NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Energy deposition and middle atmosphere electrodynamic response to a highly relativistic electron precipitation eventRocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure bremsstrahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found the be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impact flux was highly irregular, containing short-lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0 deg - 20 deg. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cu cm s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurence of similar events but with fluxes 1-2 orders of magnitude above that reported here, based on studies of earlier solar cycles (e.g., Baker et al., 1993).
Document ID
19950034672
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Goldberg, R. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Baker, D. N.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Herrero, F. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mccarthy, S. P.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Twigg, P. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Croskey, C. L.
(Pennsylvania State Univ. University Park, PA, United States)
Hale, L. C.
(Pennsylvania State Univ. University Park, PA, United States)
Date Acquired
August 16, 2013
Publication Date
October 20, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: D10
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A66271
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available