Latest Solar Differential Rotation Information.
Some may be aware I have been trying to
track down if we are experiencing any change to the differential
rotation rates of the Sun. If angular momentum changes can be tied to
solar differential rotation rates, we might have a solid causation.
Solar differential rotation can be measured in different ways but
basically, different parts of the Sun rotate at different speeds,
keeping in mind the Sun is not a solid object. The equator rotation
rate is around 27 days, with the poles at around 34 days, as seen
from earth. But there is a lot more to consider. Recently I heard back
from Dr. Rachel Howe from NOAE who specializes in this area, and the
results were quite amazing.
Her hot off the press paper here:
The graphic above is a Doppler image
from GONG which shows the regular patterns of the changing rotation
speed of the Sun with the yellow sections being the fastest. The image
is taken at 0.99R which is around 7000Km beneath the top of the
Convection zone. It is thought these patterns (darker zones mostly)
are generated at the Tachocline (a thin sheer layer between the
radiative core and the Convection zone at around 0.71R) and they
spiral out to the top of the Convection zone and are subject to spin
momentum like a garden sprinkler. As we go deeper, like the graphic
below (0.99R to 0.84R) the patterns break up, which is not what I
would expect. The overall scale of the pattern seems to remain but
loses clarity. Perhaps this is a condition of going deep with Doppler
equipment or maybe the frequency is a lot higher as we go down?
If so, then maybe what is driving the
pattern at the surface is something of much higher frequency down at
the Tachocline, like the highly elliptical orbit of Mercury every 88
days. There is a reasonable tidal effect from Mercury which may
warrant further investigation. It is thought the rotating central
radiative core spins at an even speed.
Dr. Howe's paper suggests that the
travel time interval from Tachocline to the solar surface is around 2
years and, as we will see, these Doppler patterns align very closely
to the sunspot butterfly image when overlayed. If so, then sunspot
activity is a historical account of what happened at the Tachocline 2
In the next graphic we go back further
and it displays exactly what I have been looking for. During past
grand minima, observations suggest a faster rotating Sun, as can be
seen at the equator. After 2000 there is a greater acceleration
Also noted is the much longer length
of cycle 23 (96- ?) compared to cycle 22 (86-96). So here we see two
direct links to the highly possible effect from Angular Momentum
created by the Gas Giants, increased rotation rate and the stretching
of the cycle length as the Sun takes its abnormal path every 172
The last time this occurred was in SC4
just before the Dalton Minimum and the retrograde motion we are now
part of is very similar to SC4. On average the retrograde orbit
(purple) is around 9 years, SC23 & SC4 have orbits of over 11 years.
Below is a graphic I produced by
rescaling the SIDC sunspot butterfly plots then overlaying over Dr.
Howe's graphic, as can be seen there is a direct correlation between
the two sets of data. It is thought the sunspots are created at the
poleward edge of the fast and slow zones (yellow /green), but I am
sceptical. The slower zones are what travel all the way to the
Tachocline (its like a "brakes on" feedback) and we might have to
possibly shift the overlay to the right to allow for angular momentum
as the Doppler image is taken from 7000Km below. I have asked Dr. Howe
Please email comments to customzcar_oz AT
hotmail.com and I will post.