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)

scholarly journals Polar patches observed by ESR and their possible origin in the cusp region

2000 ◽  
Vol 18 (9) ◽  
pp. 1043-1053 ◽  
Author(s):  
A. M. Smith ◽  
S. E. Pryse ◽  
L. Kersley
Keyword(s):  
Energy Distribution ◽  
Electron Density ◽  
Plasma Flow ◽  
Plasma Temperature ◽  
Soft Particle ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Particle Precipitation ◽  
Cusp Region ◽  
Reconnection Site

Abstract. Observations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles.Key words: Ionosphere (ionosphere-magnetosphere interactions; plasma temperature and density; polar ionosphere)

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)

scholarly journals An extended TRANSCAR model including ionospheric convection: simulation of EISCAT observations using inputs from AMIE

2005 ◽  
Vol 23 (2) ◽  
pp. 419-431 ◽  
Author(s):  
P.-L. Blelly ◽  
C. Lathuillère ◽  
B. Emery ◽  
J. Lilensten ◽  
J. Fontanari ◽  
...  
Keyword(s):  
Large Scale ◽  
Frictional Heating ◽  
Polar Ionosphere ◽  
Energy Inputs ◽  
Early Afternoon ◽  
High Latitude Ionosphere ◽  
Field Lines ◽  
Moment Approach ◽  
The Magnetic Field ◽  
Good Agreement

Abstract. The TRANSCAR ionospheric model was extended to account for the convection of the magnetic field lines in the auroral and polar ionosphere. A mixed Eulerian-Lagrangian 13-moment approach was used to describe the dynamics of an ionospheric plasma tube. In the present study, one focuses on large scale transports in the polar ionosphere. The model was used to simulate a 35-h period of EISCAT-UHF observations on 16-17 February 1993. The first day was magnetically quiet, and characterized by elevated electron concentrations: the diurnal F2 layer reached as much as 1012m-3, which is unusual for a winter and moderate solar activity (F10.7=130) period. An intense geomagnetic event occurred on the second day, seen in the data as a strong intensification of the ionosphere convection velocities in the early afternoon (with the northward electric field reaching 150mVm-1) and corresponding frictional heating of the ions up to 2500K. The simulation used time-dependent AMIE outputs to infer flux-tube transports in the polar region, and to provide magnetospheric particle and energy inputs to the ionosphere. The overall very good agreement, obtained between the model and the observations, demonstrates the high ability of the extended TRANSCAR model for quantitative modelling of the high-latitude ionosphere; however, some differences are found which are attributed to the precipitation of electrons with very low energy. All these results are finally discussed in the frame of modelling the auroral ionosphere with space weather applications in mind.

scholarly journals Observations of diverging field-aligned ion flow with the ESR

2004 ◽  
Vol 22 (3) ◽  
pp. 889-899 ◽  
Author(s):  
S. C. Buchert ◽  
Y. Ogawa ◽  
R. Fujii ◽  
A. P. van Eyken
Keyword(s):  
Field Line ◽  
Geomagnetic Field ◽  
Plasma Temperature ◽  
Ionization Mechanism ◽  
Soft Particle ◽  
Polar Ionosphere ◽  
Ion Composition ◽  
Ion Flow ◽  
F Region ◽  
Ionization Balance

Abstract. We report on observations of a diverging ion flow along the geomagnetic field that is often seen at the EISCAT Svalbard radar. The flow is upward above the peak of the electron density in the F-region and downward below the peak. We estimate that in such events mass transport along the field line is important for the ionization balance, and that the shape of the F-layer and its ion composition should be strongly influenced by it. Diverging flow typically occurs when there are signatures of direct entry of sheath plasma to the ionosphere in the form of intense soft particle precipitation, and we suggest that it is caused by the ionization and ionospheric electron heating associated with this precipitation. On average, 30% of all events with ion upflow also show significant ion downflow below. Key words.Ionosphere (polar ionosphere; ionization mechanism; plasma temperature and density)

scholarly journals Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

2002 ◽  
Vol 20 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
F. Pitout ◽  
P. T. Newell ◽  
S. C. Buchert
Keyword(s):  
High Latitude ◽  
Time Interval ◽  
High Latitudes ◽  
Polar Ionosphere ◽  
Plasma Convection ◽  
Low Latitude ◽  
Svalbard Archipelago ◽  
Cusp Region ◽  
Ionosphere Plasma ◽  
Particle Measurement

