scholarly journals Observation of continuum radiations from the Cluster fleet: first results from direction finding

2004 ◽  
Vol 22 (7) ◽  
pp. 2607-2624 ◽  
Author(s):  
P. M. E. Décréau ◽  
C. Ducoin ◽  
G. Le Rouzic ◽  
O. Randriamboarison ◽  
J.-L. Rauch ◽  
...  

Abstract. The Cluster fleet offers the first possibility of comparing non-thermal terrestrial continuum radiation from similarly equipped nearby observation points. A very rich data set has already been acquired on the Cluster polar orbit, between 4 and 19 Earth radii geocentric distances, and preliminary analysis has been carried out on these emissions. We focus in this paper on direction finding performed from all four spacecraft as a means to locate the position of the sources of this continuum radiation. Directions are derived from spin modulation properties, under the usual analysis assumptions of the wave vector of the radiation lying in the plane containing the spin axis and the antenna position at electric field minimum. All the spin axes of the four Cluster spacecraft are aligned perpendicular to the ecliptic, thus the aligned spacecraft antenna spin planes provide redundant 2-D views of the propagation path of the radiation and source location. Convincing 2-D triangulation results have been obtained in the vicinity of the source region. In addition, the out of spin plane component of the wave vector reveals itself to a certain extent through directivity characteristics compared at different distances of the spin plane to the ecliptic. The four case events studied (two of them taken near apogee, the other two near perigee) have confirmed general properties derived from previous observations: trapping in the lower frequency range, radiation escaping into the magnetosheath region in the higher frequency range. All propagation directions are compatible with source positions in the plasmapause region, however, at a significant distance from the equator in one case. Our observations have also revealed new properties, like the importance of small-scale density irregularities in the local amplification of continuum radiation. We conclude that more detailed generation and propagation models are needed to fit the observations.

2021 ◽  
Vol 11 (4) ◽  
pp. 1431
Author(s):  
Sungsik Wang ◽  
Tae Heung Lim ◽  
Kyoungsoo Oh ◽  
Chulhun Seo ◽  
Hosung Choo

This article proposes a method for the prediction of wide range two-dimensional refractivity for synthetic aperture radar (SAR) applications, using an inverse distance weighted (IDW) interpolation of high-altitude radio refractivity data from multiple meteorological observatories. The radio refractivity is extracted from an atmospheric data set of twenty meteorological observatories around the Korean Peninsula along a given altitude. Then, from the sparse refractive data, the two-dimensional regional radio refractivity of the entire Korean Peninsula is derived using the IDW interpolation, in consideration of the curvature of the Earth. The refractivities of the four seasons in 2019 are derived at the locations of seven meteorological observatories within the Korean Peninsula, using the refractivity data from the other nineteen observatories. The atmospheric refractivities on 15 February 2019 are then evaluated across the entire Korean Peninsula, using the atmospheric data collected from the twenty meteorological observatories. We found that the proposed IDW interpolation has the lowest average, the lowest average root-mean-square error (RMSE) of ∇M (gradient of M), and more continuous results than other methods. To compare the resulting IDW refractivity interpolation for airborne SAR applications, all the propagation path losses across Pohang and Heuksando are obtained using the standard atmospheric condition of ∇M = 118 and the observation-based interpolated atmospheric conditions on 15 February 2019. On the terrain surface ranging from 90 km to 190 km, the average path losses in the standard and derived conditions are 179.7 dB and 182.1 dB, respectively. Finally, based on the air-to-ground scenario in the SAR application, two-dimensional illuminated field intensities on the terrain surface are illustrated.


2021 ◽  
Vol 503 (2) ◽  
pp. 2688-2705
Author(s):  
C Doux ◽  
E Baxter ◽  
P Lemos ◽  
C Chang ◽  
A Alarcon ◽  
...  

