scholarly journals Heating of Solar and Stellar Chromospheres and Coronae by MHD Waves

1992 ◽  
Vol 9 ◽  
pp. 665-666
Author(s):  
Z. E. Musielak
Keyword(s):  
Primary Source ◽  
Stellar Atmospheres ◽  
Satellite Observations ◽  
Mhd Waves ◽  
Observational Constraints ◽  
Strong Magnetic Fields ◽  
Stellar Convection ◽  
Wave Heating ◽  
Recent Developments ◽  
The Mean

Ground-based and satellite observations have shown that all late-type dwarfs possess hot outer envelopes, and that the chromospheric and coronal emissions observed from these envelopes vary significantly for a given, fixed spectral type. In addition, there is growing evidence for nonhomogeneous and locally strong magnetic fields in the atmospheres of these stars. It is obvious that any heating theory must account for these two observational constraints as well as for the mean level of heating.There are at least two general classes of models that deal with the required heating. The first class assumes that outer stellar atmospheres are heated by hydrodynamic (mainly acoustic) or magnctohydrodynamic (MHD) waves, and that these waves are generated by turbulent motions in the stellar convection zones. The second class considers dissipation of currents generated by photospheric motions as the primary source of energy. Neither observation nor theory has been able to definitively determine which one of these two general classes of models dominates in the atmospheric heating. The main aim of this paper is to briefly present recent developments in the MHD wave heating theory. The key problems that will be addressed are: where and how efficiently are MHD waves generated, and how do these waves propagate and dissipate energy?

Plasma Thrombospondin as an Indicator of Intravascular Platelet Activation in Patients with Vasculitis

1987 ◽  
Vol 58 (03) ◽  
pp. 850-852 ◽  
Author(s):  
M B McCrohan ◽  
S W Huang ◽  
J W Sleasman ◽  
P A Klein ◽  
K J Kao
Keyword(s):  
Platelet Activation ◽  
Plasma Levels ◽  
Half Life ◽  
Degradation Products ◽  
Plasma Concentrations ◽  
Primary Source ◽  
Positive Correlation ◽  
Activation Marker ◽  
Fibrin Degradation Products ◽  
The Mean

SummaryThe use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791±1412 ng/ml (mean ± SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59±29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, β-thromboglobulin (P-TG), it was found that the TSP concentration inei eased exponentially as the plasma β-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than β-TG to assess intravascular platelet activation due to its longer circulation half life.

Survey of management practices used by Brazilian dairy farmers and recommendations provided by 43 dairy cattle nutritionists

2019 ◽  
Vol 99 (4) ◽  
pp. 890-904 ◽  
Author(s):  
Diego P. Silva ◽  
Alexandre M. Pedroso ◽  
Murillo C.S. Pereira ◽  
Gustavo P. Bertoldi ◽  
Daniel H.M. Watanabe ◽  
...  
Keyword(s):  
Dairy Cattle ◽  
Health Problem ◽  
Management Practices ◽  
Primary Source ◽  
Dairy Farmers ◽  
Web Based ◽  
Major Health Problem ◽  
Major Health ◽  
Nutritional Recommendations ◽  
The Mean

This work aimed to survey management practices used by dairy farmers and to report nutritional recommendations adopted by 43 dairy cattle nutritionists in Brazil. The web-based survey consisted of 80 questions. Almost 50% of the participants had clients that produce <1000 kg of milk daily and 48.8% had clients who own fewer than 100 dairy cows. Corn was the primary source of grain (97.4%), and 43.9% of the nutritionists included from 41% to 50% concentrate in lactation diets. The mean roughage inclusion in lactation diets was 50.5% and 79% of the nutritionists reported corn silage as the primary roughage source. Average crude protein and rumen-degradable protein concentrations recommended by the nutritionists for lactation diets were 15.7% and 9%, respectively. Average Ca and P concentrations recommended for lactation diets were 0.70% and 0.41%, respectively. The major health problem reported by 83.9% of the nutritionists was mastitis. The present survey provides an overview of management practices adopted by dairy farmers and nutritional recommendations currently applied by dairy cattle nutritionists in Brazil. The most critical points identified were low milk yield, mastitis as the major health problem, lack of proper mixing and delivery of rations, and destination of male calves.

