scholarly journals On the relationship between the geometrical control of scintillation indices and the data detrending problems observed at high latitudes

2009 ◽  
Vol 50 (6) ◽  
Author(s):  
B. Forte
Keyword(s):  
High Latitudes ◽  
The Relationship ◽  
Scintillation Indices

scholarly journals Temperature Affects the Time Required to Discern the Relationship between Primary Production and Export Production in the Ocean

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3085
Author(s):  
Edward Laws ◽  
Kanchan Maiti
Keyword(s):  
Primary Production ◽  
Food Web ◽  
Net Primary Production ◽  
Weighted Average ◽  
Time Interval ◽  
High Latitudes ◽  
New Production ◽  
Return To Equilibrium ◽  
Export Production ◽  
The Relationship

Knowledge of the relationship between net primary production (NPP) and export production (EP) in the ocean is required to estimate how the ocean’s biological pump is likely to respond to climate change effects. Here, we show with a theoretical food web model that the relationship between NPP and EP is obscured by the following phenomena: (1) food web dynamics, which cause EP to be a weighted average of new production (NP) over a previous temperature-dependent time interval that can vary between several weeks at 25 °C to several months at 0 °C and, hence, to be much less temporally variable than NP and (2) the temperature dependence of the resiliency of the food web to perturbations, which causes the return to equilibrium to vary from roughly 50 days at 0 °C to 5–10 days at 25 °C. The implication is that the relationship between NPP and EP can be discerned at tropical and subtropical latitudes if measurements of NPP and EP are averages or climatologies over a timeframe of roughly one month. At high latitudes, however, measurements may need to be averaged over a timeframe of roughly one year because the food webs at high latitudes are very likely far from equilibrium with respect to NPP and EP much of the time, and the model can describe only the average behavior of such physically dynamic systems.

The relationship between the theta aurora and Ulf emissions at high latitudes

1994 ◽  
Vol 18 (2) ◽  
pp. 168-174
Author(s):  
B. I. Klayn ◽  
N. A. Kurazhkovskaya ◽  
B. V. Dobnya
Keyword(s):  
High Latitudes ◽  
The Relationship

scholarly journals On the Relationship between Gravity Waves and Tropopause Height and Temperature over the Globe Revealed by COSMIC Radio Occultation Measurements

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 75 ◽  
Author(s):  
Daocheng Yu ◽  
Xiaohua Xu ◽  
Jia Luo ◽  
Juan Li
Keyword(s):  
Radio Occultation ◽  
Correlation Coefficients ◽  
Lapse Rate ◽  
Cosmic Radio ◽  
Monthly Means ◽  
High Latitudes ◽  
Tropopause Height ◽  
The Tropics ◽  
The Relationship ◽  
Peak Correlation

In this study, the relationship between gravity wave (GW) potential energy (Ep) and the tropopause height and temperature over the globe was investigated using COSMIC radio occultation (RO) dry temperature profiles during September 2006 to May 2013. The monthly means of GW Ep with a vertical resolution of 1 km and tropopause parameters were calculated for each 5° × 5° longitude-latitude grid. The correlation coefficients between Ep values at different altitudes and the tropopause height and temperature were calculated accordingly in each grid. It was found that at middle and high latitudes, GW Ep over the altitude range from lapse rate tropopause (LRT) to several km above had a significantly positive/negative correlation with LRT height (LRT-H)/ LRT temperature (LRT-T) and the peak correlation coefficients were determined over the altitudes of 10–14 km with distinct zonal distribution characteristics. While in the tropics, the distributions of the statistically significant correlation coefficients between GW Ep and LRT/cold point tropopause (CPT) parameters were dispersive and the peak correlation were are calculated over the altitudes of 14–38 km. At middle and high latitudes, the temporal variations of the monthly means and the monthly anomalies of the LRT parameters and GW Ep over the altitude of 13 km showed that LRT-H/LRT-T increases/decreases with the increase of Ep, which indicates that LRT was lifted and became cooler when GWs propagated from the troposphere to the stratosphere. In the tropical regions, statistically significant positive/negative correlations exist between GW Ep over the altitude of 17–19 km and LRT-H/LRT-T where deep convections occur and on the other hand, strong correlations exist between convections and the tropopause parameters in most seasons, which indicates that low and cold tropopause appears in deep convection regions. Thus, in the tropics, both deep convections and GWs excited accordingly have impacts on the tropopause structure.

