Magnetic field influence on aurorae and the Jovian plasma disk radial structure

Abstract. The Jovian paraboloid magnetospheric model is applied for the investigation of the planet's auroral emission and plasma disk structure in the middle magnetosphere. Jupiter's auroral emission demonstrates the electrodynamic coupling between the ionosphere and magnetosphere. For comparison of different regions in the ionospheric level and in the magnetosphere, the paraboloid model of the global magnetospheric magnetic field is used. This model provides mapping along highly-conducting magnetic field lines. The paraboloid magnetic field model is also applied for consideration of the stability of the background plasma disk in the rotating Jupiter magnetosphere with respect to the flute perturbations. Model radial distribution of the magnetic field and experimental data on the plasma angular velocity in the middle Jovian magnetosphere are used. A dispersion relation of the plasma perturbations in the case of a perfectly conducting ionosphere is obtained. Analyzing starting conditions of a flute instability in the disk, the "threshold" radial profile of the plasma density is determined. An application of the results obtained to the known data on the Jovian plasma disk is discussed.

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Rotation of the magnetic field in Earth's magnetosheath by bulk magnetosheath plasma flow

Annales Geophysicae ◽

10.5194/angeo-24-339-2006 ◽

2006 ◽

Vol 24 (1) ◽

pp. 339-354 ◽

Cited By ~ 9

Author(s):

M. Longmore ◽

S. J. Schwartz ◽

E. A. Lucek

Keyword(s):

Magnetic Field ◽

Field Line ◽

Plasma Flow ◽

Mean Value ◽

Flow Coupling ◽

Parker Spiral ◽

Magnetic Field Model ◽

Field Lines ◽

The Magnetic Field

Abstract. Orientations of the observed magnetic field in Earth's dayside magnetosheath are compared with the predicted field line-draping pattern from the Kobel and Flückiger static magnetic field model. A rotation of the overall magnetosheath draping pattern with respect to the model prediction is observed. For an earthward Parker spiral, the sense of the rotation is typically clockwise for northward IMF and anticlockwise for southward IMF. The rotation is consistent with an interpretation which considers the twisting of the magnetic field lines by the bulk plasma flow in the magnetosheath. Histogram distributions describing the differences between the observed and model magnetic field clock angles in the magnetosheath confirm the existence and sense of the rotation. A statistically significant mean value of the IMF rotation in the range 5°-30° is observed in all regions of the magnetosheath, for all IMF directions, although the associated standard deviation implies large uncertainty in the determination of an accurate value for the rotation. We discuss the role of field-flow coupling effects and dayside merging on field line draping in the magnetosheath in view of the evidence presented here and that which has previously been reported by Kaymaz et al. (1992).

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Reconstruction of the magnetic connection from Mercury to the solar corona

10.5194/egusphere-egu2020-7086 ◽

2020 ◽

Author(s):

Alessandro Ippolito ◽

Christina Plainaki ◽

Gaetano Zimbardo ◽

Stefano Massetti ◽

Anna Milillo

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Magnetic Data ◽

Monte Carlo Code ◽

Correlation Lengths ◽

Magnetic Fluctuation ◽

Magnetic Field Model ◽

Field Lines ◽

Field Correlation ◽

Accelerated Particles

The magnetic foot point of Mercury on the solar disk has been reconstructed for selected case studies, in order to better understand the interaction between the solar corona and the planet. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that gives a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a &#8220;local&#8221; diffusion coefficient, which is a function of the fluctuation level and magnetic field correlation lengths. The simulation is tailored to specific events by using the observed values of solar wind velocity and magnetic fluctuation levels. Magnetic data from MAG/MESSENGER have been considered to compute the magnetic fluctuation level, while, concerning proton fluxes, FIPS/MESSENGER data has been taken into account. A number of SEP events observed on Mercury during 2011 and 2012 have been analysed, studying, for each event, the magnetic connection from Mercury to the solar corona, and the position of the active region possibly source of the accelerated particles observed.

