Variable sunshine— researchers explain why our Sun’s brightness fluctuates

Posted: August 23, 2017 by oldbrew in Astrophysics, research, Solar physics
Tags: ,

Sunspots [image credit: NASA]

One of the authors of the research says: “The results of our study show us that we have identified the governing parameters in our model”. Both climate and exoplanet research could benefit from the findings.

The Sun shines from the heavens, seemingly calm and unvarying. In fact, it doesn’t always shine with uniform brightness, but shows dimmings and brightenings, reports

Two phenomena alone are responsible for these fluctuations: the magnetic fields on the visible surface and gigantic plasma currents, bubbling up from the star’s interior.

A team headed by the Max Planck Institute for Solar System Research in Göttingen reports this result in today’s issue of Nature Astronomy. For the first time, the scientists have managed to reconstruct fluctuations in brightness on all time scales observed to date – from minutes up to decades.

These new insights are not only important for climate research, but can also be applied to distant stars. And they may simplify the future search for exoplanets.

When an exoplanet transits in front of its parent star, the star darkens briefly. Even from a distance of many light-years, space telescopes register these changes – and thus detect the exoplanets. In theory. In practice, it’s more complicated, as the brightness of many stars fluctuates, similar to that of the Sun.

These fluctuations can overlay the signals of passing exoplanets. “However, if we are aware of the details of the star’s intrinsic brightness fluctuations, exoplanets can be detected with great precision,” says Alexander Shapiro of the Max Planck Institute for Solar System Research.

Shapiro and his colleagues have taken a first step in this direction with their current paper – with a detailed look at a special star: our Sun. Since the beginning of the space age, numerous spacecraft have delivered detailed data collected unaffected by the disturbances caused by the Earth’s atmosphere.

These data seriously challenge any model describing fluctuations in stellar brightness: can the measured fluctuations be reconstructed using a model? And is it possible to link the fluctuations to the physical properties of the star?

Continued here.

  1. Roger,

    In the short term, earth response to changes in energy from the sun is really fast. You can tell that from changes between day and night, cloudy and bright, summer and winter.

    In the longer terms, earth temperature is self correcting and bounded inside bounds that are caused by thawed oceans and more snowfall in warmer times and caused by frozen oceans and less snowfall in colder times.

    These cycles show up in short cycles, snow in October has influence in March, they show up in longer cycles, snow over several hundreds of years in a Medieval Warm period promote a Little Ice Age that occurs a few hundred years later. The year 1998 was a warmer year with more snowfall and the following few years were cooler, most likely due to the more snowfall. Look at Arctic ice extent, a more open year is often follow by some less open years. This shows up in even longer cycles, more snow that fell between 110 and 140 thousand years ago showed up in the really cold ice age between 20 and 100 thousand years ago. The lack of snowfall when the oceans were depleted and frozen allowed the ice to deplete and retreat into this modern warm period that has different characteristics than previous warm periods. We have an new normal climate with cycles that are different because of the different balance of ice on land and water in the oceans. All the forcing factors have resonated with the natural ice and water cycles to get to this point. Leighton Stewart wrote, fire, ice and paradise. This most recent ten thousand years is the paradise he described.

    Ice is not a result of temperature change as much as it is a major cause of temperature change.

    Ice core data tells this story very clearly. Ewing and Donn published this 60 years ago. Tom Wysmuller presented this to our NASA Alumni League, 9 years ago.

    Over the most recent ten thousand years, almost 40 watts per meter squared moved out of the NH above 60 degrees and moved into the SH below 60 degrees and each hemisphere adjusted snowfall to still keep temperature cycles bounded inside the same limits. Other changes to solar energy into the earth from changes in brightness and changes in greenhouse gases are small compared to the orbit parameters.

    Once the ice core data is understood, ice cores do not go back beyond 800 thousand years, but the ice was cycling in the same ways even before that. The modern ice and water journey to get to this paradise occurred since the asteroid, or whatever hit earth, 60 million years ago.


  2. oldbrew says:

    Results from this should be interesting…

    Record-shattering 2.7-million-year-old ice core reveals start of the ice ages
    By Paul Voosen Aug. 15, 2017 , 12:15 PM

    Scientists announced today that a core drilled in Antarctica has yielded 2.7-million-year-old ice, an astonishing find 1.7 million years older than the previous record-holder.

  3. tom0mason says:

    You people may also interested in this study called ‘Harmonic Analysis of Worldwide Temperature Proxies for 2000 Years’ where a lot of correlation of global temperature (whatever) with solar cycles (it also fits nicely with Jennifer Marohasy’s recent paper).
    It’s at

    [reply] thanks

  4. oldbrew says:

    From the conclusion to the above paper:
    As (Fig. 2 and Table 2) show, the periods of ~1000 and ~460 years are also apparently common in records of temperatures and cosmogenic nucleides.
    The 460y period is described as not named but frequently reported.

    460 = 115 * 4
    115y = ~13 lunar apsidal cycles and ~102 full moon cycles (13+102 = 115 tropical years)

    We showed here that the ‘quarter precession’ period should consist of 56 (7×8) such cycles, in theory at least (728 LAC (13 x 7 x 8) in the diagram).

    Multiply by 4 = 25764 years i.e. full precession in the current epoch (within a few years).

    25760 / 460 = 56