ISIS-2 Observations of Auroral Arc Systems

  1. S.-I. Akasofu and
  2. J.R. Kan
  1. J. S. Murphree,
  2. C. D. Anger and
  3. L. L. Cogger

Published Online: 26 MAR 2013

DOI: 10.1029/GM025p0015

Physics of Auroral Arc Formation

Physics of Auroral Arc Formation

How to Cite

Murphree, J. S., Anger, C. D. and Cogger, L. L. (1981) ISIS-2 Observations of Auroral Arc Systems, in Physics of Auroral Arc Formation (eds S.-I. Akasofu and J.R. Kan), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM025p0015

Author Information

  1. Department of Physics, the University of Calgary, Calgary, Alberta Canada T2N 1N4

Publication History

  1. Published Online: 26 MAR 2013
  2. Published Print: 1 JAN 1981

ISBN Information

Print ISBN: 9780875900506

Online ISBN: 9781118664360



  • Auroras—Addresses, essays, lectures


Using the global images from the Auroral Scanning Photometer on ISIS-2 the instantaneous discrete auroral morphology in the evening/midnight sector is studied. The most consistent feature during magnetically active times is the formation of an auroral bulge in the premidnight sector to which is connected an evening discrete arc system. These bulges can extend over 7° of latitude and the Magnetic Local Time of their westward leading edge has a well defined peak at 20–22 MLT. There is normally a single evening arc system which connects into the equatorward portion of the bulge. This arc system may extend into the afternoon sector and though discontinuities may exist in its morphology, the continuity of intensity and 5577Å/3914Å ratio across these discontinuities suggests a single particle source for the entire arc system. Discrete auroral arc systems, particularly these connecting to auroral bulges, occur predominantly near the poleward edge of the auroral distribution but apparently imbedded with diffuse aurora. Examples clearly show that discrete aurora can occur within the main region of diffuse auroral emission.