scholarly journals Solar and seasonal dependence of ion frictional heating

1999 ◽  
Vol 17 (5) ◽  
pp. 682-691 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
I. W. McCrea
Keyword(s):  
Response Times ◽  
Frictional Heating ◽  
Plasma Temperature ◽  
Seasonal Effects ◽  
Neutral Atmosphere ◽  
Ion Temperature ◽  
Ion Heating ◽  
Highly Correlated ◽  
Geometrical Factors ◽  
Seasonal Dependence

Abstract. Ion frictional heating constitutes one of the principal mechanisms whereby energy, originating in the solar wind, is deposited into the Earth's ionosphere and ultimately the neutral atmosphere. Common programme observations by the EISCAT UHF radar system, spanning the years 1984 to 1995, provide the basis for a comprehensive statistical study of ion frictional heating, results of which are documented in this and a previous paper by the authors. In the present work, the authors demonstrate the solar and seasonal dependence of the universal time distribution of frictional heating, and explain these results with reference to corresponding dependences of the ion velocity. Although EISCAT observes a significant increase in the occurrence of enhanced ion velocities associated with increased solar activity, the latter characterised according to the prevailing 10.7 cm solar flux, this is not reflected to such an extent in the occurrence of frictional heating. It is suggested that this is a consequence of the decreased neutral atmosphere response times associated with active solar conditions, resulting from the higher ionospheric plasma densities present. Seasonal effects on the diurnal distribution of ion frictional heating are well explained by corresponding variations in ionospheric convection, the latter principally a result of geometrical factors. It is noted that, over the entire dataset, the variations in the unperturbed F-region ion temperature, required to implement the identification criterion for ion heating, are highly correlated with model values of thermospheric temperature.Keywords. Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions; plasma temperature and density)

The BEAN experiment - An EISCAT study of ion temperature anisotropies

1995 ◽  
Vol 13 (2) ◽  
pp. 177-188 ◽  
Author(s):  
I. W. McCrea ◽  
G. O. L. Jones ◽  
M. Lester
Keyword(s):  
Velocity Distribution ◽  
Frictional Heating ◽  
Molecular Ions ◽  
Line Of Sight ◽  
Thermal Velocity ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Ion Heating ◽  
Aspect Angle ◽  
F Region

Abstract. Results are presented from a novel EISCAT special programme, SP-UK-BEAN, intended for the direct measurement of the ion temperature anisotropy during ion frictional heating events in the high-latitude F-region. The experiment employs a geometry which provides three simultaneous estimates of the ion temperature in a single F-region observing volume at a range of aspect angles from 0° to 36°. In contrast to most previous EISCAT experiments to study ion temperature anisotropies, field-aligned observations are made using the Sodankylä radar, while the Kiruna radar measures at an aspect angle of the order of 30°. Anisotropic effects can thus be studied within a small common volume whose size and altitude range is limited by the radar beamwidth, rather than in volumes which overlap but cover different altitudes. The derivation of line-of-sight ion temperature is made more complex by the presence of an unknown percentage of atomic and molecular ions at the observing altitude and the possibility of non-Maxwellian distortion of the ion thermal velocity distribution. The first problem has been partly accounted for by insisting that a constant value of electron temperature be maintained. This enables an estimate of the ion composition to be made, and facilitates the derivation of more realistic line-of-sight ion temperatures and temperature anisotropies. The latter problem has been addressed by assuming that the thermal velocity distribution remains bi-Maxwellian. The limitations of these approaches are discussed. The ion temperature anisotropies and temperature partition coefficients during two ion heating events give values intermediate between those expected for atomic and for molecular species. This result is consistent with an analysis which indicates that significant proportions of molecular ions (up to 50%) were present at the times of greatest heating.

scholarly journals EISCAT Svalbard radar observations of ionospheric signatures of magnetopause reconnection during a changing IMF Bz polarity

2002 ◽  
Vol 20 (4) ◽  
pp. 477-486
Author(s):  
S. E. Pryse ◽  
A. M. Smith ◽  
L. Kersley ◽  
I. W. McCrea
Keyword(s):  
Spatial Distribution ◽  
Frictional Heating ◽  
Plasma Temperature ◽  
Polar Ionosphere ◽  
Ion Temperature ◽  
Precipitation Field ◽  
Cusp Region ◽  
Field Lines ◽  
Imf Clock Angle ◽  
Magnetopause Reconnection

