scholarly journals Mapping of the quasi-periodic oscillations at the flank magnetopause into the ionosphere

2013 ◽  
Vol 31 (11) ◽  
pp. 1993-2011 ◽  
Author(s):  
E. R. Dougal ◽  
K. Nykyri ◽  
T. W. Moore
Keyword(s):  
Travel Time ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Radar Data ◽  
Alfven Wave ◽  
Periodic Oscillations ◽  
Cluster Data ◽  
Magnetic Field Model ◽  
Magnetometer Data ◽  
Order Of Magnitude

Abstract. We have estimated the ionospheric location, area, and travel time of quasi-periodic oscillations originating from the magnetospheric flanks. This was accomplished by utilizing global and local MHD models and Tsyganenko semi-empirical magnetic field model on multiple published and four new cases believed to be caused by the Kelvin–Helmholtz Instability. Finally, we used auroral, magnetometer, and radar instruments to observe the ionospheric signatures. The ionospheric magnetic latitude determined using global MHD and Tsyganenko models ranged from 58.3–80.2 degrees in the Northern Hemisphere and −59.6 degrees to −83.4 degrees in the Southern Hemisphere. The ionospheric magnetic local time ranged between 5.0–13.8 h in the Northern Hemisphere and 1.3–11.9 h in the Southern Hemisphere. Typical Alfvén wave travel time from spacecraft location to the closest ionosphere ranged between 0.6–3.6 min. The projected ionospheric size calculated at an altitude of 100 km ranged from 47–606 km, the same order of magnitude as previously determined ionospheric signature sizes. Stationary and traveling convection vortices were observed in SuperDARN radar data in both hemispheres. The vortices were between 1000–1800 km in size. Some events were located within the ionospheric footprint ranges. Pc5 magnetic oscillations were observed in SuperMAG magnetometer data in both hemispheres. The oscillations had periods between 4–10 min with amplitudes of 3–25 nT. They were located within the ionospheric footprint ranges. Some ground magnetometer data power spectral density peaked at frequencies within one tenth of a mHz of the peaks found in the corresponding Cluster data. These magnetometer observations were consistent with previously published results.

scholarly journals Comment on “A comparison of catchment travel times and storage deduced from deuterium and tritium tracers using StorAge Selection functions” by Rodriguez et al. (2021)

2021 ◽  
Vol 25 (12) ◽  
pp. 6333-6338
Author(s):  
Michael Kilgour Stewart ◽  
Uwe Morgenstern ◽  
Ian Cartwright
Keyword(s):  
Stable Isotopes ◽  
Travel Time ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Travel Times ◽  
Catchment Hydrology ◽  
Important Development ◽  
Combined Use ◽  
And Storage

Abstract. The combined use of deuterium and tritium to determine travel time distributions (TTDs) in streams is an important development in catchment hydrology (Rodriguez et al., 2021). This comment takes issue with Rodriguez et al.'s assertion that the truncation hypothesis may not hold for catchments in general, i.e. that the use of stable isotopes alone may not lead to underestimation of travel times or storage compared to tritium. We discuss reasons why the truncation hypothesis may not appear to hold for the catchment studied by Rodriguez et al. (2021) but could still apply to the majority of catchments. We also discuss more generally future applications of tritium in Northern Hemisphere and Southern Hemisphere catchments.

scholarly journals Variations in the occurrence of SuperDARN F region echoes

2014 ◽  
Vol 32 (2) ◽  
pp. 147-156 ◽  
Author(s):  
M. Ghezelbash ◽  
R. A. D. Fiori ◽  
A V. Koustov
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Local Time ◽  
Northern Hemisphere ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Radar Data ◽  
Occurrence Rate ◽  
Major Focus ◽  
F Region

Abstract. The occurrence of F region ionospheric echoes observed by a number of SuperDARN HF radars is analyzed statistically in order to infer solar cycle, seasonal, and diurnal trends. The major focus is on Saskatoon radar data for 1994–2012. The distribution of the echo occurrence rate is presented in terms of month of observation and magnetic local time. Clear repetitive patterns are identified during periods of solar maximum and solar minimum. For years near solar maximum, echoes are most frequent near midnight during winter. For years near solar minimum, echoes occur more frequently near noon during winter, near dusk and dawn during equinoxes and near midnight during summer. Similar features are identified for the Hankasalmi and Prince George radars in the northern hemisphere and the Bruny Island TIGER radar in the southern hemisphere. Echo occurrence for the entire SuperDARN network demonstrates patterns similar to patterns in the echo occurrence for the Saskatoon radar and for other radars considered individually. In terms of the solar cycle, the occurrence rate of nightside echoes is shown to increase by a factor of at least 3 toward solar maximum while occurrence of the near-noon echoes does not significantly change with the exception of a clear depression during the declining phase of the solar cycle.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

scholarly journals Evaluation of Fengyun-4A Lightning Mapping Imager (LMI) Performance during Multiple Convective Episodes over Beijing

