>Others have mentioned the heliospheric cuurent sheet, which leads to this paper
In the paper they introduce some "irregularity indices" λ_WN and λ_aa of "daily series of sunspot number WN and geomagnetic index aa
as a function of increasing smoothing from N = 162 to 648 days. "
In the summary they say:
>The irregularity index method is promising but still not a fully understood tool.
I agree with that. That is I couldn't understand within a decent time what they are doing. As one result it seems they somehow found some rather sharp
change in 1975 in sunspot activity and QBO. ???:
>λ_WN and λ_aa display Schwabe cycles with sharp peaks not only at cycle maxima but also at minima: we call the resulting 5.5 year variations “half Schwabe variations” (HSV).
Furthermore from the abstract:
>We propose that the HSV behavior of the irregularity index of WN may be linked to the presence of strong QBO
before 1915–1930, a transition and their disappearance around 1975, corresponding to a change in regime of solar activity.
was there such a change in 1975? I haven't heard of a sharp change of sun behaviour and/or QBO behaviour....
furthermore the summary:
>Vecchio et al. (2012), using magnetic synoptic maps from 1976 to 2003, propose that QBO are fundamental
modes associated with poleward magnetic flux migration from low to high latitudes (part of meridional circulation) during the
maximum and descending phases of the solar cycle. A strong link between QBO and the solar dynamo is inferred from these and
other works. Time variations of QBO might therefore provide information on changes in meridional flow. On the other hand, non-linearity of the solar dynamo itself could
be the source of QBO.
So it seems at least some people consider the sunwind as being able to have a possible impact on major climate features.
I find the information which is available in the net not really sufficient for saying much more on that topic.
This Nasa website
has something on the sometimes weird
shape (like a "conch shell") of the heliospheric current sheet. Moreover it seems (at least if the sheet looks more like flat disc) that the earth dips through the sheet
. In fact the earth orbit plane seems to be tilted by about 7 degrees with respect to the sheet plane. But usually the earth seems more to travel through the sheet ripples.
???? (the image on the latter page seems to be from this 1999 article
with data from 1994 (p. 28))
The weird "shell" current sheet (arising from two northpoles on the sun) was from the Ulysses mission. Now it seems they have new missons called STEREO
according to a projects participant at Max Planck Institute
and in particular the info about the old Ulysses
mission somehow disappeared.
From the Max Planck Institute's page:
>New fundamental knowledge about the Sun has been obtained with instruments (co-)developed by the Institute on board the space probes SOHO and STEREO. The measurements from the UV spectrometer SUMER on SOHO have led to the recognition of the decisive role of the magnetic field in dynamic processes, while STEREO allowed for the first time 3D observations of the Sun and the inner heliosphere
They seem to have now more fotographs from the sun. I couldnt though find anything there on the shape of the current sheet.
So concluding, sofar the pathway towards explaing a possible biennal (and in particular not-quasibiennal) forcing via the heliospheric sheet looks not
too promising, despite the fact that there seem to be sunwind influences on global climate.
In particular the suns magnetic field seems to be too erratic than that it could account for a regular biennal forcing that is even the
dipping through the sheet (which could result in annual forcings) seem to occur irregularily (?). Moreover I haven't found anything
on a possible orbit related resonance between the earth and suns magnetic fields and in fact the suns magnetic field seems way to
small (?haven't checked though) to influence the earth magnetic field in a significant way. ?