scholarly journals Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission

2008 ◽  
Vol 26 (12) ◽  
pp. 4051-4074 ◽  
Author(s):  
S. W. H. Cowley ◽  
A. J. Deason ◽  
E. J. Bunce
Keyword(s):  
Magnetic Axis ◽  
Mission Planning ◽  
Major Goal ◽  
Jovian Magnetosphere ◽  
Combined Models ◽  
Jovian System ◽  
Low Altitude ◽  
Auroral Current ◽  
Current Systems ◽  
Juno Mission

Abstract. We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 RJ of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

Characterization of auroral current systems in Saturn's magnetosphere: High-latitude Cassini observations

2009 ◽  
Vol 114 (A6) ◽  
pp. n/a-n/a ◽  
Author(s):  
D. L. Talboys ◽  
C. S. Arridge ◽  
E. J. Bunce ◽  
A. J. Coates ◽  
S. W. H. Cowley ◽  
...  
Keyword(s):  
High Latitude ◽  
Auroral Current ◽  
Current Systems

Recent results from the imagery of Juno’s Stellar Reference Unit

2020 ◽  
Author(s):  
Heidi Becker ◽  
James Alexander ◽  
Sushil Atreya ◽  
Scott Bolton ◽  
Martin Brennan ◽  
...  
Keyword(s):  
Satellite Images ◽  
Attitude Determination ◽  
High Energy ◽  
High Energy Particle ◽  
Energy Particle ◽  
Low Light ◽  
Jovian System ◽  
Dust Ring ◽  
Juno Mission

<p>The Juno Mission has recast its spacecraft engineering star camera as a visible wavelength science imager. Developed and primarily used to support onboard attitude determination, Juno’s Stellar Reference Unit (SRU) has been put to use as an in situ high energy particle detector for profiling Jupiter’s radiation belts and as a low light sensitive camera for exploring multiple phenomena and features of the Jovian system. Juno’s unprecedented polar orbit and closest approach of ~4000 km have yielded high resolution SRU imagery of Jupiter’s lightning and aurorae from as little as 50,000 km from the 1 bar level and unique Jovian dust ring and satellite images. We will present recent SRU results and discuss the implications for Jupiter’s atmosphere that stem from the SRU lightning observations.</p>

scholarly journals Investigating the auroral electrojets with low altitude polar orbiting satellites

2002 ◽  
Vol 20 (7) ◽  
pp. 1049-1061 ◽  
Author(s):  
T. Moretto ◽  
N. Olsen ◽  
P. Ritter ◽  
G. Lu
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Magnetic Measurements ◽  
Activity Index ◽  
Satellite Observations ◽  
Polar Regions ◽  
Hemispheric Differences ◽  
Ionospheric Currents ◽  
Low Altitude ◽  
Current Systems

Abstract. Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.8–0.9) is observed between the amplitudes of the derived currents and the commonly used auroral electrojet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring. A specific advantage of the satellite observations over the ground-based magnetic measurements is their coverage of the Southern Hemisphere, as well as the Northern. We utilize this in an investigation of the ionospheric currents observed in both polar regions during a period of unusually steady interplanetary magnetic field with a large negative Y-component. A pronounced asymmetry is found between the currents in the two hemispheres, which indicates real inter-hemispheric differences beyond the mirror-asymmetry between hemispheres that earlier studies have revealed. The method is also applied to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning of the magnetosphere (history of the interplanetary magnetic field) is seen to play an important role, and in the winther hemisphere, it seems to be harder to drive currents on the nightside than on the dayside.Key words. Ionosphere (electric fields and currents) – Magnetospheric physics (current systems; magnetosphere-ionosphere interactions)

scholarly journals Characteristics of the terrestrial field-aligned current system

