Solar brightness variability, illuminating paper

Posted: September 19, 2015 by tchannon in Solar physics

Tim suspects this paper is important even though it is based largely on modelling. It says the intensity of spectral lines etc. are very important in variability, ultra-violet particularly, moreover there is counter sunspot cycle. This fits with where I think we are going on understanding solar terrestrial linkage.



The role of the Fraunhofer lines in solar brightness variability
A. I. Shapiro S. K. Solanki, N. A. Krivova, R. V. Tagirov, and W. K. Schmutz

Astronomy & Astrophysics, 2015, open access with free registration.

Context. The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and reconstructing solar brightness in the past. This is, in turn, important for better understanding the solar-terrestrial and solar-stellar connections.

Results. We show that the variations in Fraunhofer lines define the amplitude of the solar brightness variability on timescales greater than a day and even the phase of the total solar irradiance variability over the 11-year cycle. We also demonstrate that molecular lines make substantial contribution to solar brightness variability on the 11-year activity cycle and centennial timescales. In particular, our model indicates that roughly a quarter of the total solar irradiance variability over the 11-year cycle originates in molecular lines. The maximum of the absolute spectral brightness variability on timescales greater than a day is associated with the CN violet system between 380 and 390 nm.

I am particularly interested in the peculiarities which run counter to the obvious visual proxy of sunspots, which do nothing as such. The sun is far more complex, magnetics and spectral variation. In this case hot details radiate.

UV change is important both as stimulating the highly radiatively active earth O3 which also has an atmospheric window, right through into water. I’ve not see long datasets on this UV, maybe readers know.

Post by Tim

  1. ren says:

    Slowly starting to shape up winter polar vortex. For now blocking it begins on the eastern Siberia. We can already see there in the stratosphere, ozone area of elevated temperature. I conclude from this that cold air from the north will now reach out to the west of North America. Let’s see how the situation develops.

  2. oldbrew says:

    Tim: have you seen this paper?

    Reconstruction of solar UV irradiance – N.A. Krivova, S.K. Solanki

  3. tchannon says:

    Not that I recall oldbrew. Solanki (same author) seems to work towards better understanding of the short end.

  4. suricat says:

    tchannon says: September 19, 2015 at 3:21 pm

    “Not that I recall oldbrew. Solanki (same author) seems to work towards better understanding of the short end.”

    Hi tchannon!

    AFAIK, UVa is the ‘long’ UV waveband, UVb is the ‘medium’ UV waveband and UVc is the ‘short’ UV waveband.

    UVc doesn’t get into the tropo. It spans the most ‘ionizing’ wavelengths of UV and its energy is ‘used up’ before it gets there (the tropo).

    Some UVb does get into the tropo and Earth’s surface, but that depends upon the ‘ozone’ population present at the time of irradiation.

    UVa is another animal. The ‘long end’ of this waveband penetrates to a ‘depth to extinction’ in Earth’s ‘atmosphere and water’ that’s greater than any other wavelength of ‘EMR’ (ElactroMagnetic Radiation) that ‘insolation’ provides other than ‘blue vis’.

    Ozone behaves like ‘virtual cloud’ at these wavelengths, so the ‘big question’ is ‘how does ozone regulate UV’?

    Sorry, I don’t have any data (I can’t find it).

    Best regards, Ray.

  5. tchannon says:

    UV a b c, agree.

    You don’t need data for me, I agree. The lack of much _real_ data is sad. It has though been made a highly political subject.. Classic, science type gets the frighteners over something just noticed, an end of the world appears.

    There are so many real problems which go unaddressed.

  6. suricat says:

    tchannon says: September 27, 2015 at 3:19 am

    “There are so many real problems which go unaddressed.”

    I concur. Here’s an old paper that addresses some of the sensitivity issues, newer papers always seem to be ‘pay walled’.

    [mod shrinking very very long link]

    Apologies for the long link.

    Best regards, Ray.