Taguchi et al, in a recently accepted paper in the Journal of Geophysical Research, (click here for pdf version of the Taguchi et al. paper) examine an event on April 12, 2001 in which LENA observed significant neutral atom fluxes in the direction of the high-latitude magnetosheath. These fluxes were composed of relatively stable high latitude and flickering low latitude emissions. The Polar spacecraft at this time was located at lower latitudes at a close longitude and showed the entry of cusp ions at the same time as the low-latitude LENA emissions. This suggests cusp ions are flowing earthward while charge exchanging with the hydrogen exosphere.

The stable higher latitude emission is associated with a persistent sheath flow in the cusp indentation creating neutral atoms (see image to the left). The lower latitude emission occurs during the southward tilting of the interplanetary magnetic field, indicating the emission is associated with newly reconnected field lines. Thus, this fortuitous positioning of two major spacecraft shows that a significant flux of the cusp ion entry occurs equatorward and separately from the cusp indentation (see image to the right). Once again, low energy neutral atom imaging has revealed the nature of mass and energy deposition into the magnetosphere and ionosphere from the solar wind.

In a paper recently accepted for publication in the Journal of Geophysical Research, Masahito Nose reports that the oxygen ion to proton energy density ratio during the October 29-31, 2003 superstorm in the near-Earth plasma sheet reached a value somewhere between 10 and 20, the largest ratio ever observed. The plasma sheet is a region on the Earth's night side containing electrically conductive gas concentrated within a few Earth radii of the equatorial plane through which important electric currents flow. By combining Geotail/EPIC and IMAGE/LENA data
(see the image to the right), Nose et al. conclude that a supply of extra oxygen ions from the Earth's ionosphere to the plasma sheet contributes to the huge oxygen abundance. This brings us closer to understanding the effects on the Earth of dangerous space weather events.

The magnetopause is the boundary that separates the region controlled by the Earth's magnetic field, the magnetosphere, from the region controlled by the Sun, the solar wind. In the past, its location could only be determined when it moved past a spacecraft. That all appears to be changing, according to Collier et al., who herald a number of new techniques which may be capable of producing, within reasonable resource constraints, a mission devoted to global magnetopause remote sensing.

As one example, in a recently published Journal of Geophysical Research paper (110, A2, A02102, 2005) Collier et al. show how charge exchange in the magnetosheath is extremely sensitive to the distance
of the magnetopause from the Earth (see image above). The predictions of a simple model for the neutral atom emission match the observations well when adjusted for the time it takes the solar wind to arrive at Earth from L1 (see the image to the right).

With real estate prices skyrocketing and science budgets being squeezed, perhaps we should consider selling the first Lagrange point, L1, to fund scientific research. L1 is the location where the gravitational forces of the Sun and Earth balance a spacecraft's orbital motion, and it is the traditional location for upstream solar wind monitors.

But do we really need L1 anymore? In a paper recently accepted for publication in Advances in Space Research, Collier et al. argue, based on X-ray observations such as those from XMM-Newton (see image above) and neutral solar wind observations such as those from IMAGE/LENA (see image to the right) that we may eventually be able to monitor the solar wind more effectively from inside the magnetosphere than we can currently from L1.