RT Journal Article
SR Electronic
T1 Relativistic electrons generated at Earthâ€™s quasi-parallel bow shock
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP eaaw1368
DO 10.1126/sciadv.aaw1368
VO 5
IS 7
A1 Liu, Terry Z.
A1 Angelopoulos, Vassilis
A1 Lu, San
YR 2019
UL http://advances.sciencemag.org/content/5/7/eaaw1368.abstract
AB Plasma shocks are the primary means of accelerating electrons in planetary and astrophysical settings throughout the universe. Which category of shocks, quasi-perpendicular or quasi-parallel, accelerates electrons more efficiently is debated. Although quasi-perpendicular shocks are thought to be more efficient electron accelerators, relativistic electron energies recently observed at quasi-parallel shocks exceed theoretical expectations. Using in situ observations at Earthâ€™s bow shock, we show that such relativistic electrons are generated by the interaction between the quasi-parallel shock and a related nonlinear structure, a foreshock transient, through two betatron accelerations. Our observations show that foreshock transients, overlooked previously, can increase electron acceleration efficiency at a quasi-parallel shock by an order of magnitude. Thus, quasi-parallel shocks could be more important in generating relativistic electrons, such as cosmic ray electrons, than previously thought.