2011 ◽  
Vol 29 (10) ◽  
pp. 1713-1729 ◽  
Author(s):  
J. W. Gjerloev ◽  
S. Ohtani ◽  
T. Iijima ◽  
B. Anderson ◽  
J. Slavin ◽  
...  
Keyword(s):  
Large Scale ◽  
Current System ◽  
Scale Size ◽  
Terrestrial Magnetosphere ◽  
Field Aligned Current ◽  
Low Altitude ◽  
String Formation ◽  
Energy And Momentum ◽  
Current Systems ◽  
The Magnetic Field

Abstract. We present the first ever comprehensive statistical study of the spatiotemporal characteristics of field-aligned currents in the terrestrial magnetosphere-ionosphere system using multi point measurements. We determine how the FAC density, variability and scale size are coupled. The three ST 5 satellites were in a pearls-on-a-string formation making measurements of the magnetic field with variable inter-spacecraft separations ranging from a few seconds to about 10 min. More than 4700 sets of satellite passes are analyzed using a robust correlation analysis aimed at determining the variability of the FAC system as a function of scale size and satellite spacing. We find significant differences between the FAC characteristics on the dayside and on the nightside in terms of dynamics of the current systems. On the dayside the FAC characteristics are found to be independent of IMF Bz and geomagnetic activity while the nightside indicates increased variability during disturbed conditions. The boundary separating highly and poorly correlated FACs can be fitted by a linear line for satellite separations shorter than 60 s (dayside) and 160 s (nightside). We interpret this as the dayside and nightside magnetospheric reconfiguration times respectively. For times exceeding this the FAC characteristics are suggested to be controlled by the solar wind (dayside) and plasma sheet (nightside) dynamics. Finally, the characteristics of FAC system with scale sizes larger than ~200 km (at ionospheric altitude) appear to be stable and repeatable on time scales of the order of a minute (i.e. comparable to the low-altitude orbiting satellite's traverse time across the auroral belt). In this sense, our results effectively validate the Iijima and Potemra (1978) assumption that on average the large-scale currents with scale sizes of the Region1 and Region2 are quasi-persistently significant in the transport of energy and momentum between the magnetosphere and the ionosphere.

scholarly journals Jovian magnetospheric and auroral effects of the SL9 impacts

1996 ◽  
Vol 156 ◽  
pp. 347-373
Author(s):  
Wing-Huen IP
Keyword(s):  
Conjugate Points ◽  
Diffusive Transport ◽  
Abrupt Increase ◽  
Short Term ◽  
X Ray ◽  
Cometary Dust ◽  
Jovian Magnetosphere ◽  
Auroral Emission ◽  
Field Aligned Current ◽  
Current Systems

The collisions of comet Shoemaker-Levy 9 with Jupiter have produced many surprising auroral and magnetospheric phenomena. The energy released during the passage of the cometary dust comas through the jovian magnetosphere and at atmospheric explosion could lead to impulsive particle acceleration, enhanced radial diffusive transport, and the establishment of field-aligned current systems connecting the comet impact sites to their respective magnetic conjugate points. Some of the observed effects such as the abrupt increase of decimetric radio emission, the excitation of infrared emissions and mid-latitude auroral emission in the ultraviolet, could be interpreted within the framework of these mechanisms. Several auroral features like the X-ray outbursts and short-term variations in the UV emissions are more puzzling and require further observation of jovian auroral dynamics in these wavelength ranges in coordination with the Galileo mission.

scholarly journals Project MONICA for the Study of Time-Variable Phenomena of the Jovian Sodium Cloud and the Io Plasma Torus

2001 ◽  
Vol 183 ◽  
pp. 281-282
Author(s):  
Chien-Pang Chang ◽  
Wing Ip
Keyword(s):  
Progress Report ◽  
Astronomical Observatory ◽  
Time Variable ◽  
Dust Particles ◽  
Galilean Satellite ◽  
Active Volcanism ◽  
Jovian Magnetosphere ◽  
Jovian System ◽  
Plasma Torus ◽  
Io Plasma Torus