scholarly journals MHD Seismology of the Solar Corona with SOHO and TRACE

2001 ◽  
Vol 203 ◽  
pp. 353-355 ◽  
Author(s):  
V. M. Nakariakov
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Decay Time ◽  
Transport Coefficients ◽  
Mhd Waves ◽  
The Mean ◽  
Temporal And Spatial ◽  
Wave Phenomena ◽  
The Magnetic Field ◽  
Imaging Telescopes

Recent discoveries of MHD wave motions in the solar corona done with EUV imaging telescopes onboard SOHO and TRACE provide an observational basis for the MHD seismology of the corona. Measuring the properties of MHD waves and oscillations (periods, wavelengths, amplitudes, temporal and spatial signatures), combined with theoretical modeling of the wave phenomena, allow us to determine values of the mean parameters of the corona (the magnetic field strength, transport coefficients, etc.). As an example, we consider post-flare decaying oscillations of loops, observed with TRACE (14th July 1998 at 12:55 UT). An analysis of the oscillations shows that they are quasi-harmonic, with a period of about 265 s, and quickly decaying with the decay time of about 14.5 min. The period of oscillations allows us to determine the Alfvén speed in the oscillating loop about 770 km/s. This value can be used for deduction of the value of the magnetic field in the loop (giving 10-30 G). The decay time, in the assumption that the decay is caused by viscous (or resistive) dissipation, gives us the Reynolds number of 105.3-6.1 (or the Lundquist number of 105.0-5.8).

Reproduction, preweaning survival, and survival of adult sea otters at Kodiak Island, Alaska

1995 ◽  
Vol 73 (6) ◽  
pp. 1161-1169 ◽  
Author(s):  
Daniel H. Monson ◽  
Anthony R. DeGange
Keyword(s):  
Primary Source ◽  
Leading Edge ◽  
Reproduction Rate ◽  
Sea Otter ◽  
Sea Otters ◽  
Kodiak Island ◽  
The Mean ◽  
Reproductive Rates ◽  
Expanding Population ◽  
Sexually Mature

Radiotelemetry methods were used to examine the demographic characteristics of sea otters inhabiting the leading edge of an expanding population on Kodiak Island, Alaska. Fifteen male and 30 female sea otters were instrumented and followed from 1986 to 1990. Twenty-one percent of females were sexually mature (had pupped) at age 2, 57% by age 3, 88% by age 4, and 100% by age 5. Fifteen females produced 26 pups, an overall reproduction rate of 94% for mature females. The reproduction rate was 17, 45, 66, and 100% for 2-, 3-, 4-, and 5-year-olds, respectively. Eighty-five percent of observed pups survived to weaning (120 days), and the percentage of pups weaned ranged from 34% for pups of 2-year-olds to 100% for pups of 5-year-olds. At least three of four known pup losses occurred within a month of parturition. The mean pup dependency period for weaned pups was 153 days and the mean gestation period was 218 days. No synchrony in pupping activity was observed. Mean annual survival of adults was high. Estimates of survival ranged from 89 to 96% for females and 86 to 91% for males. Human harvest was the primary source of known mortality of adults. Our estimates of reproductive rates and survival of adults are at the high end of those reported for sea otters, but preweaning survival stands out as being particularly high. Abundant food resources and the availability of protected water presumably contributed to the high reproductive success observed in this recently established sea otter population.