scholarly journals Analysis of the Relationship between Scintillation Parameters, Multipath and ROTI

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2877
Author(s):  
Chendong Li ◽  
Craig M. Hancock ◽  
Nicholas A. S. Hamm ◽  
Sreeja V. Veettil ◽  
Chong You
Keyword(s):  
Structural Similarity ◽  
Sampling Interval ◽  
Rate Of Change ◽  
Scintillation Index ◽  
Ionospheric Scintillation ◽  
Electron Content ◽  
Total Electron ◽  
Two Indices ◽  
The Relationship ◽  
Scintillation Indices

Global Navigation Satellite System (GNSS) operation can be affected by several environmental factors, of which ionospheric scintillation is one of the most significant. Scintillation is usually characterized by two indices, namely the amplitude scintillation index (S4) and phase scintillation index (σφ). However, these two indices can only be generated by specialized GNSS receivers, which are not widely available all around the world. To popularize the study of scintillation, this article proposes to use more accessible parameters, namely multipath (MP) and rate of change of total electron content index (ROTI), to characterize scintillation. Using GPS data obtained on six days in total from three stations, namely PRU2 and SAO0P located in Sao Paulo, Brazil and SNA0P located in Antarctica, respectively, both the time series plots and 2D maps were generated to investigate the relationship of scintillation indices (S4 and σφ) with MP and ROTI. To prevent the effect of the real multipath error, a 30-degree satellite elevation mask is applied to all the data. As the scintillation indices S4 and σφ have a sampling interval of 1 min, MP and ROTI are calculated with the same sampling interval for a more direct comparison. The results show that the structural similarity (SSIM) and correlation coefficient (CC) between parameters was greater than 0.7 for 70% of outputs. In addition, the variogram and cross-variogram are applied to investigate the spatial structure of the MP, ROTI, S4 and σφ in order to support the results of SSIM and CC. With outputs in three forms, promising spatial and temporal relationships between parameters was observed.

scholarly journals Using Chandra/LETG Spectra to Probe Stellar Coronae

2004 ◽  
Vol 219 ◽  
pp. 301-305
Author(s):  
Gaitee A. J. Hussain ◽  
Nancy Brickhouse ◽  
A. K. Dupree ◽  
Adriaan A. van Ballegooijen ◽  
Andrew Collier Cameron ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Light Curves ◽  
High Latitudes ◽  
Intrinsic Variability ◽  
Period Analysis ◽  
X Ray ◽  
Rotational Modulation ◽  
Rotating Star ◽  
The Relationship ◽  
Coronal Field

We probe the relationship between surface magnetic fields and the X-ray emitting corona in the rapidly rotating star, AB Dor. Circularly polarised spectra have been inverted to produce a surface (photospheric) magnetic field map. This surface map has been extrapolated to model AB Dor's coronal field topology and X-ray light curve. Chandra/LETG light curves of AB Dor from the same epoch show intrinsic variability at the 30% level. Period analysis indicates a fraction of this is due to rotational modulation. We measure velocity shifts in emission line centroids as a function of Prot and find evidence of rotational modulation (max. vel. ∼ 40 ± 13km s—1). This modulation may indicate the presence of a localised X-ray emitting region at mid-to-high latitudes.

scholarly journals Electromagnetic Effects on Hyperbolic Cosmic Dust Particles

1980 ◽  
Vol 90 ◽  
pp. 313-314
Author(s):  
G. E. Morfill ◽  
E. Grün
Keyword(s):  
Solar Cycle ◽  
Interstellar Dust ◽  
Equatorial Region ◽  
Dust Particles ◽  
High Latitudes ◽  
Magnetic Fluctuations ◽  
Solar Cycle Variation ◽  
Low Mass ◽  
The Relationship ◽  
Inner Heliosphere