ABSTRACT Beyond ΛCDM, physics or systematic errors may cause subsets of a cosmological data set to appear inconsistent when analysed assuming ΛCDM. We present an application of internal consistency tests to measurements from the Dark Energy Survey Year 1 (DES Y1) joint probes analysis. Our analysis relies on computing the posterior predictive distribution (PPD) for these data under the assumption of ΛCDM. We find that the DES Y1 data have an acceptable goodness of fit to ΛCDM, with a probability of finding a worse fit by random chance of p = 0.046. Using numerical PPD tests, supplemented by graphical checks, we show that most of the data vector appears completely consistent with expectations, although we observe a small tension between large- and small-scale measurements. A small part (roughly 1.5 per cent) of the data vector shows an unusually large departure from expectations; excluding this part of the data has negligible impact on cosmological constraints, but does significantly improve the p-value to 0.10. The methodology developed here will be applied to test the consistency of DES Year 3 joint probes data sets.


2012 ◽  
Vol 72 (1) ◽  
pp. 134-167 ◽  
Author(s):  
SHEILAGH OGILVIE ◽  
MARKUS KÜPKER ◽  
JANINE MAEGRAITH

The “less-developed” interior of early modern Europe, especially the rural economy, is often regarded as financially comatose. This article investigates this view using a rich data set of marriage and death inventories for seventeenth-century Germany. It first analyzes the characteristics of debts, examining borrowing purposes, familial links, communal ties, and documentary instruments. It then explores how borrowing varied with gender, age, marital status, occupation, date, and asset portfolio. It finds that ordinary people, even in a “less-developed” economy in rural central Europe, sought to invest profitably, smooth consumption, bridge low liquidity, and hold savings in financial form.


2014 ◽  
Vol 32 (6) ◽  
pp. 677-687 ◽  
Author(s):  
R. Pottelette ◽  
M. Berthomier ◽  
J. Pickett

Abstract. In the auroral kilometric radiation (AKR) source region, acceleration layers narrow in altitude and associated with parallel field-aligned potential drops of several kV can be identified by using both particles and wave-field high time-resolution measurements from the Fast Auroral SnapshoT explorer spacecraft (FAST). These so-called double layers (DLs) are recorded around density enhancements in the auroral cavity, where the enhancement can be at the edge of the cavity or even within the cavity at a small scale. Once immersed in the plasma, DLs necessarily accelerate particles along the magnetic field lines, thereby generating locally strong turbulent processes leading to the formation of nonlinear phase space holes. The FAST data reveal the asymmetric character of the turbulence: the regions located on the high-potential side of the DLs are characterized by the presence of electron holes, while on the low-potential side, ion holes are recorded. The existence of these nonlinear phase space holes may affect the AKR radiation pattern in the neighbourhood of a DL where the electron distribution function is drastically different from a horseshoe shape. We present some observations which illustrate the systematic generation of elementary radiation events occurring significantly above the local electron gyrofrequency in the presence of electron holes. These fine-scale AKR radiators are associated with a local electron distribution which presents a pronounced beam-like shape.


