Crustal magnetic fields at Mars and ion escape

2020 ◽  
Author(s):  
Eduard Dubinin ◽  
Markus Fraenz ◽  
Marin Pätzold ◽  
Joachim Woch ◽  
Kai Fan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Protective Effect ◽  
Southern Hemisphere ◽  
Shielding Effect ◽  
Oxygen Ions ◽  
Ion Escape ◽  
Crustal Field ◽  
Unsolved Issue

<p>Does an intrinsic field inhibits or enhances ion escape from planetary ionospheres is still an unsolved issue. Mars does not possess a global intrinsic magnetic field but instead has the strong crustal magnetic fields localized mainly in the southern hemisphere. The crustal magnetic field significantly influences the interaction of the solar wind with Mars adding features typical for planets with a global intrinsic magnetic field. Therefore it is interesting to compare ion losses from the ionosphere regions with and without strong crustal fields. Recently such studies were performed and have shown a protective effect of the crustal field on escape of the energized (E > 30 eV) oxygen ions (e.g. Fan et al., Geophysical Review Letters, 2019). However, the main bulk of escaping ions at Mars have energy lower than 30 eV. We will present the results of influence of the crustal magnetic field at Mars on the total losses of O<sup>+</sup> and O<sub>2</sub><sup>+</sup> ions. The global picture of ion escape occurs more complex. Effects of larger ionospheric areas above the crustal field sources exposed by solar wind compensate a shielding effect at lower altitudes. As a result, the ion losses from the southern ionosphere of Mars might be even higher than losses from the northern “unmagnetized” ionosphere.</p>

scholarly journals Azimuthal magnetic fields in Saturn’s magnetosphere: effects associated with plasma sub-corotation and the magnetopause-tail current system

2003 ◽  
Vol 21 (8) ◽  
pp. 1709-1722 ◽  
Author(s):  
E. J. Bunce ◽  
S. W. H. Cowley ◽  
J. A. Wild
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Current System ◽  
Heavy Ion ◽  
Local Times ◽  
Dynamical Process ◽  
Tail Current ◽  
Field Lines ◽  
Inner Region

Abstract. We calculate the azimuthal magnetic fields expected to be present in Saturn’s magnetosphere associated with two physical effects, and compare them with the fields observed during the flybys of the two Voyager spacecraft. The first effect is associated with the magnetosphere-ionosphere coupling currents which result from the sub-corotation of the magnetospheric plasma. This is calculated from empirical models of the plasma flow and magnetic field based on Voyager data, with the effective Pedersen conductivity of Saturn’s ionosphere being treated as an essentially free parameter. This mechanism results in a ‘lagging’ field configuration at all local times. The second effect is due to the day-night asymmetric confinement of the magnetosphere by the solar wind (i.e. the magnetopause and tail current system), which we have estimated empirically by scaling a model of the Earth’s magnetosphere to Saturn. This effect produces ‘leading’ fields in the dusk magnetosphere, and ‘lagging’ fields at dawn. Our results show that the azimuthal fields observed in the inner regions can be reasonably well accounted for by plasma sub-corotation, given a value of the effective ionospheric Pedersen conductivity of ~ 1–2 mho. This statement applies to field lines mapping to the equator within ~ 8 RS (1 RS is taken to be 60 330 km) of the planet on the dayside inbound passes, where the plasma distribution is dominated by a thin equatorial heavy-ion plasma sheet, and to field lines mapping to the equator within ~ 15 RS on the dawn side outbound passes. The contributions of the magnetopause-tail currents are estimated to be much smaller than the observed fields in these regions. If, however, we assume that the azimuthal fields observed in these regions are not due to sub-corotation but to some other process, then the above effective conductivities define an upper limit, such that values above ~ 2 mho can definitely be ruled out. Outside of this inner region the spacecraft observed both ‘lagging’ and ‘leading’ fields in the post-noon dayside magnetosphere during the inbound passes, with ‘leading’ fields being observed both adjacent to the magnetopause and in the ring current region, and ‘lagging’ fields being observed between. The observed ‘lagging’ fields are consistent in magnitude with the sub-corotation effect with an effective ionospheric conductivity of ~ 1–2 mho, while the ‘leading’ fields are considerably larger than those estimated for the magnetopause-tail currents, and appear to be indicative of the presence of another dynamical process. No ‘leading’ fields were observed outside the inner region on the dawn side outbound passes, with the azimuthal fields first falling below those expected for sub-corotation, before increasing, to exceed these values at radial distances beyond ~ 15–20 RS , where the effect of the magnetopause-tail currents becomes significant. As a by-product, our investigation also indicates that modification and scaling of terrestrial magnetic field models may represent a useful approach to modelling the three-dimensional magnetic field at Saturn.Key words. Magnetospheric physics (current systems; magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)

scholarly journals Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

2014 ◽  
Vol 32 (10) ◽  
pp. 1247-1261 ◽  
Author(s):  
L. Turc ◽  
D. Fontaine ◽  
P. Savoini ◽  
E. K. J. Kilpua
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Bow Shock ◽  
Field Direction ◽  
Magnetic Clouds ◽  
Magnetic Field Direction ◽  
Field Orientation ◽  
The Impact ◽  
The Magnetic Field

