Analysis of a Bright Point Spectrum From the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Sounding Rocket Instrument

Details Analysis of a Bright Point Spectrum From the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Sounding Rocket Instrument Analysis of a Bright Point Spectrum From the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Sounding Rocket Instrument

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsh21b..04b&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #SH21B-04

Physics

7509 Corona, 7526 Magnetic Reconnection (2723, 7835), 7546 Transition Region, 7549 Ultraviolet Emissions

Scientific paper

We present a well-calibrated spectrum of a bright point observed with EUNIS on 2006 April 12. Coordinated observations with SOHO's EIT and MDI were also obtained. The bright point brightened around 06:30 UT during a period of emerging magnetic flux, and remained bright at least until the rocket flight around 18:12 UT while the magnetic flux merged and canceled. Density-sensitive line intensity ratios yield mutually consistent coronal electron densities log Ne ~ 9.5. Based on the method of Landi & Landini (1997), the differential emission measure (DEM) curve derived from the spectrum yields a peak of log DEM ~ 20.70 at log T ~ 6.15, and a local minimum of log DEM ~ 20.15 at log T ~ 5.35. We find that photospheric (not coronal) element abundances are required to achieve equality and consistency in the DEM derived from lines of Mg V, Mg VI, Mg VII, Ca VII (with a low first ionization potential, or FIP) and lines from Ne IV and Ne V (with a high FIP) formed at transition region temperatures. The bright point's photospheric abundance is likely produced by reconnection-driven chromospheric evaporation, a process that is not only central to existing bright point models (e.g., Priest, Parnell, & Martin 1994; Longcope 1998), but also consistent with measurements of relative Doppler velocities (e.g., ± 26 km/s for Fe XIV, ± 35 km/s for Fe XVI) previously presented by Brosius, Rabin, & Thomas (2007). The EUNIS program is supported by NASA's Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. We thank the entire EUNIS team for the concerted effort that led to a successful first flight.

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