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23 December 2003 - Our Cusp Runneth Over
Taguchi et al., in a recently accepted Journal of Geophysical Research article, show that
changes in the observed LENA neutral flux from the dayside region on April 11, 2001
(as shown in thumbnail to the right) indicate that the source of
the emission shifts equatorward in the low latitude sheath and poleward in the high
latitude sheath during compressed magnetospheric periods, when the magnetopause
moves inside of geosynchronous orbit. Using a model of the magnetosheath flux and exospheric
hydrogen density (see thumbnail to the left), they show that the data
reflect motion of the magnetopause with a cusp indentation. This suggests LENA can monitor
cusp motion using neutral atom emission.
Click here
for a PDF file of the Taguchi et al. paper.
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6 October 2003 - LENA: Not Just for Earth, Anymore
The energetic neutral atom (ENA) emissions observed from the interaction of
the solar wind with the Earth's magnetosphere have implications for other
planets, such as Venus. Fok et al., in an article recently accepted to
the Journal of Geophysical Research, have shown that, at Venus,
because it has no intrinsic magnetic field, the solar wind penetrates deep
into its upper atmosphere (click thumbnail image at right). Calculating neutral
atom emissions using the global MHD model of Tanaka and Murawski [1997],
Fok et al. show that energetic neutral atom emission from Venus' magnetosheath
is comparable to or even greater than that of the Earth, leading to the natural
conclusion that low energy neutral atom imaging may be used to study the
solar wind-Venus interaction, in particular loss rates which may be used to
solve a long-standing mystery: how Venus lost its water vapor.
Click here
for a PDF file of the Fok et al. paper.
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12 August 2003 - Global outflow imaging reveals rapid ionospheric response to pressure pulses
The low energy neutral atom imager on IMAGE allows global imaging of ion outflow, exposing
critical temporal information between the ionospheric outflow and prospective source
mechanisms. In a recent publication in J. Geophys. Res., Khan et al. (2003) performed a cross
correlation analysis between density perturbations in the solar wind, which impacted the
magnetospheric boundary, and the appearance of bursts of energetic neutrals escaping the ionosphere.
The analysis revealed a rapid response of ~2min for the ionospheric outflow to react to the density
variations, and further suggested that the dominant outflow species during these events was
hydrogen. Additionally, Khan et al. (2003) were able to establish that the ion outflow was
accelerated from a source region located ~2 earth radii from the centre of the Earth, consistent with
previous suggestions of this interaction region.
Click here
for a PDF file of the Khan et al. (2003) paper.
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14 April 2003 - A Secondary Stream of Interstellar Neutrals?
In a paper to be published in Advances in Space Research, Collier et al.
propose the highly controversial idea that there exists a secondary stream
of neutral atoms entering the heliosphere from somewhere around the
direction of the Galactic center. The claim is based on observations
covering many different neutral atom-related data sets near the Earth,
four of which are discussed in the paper, including two from LENA.
Click here
for a pdf version of the Collier et al. paper (968 KBytes).
Click here
for a summary plot of the data
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