2021 ◽  
Author(s):  
◽  
Ellen Yarrow

<p>This study explores the relationship between professional contractors and the permanent employees they work with at organisations in New Zealand. This thesis uses two concepts, organisational socialisation and the psychological contract, as lenses through which the working relationship is explored. The 20th century notion of standard employment has largely been eroded, giving way to different forms of non-standard work. Professional contractors are now found performing a variety of roles in many organisations across this country. Many are doing the work of permanent employees, but they are neither employees nor permanent. Professional contractors are a type of non-standard, transient worker. As part of a blended workforce, professional contractors work alongside permanent employees, but little is known about how they work together.  This qualitative study involves 49 face-to-face interviews with professional contractors, permanent employees and managers working in the Information Technology (IT) divisions of 10 organisations in three major cities in New Zealand. This research design results in a rich data set. The data collected was subject to analysis using the software NVIVO. This data was analysed in relation to the literature on organisational socialisation and the psychological contract to further explain the working relationship between professional contractors and permanent employees.  The findings reveal professional contractors’ experience of Van Maanen’s (1979) socialisation tactics were: collective, informal, variable, random and serial. It was found that an organisation’s policy sets the tone for the treatment (induction, inclusion and management) of professional contractors. According to the professional contractors interviewed, the Chao, O'Leary-Kelly, Wolf, Klein, and Gardner (1994) socialisation content dimensions that are important are structure, culture and values and language but history was not considered important. According to the managers interviewed, contractors need to know about the processes and procedures of the client organisation, have strong technical skills and industry, sector or domain knowledge. It was found that the indicator of adjustment ‘acceptance by insiders’ (Bauer & Erdogan, 2012) may be a sign that the contractor is adjusting to their new role but it is not essential. A new indicator of adjustment for professional contractors – output – clearly emerged from the data. The notion of ‘time to productivity’ is highly relevant to professional contractors and three factors affecting it are identified (contractor capability, role complexity and organisation readiness). Another important finding is that permanent employees play a key role as socialisation agents (Feldman, 1994; Jones, 1983; Van Maanen, 1978) in the socialisation of professional contractors. Surprisingly, it was found that other professional contractors also act as socialisation agents assisting the newcomer to adjust. It was found that proactive socialisation is particularly important for professional contractors. Together these findings establish the need to reconceptualise organisational socialisation for professional contractors specifically.  The second part of this thesis explores the psychological contract by asking interviewees about their mutual expectations. The expectations of each of the three parties (managers, professional contractors, and permanent employees) are subtly different, potentially influencing the psychological contract they develop. Permanent employees expect great things, professionalism and independence from professional contractors. Managers expect speed, professionalism and value for money from contractors. On the other hand, professional contractors simply expect to be treated with respect by their colleagues. Professional contractors expect to be given autonomy by their managers and support or guidance, should they require it. This study was not able to ascertain what type of psychological contract a professional contractor may develop. It is possible that a professional contractor develops a hybrid psychological contract. Alternatively, it is possible that a professional contractor’s psychological contract moves between the types developed by Rousseau (1995) over the course of their term with the client organisation. The insights gained by exploring the expectations of professional contractors, permanent employees and their managers are two-fold. Firstly, these expectations provide a valuable insight into the working relationship. Secondly, the exploration of a breach or violation of the psychological contract indicates that a malleable psychological contract (one that will shift or adjust) is less likely to manifest a breach or violation. Therefore, it is better for a professional contractor to develop and maintain a malleable rather than rigid psychological contract.  This study’s findings highlight the interrelationship between organisational socialisation and the psychological contract. This thesis asserts that the working relationship between professional contractors and permanent employees is specifically influenced by the socialisation of contractors as newcomers and in the mutual expectations, which form the psychological contract. As a result, it contributes to theorising and understanding of the working relationship between professional contractors and permanent employees. It identifies several tensions in the co-dependent working relationship, which are: time, team, treatment and training. This study has implications for Human Resource practitioners and managers because there is a need for corporate or HR policy relating to the treatment professional contractors. The use of organisational socialisation and the psychological contract as lenses with which the working relationship is explored is both original and meaningful.</p>


2005 ◽  
Vol 2 (4) ◽  
pp. 417-435 ◽  
Author(s):  
A. Henry-Edwards ◽  
M. Tomczak

Abstract. A new water mass analysis technique is used to analyse the BATS oceanographic data set in the Sargasso Sea of 1988-1998 for changes in Labrador Sea Water (LSW) properties. The technique is based on a sequential quadratic programming method and requires careful definition of constraints to produce reliable results. Variations in LSW temperature and salinity observed in the Labrador Sea are used to define the constraints. It is shown that to minimize the residuals while matching the observed temperature and salinity changes in the source region the nitrate concentration in the Labrador Sea has to be allowed to vary as well. It is concluded that during the period of investigation nitrate underwent significant variations in the Labrador Sea.