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Magnetic Flux Transport in Protostellar Accretion Disks

International Astronomical Union Colloquium ◽

10.1017/s0252921100043451 ◽

1997 ◽

Vol 163 ◽

pp. 692-692

Author(s):

John Contopoulos ◽

Arieh Königl

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Accretion Disks ◽

Large Scale ◽

Turbulent Viscosity ◽

Flux Transport ◽

Disk Structure ◽

Large Scale Magnetic Field ◽

Field Lines ◽

Open Magnetic Field

AbstractCentrifugally driven winds from the surfaces of magnetized accretion disks are a leading candidate for the origin of bipolar outflows and have also been recognized as an attractive mechanism for removing the angular momentum of the accreted matter. The origin of the open magnetic field lines that thread the disk in this scenario is, however, still uncertain. One possibility is that the field lines are transported through the disk, but previous studies have shown that this process is inefficient in disks with turbulent viscosity and diffusivity. Here we examine whether the efficiency can be increased if angular momentum is transported from the disk surfaces by large-scale magnetic fields instead of radially by viscous stresses. In this picture, the removal of angular momentum is associated with the establishment of a global poloidal electric current driven by the radial EMF in the disc, and it does not necessarily need to involve super-Alfvénic outflows. We address this problem in the context of protostellar systems and present representative solutions of the time evolution of a resistive disk that is initially threaded by a uniform vertical field anchored at a large distance from its surfaces. We assume that the angular momentum transport in the disk is controlled by the large-scale magnetic field and take into account the influence of the field on the disk structure.

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Ionospheric Outflow at Jupiter and Saturn

10.5194/epsc2020-369 ◽

2020 ◽

Author(s):

Carley Martin ◽

Licia Ray ◽

David Constable ◽

David Southwood ◽

Marianna Felici ◽

...

Keyword(s):

Magnetic Field ◽

Fluid Model ◽

Plasma Source ◽

Atmospheric Plasma ◽

Atmospheric Conditions ◽

Centrifugal Forces ◽

Mass Source ◽

Auroral Emission ◽

Ionospheric Outflow ◽

Field Lines

Ionospheric outflow is the outward flow of atmospheric plasma, initiated by a loss of equilibrium along the magnetic field. Terrestrial ionospheric outflow presents as a polar wind triggered by the Dungey cycle, which drives much of Earth&#8217;s magnetospheric dynamics. At Saturn, Felici et al. [2016] observed ionospheric outflow in the lobes at 36 RS. Interestingly, at Jupiter, Valek et al. [2019] reported ionospheric outflow on magnetic field lines with invariant latitudes between Io&#8217;s auroral signatures and the main auroral emission, lower than the polar cap.At Jupiter and Saturn, the rapid rotation of the planet, coupled with an internal plasma source inside each magnetosphere, results in the Vasyliunas cycle, by which material is circulated throughout the system, eventually being lost down the magnetotail. This constant churning likely results in a system where ionospheric outflow occurs more readily at mid-to-high planetary latitudes that map to the middle magnetosphere, rather than solely at polar latitudes. Furthermore, ionospheric outflow at the Jupiter and Saturn will be affected by strong centrifugal forces and auroral currents, which are near omnipresent in each magnetosphere.Using a 1-dimensional, hydrodynamic, multi-fluid model, we determine the ionospheric outflow in the jovian and saturnian systems. Our model includes the effect of centrifugal forces and auroral field-aligned currents, both of which act to enhance outflow rates from previous studies. We find that ionospheric outflow may provide a significant contribution to the jovian and saturnian systems, with the mass source rates of 18.7 &#8211; 31.7 kg s-1and 5.5-17.7 kg s-1, respectively, where the range reflects the sensitivity to the assumed initial atmospheric conditions.

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Magnetospheric magnetic field modelling for the 2011 and 2012 HST Saturn aurora campaigns – implications for auroral source regions

Annales Geophysicae ◽

10.5194/angeo-32-689-2014 ◽

2014 ◽

Vol 32 (6) ◽

pp. 689-704 ◽

Cited By ~ 18

Author(s):

E. S. Belenkaya ◽

S. W. H. Cowley ◽

C. J. Meredith ◽

J. D. Nichols ◽

V. V. Kalegaev ◽

...

Keyword(s):

Magnetic Field ◽

Ring Current ◽

Hubble Space Telescope ◽

Current System ◽

Outer Edge ◽

Local Times ◽

Closed Field ◽

Principal Connection ◽

Magnetic Field Model ◽

Field Lines

Abstract. A unique set of images of Saturn's northern polar UV aurora was obtained by the Hubble Space Telescope in 2011 and 2012 at times when the Cassini spacecraft was located in the solar wind just upstream of Saturn's bow shock. This rare situation provides an opportunity to use the Kronian paraboloid magnetic field model to examine source locations of the bright auroral features by mapping them along field lines into the magnetosphere, taking account of the interplanetary magnetic field (IMF) measured near simultaneously by Cassini. It is found that the persistent dawn arc maps to closed field lines in the dawn to noon sector, with an equatorward edge generally located in the inner part of the ring current, typically at ~ 7 Saturn radii (RS) near dawn, and a poleward edge that maps variously between the centre of the ring current and beyond its outer edge at ~ 15 RS, depending on the latitudinal width of the arc. This location, together with a lack of response in properties to the concurrent IMF, suggests a principal connection with ring-current and nightside processes. The higher-latitude patchy auroras observed intermittently near to noon and at later local times extending towards dusk are instead found to straddle the model open–closed field boundary, thus mapping along field lines to the dayside outer magnetosphere and magnetopause. These emissions, which occur preferentially for northward IMF directions, are thus likely associated with reconnection and open-flux production at the magnetopause. One image for southward IMF also exhibits a prominent patch of very high latitude emissions extending poleward of patchy dawn arc emissions in the pre-noon sector. This is found to lie centrally within the region of open model field lines, suggesting an origin in the current system associated with lobe reconnection, similar to that observed in the terrestrial magnetosphere for northward IMF.

