Space Science MO&DA Programs - August 2001 - Page 1 SS Polar Quantifies Magnetospheric Drivers of...

Space Science MO&DA Programs - August 2001 -

SSPolar Quantifies Magnetospheric Drivers

of Upper Atmospheric Chemistry Changes

High resolution global imaging from Polar is a critical element for

determining solar influenced controls of the upper atmosphere

• The importance of magnetospheric dynamics on the aeronomy of the upper atmosphere is known but it has never been clear how important, how extensive, how often, and how extreme the effect can be.

• Polar imaging provides a global view of the location and allows the intensity of the energetic processes to be inferred.

• Polar investigators have shown that catalytic atmospheric species can vary by as much as a factor of ten during extreme storm conditions.

Precipitating electrons

Nitric oxide abundance


SSMeasurement

s:

Polar Quantifies Magnetospheric Drivers of Upper Atmospheric Chemistry Changes

POLARGlobal variations in energetic particle precipitation and global variations in the atmospheric O/N2 ratio at 100-300 km altitude.PIXIE: auroral X-rays quantify global >5 keV electron precipitationUVI: auroral UV (130.4, 135.6, 140-160, 160-175, 175-190 nm)

VIS: auroral visible & UV (130.4, 391.4, 557.5, 630.0, 656.3, 732.0 nm)

SNOESwaths of nitric oxide density in the 100-200 km altitude lower thermosphere.UVS: auroral UV (215, 237 nm)


SSObservations:


NO(and NO2) enhancements are often confined to the region of production which can reach into the upper stratosphere. Downward transport can extend perturbations in O3 chemistry to lower regions of the stratosphere.

measure of atmospheric nitric oxide

measure of precipitating keV electrons

measure of magnetospheric storm activity

greater than five-fold variation




Observations:

Energetic electron precipitation dissociates N2 to produce N(2D) and N(44S) that in turn produce enhanced NO and NO2. The precipitation will also dissociate water vapor enhancing HOx. Enhancements within the mesosphere-thermosphere system, and their consequences on the stratosphere, can persist for many hours and sometimes days.

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Observations:

Ring current decay precipitates energetic O and H. On reaching the atmosphere, neutral O ionizes again from collisions, and then radiatively recombines yielding the O emission.Here, the O/N2 ratio is drastically reduced during strong activity. Because N2 is relatively stable, oxygen outflow into the magnetosphere probably caused most of the variation.

Polar/UVI O/N2 ratio showing atmospheric

oxygen depletion following the July

“Bastille Day”


SSInterpretation and Implications:


• Separation of natural and human-induced effects on the abundance of stratospheric ozone and odd nitrogen species require understanding of the natural processes leading to the formation and destruction of NOx and Ox.

• POLAR, together with SAMPEX and SNOE shows how auroral and geomagnetic activity have a significant impact on Earth's atmospheric chemistry during major space weather storms.

Petrinec, S. M., W. L. Imhof, D. L. Chenette, J. Mobilia, and T. J. Rosenberg, Dayside/nightside auroral X-ray emission differences and implications for ionospheric conductance, Geophys. Res., Lett., 20, 3277, 2000.

Liou, K., P. T. Newell, C.-I. Meng, M. Brittnacher, and G. Parks, Characteristics of the solar wind controlled auroral emissions, J. Geophys. Res., 103, 17543, 1998.

Barth, C. A., Baker, D.N., Mankoff K.D., and Bailey S.M., The Northern Auroral Region as Observed in Nitric Oxide, Geophys. Res. Lett., 28, 1463, 2001.


SS


SS

Backup Slides


SSPolar Orbit 2001-

2005


SS

Strength of the Solar Cycle

Strength of Geomagnetic Activity

Solar Max vs the Declining Phase


SSEnergetic Particles and

the Solar Cycle

Phases of the solar cycle bring very different solar input conditions which in turn, result in very different magnetospheric responses

Space Science MO&DA Programs - August 2001 - Page 1 SS Polar Quantifies Magnetospheric Drivers of...

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