STUDY OF MID-LATITUDE POSITIVE BAYS DURING SUBSTORMS OVER SCANDINAVIA – A CASE STUDY

2021 ◽  
Vol 44 ◽  
pp. 28-31
Author(s):  
V. Guineva ◽  
◽  
I. Despirak ◽  
R. Werner ◽  
R. Bojilova ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Speed ◽  
Large Scale ◽  
Slow Solar Wind ◽  
The Earth ◽  
First Case ◽  
The Mean ◽  
The One ◽  
Latitudinal Range

The purpose of this work is to study the midlatitude effects during substorms observed in different interplanetary conditions over Scandinavia. To identify the substorm disturbances, data from the magnetometer networks IMAGE, SuperMAG and INTERMAGNET in the range 31.8° - 75.25° CGMLat and 92° - 104° CGMLon were used. To verify the interplanetary and geomagnetic conditions, data from the CDAWeb OMNI (http://cdaweb.gsfc.nasa.gov/), the catalog of large-scale solar wind phenomena (ftp://ftp.iki.rssi.ru/omni/) and from the WDC for geomagnetism at Kyoto (http://wdc.kugi.kyoto-u.ac.jp/index.html) were taken. Two isolated substorms were chosen, with different intensity: ALmin values ~ -270 nT and ~ -1300 nT, respectively. The first substorm occured on 6 February 2018, at 21:25 UT, under quiet conditions: during slow solar wind streams. The second substorm, at 19:10 UT on 27 September 2020, originated under moderately disturbed conditions: during a high-speed stream (HSS) in the solar wind, just after the passage of EJECTA by the Earth. It was found out, that the latitude of the bay sign conversion from negative to positive values in the case of quiet solar wind conditions, appeared at latitude, 7° higher than the one in the case of disturbed conditions. In both cases, the amplitude of the positive bays, after a maximum near the sign conversion latitude decreased gradually towards the lower latitudes, with a difference between the minimal and maximal amplitude of about 50%. The magnetic bays kept their duration throughout the whole latitudinal range, ~115 min. for the first case and ~ 60 min. for the second one. It was ascertained, that the mean positive bays amplitude in the case of disturbed conditions was 4 times higher than the amplitude during quiet conditions.

scholarly journals Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

2009 ◽  
Vol 27 (10) ◽  
pp. 3909-3922 ◽  
Author(s):  
A. B. Galvin ◽  
M. A. Popecki ◽  
K. D. C. Simunac ◽  
L. M. Kistler ◽  
L. Ellis ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Large Scale ◽  
Slow Solar Wind ◽  
Transient Event ◽  
Large Scale Structures ◽  
Close Proximity ◽  
Scale Structures

Abstract. STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

scholarly journals The influence of solar wind on extratropical cyclones – Part 1: Wilcox effect revisited

2009 ◽  
Vol 27 (1) ◽  
pp. 1-30 ◽  
Author(s):  
P. Prikryl ◽  
V. Rušin ◽  
M. Rybanský
Keyword(s):  
Time Series ◽  
Solar Wind ◽  
Northern Hemisphere ◽  
High Speed ◽  
Coronal Holes ◽  
Extratropical Cyclones ◽  
Sector Boundary ◽  
Speed Solar Wind ◽  
The Mean ◽  
High Speed Solar Wind

