020 ◽  
Author(s):  
Artem Smirnov ◽  
Max Berrendorf ◽  
Yuri Shprits ◽  
Elena A. Kronberg ◽  
Hayley J Allison ◽  
...  
Keyword(s):  
Machine Learning ◽  
Radiation Belt ◽  
Electron Flux ◽  
Learning Model ◽  
Energy Electron ◽  
Medium Energy ◽  
Outer Radiation Belt ◽  
Machine Learning Model

Response of CR-39 to medium energy electron irradiation

2005 ◽  
Vol 40 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Christopher G. Wahl ◽  
James G. McLean
Keyword(s):  
Electron Irradiation ◽  
Energy Electron ◽  
Medium Energy

Detector design of medium-energy electron imaging

2015 ◽  
Vol 27 (1) ◽  
pp. 14005
Author(s):  
贾向红 Jia Xianghong ◽  
邹鸿 Zou Hong ◽  
许峰 Xu Feng ◽  
于向前 Yu Xiangqian ◽  
杨成佳 Yang Chengjia ◽  
...  
Keyword(s):  
Energy Electron ◽  
Medium Energy ◽  
Electron Imaging ◽  
Detector Design

RADIO FADING AND THE NATURAL ELECTROMAGNETIC BACKGROUND

1965 ◽  
Vol 43 (11) ◽  
pp. 1951-1961 ◽  
Author(s):  
H. J. Duffus ◽  
G. M. Boyd ◽  
J. K. Kinnear
Keyword(s):  
Radio Signal ◽  
Spectral Component ◽  
Broad Band ◽  
Auroral Zone ◽  
Frequency Range ◽  
Single Station ◽  
D Region ◽  
Radio Signals ◽  
Signal Fluctuation ◽  
The Difference

A comparison is made between the natural geomagnetic background in the frequency range 0.006–0.6 Hz and fluctuations of the difference in received signal strength between the two magnetoionic modes of vertically incident broad-band radio signals in the range 6–16 MHz, observed at a single station near Victoria, British Columbia. At this station the following points were observed:1. During the daytime there is often a spectral component common to the radio-signal fluctuations and to the natural geomagnetic background, even during quiet magnetic times. There is seldom phase coherence, however, except for a few minutes at a time.2. There is a small but highly significant (1%) linear correlation R = 0.33 between all the hourly mean amplitudes of the radio-signal fluctuation level and the hourly mean amplitudes of the natural geomagnetic background. The correlation coefficient rises as high as R = 0.71 at 1400–1500 local time, when only a particular hour of each day is considered. It is concluded that geomagnetic micropulsations in this frequency range are a better indicator of r-f. fluctuations than is the local Kp.3. At night, there is a relationship between the occurrence of Pt's and of r-f. fluctuation, although their frequency components are not usually as closely related as are those of the daytime regimes.It is suggested that geomagnetic micropulsations can couple exospheric or auroral zone fluctuations into the upper E or F regions strongly enough to produce observable radio-signal fluctuations at mid-latitudes, even during magnetically quiet times.Lack of correlation between micropulsations and phase fluctuations of 18 kHz signals observed over an E–W 100-km path, and 80 kHz observed over an E–W 3 300-km path suggests that significant coupling does not extend down to the D region during magnetically quiet times.

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