SPATIALLY RESOLVED NONTHERMAL LINE BROADENING DURING THE IMPULSIVE PHASE OF A SOLAR FLARE

Journal Article · Thu Oct 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/740/2/70; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21587382

Milligan, Ryan O ^[1]

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1. Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

This paper presents a detailed study of excess line broadening in extreme ultraviolet (EUV) emission lines during the impulsive phase of a C-class solar flare. In this work, which utilizes data from the EUV Imaging Spectrometer on board Hinode, the broadened line profiles were observed to be cospatial with the two hard X-ray footpoints as observed by RHESSI. By plotting the derived nonthermal velocity for each pixel within the Fe XV and Fe XVI rasters against its corresponding Doppler velocity a strong correlation (|r| > 0.59) was found between the two parameters for one of the footpoints. This suggested that the excess broadening at these temperatures is due to a superposition of flows (turbulence), presumably as a result of chromospheric evaporation due to nonthermal electrons. Also presented are diagnostics of electron densities using five pairs of density-sensitive line ratios. Density maps derived using the Mg VII and Si X line pairs showed no appreciable increase in electron density at the footpoints, whereas the Fe XII, Fe XIII, and Fe XIV line pairs revealed densities approaching 10{sup 11.5} cm{sup -3}. Using this information, the nonthermal velocities derived from the widths of the two Fe XIV lines were plotted against their corresponding density values derived from their ratio. This showed that pixels with large nonthermal velocities were associated with pixels of moderately higher densities. This suggests that nonthermal broadening at these temperatures may have been due to enhanced densities at the footpoints, although estimates of the amount of opacity broadening and pressure broadening appeared to be negligible.

• OSTI ID: 21587382
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 740; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELEMENTS
EMISSION
EXTREME ULTRAVIOLET RADIATION
IRON
LINE BROADENING
MANGANESE
METALS
RADIATIONS
SEMIMETALS
SILICON
SOLAR ACTIVITY
SOLAR FLARES
STELLAR ACTIVITY
STELLAR FLARES
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION
VELOCITY