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Electron dynamics during substorm dipolarization in Mercury's magnetosphere

Annales Geophysicae ◽

10.5194/angeo-23-3389-2005 ◽

2005 ◽

Vol 23 (10) ◽

pp. 3389-3398 ◽

Cited By ~ 18

Author(s):

D. C. Delcourt ◽

K. Seki ◽

N. Terada ◽

Y. Miyoshi

Keyword(s):

Magnetic Field ◽

High Energy ◽

Expansion Phase ◽

Earth’S Magnetosphere ◽

High Energy Electrons ◽

Earth's Magnetosphere ◽

Magnetic Field Model ◽

Particle Simulations ◽

Field Lines ◽

The Magnetic Field

Abstract. We examine the nonlinear dynamics of electrons during the expansion phase of substorms at Mercury using test particle simulations. A simple model of magnetic field line dipolarization is designed by rescaling a magnetic field model of the Earth's magnetosphere. The results of the simulations demonstrate that electrons may be subjected to significant energization on the time scale (several seconds) of the magnetic field reconfiguration. In a similar manner to ions in the near-Earth's magnetosphere, it is shown that low-energy (up to several tens of eV) electrons may not conserve the second adiabatic invariant during dipolarization, which leads to clusters of bouncing particles in the innermost magnetotail. On the other hand, it is found that, because of the stretching of the magnetic field lines, high-energy electrons (several keVs and above) do not behave adiabatically and possibly experience meandering (Speiser-type) motion around the midplane. We show that dipolarization of the magnetic field lines may be responsible for significant, though transient, (a few seconds) precipitation of energetic (several keVs) electrons onto the planet's surface. Prominent injections of energetic trapped electrons toward the planet are also obtained as a result of dipolarization. These injections, however, do not exhibit short-lived temporal modulations, as observed by Mariner-10, which thus appear to follow from a different mechanism than a simple convection surge.

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A satellite study of dayside auroral conjugacy

Annales Geophysicae ◽

10.1007/s00585-995-1134-4 ◽

1995 ◽

Vol 13 (11) ◽

pp. 1134-1143 ◽

Cited By ~ 5

Author(s):

H. B. Vo ◽

J. S. Murphree ◽

D. Hearn ◽

P. T. Newell ◽

C.-I. Meng

Keyword(s):

Magnetic Field ◽

Field Model ◽

Conjugate Point ◽

Source Region ◽

Conjugate Points ◽

Opposite Hemisphere ◽

The North ◽

Magnetic Field Model ◽

Field Lines ◽

Dipole Tilt

Abstract. A study of dayside auroral conjugacy has been done using the cleft/boundary layer auroral particle boundaries observed by the DMSP-F7 satellite in the southern hemisphere and the global UV auroral images taken by the Viking spacecraft in the northern hemisphere. The 22 events have been studied on the basis of an internal IGRF 1985 magnetic field; it is shown that there is a displacement of up to 4° in latitude from the conjugate points with the northern aurora appearing to be located poleward of the conjugate point. No local time dependence of the north-south auroral location difference was seen. The use of a more realistic magnetic field model for tracing field lines which incorporates the dipole tilt angle and Kp index, the Tsyganenko 1987 long model plus the IGRF 1985 internal magnetic field model, appears to organize the data better. Although with this external plus internal model some tracings did not close in the opposite hemisphere, 70% of those that did indicated satisfactory conjugacy. The study shows that the degree of auroral conjugacy is dependent upon the accuracy of the magnetic field model used to trace to the conjugate point, especially in the dayside region where the field lines can either go to the dayside magnetopause near the subsolar point or sweep all the way back to the flanks of the magnetotail. Also the discrepancy in the latitude of northern and southern aurora can be partially explained by the displacement of the neutral sheet (source region of the aurora) by the dipole tilt effect.