Abstract. Observations by the EISCAT Svalbard radar are presented that show the response of the spatial structure of the ionosphere in the dayside cusp region to a rotational trend in the IMF clock angle. Over a period of one hour, the clock angle increased from about 45° to some 150°, moving the likely location of the magnetopause reconnection site from the high-latitude lobe to near the equatorial plane. Increased topside electron temperatures measured by the ESR identified footprints of the reconnection process. Temporal changes in the spatial distribution of the temperature reflected the change from lobe to equatorial reconnection. Discrete spatial enhancements in ion temperature were found resulting from ion-neutral frictional heating in the fast flows where it was likely that field lines were being convected from the reconnection locations. The corresponding electron density structuring is interpreted in terms of the particle precipitation, field-aligned currents and convection flows driven by the IMF.Key words. Ionosphere (ionosphere – magnetosphere interactions; plasma temperature and density; polar ionosphere)

Structure and behavior of white pelican formation flocks

1982 ◽  
Vol 60 (6) ◽  
pp. 1388-1396 ◽  
Author(s):  
J. Brian E. O'Malley ◽  
Roger M. Evans
Keyword(s):  
Response Times ◽  
Formation Flight ◽  
Flock Size ◽  
Wingbeat Frequency ◽  
Percent Time ◽  
Column Formation ◽  
Highly Correlated ◽  
And Behavior

Observations of white pelicans commuting between nesting colonies and foraging areas revealed transitions from small, simple linear flock formations to larger, more complex vee and jay formations during departures, and the reverse during the return approach. Large, less-organized types of formations were relatively uncommon and short lived.Formation angles measured for filmed flocks ranged from 24° to 122° and were highly correlated with mean relative interbird distances within flocks. The number of wingbeats per hour, calculated from wingbeat frequency (beats per minute) and percent time flapping, was lowest in vee formation, progressively greater in jay, echelon, and column formation, and greatest for single birds. Wingbeats per hour decreased behind the lead bird, which usually had the highest rate, within each type of formation.Shifts between flapping and gliding were usually initiated by lead birds. Response times for these shifts were negatively related to flock size, and were shorter in vee and jay formations than in column and echelon formations.Our data suggests formation flight provides both aerodynamic–energetic and communication advantages over solitary flight.

scholarly journals Major, minor and trace element composition of cloudwater and rainwater at Plynlimon

1997 ◽  
Vol 1 (3) ◽  
pp. 557-569 ◽  
Author(s):  
J. Wilkinson ◽  
B. Reynolds ◽  
C. Neal ◽  
S. Hill ◽  
M. Neal ◽  
...  
Keyword(s):  
Trace Element Composition ◽  
Anthropogenic Sources ◽  
Seasonal Effects ◽  
Anthropogenic Contamination ◽  
Forested Catchments ◽  
Weather Patterns ◽  
Highly Correlated ◽  
The Uk ◽  
Cracking Process ◽  
Inorganic Constituents

Abstract. The composition of cloudwater samples collected at Plynlimon, Mid Wales by the Institute of Hydrology is described based on one of the most comprehensive chemical records for deposition in the UK. Comparison with bulk rainwater samples for the same area demonstrates a tenfold enrichment of most elements in cloudwater. Large variations in cloudwater composition occur due to variations in marine and terrestrial/anthropogenic sources, general weather patterns, atmospheric circulation and seasonal effects. All trace metal concentrations are associated with anthropogenic contamination. The lanthanides La, Cc and Pr, and Y are highly correlated in ratios associated with lithogenic sources and fossil fuel combustion. Outliers suggest the influence of catalysts used in the petrochemical cracking process. Plantation forestry significantly enhances the annual deposition of solutes from cloudwater; between 15 and 40% of most constituents to upland forested catchments and around 50% for NO3, B and Cd come from cloud deposition. In upland moorland areas, only 10% of the annual deposited load of inorganic constituents comes from cloudwater.