Abstract. A sun-weather correlation, namely the link between solar magnetic sector boundary passage (SBP) by the Earth and upper-level tropospheric vorticity area index (VAI), that was found by Wilcox et al. (1974) and shown to be statistically significant by Hines and Halevy (1977) is revisited. A minimum in the VAI one day after SBP followed by an increase a few days later was observed. Using the ECMWF ERA-40 re-analysis dataset for the original period from 1963 to 1973 and extending it to 2002, we have verified what has become known as the "Wilcox effect" for the Northern as well as the Southern Hemisphere winters. The effect persists through years of high and low volcanic aerosol loading except for the Northern Hemisphere at 500 mb, when the VAI minimum is weak during the low aerosol years after 1973, particularly for sector boundaries associated with south-to-north reversals of the interplanetary magnetic field (IMF) BZ component. The "disappearance" of the Wilcox effect was found previously by Tinsley et al. (1994) who suggested that enhanced stratospheric volcanic aerosols and changes in air-earth current density are necessary conditions for the effect. The present results indicate that the Wilcox effect does not require high aerosol loading to be detected. The results are corroborated by a correlation with coronal holes where the fast solar wind originates. Ground-based measurements of the green coronal emission line (Fe XIV, 530.3 nm) are used in the superposed epoch analysis keyed by the times of sector boundary passage to show a one-to-one correspondence between the mean VAI variations and coronal holes. The VAI is modulated by high-speed solar wind streams with a delay of 1–2 days. The Fourier spectra of VAI time series show peaks at periods similar to those found in the solar corona and solar wind time series. In the modulation of VAI by solar wind the IMF BZ seems to control the phase of the Wilcox effect and the depth of the VAI minimum. The mean VAI response to SBP associated with the north-to-south reversal of BZ is leading by up to 2 days the mean VAI response to SBP associated with the south-to-north reversal of BZ. For the latter, less geoeffective events, the VAI minimum deepens (with the above exception of the Northern Hemisphere low-aerosol 500-mb VAI) and the VAI maximum is delayed. The phase shift between the mean VAI responses obtained for these two subsets of SBP events may explain the reduced amplitude of the overall Wilcox effect. In a companion paper, Prikryl et al. (2009) propose a new mechanism to explain the Wilcox effect, namely that solar-wind-generated auroral atmospheric gravity waves (AGWs) influence the growth of extratropical cyclones. It is also observed that severe extratropical storms, explosive cyclogenesis and significant sea level pressure deepenings of extratropical storms tend to occur within a few days of the arrival of high-speed solar wind. These observations are discussed in the context of the proposed AGW mechanism as well as the previously suggested atmospheric electrical current (AEC) model (Tinsley et al., 1994), which requires the presence of stratospheric aerosols for a significant (Wilcox) effect.

How “The Three Rules” guide strategy and investment decisions at Deloitte Consulting LLP

2015 ◽  
Vol 43 (3) ◽  
pp. 7-14 ◽  
Author(s):  
Jim Moffatt
Keyword(s):  
Design Methodology ◽  
Large Scale ◽  
Investment Decisions ◽  
Decision Makers ◽  
Research Project ◽  
Content Type ◽  
First Case ◽  
Practical Implications ◽  
Thought Leadership

Purpose – This case example looks at how Deloitte Consulting applies the Three Rules synthesized by Michael Raynor and Mumtaz Ahmed based on their large-scale research project that identified patterns in the way exceptional companies think. Design/methodology/approach – The Three Rules concept is a key piece of Deloitte Consulting’s thought leadership program. So how are the three rules helping the organization perform? Now that research has shown how exceptional companies think, CEO Jim Moffatt could address the question, “Does Deloitte think like an exceptional company?” Findings – Deloitte has had success with an approach that promotes a bias towards non-price value over price and revenue over costs. Practical implications – It’s critical that all decision makers in an organization understand how decisions that are consistent with the three rules have contributed to past success as well as how they can apply the rules to difficult challenges they face today. Originality/value – This is the first case study written from a CEO’s perspective that looks at how the Three Rules approach of Michael Raynor and Mumtaz Ahmed can foster a firm’s growth and exceptional performance.

Ion-scale break of the plasma fluctuation spectra in different large-scale solar wind streams

2021 ◽  
Author(s):  
Maria Riazantseva ◽  
Liudmila Rakhmanova ◽  
Yuri Yermolaev ◽  
Irina Lodkina ◽  
Georgy Zastenker ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Plasma Heating ◽  
Coronal Holes ◽  
Magnetic Clouds ◽  
Alfven Wave ◽  
Slow Solar Wind ◽  
P Value ◽  
High Temporal Resolution ◽  
Turbulent Cascade