scholarly journals Small-Scale Dissipative Processes in Stellar Atmospheres

1980 ◽  
Vol 5 ◽  
pp. 581-590
Author(s):  
J. W. Leibacher ◽  
R. F. Stein
Keyword(s):  
Velocity Field ◽  
Energy Flux ◽  
Thermal Energy ◽  
Solar Flares ◽  
Acoustic Waves ◽  
High Current Density ◽  
Stellar Atmospheres ◽  
Small Scale ◽  
High Current ◽  
Strong Magnetic Fields

AbstractThe outer atmospheres of stars must be heated by some non-thermal energy flux to produce chromospheres and coronae. We discuss processes which convert the non-thermal energy flux of organized, macroscopic motions into random, microscopic (thermal) motions. Recent advances in our description of the chromosphere velocity field suggest that the acoustic waves observed there transmit very little energy, and hence are probably incapable of heating the upper chromosphere and corona. The apparent failure of this long held mechanism and the growing appreciation of the importance of strong magnetic fields in the chromosphere and corona have led to hypotheses of heating by the dissipation of currents (both oscillatory and quasi-steady). This follows discoveries in laboratory and ionospheric plasmas and work on solar flares, that instabilities can concentrate currents into thin high current density filaments where they dissipate rapidly.

scholarly journals Radiative characteristics of aerosol under smoke mist conditions in Siberia during summer 2012

2016 ◽  
Author(s):  
Tatiana B. Zhuravleva ◽  
Dmitriy M. Kabanov ◽  
Ilmir M. Nasrtdinov ◽  
Tatiana V. Russkova ◽  
Sergey M. Sakerin ◽  
...  
Keyword(s):  
Western Siberia ◽  
Volume Concentration ◽  
Single Scattering ◽  
Satellite Observations ◽  
Aerosol Size Distribution ◽  
Radiative Effects ◽  
Fire Event ◽  
Fine Mode ◽  
The Mean ◽  
Radiative Characteristics

Abstract. Microphysical and optical properties of aerosol were studied during mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solar radiation at AERONET site in Tomsk and satellite observations. The data were analyzed using multiyear (2003–2013) measurements of aerosol characteristics under background conditions and for less intense fires, differing in burning biomass type, stage of fire, remoteness from observation site, etc. ("ordinary fires"). In June–August 2012, the average aerosol optical depth (AOD, 500 nm) had been 0.95 &amp;pm; 0.86, about a factor of 6 larger than background values (0.16 &amp;pm; 0.08), and a factor of 2.5 larger than in "ordinary smokes". The AOD values were extremely high on July 24–28 and reached 3–5. Comparison with satellite observations showed that ground-based measurements in the region of Tomsk not only reflect the local AOD features, but also are characteristic for the territory of the Western Siberia as a whole. Single scattering albedo (SSA, 440 nm) in this period ranged from 0.91 to 0.99 with the average of ~ 0.96 in the entire wavelength range of 440–1020 nm. The increase in absorptance of aerosol particles (SSA(440 nm)=0,92) and decrease in SSA with wavelength, observed in "ordinary smokes", agree with the data of multiyear observations in analogous situations in boreal zone of USA and Canada. Volume aerosol size distribution in smoke mist and ordinary smokes had bimodal character with significant prevalence of fine mode particles, but in summer 2012 the mean median radius and the width of the fine mode distribution somewhat increased. In contrast to data of multiyear observations, in summer 2012 an increase in the volume concentration and median radius of the coarse mode was observed with the growing AOD. The calculations of the "average" radiative effects of smoke and background aerosol are presented. As compared to background conditions and "ordinary smokes", under the conditions of smoke mist the cooling effect of aerosol considerably intensifies: direct radiative effects (DRE) at the bottom (BOA) and at the top of the atmosphere (TOA) are −13, −35, and −60 W m−2 and −5, −14, and −35 W m−2 respectively. The maximal values of DRE were observed on July 27 (AOD(500 nm)=3.5), when DRE(BOA) reached −180 W m−2, while DRE(TOA) and DRE of the atmosphere were −80 W m−2.