Abstract. Magnetic clouds (MCs) are large-scale magnetic flux ropes ejected from the Sun into the interplanetary space. They play a central role in solar–terrestrial relations as they can efficiently drive magnetic activity in the near-Earth environment. Their impact on the Earth's magnetosphere is often attributed to the presence of southward magnetic fields inside the MC, as observed in the upstream solar wind. However, when they arrive in the vicinity of the Earth, MCs first encounter the bow shock, which is expected to modify their properties, including their magnetic field strength and direction. If these changes are significant, they can in turn affect the interaction of the MC with the magnetosphere. In this paper, we use data from the Cluster and Geotail spacecraft inside the magnetosheath and from the Advanced Composition Explorer (ACE) upstream of the Earth's environment to investigate the impact of the bow shock's crossing on the magnetic structure of MCs. Through four example MCs, we show that the evolution of the MC's structure from the solar wind to the magnetosheath differs largely from one event to another. The smooth rotation of the MC can either be preserved inside the magnetosheath, be modified, i.e. the magnetic field still rotates slowly but at different angles, or even disappear. The alteration of the magnetic field orientation across the bow shock can vary with time during the MC's passage and with the location inside the magnetosheath. We examine the conditions encountered at the bow shock from direct observations, when Cluster or Geotail cross it, or indirectly by applying a magnetosheath model. We obtain a good agreement between the observed and modelled magnetic field direction and shock configuration, which varies from quasi-perpendicular to quasi-parallel in our study. We find that the variations in the angle between the magnetic fields in the solar wind and in the magnetosheath are anti-correlated with the variations in the shock obliquity. When the shock is in a quasi-parallel regime, the magnetic field direction varies significantly from the solar wind to the magnetosheath. In such cases, the magnetic field reaching the magnetopause cannot be approximated by the upstream magnetic field. Therefore, it is important to take into account the conditions at the bow shock when estimating the impact of an MC with the Earth's environment because these conditions are crucial in determining the magnetosheath magnetic field, which then interacts with the magnetosphere.

Degenerate induced magnetospheres

2020 ◽  
Author(s):  
Stas Barabash ◽  
Andrii Voshchepynets ◽  
Mats Holmström ◽  
Futaana Yoshifumi ◽  
Robin Ramstad
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Interplanetary Magnetic Field ◽  
Solar Wind Plasma ◽  
Stellar Winds ◽  
Ionospheric Currents ◽  
Magnetic Barrier ◽  
Atmospheric Escape ◽  
The Subject

<p>Induced magnetospheres of non-magnetized atmospheric bodies like Mars and Venus are formed by magnetic fields of ionospheric currents induced by the convective electric field E = - V x B/c of the solar wind. The induced magnetic fields create a magnetic barrier which forms a void of the solar wind plasma, an induced magnetosphere. But what happens when the interplanetary magnetic field is mostly radial and the convective field E ≈ 0? Do a magnetic barrier and solar wind void form? If yes, how such a degenerate induced magnetosphere work? The question is directly related to the problem of the atmospheric escape due to the interaction with the solar and stellar winds. The radial interplanetary magnetic field in the inner solar system is typical for the ancient Sun conditions and exoplanets on near-star orbits. Also, the radial interplanetary field may provide stronger coupling of the near-planet environment with the solar/stellar winds and thus effectively channels the solar/stellar wind energy to the ionospheric ions. We review the current works on the subject, show examples of degenerate induced magnetospheres of Mars and Venus from Mars Express, Venus Express, and MAVEN measurements and hybrid simulations, discuss physics of degenerate induced magnetospheres, and impact of such configurations on the escape processes.</p>

Shielding from external magnetic fields by rotating magnetic conducting cylindrical shells

2015 ◽  
Vol 34 (2) ◽  
pp. 505-513
Author(s):  
Marcin Ziolkowski ◽  
Stanislaw Gratkowski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Static Magnetic Field ◽  
Analytical Solutions ◽  
Separation Of Variables ◽  
Shielding Effect ◽  
Magnetic Vector Potential ◽  
Content Type ◽  
Shielding Factor ◽  
Cylindrical Screen

