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Electron‐impact ionization of interstellar hydrogen and helium at interplanetary shocks
Author(s) -
Isenberg Philip A.,
Feldman William C.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl00703
Subject(s) - physics , ionization , photoionization , electron , atomic physics , interplanetary spaceflight , helium , hydrogen , heliosphere , electron ionization , ion , interplanetary medium , interstellar medium , solar wind , astrophysics , plasma , astrobiology , nuclear physics , galaxy , quantum mechanics
We investigate the ionization of interstellar hydrogen and helium due to electron impact by shock‐heated electrons. Taking the electron distributions measured at four interplanetary shocks at 1 AU, we show that the electrons in the downstream region of strong shocks can ionize interstellar atoms at rates matching or exceeding the nominal photoionization or charge‐exchange rates. We suggest that this process may explain some puzzling observations of interstellar pickup ions made by the Ulysses spacecraft.