Toroidal plasma conditions where the p-11B fusion Lawson criterion could be eased

2020 ◽  
Author(s):  
Yueng-Kay Peng ◽  
Yuejiang Shi ◽  
Mingyuan Wang ◽  
Bing Liu ◽  
Xueqing Yan
Keyword(s):  
Fusion Reaction ◽  
Plasma Temperature ◽  
Reaction Rates ◽  
Tokamak Plasmas ◽  
Carbon Ions ◽  
Ion Temperature ◽  
Order Unity ◽  
Toroidal Plasma ◽  
Order Of Magnitude ◽  
Boron Ions

Abstract We examine the theoretical conditions in which the Lawson ignition criterion for p-11B fusion in a magnetized toroidal plasma can be reduced substantially. It is determined that a velocity differential between the protons and the boron ions of the order of the plasma sound speed (Mach number of 1 or 2 at a plasma temperature of ~102 keV) could raise the p-11B fusion reaction rate to ~2x10-22 m3/s or ~6x10-22 m^3/s, respectively, from the ~1x10-22 m3/s level in a static plasma. The Lawson triple product (ni τE Ti) required for ignition can thereby be reduced to as low as ~1023 m-3 s keV, which is one order of magnitude above the ITER requirement for D-T burn. Since order-unity Mach numbers in velocity differentials between deuterons and impurity carbon ions have been maintained in tokamak plasmas under excellent confinement conditions, similar levels of velocity differentials between protons and minority boron-11 ions could in principle be maintained also. A theoretical possibility of achieving p-11B fusion ignition in a toroidal plasma of ~102 keV in ion temperature is hereby presented. Similar p-13C plasmas, for example, will introduce a possibility of measuring the CNO fusion chain reaction rates in a laboratory.

scholarly journals A statistical study of ion frictional heating observed by EISCAT

1997 ◽  
Vol 15 (11) ◽  
pp. 1399-1411 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
I. W. McCrea
Keyword(s):  
Geomagnetic Activity ◽  
Large Scale ◽  
Frictional Heating ◽  
Selection Criterion ◽  
Ion Temperature ◽  
F Region ◽  
Diurnal Distribution ◽  
Statistical Survey ◽  
Uhf Radar ◽  
The Imf

Abstract. Results of a statistical survey of F-region ion frictional heating are presented, a survey which is based on over 4000 h of common programme observations taken by the European incoherent scatter (EISCAT) UHF radar facility. The criterion adopted in this study for the identification of ion frictional heating was that defined by McCrea et al., requiring an enhancement in the F-region field-parallel ion temperature exceeding 100 K over two consecutive integration periods, which was itself based on a selection criterion for frictional heating derived for the study of high-latitude F-region ion temperature observations from the Atmospheric Explorer-C satellite. In the present study, the diurnal distribution of ion frictional heating observed by EISCAT is established and, furthermore, its dependence on geomagnetic activity and the orientation of the interplanetary magnetic field (IMF) is investigated; results are interpreted with reference to corresponding distributions of enhanced ion velocity, again derived from the extended set of EISCAT UHF common programme observations. The radar, due to its location relative to the large-scale convection pattern, observes ion frictional heating principally during the night, although preferentially during the post-midnight hours where there is reduced coupling between the ion and neutral populations. There is an increased preponderance of frictional heating during intervals of high geomagnetic activity and for a southward z component of the IMF and, moreover, evidence of asymmetries introduced by the y component of the IMF.

scholarly journals On the usefulness of <i>E</i> region electron temperatures and lower <i>F</i> region ion temperatures for the extraction of thermospheric parameters: a case study

1999 ◽  
Vol 17 (9) ◽  
pp. 1182-1198 ◽  
Author(s):  
J.-P. St.-Maurice ◽  
C. Cussenot ◽  
W. Kofman
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Plasma Temperature ◽  
Ion Temperature ◽  
Heating Rates ◽  
Neutral Winds ◽  
F Region ◽  
E Region ◽  
Effective Electric Field ◽  
Temperature Observations