Purpose – In many different engineering fields often there is a need to protect regions from electromagnetic interference. According to static and low-frequency magnetic fields the common strategy bases on using a shield made of conductive or ferromagnetic material. Another screening technique uses solenoids that generate an opposite magnetic field to the external one. The purpose of this paper is to discuss the shielding effect for a magnetic and conducting cylindrical screen rotating in an external static magnetic field. Design/methodology/approach – The magnetic flux density is expressed in terms of the magnetic vector potential. Applying the separation of variables method analytical solutions are obtained for an infinitely long magnetic conducting cylindrical screen rotating in a uniform static transverse magnetic field. Findings – Analytical formulas of the shielding factor for a cylindrical screen of arbitrary conductivity and magnetic permeability are given. A magnetic Reynolds number is found to be an appropriate indication of the change in magnetic field inside the screen. Useful simplified expressions are presented. Originality/value – This paper treats in a qualitative way the possibility of static magnetic field shielding by using rotating conducting magnetic cylindrical screens. Analytical solutions are given. If the angular velocity is equal to zero or the relative permeability of the shield is equal to one the shielding factor has forms well known from literature.

scholarly journals Understanding the origins of the heliosphere: integrating observations and measurements from Parker Solar Probe, Solar Orbiter, and other space- and ground-based observatories

2020 ◽  
Vol 642 ◽  
pp. A4 ◽  
Author(s):  
M. Velli ◽  
L. K. Harra ◽  
A. Vourlidas ◽  
N. Schwadron ◽  
O. Panasenco ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Energetic Particles ◽  
Solar Energetic Particles ◽  
Coronal Plasma ◽  
Solar Dynamics Observatory ◽  
Surface Magnetic Field ◽  
In Situ Observations

Context. The launch of Parker Solar Probe (PSP) in 2018, followed by Solar Orbiter (SO) in February 2020, has opened a new window in the exploration of solar magnetic activity and the origin of the heliosphere. These missions, together with other space observatories dedicated to solar observations, such as the Solar Dynamics Observatory, Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations from WIND and ACE, and ground based multi-wavelength observations including the DKIST observatory that has just seen first light, promise to revolutionize our understanding of the solar atmosphere and of solar activity, from the generation and emergence of the Sun’s magnetic field to the creation of the solar wind and the acceleration of solar energetic particles. Aims. Here we describe the scientific objectives of the PSP and SO missions, and highlight the potential for discovery arising from synergistic observations. Here we put particular emphasis on how the combined remote sensing and in situ observations of SO, that bracket the outer coronal and inner heliospheric observations by PSP, may provide a reconstruction of the solar wind and magnetic field expansion from the Sun out to beyond the orbit of Mercury in the first phases of the mission. In the later, out-of-ecliptic portions of the SO mission, the solar surface magnetic field measurements from SO and the multi-point white-light observations from both PSP and SO will shed light on the dynamic, intermittent solar wind escaping from helmet streamers, pseudo-streamers, and the confined coronal plasma, and on solar energetic particle transport. Methods. Joint measurements during PSP–SO alignments, and magnetic connections along the same flux tube complemented by alignments with Earth, dual PSP–Earth, and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will allow a better understanding of the in situ evolution of solar-wind plasma flows and the full three-dimensional distribution of the solar wind from a purely observational point of view. Spectroscopic observations of the corona, and optical and radio observations, combined with direct in situ observations of the accelerating solar wind will provide a new foundation for understanding the fundamental physical processes leading to the energy transformations from solar photospheric flows and magnetic fields into the hot coronal plasma and magnetic fields and finally into the bulk kinetic energy of the solar wind and solar energetic particles. Results. We discuss the initial PSP observations, which already provide a compelling rationale for new measurement campaigns by SO, along with ground- and space-based assets within the synergistic context described above.

Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach

2021 ◽  
Author(s):  
Elena Kronberg ◽  
Fabio Gastaldello ◽  
Stein Haaland ◽  
Artem Smirnov ◽  
Max Berrendorf ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Machine Learning ◽  
Solar Wind ◽  
Southern Hemisphere ◽  
Solar Wind Speed ◽  
Flank Region ◽  
Learning Approach ◽  
X Ray ◽  
Machine Learning Approach ◽  
Field Lines

<p>One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes flying mainly in the magnetosphere are soft protons with few tens to hundreds of keV concentrated. One such telescope is the X-ray Multi-Mirror Mission (XMM-Newton) by ESA. Its observing time lost due to the contamination is  about 40%. This affects all the major broad science goals of XMM, ranging from cosmology to astrophysics of neutron stars and black holes. The soft proton background could dramatically impact future X-ray missions such Athena and SMILE missions. Magnetopsheric processes that trigger this background are still poorly understood. We use a machine learning approach to delineate related important parameters and to develop a model to predict the background contamination using 12 years of XMM observations. As predictors we use the location of XMM, solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in southern direction, ZGSE, (XMM observations were in the southern hemisphere), the solar wind velocity and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the best two individual predictors and a machine learning model which utilizes an ensemble of the predictors (Extra Trees Regressor) and gives better performance. Based on our analysis, future X-Ray missions in the magnetosphere should minimize observations during  times  associated with high solar wind speed  and avoid closed magnetic field lines, especially at the dusk flank region at least in the southern hemisphere. </p>

scholarly journals On the relaxation of magnetospheric convection when <I>B</I><sub>z</sub> turns northward

2012 ◽  
Vol 30 (6) ◽  
pp. 927-928 ◽  
Author(s):  
M. C. Kelley
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Interplanetary Magnetic Field ◽  
Time Constant ◽  
Joule Heat ◽  
Upper Atmosphere ◽  
Joule Dissipation ◽  
Polar Cap ◽  
Magnetospheric Convection

Abstract. The solar wind inputs considerable energy into the upper atmosphere, particularly when the interplanetary magnetic field (IMF) is southward. According to Poynting's theorem (Kelley, 2009), this energy becomes stored as magnetic fields and then is dissipated by Joule heat and by energizing the plasmasheet plasma. If the IMF turns suddenly northward, very little energy is transferred into the system while Joule dissipation continues. In this process, the polar cap potential (PCP) decreases. Experimentally, it was shown many years ago that the energy stored in the magnetosphere begins to decay with a time constant of two hours. Here we use Poynting's theorem to calculate this time constant and find a result that is consistent with the data.

Possible Magnetic Interaction of Asteroids with the Solar Wind

1971 ◽  
Vol 12 ◽  
pp. 567-575 ◽  
Author(s):  
Eugene W. Greenstadt
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Magnetic Interaction ◽  
Planetary Body ◽  
Surface Magnetic Field

Investigation of extraterrestrial objects is habitually accompanied by the observation of extraterrestrial magnetic fields, which often have significant effects on the solar wind in the vicinity of the objects. Should we be surprised to find this experience repeated at an asteroid?A recent study considered the conditions that would have to be satisfied by the surface magnetic field of a small planetary body at asteroidal distances so that the field would be an obstacle capable of stopping the solar wind or deflecting it sufficiently to generate a detectable magnetic interaction (Greenstadt, 1971).

scholarly journals The global heliospheric magnetic field polarity distribution as seen at Ulysses

2003 ◽  
Vol 21 (6) ◽  
pp. 1377-1382 ◽  
Author(s):  
G. H. Jones ◽  
A. Balogh
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Activity ◽  
Magnetic Fields ◽  
Current Sheet ◽  
Heliospheric Current Sheet ◽  
Field Polarity ◽  
Heliospheric Magnetic Field ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics

Abstract. The Ulysses spacecraft is in a near-polar solar orbit with a period of 6.2 years. The heliospheric magnetic field polarity detected by Ulysses from its 1992 Jupiter encounter to the current time is presented, following ballistic mapping of the polarity information to the solar wind source surface, at approximately 2.5 solar radii. The spacecraft’s first foray to polar latitudes and first rapid heliolatitude scan occurred in 1994–1995, near a minimum in solar activity. The heliospheric current sheet during this period was confined to low heliolatitudes. In 2000–2001, Ulysses returned in situ data from the same region of its orbit as in 1994–1995, but near to the maximum in solar activity. Unlike at solar minimum, heliospheric current sheet crossings were detected at the spacecraft over a wide heliolatitude range, which is consistent with the reversal of the solar magnetic dipole occurring during solar maximum. Despite complexity in the solar wind parameters during the latest fast latitude scan (McComas et al., 2002), the underlying magnetic field structure appears consistent with a simple dipole inclined at a large angle to the solar rotational axis. The most recent data show the heliospheric current sheet returning to lower heliolatitudes, indicating that the dipole and rotational axes are realigning, with the Sun’s magnetic polarity having reversed.Key words. Interplanetary physics (interplanetary magnetic fields; sources of the solar wind) – Solar physics, astrophysics and astronomy (magnetic fields)

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