On signal decrease in HF circuits during PCA events /

• Main Authors: Wong, M. S., Air Force Cambridge Research Laboratories (U.S.)
• Format: Text
• Language: English
• Published: L.G. Hanscom Field, Bedford, Massachusetts : Air Force Cambridge Research Laboratories, Air Force Systems Command, United States Air Force 1973
• Subjects: Radio; Ionosphere; Solar noise storms; Solar radio emission; Barrow; Alaska
• Online Access: http://hdl.handle.net/2027/mdp.39015095126010

The principal morphological features of ionospheric absorption of cosmic radio noise at vertical incidence -due to influx into the polar ionosphere of solar protons with particle energy near 10 MeV, and as measured by ground-based riometers operated usually at 30 MHz- are reviewed with figures and brief descriptions. HF signal-intensity observations in two oblique-incidence circuits, Thule to College and Pt. Barrow to Kenai (Alaska), are compared with riometer measurements for several PCA events. It is suggested that a 'stand-by' propagation mode, involving a combination of scattering and ducting of HF radio waves near the ionospheric-bottom-boundary, comes into play. It is also suggested that, during disturbed inospheric conditions, diminutions in ionospheric electron density -in addition to, or in conjunction with, increased ionospheric absorption- is an important contributing cause to HF radio blackouts. (Modified author abstract). "Ionospheric Physics Laboratory Project 8666." AD0772656 (from http://www.dtic.mil). "2 May 1973." Includes bibliographical references (page 17). The principal morphological features of ionospheric absorption of cosmic radio noise at vertical incidence -due to influx into the polar ionosphere of solar protons with particle energy near 10 MeV, and as measured by ground-based riometers operated usually at 30 MHz- are reviewed with figures and brief descriptions. HF signal-intensity observations in two oblique-incidence circuits, Thule to College and Pt. Barrow to Kenai (Alaska), are compared with riometer measurements for several PCA events. It is suggested that a 'stand-by' propagation mode, involving a combination of scattering and ducting of HF radio waves near the ionospheric-bottom-boundary, comes into play. It is also suggested that, during disturbed inospheric conditions, diminutions in ionospheric electron density -in addition to, or in conjunction with, increased ionospheric absorption- is an important contributing cause to HF radio blackouts. (Modified author abstract). Mode of access: Internet.