Alphonse C. Sterling, NASA Marshall Space Flight Center

Solar eruptions are the largest explosions in the solar system.  They frequently (once per

day as a rough average) eject coronal mass ejections (CMEs) into the heliosphere.  Some CMEs

are capable of damaging satellites in Earth orbit, and are potentially a danger to astronauts

traveling beyond the Earth’s protective magnetic field.  Frequently CMEs start with the

eruption from the solar surface of arcades of relatively cool  (compared to the

surrounding million-K solar corona) plasma called “filaments.”  While it is understood that

the ultimate energy source of filament eruptions and CMEs is the Sun’s magnetic field, just

what causes the field to sporadically convulse and produce violent eruptions is a

long-standing mystery of solar science.  In contrast to the large-scale eruptions, “solar

coronal jets” are transient (lasting tens of minutes) features emanating from the Sun at

the rate of several per hour.  They are observed in coronal emission (X-rays and EUV), and

are much smaller than the large-scale eruptions that produce CMEs.  Recent work, by our

group and by other workers, have shown that many (if not most or all) coronal jets result

from eruptions of “minifilaments,” of size ~5—10 times smaller than the large-scale

filaments that erupt to cause CMEs.  Our most recent studies of jet-producing minifilament

eruptions are providing new clues as to what produces large-scale eruptions.  Moreover,

we speculate that similar eruptions occurring on still-smaller spatial scales may produce

some of the ubiquitous small-scale solar features called “spicules.”