Solar wind test of the de Broglie-Proca massive photon with Cluster multi-spacecraft data
Alessandro Retinò · Alessandro D.A.M. Spallicci · Andris Vaivads
Abstract and summary · read the original at the source
In one page
Alessandro Retinò, Alessandro Spallicci and Andris Vaivads use the four Cluster spacecraft, flying in formation in the solar wind at the Earth’s distance from the Sun, to test whether light’s particle carries a mass. If the photon has even a tiny mass, Ampère’s law picks up an extra term set by the vector potential — which in that theory stops being bookkeeping and becomes a physical quantity whose value changes the fields. So the team measures one electric current two ways: from the curl of the magnetic field, using the four spacecraft as the corners of a tetrahedron, and from the ion and electron velocities read by the particle detectors. Any mismatch bounds the mass. For the cleanest event, 7 March 2006, the upper limit lands somewhere between ten to the minus forty-ninth and ten to the minus fifty-first kilograms — roughly twenty orders of magnitude below the mass of an electron — depending on which estimate of the ambient vector potential is used. It is a deliberately cautious bound, measured in place rather than modelled.
Why it matters hereChapter ten turns on the vector potential being a real, physical quantity rather than a gauge convention, and this is a spacecraft experiment whose entire result depends on assigning the interplanetary potential a value. It also shows chapter one’s discipline in action: a bound is only as good as the assumptions under it, and these authors deliberately trade a tighter number for fewer of them.
What it claims
01In de Broglie-Proca electromagnetism the curl of the magnetic field gains a term equal to minus the photon mass parameter squared times the vector potential, so a massive photon shows up as a discrepancy in Ampère’s law rather than as anything exotic.Section 1, equations (1) to (4)
Published and peer-reviewed02Because the theory is not Lorenz gauge invariant, the vector potential is perceived as a measurable quantity whose value implies a change in the fields — the paper has to estimate the interplanetary potential three separate ways before it can quote a mass limit at all.Section 2.1
Published and peer-reviewed03The test measures one current twice: from the curl of the magnetic field, computed by the curlometer technique across four spacecraft separated by about six million metres, and from the ion and electron velocities measured by the particle detectors, with the difference between them setting the bound.Section 2, equation (7); Figure 2
Published and peer-reviewed04For the 7 March 2006 solar-wind event the three estimates of the ambient vector potential — 0.4, 29 and 637 tesla metres — give photon-mass upper limits of 1.4 times ten to the minus forty-ninth, 1.6 times ten to the minus fiftieth and 3.4 times ten to the minus fifty-first kilograms.Section 2.2, Table 1
Published and peer-reviewed05These bounds are deliberately weaker than the ten to the minus fifty-second and minus fifty-fourth kilogram figures usually quoted for the solar wind, because those rest on a steady-state Parker model and an argument about integrated magnetic stresses, while this test uses the field measured in situ and propagates the experimental errors.Section 3; Section 4
Published and peer-reviewed06The limit is instrumental, not fundamental: reaching ten to the minus fifty-second kilograms would mean resolving an ion-electron velocity difference of a few centimetres to a few tens of metres per second against the 6.8 times ten to the fourth metres per second now resolvable, so better particle detectors and further multi-spacecraft missions, MMS among them, are what would sharpen the answer.Section 3, equation (16) and Figure 3; Section 5
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Read it · abstract
Abstract
Our understanding of the universe at large and small scales relies largely on electromagnetic observations. As photons are the messengers, fundamental physics has a concern in testing their properties, including the absence of mass. We use Cluster four spacecraft data in the solar wind at 1 AU to estimate the mass upper limit for the photon. We look for deviations from Ampère's law, through the curlometer technique for the computation of the magnetic field, and through the measurements of ion and electron velocities for the computation of the current. We show that the upper bound for mγ lies between 1.4 × 10⁻⁴⁹ and 3.4 × 10⁻⁵¹ kg, and thereby discuss the currently accepted lower limits in the solar wind.
The way in
https://doi.org/10.1016/j.astropartphys.2016.05.006Published as Astroparticle Physics 82 (2016) 49–53. The author copy, arXiv:1302.6168v4 of 22 May 2016, is posted under the arXiv.org perpetual non-exclusive licence rather than a Creative Commons licence, and the publisher deposit carries the Elsevier text-and-data-mining user licence, which is not a licence to readers, so this page carries the summary, the claims and the authors’ own abstract and sends the reader to the source, which is free to read in full at arxiv.org/abs/1302.6168.
How to cite it
Alessandro Retinò, Alessandro D.A.M. Spallicci, Andris Vaivads (2016) Solar wind test of the de Broglie-Proca massive photon with Cluster multi-spacecraft data. doi:10.1016/j.astropartphys.2016.05.006
Where it sits in the curriculum
Scalar waves and the field behind the fieldsThe unified pictureThe evidence ladder