<p>Appearance of measurements of the interplanetary medium parameters with high temporal resolution gave rise to a variety of investigations of turbulent cascade at ion kinetic scales at which processes of plasma heating was believed to operate. Our recent studies based on high frequency plasma measurements at Spektr-R spacecraft have shown that the turbulent cascade was not stable and dynamically changed depending on the plasma conditions in different large-scale solar wind structures. These changes was most significant at the kinetic scales of the turbulent cascade. Slow undisturbed solar wind was characterized by the consistency of the spectra to the predictions of the kinetic Alfven wave turbulence model. On the other hand, the discrepancy between the model predictions and registered spectra were found in stream interaction regions characterized by crucial steepening of spectra at the kinetic scales with slopes having values up to -(4-5). This discrepancy was clearly shown for plasma compression region Sheath in front of the magnetic clouds and CIR in front of high speed streams associated with coronal holes. Present study is focused on the break preceding the kinetic scales. Currently the characteristic plasma parameters associated with the formation of the break is still debated. Number of studies demonstrated that the break was consistent with distinct characteristic frequencies for different values ​​of the plasma proton parameter beta βp. Present study consider the ratio between the break frequency determined for ion flux fluctuation spectra according to Spektr-R data and several characteristic plasma frequencies used traditionally in such cases. The value of this ratio is statistically compared for different large-scale solar wind streams. We analyze both the classical spectrum view with two slopes and one break and the spectrum with flattening between magnetohydrodynamic and kinetic scales.  Our results show that for the Sheath and CIR regions characterized typically by βp ≤1 the break corresponds statistically to the frequency determined by the proton gyroradius. At the same time such correspondence are not observed either for the undisturbed slow solar wind with similar βp value or for disturbed flows associated with interplanetary manifestations of coronal mass ejections, where βp << 1. The results also shows that in slow undisturbed solar wind the break is closer to the frequency determined by the inertial proton length. Thus, apparently the transition between streams of different speeds may result in the change of dissipation regimes and plays role in plasma heating at these areas. This work was supported by the RFBR grant No. 19-02-00177a</p>

482Direct oral anticoagulant rivaroxaban in very old and frail patients: A one-year prospective follow-up of a large-scale cohort (SAFIR-AC)

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
O Hanon ◽  
J Vidal ◽  
E Chaussade ◽  
J P David ◽  
N Boulloche ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Major Bleeding ◽  
Large Scale ◽  
Bleeding Risk ◽  
Geriatric Population ◽  
Very Old ◽  
The Mean ◽  
One Year ◽  
The One

Abstract Background/Introduction Age is one of the strongest predictors/risk factors for ischemic stroke in subjects with atrial fibrillation (AF). Direct oral anticoagulants (DOACs) have been shown to be effective in the prevention of this condition; however, clinical evidence on bleeding risk with this therapeutic strategy in very old and frail geriatric patients is poor. Purpose To assess bleeding risk in French geriatric patients aged ≥80 years and diagnosed with AF newly treated with rivaroxaban. Methods Subjects, presenting to one of 33 geriatric centers, with non-valvular AF and recent initiation of a treatment with rivaroxaban were enrolled in the study and followed-up every 3 months for 12 months. Clinical and routine laboratory data and evaluation scores, such as HAS-BLED, HEMORR2HAGES, ATRIA, and CHA2DS2-VASc, as well as comprehensive geriatric evaluation were reported. Major bleeding, as defined in ROCKET AF study, was reported at each visit, and this primary outcome was adjudicated by an independent committee. Results of this cohort were compared with findings from a similar cohort treated with vitamin K antagonists (VKAs) from the same centers (n=924). Results A total of 1045 subjects were enrolled in the study of whom 995 (95%) had a one-year follow-up (analyzed population). The mean (standard deviation (SD)) age was 86.0 (4.3) years, with the majority of patients being female (61%), 23% aged 90 years or older, and 48% having an estimated glomerular filtration rate (eGFR) <50 mL/min. The main comorbidities were hypertension in 77% of subjects, malnutrition 49%, anemia 43%, dementia 39%, heart failure 36%, and falls 27%. The mean (SD) score for CHA2DS2-VASc was 4.8 (1.4), HAS-BLED 2.4 (0.9), Mini-Mental State Examination (MMSE) 21.5 (6.9), Activities of Daily Living (ADL) 4.4 (1.9), and Charlson Comorbidity Index 6.7 (2.0). The one-year rate of major bleeding events was 6.4% of which 0.8% were fatal and 1.1% intracranial hemorrhages (ICH), whereas the one-year rate of ischemic stroke was 1.4% and all-cause mortality 17.9%. Computed with VKA cohort findings and adjusted for age, gender, eGFR and Charlson score, this would result in a hazard ratio of 0.54 (95% confidence interval [CI], 0.38 to 0.78) for major bleeding, 0.36 (0.17 to 0.76) for ICH, 0.62 (0.29 to 1.33) for ischemic stroke, and 0.82 (0.65 to 1.02) for all-cause mortality, in favor of rivaroxaban. Conclusions This is the first large-scale prospective study in geriatric population in AF subjects treated with DOAC (rivaroxaban) Major bleeding risk appeared higher in very old than younger population, however major bleeding and ICH rates were significantly lower with rivaroxaban than with VKAs when used in the same geriatric population. This study indicates that Rivaroxaban can be used in very old and frail patients for the treatment of non-valvular AF. Acknowledgement/Funding Unrestricted grant from Bayer

