THERMAL CONDUCTIVITY AND ELEMENT FRACTIONATION IN EV Lac

Journal Article · Thu Dec 10 04:00:00 EST 2009 · Astrophysical Journal (Online)

DOI:https://doi.org/10.1088/0004-637X/707/1/L60· OSTI ID:21389290

Laming, J Martin ^[1]; Hwang, Una ^[2]

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1. Space Science Division, Naval Research Laboratory, Code 7674L, Washington, DC 20375 (United States)
2. NASA/GSFC Code 662, Greenbelt MD 20771, and Johns Hopkins University, Baltimore, MD 21218 (United States)

We present a 100 ks Suzaku observation of the dMe flare star EV Lac, in which the star was captured undergoing a moderate 1500 s flare. During the flare, the count rate increased by about a factor of 50 and the spectrum showed overall enhanced element abundances relative to quiescence. While the quiescent element abundances confirm the inverse first ionization potential (FIP) effect previously documented for EV Lac, with relatively higher depletions for low FIP elements, abundances during the flare spectra show a composition closer to that of the stellar photosphere. We discuss these results in the context of models that explain abundance fractionation in the stellar chromosphere as a result of the ponderomotive force due to Alfven waves. Stars with FIP or inverse FIP effects arising from differently directed ponderomotive forces may have quite different abundance signatures in their evaporated chromospheric plasma during flares, if the same ponderomotive force also affects thermal conduction downward from the corona. The regulation of the thermal conductivity by the ponderomotive force requires a level of turbulence that is somewhat higher than is normally assumed, but plausible in filamentary conduction models.

• OSTI ID: 21389290
• Journal Information: Astrophysical Journal (Online), Journal Name: Astrophysical Journal (Online) Journal Issue: 1 Vol. 707; ISSN 1538-4357
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ALFVEN WAVES
ATMOSPHERES
ELEMENT ABUNDANCE
ENERGY TRANSFER
FRACTIONATION
HEAT TRANSFER
HYDROMAGNETIC WAVES
IONIZATION POTENTIAL
PHOTOSPHERE
PHYSICAL PROPERTIES
PLASMA
PONDEROMOTIVE FORCE
SEPARATION PROCESSES
SOLAR ATMOSPHERE
STARS
STELLAR ATMOSPHERES
STELLAR CHROMOSPHERES
THERMAL CONDUCTION
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES
TURBULENCE