Abstract. Using EISCAT data, we have studied the behavior of the E region electron temperature and of the lower F region ion temperature during a period that was particularly active geomagnetically. We have found that the E region electron temperatures responded quite predictably to the effective electric field. For this reason, the E region electron temperature correlated well with the lower F region ion temperature. However, there were several instances during the period under study when the magnitude of the E region electron temperature response was much larger than expected from the ion temperature observations at higher altitudes. We discovered that these instances were related to very strong neutral winds in the 110-175 km altitude region. In one instance that was scrutinized in detail using E region ion drift measurement in conjunction with the temperature observations, we uncovered that, as suspected, the wind was moving in a direction closely matching that of the ions, strongly suggesting that ion drag was at work. In this particular instance the wind reached a magnitude of the order of 350 m/s at 115 km and of at least 750 m/s at 160 km altitude. Curiously enough, there was no indication of strong upper F region neutral winds at the time; this might have been because the event was uncovered around noon, at a time when, in the F region, the E×B drift was strongly westward but the pressure gradients strongly northward in the F region. Our study indicates that both the lower F region ion temperatures and the E region electron temperatures can be used to extract useful geophysical parameters such as the neutral density (through a determination of ion-neutral collision frequencies) and Joule heating rates (through the direct connection that we have confirmed exists between temperatures and the effective electric field).Key words. Ionosphere (auroral ionosphere; ionosphere atmosphere interactions; plasma temperature and density)

Behaviour of ion temperature in electron and ion heating regimes observed with ECH, NBI and ICRF discharges of LHD

2002 ◽  
Vol 42 (10) ◽  
pp. 1179-1183 ◽  
Author(s):  
S. Morita ◽  
M. Goto ◽  
S. Kubo ◽  
S. Murakami ◽  
K. Narihara ◽  
...  
Keyword(s):  
Ion Temperature ◽  
Ion Heating

scholarly journals Ion-neutral coupling in the high-latitude F-layer from incoherent scatter and Fabry-Perot interferometer measurements

2000 ◽  
Vol 18 (9) ◽  
pp. 1145-1153 ◽  
Author(s):  
K. Cierpka ◽  
M. J. Kosch ◽  
M. Rietveld ◽  
K. Schlegel ◽  
T. Hagfors
Keyword(s):  
High Latitude ◽  
Frictional Heating ◽  
Neutral Wind ◽  
Auroral Ionosphere ◽  
Quiet Period ◽  
Ion Temperature ◽  
Incoherent Scatter ◽  
F Region ◽  
Fabry Perot ◽  
Energy Sink

Abstract. Since the auroral ionosphere provides an important energy sink for the magnetosphere, ionosphere-thermosphere coupling must be investigated when considering the energy budget of the ionosphere-magnetosphere coupling. We present the first Scandinavian ground-based study of high-latitude F-region ion-neutral frictional heating where ion velocity and temperature are measured by the EISCAT incoherent scatter radar as well as neutral wind and temperature being measured simultaneously by a Fabry-Perot interferometer. A geomagnetically active period (Kp = 7– – 5–) and quiet period (Kp = 0+ – 0) were studied. Neglecting the neutral wind can result in errors of frictional heating estimates of 60% or more in the F-layer. About 96% of the local ion temperature enhancement over the neutral temperature is accounted for by ion-neutral frictional heating.Key words: Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions)

scholarly journals Deriving the normalised ion-neutral collision frequency from EISCAT observations

1997 ◽  
Vol 15 (12) ◽  
pp. 1557-1569 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
T. R. Robinson
Keyword(s):  
Electric Field ◽  
Collision Frequency ◽  
Neutral Atmosphere ◽  
Ion Temperature ◽  
Neutral Winds ◽  
Velocity Magnitude ◽  
F Region ◽  
E Region ◽  
Ion Velocity ◽  
The Difference

Abstract. Common programme observations by the EISCAT UHF radar revealed an extended interval, post geomagnetic local noon on 03 April 1992, during which the F-region ion velocity orthogonal to the geomagnetic field was significantly enhanced, to values exceeding 2 km s–1 corresponding to a perpendicular electric field of some 100 mV m–1. Observations from this interval are used to illustrate a method by which estimates of the E-region ion-neutral collision frequency may be derived in the presence of enhanced electric field. From both the rotation of the ion velocity vector and the reduction in the ion velocity magnitude relative to that in the F-region, independent estimates of the normalised ion-neutral collision frequency are made at the UHF E-region tristatic altitudes; the derived values are, in general, lower than model predictions. Although initial calculations assume a stationary neutral atmosphere, first-order estimates of the E-region neutral wind are subsequently employed to calculate revised estimates of the normalised ion-neutral collision frequency; these neutral winds are derived by attributing the difference between predicted and observed enhancements in field-parallel ion temperature to thermospheric motion. The inclusion of neutral winds, which are themselves not inconsiderable, appears to have only a limited effect on the normalised collision frequencies derived.

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