scholarly journals High-speed solar wind stream effects on the topside ionosphere over Arecibo: A case study during solar minimum

2017 ◽  
Vol 44 (15) ◽  
pp. 7607-7617 ◽  
Author(s):  
Rajkumar Hajra ◽  
Bruce T. Tsurutani ◽  
Christiano G. M. Brum ◽  
Ezequiel Echer
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
High Speed ◽  
Topside Ionosphere ◽  
Solar Wind Stream ◽  
Speed Solar Wind ◽  
High Speed Solar Wind

scholarly journals Spatial distribution of tracers for optical sensing of stream surface flow

2020 ◽  
Author(s):  
Alonso Pizarro ◽  
Silvano F. Dal Sasso ◽  
Matthew Perks ◽  
Salvatore Manfreda
Keyword(s):  
Large Scale ◽  
Optical Sensing ◽  
Surface Flow ◽  
Seeding Density ◽  
Stream Surface ◽  
Image Velocimetry ◽  
Level Of Aggregation ◽  
Scale Particle ◽  
The One

Abstract. River monitoring is of particular interest for our society that is facing increasing complexity in water management. Emerging technologies have contributed to opening new avenues for improving our monitoring capabilities, but also generating new challenges for the harmonised use of devices and algorithms. In this context, optical sensing techniques for stream surface flow velocities are strongly influenced by tracer characteristics such as seeding density and level of aggregation. Therefore, a requirement is the identification of how these properties affect the accuracy of such methods. To this aim, numerical simulations were performed to consider different levels of particle aggregation, particle colour (in terms of greyscale intensity), seeding density, and background noise. Two widely used image-velocimetry algorithms were adopted: i) Particle Tracking Velocimetry (PTV), and ii) Large-Scale Particle Image Velocimetry (LSPIV). A descriptor of the seeding characteristics (based on density and aggregation) was introduced based on a newly developed metric π. This value can be approximated and used in practice as π = ν0.1 / (ρ / ρcν1) where ν, ρ, and ρcν1 are the aggregation level, the seeding density, and the converging seeding density at ν = 1, respectively. A reduction of image-velocimetry errors was systematically observed by decreasing the values of π; and therefore, the optimal frame window was defined as the one that minimises π. In addition to numerical analyses, the Basento field case study (located in southern Italy) was considered as a proof-of-concept of the proposed framework. Field results corroborated numerical findings, and an error reduction of about 15.9 and 16.1 % was calculated – using PTV and PIV, respectively – by employing the optimal frame window.

scholarly journals The Dipolar Solar Minimum Corona

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 507
Author(s):  
Daniele Telloni
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Large Scale ◽  
Slow Solar Wind ◽  
Kinetic Temperature ◽  
Solar Cycles ◽  
Heliospheric Observatory ◽  
Oxygen Ions ◽  
Uv Emission ◽  
The Magnetic Field

The large-scale configuration of the UV solar corona at the minimum activity between solar cycles 22 and 23 is explored in this paper. Exploiting a large sample of spectroscopic observations acquired by the Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory in the two-year period of 1996–1997, this work provides the first-ever monochromatic O vi 1032 Å image of the extended corona, and the first-ever two-dimensional maps of the kinetic temperature of oxygen ions and the O vi 1037/1032 Å doublet intensity ratio (a proxy for the outflow velocity of the oxygen component of the solar wind), statistically representative of solar minimum conditions. A clear dipolar magnetic structure, both equator- and axis-symmetric, is distinctly shown to shape the solar minimum corona, both in UV emission and in temperature and expansion rate. This statistical approach allows for robust establishment of the key role played by the magnetic field divergence in modulating the speed and temperature of the coronal flows, and identification of the coronal sources of the fast and slow solar wind.

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