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Sol-Geo Dipolar Field Angles

09/30/2021 12:39 AM

Can Sol field and Geo field be roughly modeled as dipolar field sources? If so, what are the angular relationships between those fields? Do those angles change?
Is the dipolar relationship repulsive, attractive, or neutral? Does it change with the 11 year dyno-magnetic cycle of the Sun?

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#1

Re: Sol-Geo Dipolar Field Angles.

09/30/2021 1:13 AM

..."First, we consider the influence of the dipole tilt angle on the efficiency of the coupling between the solar wind and the magnetosphere. I. Cnossen et al. (The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind-magnetosphere-ionosphere coupling, submitted to (Journal of Geophysical Research, 2012) showed that the strongest coupling tends to occur when the dipole axis is aligned with the geocentric solar magnetospheric (GSM) z axis, with progressively weaker coupling taking place as the angle μ between these axes becomes larger. We remind the reader that the GSM y axis is defined as perpendicular to the dipole axis, so that the dipole axis is always contained in the x-z plane. The x axis points from the Earth to the Sun, which means that the angle μ between the dipole axis and the z axis varies both as a function of season and as a function of time of day, due to the angle between the Earth's equatorial plane and the ecliptic plane (∼23.5°) and the angle between the Earth's rotation axis and the dipole axis (the dipole tilt), respectively. We note that μ is also sometimes referred to as “dipole tilt.” However, in this study we will always consider “dipole tilt” to mean the angle between the Earth's rotation axis and the dipole axis. Since the dipole tilt influences how μvaries as a function of UT, a change in dipole tilt can modify the temporal variation in the efficiency of the coupling between the solar wind and the magnetosphere. In turn, a stronger solar wind-magnetosphere coupling will, in general, lead to a stronger magnetospheric driving of the polar ionosphere, which is associated with stronger ion flows and more Joule heating. As we shall see, this has consequences for the rest of the ionosphere-thermosphere system as well."...

" A second, perhaps more obvious, effect of a change in tilt angle is that the geographic locations of the magnetic poles will change and with them the locations of the polar caps, where most of the coupling with the magnetosphere occurs. We define the polar caps here as the regions enclosed by the boundary between open and closed magnetic field lines, i.e., those connected to the IMF carried by the solar wind, and those that have both foot points on the Earth. The size of the polar caps can vary in response to variations in solar wind-magnetosphere coupling, but they are generally centered on the magnetic poles. The dipole tilt angle may therefore not only modulate the strength of the magnetospheric driving of the ionosphere, it also affects where this occurs geographically and thereby determines the location of the magnetospherically driven ionospheric convection patterns and the spatial distribution of energetic particle precipitation and Joule heating. Figure 1 shows schematically how changes in tilt angle between 0 and 60° affect the position of the magnetic poles and the approximate location of the polar caps. Siscoe and Christopher [1975]already pointed out that phenomena such as auroral displays, which we normally associate with high latitudes, could occur at much lower latitudes, given a large enough tilt angle. The interaction of polar cap phenomena with a low-latitude background thermosphere and ionosphere might also be different. In addition, the polar caps become associated with the specific longitudinal sectors in which the magnetic poles are located, which may result in more longitudinal variation in the ionosphere-thermosphere system.

Figure 1 Open in figure viewer PowerPoint The locations of the magnetic poles (markers), the approximate locations of the polar caps (dashed lines), and the location of the magnetic equator (solid lines) for tilt angles of 0, 10, 20, 40 and 60° (labeled as T0, T10, etc.). The longitude of the Northern Hemisphere (NH) magnetic pole was set to 70°W in all cases, and correspondingly, the longitude of the Southern Hemisphere (SH) magnetic pole was set to 110°E. The polar caps were approximated as circles with a 20° radius around the magnetic poles (distortion of the circular shape is due to the projection).

