and ionized hydrogen, have not been able to explain the mechanism of exci­tation. The fine detailed, vertically curtained aurora with its "drapes" par­allel to the earth 's magnetic field lines suggests the excitation of atmospheric gases by incoming extra-terrestrial charged particles. The high luminosity of auroral pa t te rns throughout an alti­tude range of hundreds of kilometers is harder to explain, as are the other types of aurorae having no visible vertical s t ructure at all.

M a g n e t i c S t o r m s . Closely con­nected with the aurorae are the so-called magnetic storms, the association having been made as early as the mid 18th century. Small variations in the ground level direction and intensity of the measured ear th field are evidence of upper atmosphere fields which in tu rn indicate some sort of current flow in the ionized regions. Sheets or streams of ionospheric particles at high altitudes have been postulated in many forms by as many people. Others say tha t the magnetic variations can be ex­plained by the effects of charged solar particle streams impinging on the earth 's magnetic field.

One reason for the present intense interest in these solar emissions is the high energy with which they apparently enter our atmosphere. Rocket probes of the auroral sky have recorded charged particle activity in the million-electron-volt region, thus indicating a very high energy for the pr imary auroral particles. The current aggre­gate of evidence favors the sun as their initial source. However, if they leave the sun with solar thermal energy, then an accelerating mechanism of million-electron-volt or billion-electron-volt proportions between the sun and earth must be postulated.

One suggestion of interest postulates particle acceleration from radiation pressure in the vicinity of the sun; another theory suggests explosive-type emission from the sun which would im­par t equal velocities to heavy and light particles so tha t the heavy ones would have sufficient initial energy to penetrate our atmosphere to auroral levels. Other theories utilize Fermi and betatron mechanisms, and still an­other postulates magnetic separation of particles of unlike charge with the resulting electric field becoming the source of acceleration. Satellite-borne instrumentation is being built to in­vestigate such phenomena by mapping the magnetic field of the earth at very high altitudes.

Sun Spots . Last, but of t remen­dous importance, is the optical s tudy of solar flares, sun spots, and their corre­lation with the appearance of high

REPORT FOR ANALYTICAL CHEMISTS

IGY composition experiment prior to a test in the preparation area at Fort Churchi l l . A f te r the test the rocket is taken to the launching tower through the tunnel in the background

energy ultraviolet and x-radiation in our upper atmosphere. Special empha­sis will be placed on this program dur­ing the maximum of the 11-year sun-spot activity cycle in 1958.

Upper Atmosphere Tools

One can readily see how closely con­nected are these many lines of endeavor. Yet, the variety of tools used for these investigations gives little evidence of the common goal, t ha t of finding out what goes on both inside and outside the atmosphere. Many of these tools are adaptations of appara tus familiar to most scientific people; others are developed specifically for use in this newly acquired "laboratory." Some of the more recent information ac­quired by these instruments is summa­rized in Figure 1.

In the far right are shown, at typical peak-of-flight altitudes, the rocket vehicles most often used for this re­search work. The solid-fueled Rockoon is light and manageable enough to be carried by balloon to about 15 miles, where it is fired. By balloon-lifting the rocket through most of the earth's atmosphere prior to firing, the amount of rocket performance lost through atmospheric friction is minimized. The Nike-Cajun comprises a solid fuel Cajun rocket and a Nike solid fuel booster. This medium-high altitude combination is easy to handle and requires a mini­mum in the way of launching facilities compared to the Aerobee-Hi which is a liquid-fueled, boosted rocket travel­ing 50 miles higher than the Nike-Cajun. Satellites are now making measurements at higher altitudes where the atmospheric drag is low enough to allow many complete orbits of data gathering before satellite destruction in the lower atmosphere.

. In the center of Figure 1 is the dominant source of activity, the sun. To the right of center is seen a tempera­ture graph, pressure (in atmospheres) , and mean free pa th figures, all of

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Circle No. 21 A on Readers' Service Card, page 101 A VOL. 30 , NO. 9, SEPTEMBER 1958 · 2 1 A