Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate

ABSTRACT Intrinsic magnetic fields have long been thought to shield planets from atmospheric erosion via stellar winds; however, the influence of the plasma environment on atmospheric escape is complex. Here we study the influence of a weak intrinsic dipolar planetary magnetic field on the plasma environment and subsequent ion escape from a Mars-sized planet in a global three-dimensional hybrid simulation. We find that increasing the strength of a planet’s magnetic field enhances ion escape until the magnetic dipole’s standoff distance reaches the induced magnetosphere boundary. After this point increasing the planetary magnetic field begins to inhibit ion escape. This reflects a balance between shielding of the Southern hemisphere from ‘misaligned’ ion pickup forces and trapping of escaping ions by an equatorial plasmasphere. Thus, the planetary magnetic field associated with the peak ion escape rate is critically dependent on the stellar wind pressure. Where possible we have fit power laws for the variation of fundamental parameters (escape rate, escape power, polar cap opening angle, and effective interaction area) with magnetic field, and assessed upper and lower limits for the relationships.

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Heavy ion escape from Martian wake enhanced by magnetic reconnection

10.21203/rs.3.rs-902571/v1 ◽

2021 ◽

Author(s):

Lei Wang ◽

Can Huang ◽

Yasong Ge ◽

A. M. Du ◽

Rongsheng Wang ◽

...

Keyword(s):

Magnetic Reconnection ◽

Flux Rope ◽

Heavy Ion ◽

Escape Rate ◽

Wake Region ◽

Atmospheric Evolution ◽

Oxygen Ions ◽

Plasma Environment ◽

Ion Escape ◽

Reconnection Region

Abstract How ion escape from the near-Mars space is one of the biggest puzzles for understanding the atmospheric evolution of Mars. Ions in the plasma wake region continuously escape from the unmagnetized planet. Although the average ion escape rate in the wake region is relatively low, observations also have revealed the presence of events that contribute bursty and enhanced ion escape fluxes. Boundary instabilities and magnetic reconnection are suggested to be the candidate mechanisms. However, there is a lack of evaluation of ion escape caused by reconnection and comparison of the two mechanisms under a similar plasma environment. Here, we show an exciting reconnection event in the Martian wake. Two types of flux ropes are observed during the event. One was generated by reconnection, while others were produced by dayside boundary instability and convected to tail. The escape rate of oxygen ions in the reconnection region was estimated to be about 53–72% of the total tailward escape. Furthermore, the escape flux in the flux rope produced by reconnection was over twice that caused by dayside instabilities.

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Crustal magnetic fields at Mars and ion escape

10.5194/egusphere-egu2020-7864 ◽

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

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 &#64257;eld but instead has the strong crustal magnetic fields localized mainly in the southern hemisphere. The crustal magnetic field significantly in&#64258;uences 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+ and O2+ 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 &#8220;unmagnetized&#8221; ionosphere.

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Heavy ion escape from Mars, influence from solar wind conditions and crustal magnetic fields

Icarus ◽

10.1016/j.icarus.2011.08.003 ◽

2011 ◽

Vol 215 (2) ◽

pp. 475-484 ◽

Cited By ~ 76

Author(s):

Hans Nilsson ◽

Niklas J.T. Edberg ◽

Gabriella Stenberg ◽

Stas Barabash ◽

Mats Holmström ◽

...

Keyword(s):

Solar Wind ◽

Magnetic Fields ◽

Heavy Ion ◽

Ion Escape

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Phobos 2/ASPERA data revisited: Planetary ion escape rate from Mars near the 1989 solar maximum

Geophysical Research Letters ◽

10.1002/grl.50149 ◽

2013 ◽

Vol 40 (3) ◽

pp. 477-481 ◽

Cited By ~ 24

Author(s):

Robin Ramstad ◽

Yoshifumi Futaana ◽

Stas Barabash ◽

Hans Nilsson ◽

Sergio Martin del Campo B ◽

...