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Reconstruction of the magnetic connection from Mercury to the solar corona, during events in the solar proton fluxes observed by MESSENGER

10.5194/epsc2021-115 ◽

2021 ◽

Author(s):

Alessandro Ippolito ◽

Christina Plainaki ◽

Gaetano Zimbardo ◽

Tommaso Alberti ◽

Stefano Massetti ◽

...

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Solar Proton ◽

Source Surface ◽

Monte Carlo Code ◽

Correlation Lengths ◽

Magnetic Turbulence ◽

Proton Fluxes ◽

Magnetic Field Model ◽

Field Lines

We present a study conducted on a number of selected events characterised by a significant increase in the solar proton fluxes measured by FIPS-MESSENGER during the period 2011-2013. For each of them, the magnetic connection between Mercury and the solar corona (Source Surface Field @2.5 RS) has been reconstructed, in order to identify the possible source of the accelerated particles on the solar surface. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that computes a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a &#8220;local&#8221; diffusion coefficient, which is a function of the fluctuation level and magnetic turbulence correlation lengths. The simulation is tailored to the specific events by using the observed values of solar wind velocity and magnetic fluctuation levels.

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Coronal Loop Mapping to Infer the Best Magnetic Field Models for Active Region Prominences

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313011344 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 416-417

Author(s):

G. Allen Gary ◽

Qiang Hu ◽

Jong Kwan Lee

Keyword(s):

Magnetic Field ◽

Coronal Loop ◽

Field Model ◽

Three Dimensional ◽

Coronal Loops ◽

Magnetic Field Model ◽

Free Parameters ◽

Field Lines ◽

Fitness Parameter ◽

The Magnetic Field

AbstractThis article comments on the results of a new, rapid, and flexible manual method to map on-disk individual coronal loops of a two-dimensional EUV image into the three-dimensional coronal loops. The method by Gary, Hu, and Lee (2013) employs cubic Bézier splines to map coronal loops using only four free parameters per loop. A set of 2D splines for coronal loops is transformed to the best 3D pseudo-magnetic field lines for a particular coronal model. The results restrict the magnetic field models derived from extrapolations of magnetograms to those admissible and inadmissible via a fitness parameter. This method uses the minimization of the misalignment angles between the magnetic field model and the best set of 3D field lines that match a set of closed coronal loops. We comment on the implication of the fitness parameter in connection with the magnetic free energy and comment on extensions of our earlier work by considering the issues of employing open coronal loops or employing partial coronal loop.

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Ganymede’s magnetic footprint mapping: Modeling and HST observations

10.5194/epsc2020-105 ◽

2020 ◽

Author(s):

Tatphicha Promfu ◽

Suwicha Wannawichian ◽

Jonathan Nichols ◽

John Clarke

Keyword(s):

Magnetic Field ◽

Hubble Space Telescope ◽

Volcanic Eruptions ◽

Plasma Pressure ◽

Magnetic Field Mapping ◽

Hot Plasma ◽

Pressure Anisotropy ◽

Magnetic Field Model ◽

Field Lines ◽

The Magnetic Field

In this work, the locations of observed Ganymede&#8217;s magnetic footprint were compared with the locations predicted by the magnetic field model under different plasma conditions. The shifts of Ganymede's magnetic footprint locations from average footpath given by Grodent et al. (2008) were analyzed. The average path is created from about 1000 images taken by instruments onboarded Hubble Space Telescope (HST). The position shifts indicate the variation of magnetic field line mapping from Ganymede to Jupiter&#8217;s ionosphere. The two sets of data from HST were analyzed to obtain the locations of Ganymede&#8217;s magnetic footprint in 2007 and 2016. For both sets of data, at longitude ranging approximately from 170&#176; to 180&#176;, we found that the locations were significantly shifted in poleward direction between 0.5&#176; to 2&#176; from the average footpath. Different from data in May 2007, the Ganymede&#8217;s magnetic footprint locations in May 2016 at longitude about 160&#176; could possibly locate in equatorward direction. At orbital distance of Ganymede about 15 RJ, in Jupiter&#8217;s middle magnetosphere, there is strong influence of plasma, whose major source is Io&#8217;s volcanic eruptions. Thus, the variations of plasma resulting in the stretching of magnetic field lines affect the magnetic field mapping from Ganymede to ionosphere. Furthermore, based on the magnetodisc model, the hot plasma pressure anisotropy&#160;strongly influences the stretching of the field lines and the mapped locations of Ganymede&#8217;s footprint in ionosphere to be shifted in either poleward or equatorward directions. In this study, we detected both poleward and equatorward shifts in different observations, whose connection with the plasma environment in the middle magnetosphere awaits for further study.

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