When the sun goes TILT

The Heliospheric Current Sheet Tilt Angle and Implications for Friis-Christensen and Lassen Theory

Guest post by David Archibald

The Chairman of NOAA’s Solar Cycle 24 review panel, Douglas Biesecker, said back in March 2007 that the flattening of the heliospheric current sheet was one of the expected signatures of solar minimum (the Solar Cycle 23/24 transition). At times of weak solar activity, the month of transition can be relatively hard to pick, except for the flattening of the heliospheric current sheet, shown following:

This graph of the heliospheric current sheet tilt angle from 1976 shows sharp transitions from one solar cycle to the next. The data is from www.wso.stanford.edu

By comparison, Dr Svalgaard’s plot of four solar parameters from 2008, available at http://www.leif.org/research/TSI-SORCE-2008-now.png , shows a lot of latitude in picking the month of transition:

On top of his graphic I have plotted December 2008 which is commonly accepted as the month of the Solar Cycle 23/24 transition and October 2009, which was Carrington rotation 2089 and the month of transition based on flattening of the heliospheric current sheet. The MF doesn’t change character until this later date.

The big question is,”What are the implications for Friis-Christensen and Lassen theory?” Friis-Christensen and Lassen based their theory on a couple of hundred years of sunspot data, but what if the true relationship between solar cycle length and the Earth’s temperature over the following solar cycle is based on solar cycle length as measured from the flattening of the heliospheric current sheet rather than the rather subjective choice of minimum sunspot number? We will need possibly another hundred years of tilt angle data to get a definitive result, but in the meantime we can calculate the consequences.

Plotting the heliospheric current sheet-based data onto Butler and Johnson’s 1996 graphic for Armagh, Northern Ireland results in having to plot outside their graphic. These solar cycle length conditions are unprecedented in recorded Armagh history. They result in the predicted temperature decline over Solar Cycle 24 at Armagh to be 2.4°C, a full one degree cooler than the result based on commonly accepted solar cycle length data.

Applying heliospheric current sheet-based data to the plot for Hanover, New Hampshire derives a 3.1°C temperature decline, about one degree more than previously calculated. This is more than four times the purported 0.7°C temperature rise of the 20^th century.

There is one way to determine whether or not Friis-Christensen and Lassen theory should be based on solar cycle length based on flattening of the heliospheric current sheet. If the average temperature decline at Hanover, New Hampshire over Solar Cycle 24 is 3.1°C rather than the previously predicted 2.2°C, then that will be early confirmation that flattening of the heliospheric current sheet should be used. We will only have to wait until early next decade for that data.

David Archibald

August, 2010