ARE CORONAL MASS EJECTIONS CAUSED BY MAGNETIC PUMPING

Magnetic pumping in the solar corona is revisited. We derive condition s under which magnetic pumping can be the cause of heating of loops ra ther than of particle acceleration. Candidate sources for such a proce ss are coronal mass ejections (CMEs). Large loops are susceptible to h eating primarily of protons by magnetic compressions with periods betw een 50 and 5000 s, the observed spectrum of the photospheric driver. E fficient heating by pumping occurs since in these large loops the dens ity is low enough that the proton-proton collision time is comparable to the periods of the external compressions. We suggest that CMEs may be pressure-driven explosions of large-beta loops caused by magnetic p umping, in contrast to current-driven 'fares' in low-beta environments .