The sun may be cooling down. From David Archibald at whatsupwiththat.com:
The solar plasma temperature has plunged to a new low for the instrument record. Coincidentally or not, the temperature of the southern hemisphere has also plunged over the last couple of weeks. When do we start worrying?
Figure 1: Temperature of the solar wind plasma
As Figure 1 shows, the temperature of the solar wind has hit a new low for the instrument record. As it is energy from the Sun that keeps the Earth from looking like Pluto, the lower plasma temperature indicates that the Sun’s surface is cooling. Surely the Earth’s surface will follow.
Figure 2: Alpha particle to proton ratio in the solar wind
Similarly the alpha particle to proton ratio has hit a new low for the almost 50 years of the instrument record. The decline for the peak ratio in each solar cycle is even more dramatic. The question that naturally arises is this: Is there a lower bound for this ratio?