The effects of electromagnetic forces on charged interstellar grains and β-meteoroids - both moving on hyperbolic orbits - are investigated. It is shown that the unipolar field regimes at high latitudes lead either to a “focussing” or a “defocussing” of interstellar dust and β-meteoroids with respect to the solar magnetic equator. This should lead to a solar cycle variation. The stochastic magnetic fluctuations in the equatorial region, caused by the warping of the current sheet which separates the polar fields, lead to a diffusive description of particle transport at the low mass end. Consequences for the ability of interstellar dust particles to penetrate the inner heliosphere are discussed. It is concluded that dust particles with radii s > 10−5cm can penetrate deeply into the heliosphere if their incidence direction at the heliopause is almost radially inward and close to the solar magnetic equatorial plane, whereas dust particles with radii s < 10−5 cm are prevented from reaching the inner heliosphere. The relationship between interstellar dust and β-meteoroids is discussed.

scholarly journals GPS phase scintillation and proxy index at high latitudes during a moderate geomagnetic storm

2013 ◽  
Vol 31 (5) ◽  
pp. 805-816 ◽  
Author(s):  
P. Prikryl ◽  
R. Ghoddousi-Fard ◽  
B. S. R. Kunduri ◽  
E. G. Thomas ◽  
A. J. Coster ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Solar Wind Plasma ◽  
High Rate ◽  
Ionospheric Scintillation ◽  
Plasma Stream ◽  
High Latitudes ◽  
Polar Cap ◽  
Network Chain ◽  
The Impact ◽  
Scintillation Indices

Abstract. The amplitude and phase scintillation indices are customarily obtained by specialised GPS Ionospheric Scintillation and TEC Monitors (GISTMs) from L1 signal recorded at the rate of 50 Hz. The scintillation indices S4 and σΦ are stored in real time from an array of high-rate scintillation receivers of the Canadian High Arctic Ionospheric Network (CHAIN). Ionospheric phase scintillation was observed at high latitudes during a moderate geomagnetic storm (Dst = −61 nT) that was caused by a moderate solar wind plasma stream compounded with the impact of two coronal mass ejections. The most intense phase scintillation (σΦ ~ 1 rad) occurred in the cusp and the polar cap where it was co-located with a strong ionospheric convection, an extended tongue of ionisation and dense polar cap patches that were observed with ionosondes and HF radars. At sub-auroral latitudes, a sub-auroral polarisation stream that was observed by mid-latitude radars was associated with weak scintillation (defined arbitrarily as σΦ < 0.5 rad). In the auroral zone, moderate scintillation coincided with auroral breakups observed by an all-sky imager, a riometer and a magnetometer in Yellowknife. To overcome the limited geographic coverage by GISTMs other GNSS data sampled at 1 Hz can be used to obtain scintillation proxy indices. In this study, a phase scintillation proxy index (delta phase rate, DPR) is obtained from 1-Hz data from CHAIN and other GPS receivers. The 50-Hz and 1-Hz phase scintillation indices are correlated. The percentage occurrences of σΦ > 0.1 rad and DPR > 2 mm s−1, both mapped as a function of magnetic latitude and magnetic local time, are very similar.

Motions of neutral hydrogen at high latitudes

1967 ◽  
Vol 31 ◽  
pp. 265-278 ◽  
Author(s):  
A. Blaauw ◽  
I. Fejes ◽  
C. R. Tolbert ◽  
A. N. M. Hulsbosch ◽  
E. Raimond
Keyword(s):  
Surface Density ◽  
Velocity Dispersion ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
High Latitudes ◽  
Low Velocity

Earlier investigations have shown that there is a preponderance of negative velocities in the hydrogen gas at high latitudes, and that in certain areas very little low-velocity gas occurs. In the region 100° &lt;l&lt; 250°, + 40° &lt;b&lt; + 85°, there appears to be a disturbance, with velocities between - 30 and - 80 km/sec. This ‘streaming’ involves about 3000 (r/100)2solar masses (rin pc). In the same region there is a low surface density at low velocities (|V| &lt; 30 km/sec). About 40% of the gas in the disturbance is in the form of separate concentrations superimposed on a relatively smooth background. The number of these concentrations as a function of velocity remains constant from - 30 to - 60 km/sec but drops rapidly at higher negative velocities. The velocity dispersion in the concentrations varies little about 6·2 km/sec. Concentrations at positive velocities are much less abundant.

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