AbstractBecause of active volcanism, large amounts of gas and dust particles are being injected from the Galilean satellite, Io, into the Jovian system. The neutral cloud of sodium atoms and the plasma torus of sulfur ions provide very useful information on Io’s interaction with the Jovian magnetosphere. A program called MONICA (Monitoring of Neutral and Ionized Atoms Clouds) was established at NCU with a view to participate in an international campaign during the flyby of the Jovian system by the Cassini spacecraft in December, 2000. Spectrographic observations were carried out using the 2.16m spectrograph of the Beijing Astronomical Observatory in Xing-Long. A progress report is presented here.

scholarly journals LOW-ALTITUDE LONG-ENDURANCE SOLAR UNMANNED PLANE FOR FOREST FIRE PREVENTION: APPLICATION TO THE NATURAL PARK OF SERRA DO XURES (SPAIN)

2017 ◽  
Vol XLII-2/W6 ◽  
pp. 135-139 ◽  
Author(s):  
H. González-Jorge ◽  
M. Bueno ◽  
J. Martínez-Sánchez ◽  
P. Arias
Keyword(s):  
Forest Fires ◽  
Mission Planning ◽  
Pixel Resolution ◽  
Natural Park ◽  
Forest Fire Prevention ◽  
Unmanned System ◽  
Low Altitude ◽  
Illegal Activities ◽  
Aerial Systems ◽  
Long Endurance

Unamnned aerial systems (UAS) show great potential in operations related to surveillance. These systems can be successfully applied to the prevention of forest fires, especially those caused by human intervention. The present works focuses on a study of the operational possibilities of the unmanned system “AtlantikSolar” developed by the ETH Zurich for the prevention of forest fires in the Spanish natural park of Serra do Xurés, an area of 20,920&amp;thinsp;ha with height variations between 300&amp;thinsp;m and 1,500&amp;thinsp;m. <br><br> The operation evaluation of AtlantikSolar is based on the use of Flir Tau 2 LWIR camera as imaging payload which could detect illegal activities in the forest, such as bonfires, uncontrolled burning or pyromaniacs. Flight surveillance is planned for an altitude of 100&amp;thinsp;m to obey the legal limit of the Spanish UAS regulation. This altitude produces a swath width of 346.4&amp;thinsp;m and pixel resolution between 1.5 and 1.8&amp;thinsp;pixels/m. Operation is planned to adapt altitude to the change on the topography and obtain a constant ground resolution. Operational speed is selected to 52&amp;thinsp;km/h. The UAS trajectory is adapted to the limits of the natural park and the border between Spain and Portugal. Matlab code is developed for mission planning. The complete surveillance of the natural park requires a total time of 15.6 hours for a distance of 811.6&amp;thinsp;km.

scholarly journals Threat Assessment Method of Low Altitude Slow Small (LSS) Targets Based on Information Entropy and AHP

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1292
Author(s):  
Ruining Luo ◽  
Shucai Huang ◽  
Yan Zhao ◽  
Yafei Song
Keyword(s):  
Information Entropy ◽  
Threat Assessment ◽  
Assessment Method ◽  
Mission Planning ◽  
Experimental Simulation ◽  
Detection Capability ◽  
Analytic Hierarchy ◽  
Air Defense ◽  
Low Altitude ◽  
Hierarchy Process

In order to deal with the new threat of low altitude slow small (LSS) targets in air defense operations and provide support for LSS target interception decision, we propose a simple and reliable LSS target threat assessment method. Based on the detection capability of LSS targets and their threat characteristics, this paper proposes a threat evaluation factor and threat degree quantization function in line with the characteristics of LSS targets. LSS targets not only have the same threat characteristics as traditional air targets but also have the unique characteristics of flexible mobility and dynamic mission planning. Therefore, we use analytic hierarchy process (AHP) and information entropy to determine the subjective and objective threat factor weights of LSS targets and use the optimization model to combine them to obtain more reliable evaluation weights. Finally, the effectiveness and credibility of the proposed method are verified by experimental simulation.

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