[7] A third consequence of a change in tilt angle is the change in the orientation of magnetic field lines at a given geographic location. Field lines are by definition vertical at the magnetic poles and horizontal at the magnetic equator, with intermediate inclinations in between. The changes in the position of the magnetic equator with changing tilt angle were shown in Figure 1, and the circles that indicate the approximate location of the polar caps also represent a constant inclination contour. The orientation of the magnetic field is important for the ionosphere, because ionospheric plasma moves much more easily along field lines than across them. Changes in the inclination of the field can therefore change the vertical component of plasma transport, which is likely to affect key ionospheric parameters, such as the peak electron density of the F2 layer, NmF2, and the height of the peak of the F2 later, hmF2. Changes in the declination, the angle between the magnetic and geographic north direction, can also influence plasma transport, but this effect tends to be less important [Cnossen and Richmond, 2008].

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012JA018056

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#2
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Re: Sol-Geo Dipolar Field Angles.

09/30/2021 2:19 AM
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Re: Sol-Geo Dipolar Field Angles.

09/30/2021 2:51 AM

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Re: Sol-Geo Dipolar Field Angles.

09/30/2021 4:29 AM
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#6
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Re: Sol-Geo Dipolar Field Angles.

09/30/2021 10:14 PM

" A second, perhaps more obvious, effect of a change in tilt angle is that the geographic locations of the magnetic poles will change and with them the locations of the polar caps, where most of the coupling with the magnetosphere occurs. We define the polar caps here as the regions enclosed by the boundary between open and closed magnetic field lines, i.e"
Are we assuming magnetic polarity parallels spin axis? Is our spin axis drifting with the poles? How does rotational inertia play into the rate of change in the spin axis if it follows polarity?

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#9
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Re: Sol-Geo Dipolar Field Angles.

10/03/2021 1:06 AM

Would there be hysteresis between magnetic drift and spin axis?
Hopefully I am using that big word in proper context; where spin axis first lags dipole axis and then overshoots dipole axis?

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#5

Re: Sol-Geo Dipolar Field Angles

09/30/2021 8:40 AM

Can Sol field and Geo field be roughly modeled as dipolar field sources?

The simple answer to this is no. The sun's magnetic field is driven outward by the charged particles in the solar wind and is much stronger in the earth's vicinity than if the sun were a simple magnetic dipole.

"The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. If space were a vacuum, then the Sun's magnetic dipole field — about 10−4 teslas at the surface of the Sun — would reduce with the inverse cube of the distance to about 10−11 teslas. But satellite observations show that it is about 100 times greater at around 10−9 teslas. Magnetohydrodynamic (MHD) theory predicts that the motion of a conducting fluid (e.g., the interplanetary medium) in a magnetic field induces electric currents, which in turn generates magnetic fields — and, in this respect, it behaves like an MHD dynamo."

Interplanetary magnetic field - Wikipedia

The sun's magnetic field reverses about every 11 years, whereas the earth's field remains the same polarity for long periods of time.

The Sun's Magnetic Poles Have Flipped...Solar Max is Here! - The Sun Today with C. Alex Young, Ph.D.

Is the dipolar relationship repulsive, attractive, or neutral? Does it change with the 11 year dyno-magnetic cycle of the Sun?

Theoretically, the magnetic interaction would cycle between attractive and repulsive every 11 years, but the magnetic interaction between the sun and earth is negligible compared to the gravitational attraction.

626531main_Solar_System_Magnetism.pdf (nasa.gov)

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#7
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Re: Sol-Geo Dipolar Field Angles

10/02/2021 5:07 PM

You are assuming that he wants to be reasonably close to accurate.

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#8

Re: Sol-Geo Dipolar Field Angles

10/03/2021 12:52 AM

I am looking for the angles between x axes and y axes of the two dipolar fields. Where the x axis is perpendicular to the dipole axis and the y axis is the dipole axis.
Solar Eagle came up with some great links. I believe one even included dipole field strength at Earth orbital radius.
Some one said the magnet force would be inconsequential compared to gravitational force. BUT; gravitational force does not torque the spinning mass; dipolar interaction does?
Perhaps the short "magnetic flip" of the sun every 11 years keeps the moment of inertia of our little dynamo in space somewhat stable in both the x and y axis of the dipole?

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