PT - JOURNAL ARTICLE
AU - Liu, Terry Z.
AU - Angelopoulos, Vassilis
AU - Lu, San
TI - Relativistic electrons generated at Earthâ€™s quasi-parallel bow shock
AID - 10.1126/sciadv.aaw1368
DP - 2019 Jul 01
TA - Science Advances
PG - eaaw1368
VI - 5
IP - 7
4099 - http://advances.sciencemag.org/content/5/7/eaaw1368.short
4100 - http://advances.sciencemag.org/content/5/7/eaaw1368.full
SO - Sci Adv2019 Jul 01; 5
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.