  The familiar correlation between the speed and angular width of coronal mass
ejections (CMEs) is also found in solar cycle 24, but the regression line has a
larger slope: for a given CME speed, cycle 24 CMEs are significantly wider than
those in cycle 23. The slope change indicates a significant change in the
physical state of the heliosphere, due to the weak solar activity. The total
pressure in the heliosphere (magnetic + plasma) is reduced by ~40%, which leads
to the anomalous expansion of CMEs explaining the increased slope. The excess
CME expansion contributes to the diminished effectiveness of CMEs in producing
magnetic storms during cycle 24, both because the magnetic content of the CMEs
is diluted and also because of the weaker ambient fields. The reduced magnetic
field in the heliosphere may contribute to the lack of solar energetic
particles accelerated to very high energies during this cycle.
