scholarly journals Multi-instrument Observations of Ion-Neutral Coupling in the Dayside Cusp

2020 ◽  
Author(s):  
James Wild ◽  
Daniel Billett ◽  
Keisuke Hosokawa ◽  
Adrian Grocott ◽  
Anasuya Aruliah ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Change ◽  
Neutral Winds ◽  
Cusp Region ◽  
Doppler Imager ◽  
F Region ◽  
Radar Network ◽  
Magnetic Field Change ◽  
Using Data

<p>Using data from the Scanning Doppler Imager, the Super Dual Auroral Radar Network, the EISCAT Svalbard Radar and an auroral all-sky imager, we examine an instance of F-region neutral winds which have been influenced by the presence of poleward moving auroral forms near the dayside cusp region. We observe a reduction in the time taken for the ion-drag force to re-orientate the neutrals into the direction of the convective plasma (on the order of minutes), compared to before the auroral activity began. Additionally, because the ionosphere near the cusp is influenced much more readily by changes in the solar wind via dayside reconnection, we observe the neutrals responding to an interplanetary magnetic field change within minutes of it occurring. This has implications on the rate that energy is deposited into the ionosphere via Joule heating, which we show to become dampened by the neutral winds.</p>

The Role of Field-Aligned Current Closure on the E and F-Region Coupled Thermosphere-Ionosphere

2020 ◽  
Author(s):  
Daniel Billett ◽  
Kathryn McWilliams ◽  
Mark Conde
Keyword(s):  
Temporal Structure ◽  
Plasma Velocity ◽  
Velocity Data ◽  
Neutral Winds ◽  
Doppler Imager ◽  
F Region ◽  
Radar Network ◽  
Field Aligned Current ◽  
Auroral Emissions

<p>In this study, the behaviour of both E and F-region neutral winds are examined in the vicinity of intense R1 and R2 field-aligned currents (FACs), measured by AMPERE. This is achieved through the dual sampling of both the green (557.5nm) and red (630nm) auroral emissions, sequentially, from a ground based Scanning Doppler Imager (SDI) located in Alaska.</p><p>With the addition of plasma velocity data from the Super Dual Auroral Radar Network (SuperDARN) and ionospheric parameters from the Poker Flat Incoheerent Scatter Radar (PFISR), we assess how the large closure of Pedersen currents (implied by the strong FACs) modifies the spatial and temporal structure of the neutral wind at different altitudes. We find that the thermosphere becomes significantly height dependent, which could indicate a broader altitude range where the Pedersen conductivity is more important during intense FAC closure.</p>

scholarly journals Magnetic holes in the solar wind between 0.3 AU and 17 AU

2000 ◽  
Vol 7 (3/4) ◽  
pp. 191-200 ◽  
Author(s):  
K. Sperveslage ◽  
F. M. Neubauer ◽  
K. Baumgärtel ◽  
N. F. Ness
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Heliocentric Distance ◽  
Occurrence Rate ◽  
Automatic Identification ◽  
Soliton Theory ◽  
Theoretical Approaches ◽  
Maximum Angle ◽  
Using Data ◽  
Initial Magnetic Field

Abstract. Magnetic holes (MHs) are depressions of the magnetic field magnitude. Turner et al. (1977) identified the first MHs in the solar wind and determined an occurrence rate of 1.5 MHs/d. Winterhalter et al. (1994) developed an automatic identification criterion to search for MHs in Ulysses data in the solar wind between 1 AU and 5.4 AU. We adopt their criterion to expand the search to the heliocentric distances down to 0.3 AU using data from Helios 1 and 2 and up to 17 AU using data from Voyager 2. We relate our observations to two theoretical approaches which describe the so-called linear MHs in which the magnetic vector varies in magnitude rather than direction. Therefore we focus on such linear MHs with a directional change less than 10º. With our observations of about 850 MHs we present the following results: Approximately 30% of all the identified MHs are linear. The maximum angle between the initial magnetic field vector and any vector inside the MH is 20º in average and shows a weak relation to the depth of the MHs. The angle between the initial magnetic field and the minimum variance direction of those structures is large and very probably close to 90º. The MHs are placed in a high β environment even though the average solar wind shows a smaller β. The widths decrease from about 50 proton inertial length in a region between 0.3 AU and 0.4 AU heliocentric distance to about 15 proton inertial length at distances larger than 10 AU. This quantity is correlated with the β of the MH environments with respect to the heliocentric distance. There is a clear preference for the occurrence of depressions instead of compressions. We discuss these results with regard to the main theories of MHs, the mirror instability and the alternative soliton approach. Although our observational results are more consistent with the soliton theory we favour a combination of both. MHs might be the remnants of initial mirror mode structures which can be described as solitons during the main part of their lifetime.

Magnetocaloric Effect in Ni-Mn-Ga and Ni-Co-Mn-In Heusler Alloys

2009 ◽  
Vol 1200 ◽  
Author(s):  
Vasiliy Buchelnikov ◽  
Sergey Taskaev ◽  
Mikhail Drobosyuk ◽  
Vladimir Sokolovskiy ◽  
Viktor Koledov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Curie Point ◽  
Direct Method ◽  
Heusler Alloys ◽  
Field Change ◽  
Adiabatic Temperature Change ◽  
Magnetic Field Change ◽  
A Direct Method ◽  
The Magnetic Field

AbstractThe positive magnetocaloric effect (MCE) in the vicinity of the Curie point in Ni2+xMn1-xGa (x=0.33, 0.36, 0.39) Heusler alloys and the negative and positive MCE near the metamagnetostructural (MMS) transition and the Curie point, respectively, in Ni45Co5Mn36.5In13.5 Heusler alloy has been measured by a direct method. For the magnetic field change ΔH = 2 T, the maximal adiabatic temperature change ΔTad at the Curie point in Ni2+xMn1-xGa alloys is larger than 0.6 K. For Ni45Co5Mn36.5In13.5 alloy, the maximal value of ΔTad = 1.68 K (for the same magnetic field change, ΔH = 2 T) is observed at the MMS phase transition temperature.

