NTRS - NASA Technical Reports Server

Back to Results
Statistical Correlation of Low-Altitude ENA Emissions with Geomagnetic Activity from IMAGE MENA ObservationsPlasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low-altitude (300-800 km) ion precipitation in the high-latitude atmosphere/ionosphere are termed low-altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90deg. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Mackler, D. A. (Texas Univ. San Antonio, TX, United States)
Jahn, J.- M. (Texas Univ. San Antonio, TX, United States)
Perez, J. D. (Auburn Univ. AL, United States)
Pollock, C. J. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Valek, P. W. (Texas Univ. San Antonio, TX, United States)
Date Acquired
April 7, 2017
Publication Date
March 4, 2016
Publication Information
Publication: Journal of Geophysical Research: Space Physics
Volume: 121
Issue: 3
ISSN: 2169-9380
Subject Category
Geosciences (General)
Report/Patent Number
Funding Number(s)
Distribution Limits