New Instrument Offers Clearer View of Sun's Fury

A paradoxof measuring solar rays without optic tools such as mirrors and lenses may havebeen solved by two physicists.

A newinstrument, designed by Darrell Judge and Leonid Didkovsky, both at the University of Southern California, could provide a hassle-free technique for measuring theextreme ultraviolet (EUV) range of solarradiation.

Muchimportant solar research deals with detecting and measuring the high-energyparticles in this range, particularly those released during solarflares.

Immuneto solar flares

Solarflares ? abrupt emissions on the sun's surface that release massive amounts ofenergy ? can render satellites temporarily useless. Major flares can knock outelectricity grids and even affect our weather.

Moregenerally, EUV-driven activity in the Earth's atmosphere has long-termeffects on radio communications and climate. So scientists have good reasonto point their light-measuring spectrometers toward the sun, although theseinstruments currently suffer from technological limitations.

Aspectrometer measures electromagnetic intensity over a specified range ofwavelengths, using metal filters to prevent all but the desired wavelengths oflight from being captured. Unfortunately, the process necessarily causes asteady loss in instrument sensitivity.

Gaseouselements floating in the solar observatory spacecraft, such as NASA's Solar andHeliospheric Obervatory, become imprinted onto the optical surfaces and filtersof spectrometers by rays of solar radiation ? the very stuff being measured. Asa result, the lenses, mirrors and prisms lose precision, and must be regularlycalibrated.

"Thisis a problem with any EUV spectrometer," Didkovsky told "Butthe optics-free spectrometer may be totally free from this problem because wehave no optical or filter-based elements."

Designed atthe University of Southern California Space Sciences Center, the optics-freespectrometer (OFS) measures EUV rays without any of the traditional equipmentthat tends to degrade in space.

Nooptics needed

The OFSconsists of a small cylinder whose main chamber is filled with neon gas. Uponinteracting with solar photons, the neon molecules ionize to produce electrons.

An electricfield focuses a narrow stream of these electrons to a detector at the back ofthe cylinder. This field can be adjusted to collect electrons from interactionsacross a range of photon wavelengths. The desired EUV activity is mapped byscanning through this range.

Having nooptical surfaces to calibrate, the OFS should require no maintenance. "Itcan look at the sun day after day, year after year, without harm," Judgesaid.

The OFScould usher in a new generation of spectrometers that require little or noupkeep and that maintain a high level of sensitivity throughout their lives.These instruments would prove important for improving radio communications,preventing electricity blackouts and understanding climate change.

"Theseare real effects," Judge said, adding that a better understanding of solarflares could lead to the development of an early-warningsystem for weather forecasters, satellite operators, astronauts and others.

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