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.

scholarly journals Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1589-1612 ◽  
Author(s):  
M. Lockwood ◽  
H. Opgenoorth ◽  
A. P. van Eyken ◽  
A. Fazakerley ◽  
J.-M. Bosqued ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Propagation Delay ◽  
Polar Cap ◽  
F Region ◽  
Electrons And Ions ◽  
Transient Events ◽  
Low Energy Electron ◽  
Convection Patterns ◽  
Magnetopause Reconnection

Abstract. During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR) at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches"), with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5) min, the interplanetary magnetic field (IMF) had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model (with input conditions prevailing during this event), was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns (derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites) show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster (10–20 eV) and the topside ionospheric enhancements seen by the ESR (at 400–700 km). We suggest that a potential barrier at the magnetopause, which prevents the lowest energy electrons from entering the magnetosphere, is reduced when and where the boundary-normal magnetic field is enhanced and that the observed polar cap patches are produced by the consequent enhanced precipitation of the lowest energy electrons, making them and the low energy electron precipitation fossil remnants of the magnetopause reconnection rate pulses.Key words. Magnetospheric physics (polar cap phenomena; solar wind – magnetosphere interactions; magnetosphere – ionosphere interactions)

Magnetic Properties and Magnetocaloric Effect of Gd3Ni in Crystalline and Amorphous States

2012 ◽  
Vol 190 ◽  
pp. 355-358 ◽  
Author(s):  
D.A. Shishkin ◽  
N.V. Baranov ◽  
A.V. Proshkin ◽  
S.V. Andreev ◽  
A.S. Volegov
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
Rapid Quenching ◽  
Antiferromagnetic Order ◽  
Cooling Power ◽  
Ferromagnetic Behavior ◽  
Field Change ◽  
Ni Alloy ◽  
Magnetic Field Change

The liquid quenched Gd3Ni alloy is observed to exhibit a ferromagnetic behavior below TC = 117 K unlike crystalline compound having an antiferromagnetic order at T < TN = 99 K. Rapid quenching from the melt results in a considerable enhancement of the magnetocaloric effect in Gd3Ni at low magnetic fields. The maximal value of the isothermal magnetic entropy change at a magnetic field change of 20 kOe for the amorphous Gd3Ni surpasses by more than 8 times the SM value for the polycrystalline counterpart. The relative cooling power for the amorphous Gd3Ni alloy is estimated as 265 J kg-1 and 676 J kg-1 at a magnetic field change of 20 kOe and 50 kOe, respectively.

The Magnetocaloric Effect in Ni-Mn-X (X=Ga, in) Heusler Alloys and Manganites with Magnetic Transition close to Room Temperature

2010 ◽  
Vol 168-169 ◽  
pp. 165-168
Author(s):  
Vasiliy D. Buchelnikov ◽  
Mikhail Drobosyuk ◽  
E.A. Smyshlyaev ◽  
O.O. Pavlukhina ◽  
A.V. Andreevskikh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Room Temperature ◽  
Direct Method ◽  
Magnetic Transition ◽  
Heusler Alloys ◽  
Field Change ◽  
Adiabatic Temperature Change ◽  
Magnetic Field Change ◽  
The Magnetic Field

The magnetocaloric effect (MCE) in theNi2+xMn1-xGa (x = 0.33, 0.36, 0.39), Ni50Mn25In25, Ni54Mn21Ga18In7, Ni53.5Mn21.5Ga16In9, Ni45Co5Mn36.5In13.5 Heusler alloys and in the La0.7BayCa0.3-yMnO3 (y = 0.12, 0.24, 0.3) manganites at the Curie points have been measured by the direct method. For the magnetic field change H = 2 T, the maximal adiabatic temperature change Tad in the Ni2+xMn1-xGa alloys is larger than 0.6 K. For the Ni50Mn25In25 alloy the maximal value of Tad = 1.51 K (for the same magnetic field change H = 2 T) is observed at the magnetic phase transition temperature.

The Research of Capacitance Characteristics of MRF

2012 ◽  
Vol 246-247 ◽  
pp. 1096-1101
Author(s):  
Song Wang ◽  
Guo Tian He ◽  
Li Song ◽  
Ze Yu Xu ◽  
Ying Chun Ran
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Electrical Characteristics ◽  
Field Change ◽  
Aircraft Manufacturing ◽  
Magnetic Field Change ◽  
Capacitance Characteristics ◽  
Magneto Rheological ◽  
Magnetic Induction Intensity ◽  
The Magnetic Field

With the development of theory that research on Magneto-Rheological Fluids (MRF), the MRF have been used in many fields in our life. The electrical characteristics of MRF can be widely used in automatic control, medical, automotive, aircraft manufacturing and many other areas .Firstly, this article have derived the formula of MRF between capacitance and Dielectric constant, made the Capacitors which can load the MRF. And then we measure the change of capacitance which is filled with the MRF when the time of magnetic field change, And we also measure the sensitivity of the dielectric constant of different concentrations of MRF as the magnetic field changes. And at last, we have made the curve of the capacitance - magnetic induction intensity the experimental results have been analyzed. We have the conclusion that when the magnetic field increases, the dielectric constant is also increases, resulting in increased capacitance of the conclusions of MRF. Introduction

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