Abstract. We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

scholarly journals The cusp: a window for particle exchange between the radiation belt and the solar wind

2006 ◽  
Vol 24 (11) ◽  
pp. 3131-3137 ◽  
Author(s):  
X.-Z. Zhou ◽  
T. A. Fritz ◽  
Q.-G. Zong ◽  
Z. Y. Pu ◽  
Y.-Q. Hao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Open Field ◽  
Test Particle ◽  
Radiation Belt ◽  
Magnetospheric Convection ◽  
Cusp Region ◽  
Particle Simulations ◽  
Particle Exchange ◽  
Field Lines

Abstract. The study focuses on a single particle dynamics in the cusp region. The topology of the cusp region in terms of magnetic field iso-B contours has been studied using the Tsyganenko 96 model (T96) as an example, to show the importance of an off-equatorial minimum on particle trapping. We carry out test particle simulations to demonstrate the bounce and drift motion. The "cusp trapping limit" concept is introduced to reflect the particle motion in the high latitude magnetospheric region. The spatial distribution of the "cusp trapping limit" shows that only those particles with near 90° pitch-angles can be trapped and drift around the cusp. Those with smaller pitch angles may be partly trapped in the iso-B contours, however, they will eventually escape along one of the magnetic field lines. There exist both open field lines and closed ones within the same drift orbit, indicating two possible destinations of these particles: those particles being lost along open field lines will be connected to the surface of the magnetopause and the solar wind, while those along closed ones will enter the equatorial radiation belt. Thus, it is believed that the cusp region can provide a window for particle exchange between these two regions. Some of the factors, such as dipole tilt angle, magnetospheric convection, IMF and the Birkeland current system, may influence the cusp's trapping capability and therefore affect the particle exchanging mechanism. Their roles are examined by both the analysis of cusp magnetic topology and test particle simulations.

Ionospheric heating in the F -region

1964 ◽  
Vol 281 (1384) ◽  
pp. 140-149 ◽  
Keyword(s):  
Electron Temperature ◽  
Energy Input ◽  
Particle Flux ◽  
Electron Interaction ◽  
Ion Temperature ◽  
Ionospheric Heating ◽  
F Region ◽  
Field Lines ◽  
Photo Ionization ◽  
Made In

Measurements of electron temperature made in Ariel I have been analyzed to calculate the ionospheric energy input required to maintain the electron temperature above the ion temperature. The results are found to be consistent with the energy input due to photo-ionization in the daytime, provided that allowance is made for the effects of the escaping flux of photoelectrons spiralling upwards along the geomagnetic field lines which impartenergy to the ionosphere by electron-electron interaction. However, it is found that during the night an energy input of particle origin is observed, a close agreement being found between the distribution of energy input and that of the fluxes of low-energy particles observed by Savenko, Shavrin & Pisavenko 1963. The particle flux contributes less than 30% to the heat input in the daytime and its diurnal variation is small.

scholarly journals Simultaneous Double Star and Cluster FTEs observations on the dawnside flank of the magnetosphere

2005 ◽  
Vol 23 (8) ◽  
pp. 2877-2887 ◽  
Author(s):  
A. Marchaudon ◽  
C. J. Owen ◽  
J.-M. Bosqued ◽  
R. C. Fear ◽  
A. N. Fazakerley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Southern Hemisphere ◽  
Double Star ◽  
Simultaneous Observation ◽  
Flux Transfer Events ◽  
Reconnection Site ◽  
Field Lines ◽  
Almost All ◽  
Magnetospheric Field ◽  
Imf Clock Angle

Abstract. We present Cluster and Double Star-1 (TC-1) observations from a close magnetic conjunction on 8 May 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the Southern Hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8h (between 08:00-16:00 UT). Flux Transfer Events (FTEs), moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT) sector as TC-1 and remained close to the magnetopause boundary layer in the Southern Hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5h between 07:30 and 14:00 UT. The very clear signatures and the finite transverse sizes of the FTEs observed by TC-1 and Cluster imply that, during this event, sporadic reconnection occurred. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF) conditions and IMF-Bz turnings, the IMF clock angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2h in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT.

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.

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