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Magnetic Switchbacks

2 December 2023
Astronomy, cosmology, Electromagnetism

The Parker Solar Probe has led to a new explanation on how magnetic switchbacks form in the solar wind. See https://phys.org/news/2023-11-theory-magnetic-switchbacks-solar.html … the theory is outlined in a research paper in The Astrophycial Journal. Magnetic switchbacks are reversals of the radial magnetic field in the solar wind. These are typical components of solar wind fluctuations in the inner heliosphere as seen by the Parker Solar Probe. They consist of spherically polarised Alfven waves. The data beamed back to earth from the probe was unexpected, we are told. The Alfven waves originate near the Sun’s surface and becomes part of the solar wind. The velocity of the plasma oscillates because the magnetic field itself oscillates. They also looked at how the solar wind is heated. Again, this is blamed on Alfven waves.

At https://phys.org/news/2023-11-largest-magnetic-storms-history-quantified.html … a solar storm in November led to auroral phenomena seen as far south as Texas and Italy. Back in 1872, a solar storm generated aurora as far south as Bombay and Khartoum, not too distant from the equator. The two biggest solar storms of recent times were in 1859, the Carrington Event, and 1921. The new study claims the 1872 one was equally impressive – or as far as one can tell. Telegraph communications between Bombay and Aden were disrupted for hours and a land line between Cairo and Khartoum was affected. Yet, it originated in a medium size sun spot group near the solar disc centre. It was a superstorm with with aurora visible from the poles to the tropics. See the reseearch paper at https://doi.org/10.3847/1538-4357/acc6cc … Note, the medium size of the sun spot group is explained in a book review in SIS C&C Review 2023:3

At https://phys.org/news/2023-11-anisotropic-density-turbulence-sun-au.html … density turbuence in the solar corona and solar wind is evident via the properties of solar radio bursts. Angular scattering of extra solar radio noises observed in the solar atmosphere can be measured in situ in the solar wind. A visible density turbulence model should simultaneously explain all three types of density fluctuations.

Solar radio bursts are produced predominantly via plasma mechanisms at frequencies either at the local plasma frequency or its double [harmonic], and these are strongly affected by scattering of radio noises in the corona. The study is published in The Astrophysical Journal, by Kontar et al. – who looked at radio wave propagation in tubulent plasma simulations. They were then compared to solar observations published in the literature.

Bob Johnson had an article on anistropy and the Sun in SIS C&C Review a few years back.

The full paper by Kontar et al can be seen via https://doi.org/10.3847/1538-4357/acf6c1

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