Keyword(s):

Solar Maximum ◽

Escape Rate ◽

Ion Escape

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The Martian atmospheric ion escape rate dependence on solar wind and solar EUV conditions: 1. Seven years of Mars Express observations

Journal of Geophysical Research Planets ◽

10.1002/2015je004816 ◽

2015 ◽

Vol 120 (7) ◽

pp. 1298-1309 ◽

Cited By ~ 36

Author(s):

Robin Ramstad ◽

Stas Barabash ◽

Yoshifumi Futaana ◽

Hans Nilsson ◽

Xiao-Dong Wang ◽

...

Keyword(s):

Solar Wind ◽

Rate Dependence ◽

Escape Rate ◽

Mars Express ◽

Ion Escape

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Reduced Atmospheric Ion Escape Above Martian Crustal Magnetic Fields

Geophysical Research Letters ◽

10.1029/2019gl084729 ◽

2019 ◽

Vol 46 (21) ◽

pp. 11764-11772 ◽

Cited By ~ 3

Author(s):

Kai Fan ◽

Markus Fraenz ◽

Yong Wei ◽

Qianqian Han ◽

Eduard Dubinin ◽

...

Keyword(s):

Magnetic Fields ◽

Ion Escape

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The escape of CO2+ and other heavy minor ions from Mars

10.5194/epsc2020-410 ◽

2020 ◽

Author(s):

Lukas Maes ◽

Markus Fraenz ◽

James McFadden ◽

Mehdi Benna

Keyword(s):

Mass Spectra ◽

Heavy Ion ◽

Escape Rate ◽

Neutral Gas ◽

Peak Fitting ◽

Ion Escape ◽

Fitting Method ◽

Static Data ◽

Martian Ionosphere ◽

Ion Species

Next to its main constituent O2+, the Martian ionosphere consists of several other ion species, like CO2+, O+, CO+, HCO+, N2+, etc. The ionospheric escape is dominated by O2+ and O+ ions, and as a result the escape of these species is well studied. The other, minor ion species are more difficult to measure in the escaping plasma, because their contribution is typically obscured in the mass spectra of ion instruments by the more abundant O2+ peak. In this study we use data from the SupraThermal And Thermal Ion Composition instrument (STATIC) on board MAVEN to investigate the escape of these ions. We use a peak-fitting method to separate the contribution of several ion species, including O2+, CO2+, O+ and ions with a mass between 28-30 AMU. Our method is validated against Neutral Gas and Ion Mass Spectrometer (NGIMS), also onboard MAVEN, and results in the ionosphere agree qualitatively very well. We apply this method to STATIC data from January 2016 until May 2019 to perform a statistical study examining the escape of low energy (<100 eV) heavy (>=16 AMU) ions throughout the Martian magnetosphere and its surrounding. We find that CO2+ ions do escape through the tail but at a very limited rate, namely at less than 1% of the O2+ escape rate. Ions with a mass between 28-30 AMU, however, are found to constitute a significant part of the ionospheric outflow, with an escape rate 30% of the O2+ rate and 15% of the total heavy ion escape.

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Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

International Astronomical Union Colloquium ◽

10.1017/s0252921100026038 ◽

1994 ◽

Vol 144 ◽

pp. 559-564

Author(s):

P. Ambrož ◽

J. Sýkora

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Magnetic Fields ◽

Solar Corona ◽

Coronal Magnetic Field ◽

Coronal Magnetic Fields ◽

Solar Eclipses ◽

Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

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Radio Measurements of Coronal Magnetic Fields

International Astronomical Union Colloquium ◽

10.1017/s0252921100024933 ◽

1994 ◽

Vol 144 ◽

pp. 21-28 ◽

Cited By ~ 4

Author(s):

G. B. Gelfreikh

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Solar Corona ◽

Active Regions ◽

High Sensitivity ◽

Coronal Magnetic Field ◽

Transverse Magnetic ◽

Radio Sources ◽

Radio Waves ◽

Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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