scholarly journals Analysis of dynamics for anomalies of the ice cover in the Okhotsk Sea in the period from 1882 to 2015

2016 ◽  
Vol 185 (2) ◽  
pp. 228-239
Author(s):  
Vladimir M. Pishchalnik ◽  
Valery A. Romanyuk ◽  
Igor G. Minervin ◽  
Alevtina S. Batuhtina
Keyword(s):  
Time Series ◽  
Air Temperature ◽  
Regime Shift ◽  
Ice Cover ◽  
Satellite Observations ◽  
Okhotsk Sea ◽  
Ice Conditions ◽  
The Mean ◽  
Analysis Of Dynamics

The time-series for the ice cover dynamics in the Okhotsk Sea in the period from 1882 to 2015 are reconstructed on the base of shipboard, airborne, and satellite observations and measurements of the air temperature at the coastal meteorological stations. Abnormality of the ice conditions is estimated relative to the “climate norm” determined as the mean seasonal variation for the 1961-1990. Long-term variability of the ice cover is analyzed. Its regime shift with change of trend is revealed in the late 1970s - early 1980s that corresponds to the regime shift of the air temperature variability in the northern hemisphere.

scholarly journals On the performance of satellite-based observations of <i>CO</i><sub>2</sub> in capturing the NOAA Carbon Tracker model and ground-based flask observations over Africa land mass

2019 ◽  
Author(s):  
Anteneh Getachew Mengistu ◽  
Gizaw Mengistu Tsidu
Keyword(s):  
Model Simulation ◽  
Satellite Observation ◽  
Satellite Observations ◽  
Lower Altitude ◽  
Equatorial Africa ◽  
In Situ Observations ◽  
The Mean ◽  
Data Gap ◽  
Good Agreement

Abstract. Africa is one of the most data-scarce regions as satellite observation at the equator is limited by cloud cover and there are a very limited number of ground-based measurements. As a result, the use of simulations from models are mandatory to fill this data gap. A comparison of satellite observation with model and available in-situ observations will be useful to estimate the performance of satellites in the region. In this study, GOSAT XCO2 is compared with the NOAA CT2016 and six flask observations over Africa using five years of data covering the period from May 2009 to April 2014. Ditto for OCO-2 XCO2 against NOAA CT16NRT17 and eight flask observations over Africa using two years of data covering the period from January 2015 to December 2016. The analysis shows that the XCO2 from GOSAT is higher than XCO2 simulated by CT2016 by 0.28 ppm whereas OCO-2 XCO2 is lower than CT16NRT17 by 0.34 ppm on African landmass on average. The mean correlations of 0.83 and 0.60 and average RMSD of 2.30 and 2.57 ppm are found between the model and the respective datasets from GOSAT and OCO-2 implying the existence of a reasonably good agreement between CT and the two satellites over Africa's land region. However, significant variations were observed in some regions. For example, OCO-2 XCO2 are lower than that of CT16NRT17 by up to 3 ppm over some regions in North Africa (e.g., Egypt, Libya, and Mali) whereas it exceeds CT16NRT17 XCO2 by 2 ppm over Equatorial Africa (10° S–10° N). This regional difference is also noted in the comparison of model simulations and satellite observations with flask observations over the continent. For example, CT shows a better sensitivity in capturing flask observations over sites located in Northern Africa. In contrast, satellite observations have better sensitivity in capturing flask observations in lower altitude island sites. CT2016 shows a high spatial mean of seasonal mean RMSD of 1.91 ppm during DJF with respect to GOSAT while CT16NRT17 shows 1.75 ppm during MAM with respect to OCO-2. On the other hand, low RMSD of 1.00 and 1.07 ppm during SON in the model XCO2 with respect to GOSAT and OCO-2 are determined respectively indicating better agreement during autumn. The model simulation and satellite observations exhibit similar seasonal cycles of XCO2 with a small discrepancy over Southern Africa and during wet seasons over all regions.

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