Author(s):  
Petra Koucká Knížová ◽  
Jan Laštovička ◽  
Daniel Kouba ◽  
Zbyšek Mošna ◽  
Katerina Podolská ◽  
...  

The ionosphere represents part of the upper atmosphere. Its variability is observed on a wide-scale temporal range from minutes, or even shorter, up to scales of the solar cycle and secular variations of solar energy input. Ionosphere behavior is predominantly determined by solar and geomagnetic forcing. However, the lower-lying atmospheric regions can contribute significantly to the resulting energy budget. The energy transfer between distant atmospheric parts happens due to atmospheric waves that propagate from their source region up to ionospheric heights. Experimental observations show the importance of the involvement of the lower atmosphere in ionospheric variability studies in order to accurately capture small-scale features of the upper atmosphere. In the Part I Coupling, we provide a brief overview of the influence of the lower atmosphere on the ionosphere and summarize the current knowledge. In the Part II Coupling Evidences Within Ionospheric Plasma—Experiments in Midlatitudes, we demonstrate experimental evidence from mid-latitudes, particularly those based on observations by instruments operated by the Institute of Atmospheric Physics, Czech Academy of Sciences. The focus will mainly be on coupling by atmospheric waves.


Author(s):  
K M Ahtesham Hossain Raju ◽  
Shinji Sato

Response of sand dune when overwashed by tsunami or storm surge, is investigated by conducting small scale laboratory study. Dune consisting of initially wet sand and initially dry sand are tested for three different sand grain sizes. Overtopping of water and the corresponding sediment transport are analyzed. These data set can be used to validate mathematical models associated with dune sediment transport as well as prediction of dune profile.


2020 ◽  
Vol 14 (7) ◽  
pp. 2189-2203
Author(s):  
H. Jakob Belter ◽  
Thomas Krumpen ◽  
Stefan Hendricks ◽  
Jens Hoelemann ◽  
Markus A. Janout ◽  
...  

Abstract. The gridded sea ice thickness (SIT) climate data record (CDR) produced by the European Space Agency (ESA) Sea Ice Climate Change Initiative Phase 2 (CCI-2) is the longest available, Arctic-wide SIT record covering the period from 2002 to 2017. SIT data are based on radar altimetry measurements of sea ice freeboard from the Environmental Satellite (ENVISAT) and CryoSat-2 (CS2). The CCI-2 SIT has previously been validated with in situ observations from drilling, airborne remote sensing, electromagnetic (EM) measurements and upward-looking sonars (ULSs) from multiple ice-covered regions of the Arctic. Here we present the Laptev Sea CCI-2 SIT record from 2002 to 2017 and use newly acquired ULS and upward-looking acoustic Doppler current profiler (ADCP) sea ice draft (VAL) data for validation of the gridded CCI-2 and additional satellite SIT products. The ULS and ADCP time series provide the first long-term satellite SIT validation data set from this important source region of sea ice in the Transpolar Drift. The comparison of VAL sea ice draft data with gridded monthly mean and orbit trajectory CCI-2 data, as well as merged CryoSat-2–SMOS (CS2SMOS) sea ice draft, shows that the agreement between the satellite and VAL draft data strongly depends on the thickness of the sampled ice. Rather than providing mean sea ice draft, the considered satellite products provide modal sea ice draft in the Laptev Sea. Ice drafts thinner than 0.7 m are overestimated, while drafts thicker than approximately 1.3 m are increasingly underestimated by all satellite products investigated for this study. The tendency of the satellite SIT products to better agree with modal sea ice draft and underestimate thicker ice needs to be considered for all past and future investigations into SIT changes in this important region. The performance of the CCI-2 SIT CDR is considered stable over time; however, observed trends in gridded CCI-2 SIT are strongly influenced by the uncertainties of ENVISAT and CS2 and the comparably short investigation period.


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