The Solar X-ray Limb III
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== Introduction == | == Introduction == | ||
| - | How big is the Sun? This question has to be answered with "it depends". The IAU nominal value for the solar radius is given as 695.7 km [http://adsabs.harvard.edu/abs/2016AJ....152...41P Prsa et al. 2016]. This value is based on optical measurements and depends on details of the atmosphere and radiative transfer models. In two previous nuggets we described a new technique that uses RHESSI visibilities to measure the height of the X-ray limb ([[The X-ray Limb]]) and reported on preliminary analysis of a suitable solar flare ([[The Solar X-ray Limb II]]). As reported in the second nugget there were some problems with the chosen flare, but having found a better suited candidate we can finally claim success! | + | How big is the Sun? This question has to be answered with "it depends", since the observed diameter is wavelength dependent. The IAU nominal value for the solar radius is given as 695.7 km ([http://adsabs.harvard.edu/abs/2016AJ....152...41P Prsa et al. 2016]). This value is based on optical measurements and depends on details of the atmosphere and radiative transfer models. In two previous nuggets we described a new technique that uses RHESSI visibilities of occulted solar flare sources to measure the height of the X-ray limb ([[The X-ray Limb]]) and reported on preliminary analysis of a suitable solar flare ([[The Solar X-ray Limb II]]). As reported in the second nugget there were some problems with the chosen flare, but having found a better suited candidate we can finally claim success! |
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| + | == The event == | ||
| + | The event that lead to our success, SOL2011-10-20T03:25, is the perfect candidate for several reasons. AIA context images provide independent confirmation that the event was indeed occulted. In addition, RHESSI's detector 2 was working well enough to provide usable data for this kind of work. This allowed us to perform a set of rigorous tests that | ||
Revision as of 13:10, 8 June 2017
Introduction
How big is the Sun? This question has to be answered with "it depends", since the observed diameter is wavelength dependent. The IAU nominal value for the solar radius is given as 695.7 km (Prsa et al. 2016). This value is based on optical measurements and depends on details of the atmosphere and radiative transfer models. In two previous nuggets we described a new technique that uses RHESSI visibilities of occulted solar flare sources to measure the height of the X-ray limb (The X-ray Limb) and reported on preliminary analysis of a suitable solar flare (The Solar X-ray Limb II). As reported in the second nugget there were some problems with the chosen flare, but having found a better suited candidate we can finally claim success!
The event
The event that lead to our success, SOL2011-10-20T03:25, is the perfect candidate for several reasons. AIA context images provide independent confirmation that the event was indeed occulted. In addition, RHESSI's detector 2 was working well enough to provide usable data for this kind of work. This allowed us to perform a set of rigorous tests that
