scholarly journals The Polar Wind Modulated by the Spatial Inhomogeneity of the Strength of the Earth’s Magnetic Field

2020 ◽  
Author(s):  
Kun Li ◽  
Matthias Förster ◽  
Zhaojin Rong ◽  
Stein Haaland ◽  
Elena Kronberg ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spatial Inhomogeneity ◽  
Polar Cap ◽  
Polar Wind ◽  
The Earth ◽  
Polar Rain ◽  
Ionospheric Outflow ◽  
Low Energy Ions ◽  
The Magnetic Field ◽  
Positively Charged

<p>When the geomagnetic field is weak, the small mirror force allows precipitating charged particles to deposit energy in the ionosphere. This leads to an increase in ionospheric outflow from the Earth’s polar cap region, but such an effect has not been previously observed because the energies of the ions of the polar ionospheric outflow are too low, making it difficult to detect the low-energy ions with a positively charged spacecraft. In this study, we found anti-correlation between ionospheric outflow and the strength of the Earth’s magnetic field. Our results suggest that the electron precipitation through the polar rain can be a main energy source of the polar wind during periods of high levels of solar activity. The decreased magnetic field due to spatial inhomogeneity of the Earth’s magnetic field and its effect on outflow can be used to study the outflow in history when the magnetic field was at similar levels.</p>

Evolution of the Earth’s polar wind escape from mid-Archean to present

2020 ◽  
Author(s):  
Kristina Kislyakova ◽  
Colin Johnstone ◽  
Manuel Scherf ◽  
Helmut Lammer ◽  
Mats Holmström ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Direct Simulation Monte Carlo ◽  
Opening Angle ◽  
Polar Wind ◽  
Oxygen Ions ◽  
Atmospheric Escape ◽  
The Earth ◽  
Time Period ◽  
Upper Limits ◽  
The Magnetic Field

<p>The evolution of habitable conditions on Earth is tightly connected to the evolution of its atmosphere which, in turn, is strongly influenced by atmospheric escape. We investigate the evolution of the the polar wind outflow from the magnetic cusps which is the dominant escape mechanism on the Earth. We perform Direct Simulation Monte Carlo (DSMC) simulations and estimate the upper limits on escape rates from the Earth's cusps starting from three gigayears ago (Ga) to present assuming the present-day composition of the atmosphere. We perform one additional simulation with a lower mixing ratio of oxygen of 1% to account for the conditions shortly after the Great Oxydation Event (GOE). We account for the evolution of the magnetic field of the Earth by adjusting the polar opening angle and the location of the magnetosphere's substellar point.</p><p>Our results present an upper limit on the escape rates, but they indicate that polar wind escape rates for nitrogen and oxygen ions were likely much higher in the past.  We estimate the maximum total loss rates due to polar wind of 2.0x10<sup>18</sup> kg and 5.2x10<sup>17</sup> kg for oxygen and nitrogen, respectively. According to our results, the main factors that governed the polar wind outflow in the considered time period are the evolution of the XUV radiation of the Sun and the atmosphere's composition. The evolution of the Earth's magnetic field plays a less important role. We conclude that although the atmosphere with the present-day composition can survive the escape due to polar wind outflow, a higher level of CO<sub>2</sub> between 3.0 and 2.0 Ga is likely necessary to reduce the escape.</p>

scholarly journals On the differential system govering flows in magnetic field with data inLp

1998 ◽  
Vol 21 (2) ◽  
pp. 299-305 ◽  
Author(s):  
Fengxin Chen ◽  
Ping Wang ◽  
Chaoshun Qu
Keyword(s):  
Magnetic Field ◽  
Initial Data ◽  
Boundary Conditions ◽  
Differential System ◽  
Existence And Uniqueness ◽  
Mhd Equations ◽  
The Earth ◽  
Initial And Boundary Conditions ◽  
Time Existence ◽  
The Magnetic Field

In this paper we study the system governing flows in the magnetic field within the earth. The system is similar to the magnetohydrodynamic (MHD) equations. For initial data in spaceLp, we obtained the local in time existence and uniqueness ofweak solutions of the system subject to appropriate initial and boundary conditions.

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