Computer Science – Sound
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmsp51a..06b&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #SP51A-06
Computer Science
Sound
7509 Corona, 7546 Transition Region, 7549 Ultraviolet Emissions
Scientific paper
We observed a transient brightening in the quiet Sun at rapid cadence (2.10 s) with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-06) sounding rocket instrument on 2006 April 12. The transient was visible only in He II at 303.78 Å (T ≍ 5 × 104 K), and its maximum temperature T was < 4 × 105 K. Taking its linear extent along the EUNIS slit to be the diameter of a circular feature, the transient's solar surface area was 7.8 × 107 km2. EUNIS observed the brightening to begin at 18:12:52 and peak at 18:13:29 UT; coordinated observations with SOHO's EIT confirm that EUNIS observed the onset of the brightening. EUNIS spectra yield maximum and average He II intensity enhancements of 2.09 and 1.46, respectively, relative to the pre-event quiet Sun. He II line profiles from EUNIS reveal that relative upflows were persistent during the transient (with a maximum speed around 20 km s-1) and that the upflow speed and intensity were positively correlated. Variations in the observed He II intensity and relative Doppler velocity were neither abrupt not impulsive, but occurred slowly compared to the EUNIS cadence. The local photospheric magnetic flux measured with SOHO's MDI revealed no significant variability. The transient's measured properties are consistent with its identification as a blinker or an elementary blinker, and its observed behavior suggests a formation mechanism involving gentle chromospheric evaporation. The EUNIS program is supported by NASA's Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics.
Brosius Jeffrey W.
Rabin Douglas M.
Thomas Robert J.
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