2021 ◽  
Vol 13 (9) ◽  
pp. 1746
Author(s):  
Zhixiong Chen ◽  
Xiushu Qie ◽  
Juanzhen Sun ◽  
Xian Xiao ◽  
Yuxin Zhang ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Detection Efficiency ◽  
Ground Truth ◽  
Radar Data ◽  
Detection Capability ◽  
Cloud Properties ◽  
Order Of Magnitude ◽  
Total Lightning ◽  
Matching Criteria ◽  
Event Based

This study investigates the characteristics of space-borne Lightning Mapping Imager (LMI) lightning products and their relationships with cloud properties using ground-based total lightning observations from the Beijing Broadband Lightning Network (BLNET) and cloud information from S-band Doppler radar data. LMI showed generally consistent lightning spatial distributions with those of BLNET, and yielded a considerable lightning detection capability over regions with complex terrain. The ratios between the LMI events, groups and flashes were approximately 9:3:1, and the number of LMI-detected flashes was roughly one order of magnitude smaller than the number of BLNET-detected flashes. However, in different convective episodes, the LMI detection capability was likely to be affected by cloud properties, especially in strongly electrified convective episodes associated with frequent lightning discharging and thick cloud depth. As a result, LMI tended to detect lightning flashes located in weaker and shallower cloud portions associated with fewer cloud shielding effects. With reference to the BLNET total lightning data as the ground truth of observation (both intra-cloud lightning and cloud-to-ground lightning flashes), the LMI event-based detection efficiency (DE) was estimated to reach 28% under rational spatiotemporal matching criteria (1.5 s and 65 km) over Beijing. In terms of LMI flash-based DE, it was much reduced compared with event-based DE. The LMI flash-based ranged between 1.5% and 3.5% with 1.5 s and 35–65 km matching scales. For 330 ms and 35 km, the spatiotemporal matching criteria used to evaluate Geostationary Lightning Mapper (GLM), the LMI flash-based DE was smaller (<1%).

scholarly journals First results of low frequency electromagnetic wave detector of TC-2/Double Star program

2005 ◽  
Vol 23 (8) ◽  
pp. 2803-2811 ◽  
Author(s):  
J. B. Cao ◽  
Z. X. Liu ◽  
J. Y. Yang ◽  
C. X. Yian ◽  
Z. G. Wang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Geomagnetic Storms ◽  
Low Frequency ◽  
Wave Detector ◽  
Ion Cyclotron Waves ◽  
Satellite Platform ◽  
Ion Cyclotron ◽  
First Results

Abstract. LFEW is a low frequency electromagnetic wave detector mounted on TC-2, which can measure the magnetic fluctuation of low frequency electromagnetic waves. The frequency range is 8 Hz to 10 kHz. LFEW comprises a boom-mounted, three-axis search coil magnetometer, a preamplifier and an electronics box that houses a Digital Spectrum Analyzer. LFEW was calibrated at Chambon-la-Forêt in France. The ground calibration results show that the performance of LFEW is similar to that of STAFF on TC-1. The first results of LFEW show that it works normally on board, and that the AC magnetic interference of the satellite platform is very small. In the plasmasphere, LFEW observed the ion cyclotron waves. During the geomagnetic storm on 8 November 2004, LFEW observed a wave burst associated with the oxygen ion cyclotron waves. This observation shows that during geomagnetic storms, the oxygen ions are very active in the inner magnetosphere. Outside the plasmasphere, LFEW observed the chorus on 3 November 2004. LFEW also observed the plasmaspheric hiss and mid-latitude hiss both in the Southern Hemisphere and Northern Hemisphere on 8 November 2004. The hiss in the Southern Hemisphere may be the reflected waves of the hiss in the Northern Hemisphere.

