Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-02-11
Astrophys.J. 607 (2004) 596-610
Astronomy and Astrophysics
Astrophysics
14 pages, color figures, uses emulateapj style. ApJ in press
Scientific paper
10.1086/383410
We have analyzed data from two sets of calibration observations of the Moon made by the Chandra X-ray Observatory. In addition to obtaining a spectrum of the bright side that shows several distinct fluorescence lines, we also clearly detect time-variable soft X-ray emission, primarily O VII Ka and O VIII Lya, when viewing the optically dark side. The apparent dark-side brightness varied by at least an order of magnitude, up to 2x10^-6 phot/s/arcmin^2/cm^2 between 500 and 900 eV, which is comparable to the typical 3/4-keV-band background emission measured in the ROSAT All-Sky Survey. The spectrum is also very similar to background spectra recorded by Chandra in low or moderate-brightness regions of the sky. Over a decade ago, ROSAT also detected soft X-rays from the dark side of the Moon, which were tentatively ascribed to continuum emission from energetic solar wind electrons impacting the lunar surface. The Chandra observations, however, with their better spectral resolution, combined with contemporaneous measurements of solar-wind parameters, strongly favor charge transfer between highly charged solar-wind ions and neutral hydrogen in the Earth's geocorona as the mechanism for this emission. We present a theoretical model of geocoronal emission and show that predicted spectra and intensities match the Chandra observations very well. We also model the closely related process of heliospheric charge transfer and estimate that the total charge transfer flux observed from Earth amounts to a significant fraction of the soft X-ray background, particularly in the ROSAT 3/4-keV band.
Dalgarno Alexander
Edgar Richard
Juda Michael
Kharchenko Vasili
Markevitch Maxim
No associations
LandOfFree
Chandra Observations of the "Dark" Moon and Geocoronal Solar-Wind Charge Transfer does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Chandra Observations of the "Dark" Moon and Geocoronal Solar-Wind Charge Transfer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chandra Observations of the "Dark" Moon and Geocoronal Solar-Wind Charge Transfer will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-698720