On a possible geological cause of changes in the position of the axis of the earth's crust

1867 ◽  
Vol 15 ◽  
pp. 46-54 ◽  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Earth’S Crust ◽  
The Subject ◽  
Earth's Crust ◽  
Geological Observation

At a time when the causes which have led to climatal changes in various parts of the globe are the subject of so much discussion, but little apology is needed for calling the attention of this Society to what possibly may have been one of these causes, though it has apparently hitherto escaped observation. That great changes of climate have taken place, at all events in the northern hemisphere of the globe, is one of the best established facts of geology, and that corresponding changes have not been noticed to the same extent in the southern hemisphere may possibly be considered as due, rather to a more limited amount of geological observation, than to an absence of the phenomena indicative of such alterations in climatal con­ditions having occurred.

scholarly journals Interannual variability of precipitable water

1996 ◽  
Vol 14 (4) ◽  
pp. 464-467 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Precipitable Water ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Zonal Winds ◽  
Low Latitudes ◽  
Linear Trends

Abstract. The 12-month running means of the surface-to-500 mb precipitable water obtained from analysis of radiosonde data at seven selected locations showed three types of variability viz: (1) quasi-biennial oscillations; these were different in nature at different latitudes and also different from the QBO of the stratospheric tropical zonal winds; (2) decadal effects; these were prominent at middle and high latitudes and (3) linear trends; these were prominent at low latitudes, up trends in the Northern Hemisphere and downtrends in the Southern Hemisphere.

scholarly journals Subauroral red arcs as a conjugate phenomenon: comparison of OV1-10 satellite data with numerical calculations

1997 ◽  
Vol 15 (8) ◽  
pp. 984-998 ◽  
Author(s):  
A. V. Pavlov
Keyword(s):  
Electron Density ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Atomic Oxygen ◽  
Major Ions ◽  
Integral Intensity ◽  
Rate Coefficients ◽  
Vibrationally Excited ◽  
Vibrational Distribution ◽  
Vibrational Levels

Abstract. This study compares the OV1-10 satellite measurements of the integral airglow intensities at 630 nm in the SAR arc regions observed in the northern and southern hemisphere as a conjugate phenomenon, with the model results obtained using the time-dependent one-dimensional mathematical model of the Earth ionosphere and plasmasphere (the IZMIRAN model) during the geomagnetic storm of the period 15–17 February 1967. The major enhancements to the IZMIRAN model developed in this study are the inclusion of He+ ions (three major ions: O+, H+, and He+, and three ion temperatures), the updated photochemistry and energy balance equations for ions and electrons, the diffusion of NO+ and O2+ ions and O(1D) and the revised electron cooling rates arising from their collisions with unexcited N2, O2 molecules and N2 molecules at the first vibrational level. The updated model includes the option to use the models of the Boltzmann or non-Boltzmann distributions of vibrationally excited molecular nitrogen. Deviations from the Boltzmann distribution for the first five vibrational levels of N2 were calculated. The calculated distribution is highly non-Boltzmann at vibrational levels v > 2 and leads to a decrease in the calculated electron density and integral intensity at 630 nm in the northern and southern hemispheres in comparison with the electron density and integral intensity calculated using the Boltzmann vibrational distribution of N2. It is found that the intensity at 630 nm is very sensitive to the oxygen number densities. Good agreement between the modelled and measured intensities is obtained provided that at all altitudes of the southern hemisphere a reduction of about factor 1.35 in MSIS-86 atomic oxygen densities is included in the IZMIRAN model with the non-Boltzmann vibrational distribution of N2. The effect of using of the O(1D) diffusion results in the decrease of 4–6% in the calculated integral intensity of the northern hemisphere and 7–13% in the calculated integral intensity of the southern hemisphere. It is found that the modelled intensities of the southern hemisphere are more sensitive to the assumed values of the rate coefficients of O+(4S) ions with the vibrationally excited nitrogen molecules and quenching of O+(2D) by atomic oxygen than the modelled intensities of the northern hemisphere.

On Growing a Journal

Transfers ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 36-48
Author(s):  
Georgine Clarsen
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Academic Journal ◽  
Arts And Humanities ◽  
The Arts ◽  
National Life ◽  
Feminist Historian

In this era of the neo-liberal academy, establishing an academic journal is a labor of love and hope. In this article, I celebrate the dedication and commitment of its many contributors and reflect on the value of the arts and humanities to the mobilities paradigm. I do that from the perspective of a feminist historian from a settler colonial polity in the southern hemisphere, where uneven mobilities and the violence of dispossession continue to shape national life. I consider how a mobilities framework that derived from the northern hemisphere has spoken to the intellectual and political projects that played out in a colonial settler nation in the southern hemisphere.

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