Birkeland’s paper in Archive des Sciences Physiques et Naturelles 1916 (
here is the link to the pfd or any other format, just to save you from searching if you need it). There are two papers, one from page 22 to 37 and one from page 109 to124, written in 1915 during Birkelands stay in Egypt. Both are called:
Les rayons corpusculaires du soleil qui penètre dan l’atmosphere terrestre sont-ils négatifs ou positives? and belong together.
It is quaint reading for a modern scientist, as a lot of extra text is inserted that nowadays would not get through the referee process anymore, maybe a loss? But anyway, before I digress, let’s go to the first claim that Birkeland (henceforth B) makes on page 23, regarding M. Prof. Störmer:
B said:
M. Stôrmer termine sa publication en se demandant si les rayons de l'aurore boréale sont produits par des corpuscules positifs ou négatifs et il croit pouvoir prouver qu'il s'agit de particules électriques chargées positivement.
Je pense que le raisonnement qui conduit le prof. Stôrmer à cette conclusion est certainement inexact à cause de la manière dont il traite les orages magnétiques polaires.
So, this deals (like the title says) with the particles that penetrate the Earth’s atmosphere and produces the aurora. Apparently, see quote, Störmer claimes that positive charges are creating the aurora. B is not in agreement with that, he thinks that the charges are negative (and as we now know, he is right, but that as an aside), and points to his Norwegian Expedition book, page 609.
Then some discussion about his terrella, and about positive and negative auroras, where the positive ones apparently are produced in the afternoon, whereas the aurora borealis and the negavit polar storms happen in the night with a maximum near midnight. (see for an explanation his book pages 580-571, don’t know why the numbers are reversed and pages 536-540). He discusses that the measurements he made are in agreement with negative charge leading to aurora
Then on page 24 he makes the following claim about positive charges:
B said:
Il semble après cela que si des rayons positifs pénètrent dans l'atmosphère terrestre c'est à peine s'ils peuvent donner lieu à un effet magnétique perceptible, parce que leur action devrait précisément être un maximum pendant la période que nous avons reconnu être absolument calme.
Mais dans les espaces cosmiques, les rayons polaires positives qui existent probablement et même certainement ne semblent pas s'approcher assez de la terre pour qu'on puisse affirmer leur présence dans notre atmosphère. Il serait d'un grand intérêt d'effectuer des observations au levant de la terre sur ce phénomène, et de prouver par là l'existence de rayons solaires positifs; en ce qui me concerne je n'ai jamais rien pu observer de ce genre.
So, if the positive charges would penetrate than it would be in a region where the magnetic field is calm and this leads to his conclusion that the positive charges do not enter the atmosphere. But the positive charges that
probably exist in space, do not get close enough to the Earth to be measured, we will have to go there to prove their existence. And B himself has never been able to observe these positive rays.
Before he will show that Störmer is wrong he takes a sidestep to the zodiacal light in §2page 25. Naturally this goes back to his idea that the zodiacal light is also some sort of discharge (which we now know it wrong, it is just reflected light off dust, to keep it simple). He then claims that, page 25:
B said:
Au point de vue physique, il est très probable que ces nouveaux rayons solaires ne sont exclusivement ni des rayons positifs ni des rayons négatifs, mais sont des rayons des deux sortes.
So the zodiacal light is produced by both positive and negative rays in his view. I will not go into the whole description of the zodiacal light, you can read it for yourself in the link. However, I will give one more quote here about the zodiacal light, which is “reproduced” in the terrella with the terrella itself as a cathode. From page 27
B said:
Nous avons vu comment autour de la sphère magnétique qui sert de cathode, il se forme un faisceau de rayons dans le plan de l'équateur magnétique. Je suppose qu'un faisceau pareil, mais de dimensions considérables, se trouve autour du soleil et tourne avec lui à cause de la manière dont il a été formé.
So, he could imagine that a similar disk as in his terrella chamber (Fig. 2) could exist around the sun giving rise to the zodiacal light. Indeed, on page 18 B writes:
B said:
L'on observe cette période régulièrement, qu'il y ait des taches solaires ou non; elle est bien marquée aussi bien pour un minimum que pour un maximum des taches solaires. Ce fait considéré avec ma théorie des orages polaires magnétiques appuie l'idée que l'immense disque de rayons autour du soleil tourne toujours avec lui. Daus mon ouvrage A. P., p. 623, j'ai mentionné quelques faits connus au sujet du pouvoir de la matière radiante d'absorber et de diffuser la lumière solaire. Il est concevable que les rayons hélio-cathodiques lors de leur collision avec des ions dans l'espace cosmique produisent un grand nombre d'électrons de dispersion qui peuvent être entraînés et se trouver en raisonnance avec les ondes lumineuses provenant du soleil. Il est probable que c'est de cette manière que le disque de rayons corpusculaires autour du soleil nous est visible comme une lumière zodiacale.
(taches solaires = sun spots) So, he claims that there can be a immense disk of “rays” (of corpuscules) rotating around the sun. The cathode rays (electrons) can hit ions in this disk, liberating more electrons. These can all interact with the sunlight, and if I interpret this text correctly, he steps down from the discharge model for the zodiacal light, but says it is probably scattered sun light.
Then the discussion turns to Saturn’s rings, which I will skip and on page 29 in §3 the
causes de grand changements climateriques de la periode tertiaire are discussed, which I will skip too, because this was going to be an the positive and negative charges emitted by the cathode Sun, and not whether variations in the solar emission can have an effect on the climate (though interesting that B also was thinking about that).
Then a discussion about the aurora again, the particles arrive and leave the atmosphere at an estimated height of 500 km. And I think B is also describing the westward surge of a substorm on page 32.
Now B keeps on talking about the
rayons cathodiques solaires, and in the time of his experiments these cathode rays were electrons and up to page 34 I have no doubt that B means electrons when he uses this term. On page 34 he refers again to this book page 591-595, where experiments are done with cathode rays of various energy (1800 and 2400 V) and shows how the energy of the cathode rays makes the location of the auroral rings on his terrella change location. He estimates the product of the magnetic field H and the larmor radius ρ and he came to the conclusion that, page 35:
B said:
De ces expériences j'ai tiré la conclusion que pour les rayons corpusculaires solaires qui pénètrent dans la zone aurorale on a :
H ρ = 3 X 106 (A. P., 595 ).
Mais j'ai admis que la valeur de Ho n'est pas toujours la meme et peut varier de 1 à 10 millions.
Then some discussion about Störmer again and then at the end of part 1, page 37:
B said:
Ce n'est que plus tard, lorsque j'eus trouvé que Hp valait 3 millions pour les rayons projetés dans la zoneaurorale, que j'eus l'idée que nous avions à faire à des rayons cathodiques très puissants que j'ai appelés les rayons hélio-cathodiques; j'ai calculé que la tension électrique négative nécessaire à la projection de ces rayons était de 600 millions de volts.
So, he needs highly energetic cathode rays, which he calls helio-cathode rays, and he calculated that the “negative electrical tension” to emit those rays would have to be 600 million Volts. B concludes the first part then with, page 37:
B said:
D'après cela, il semble que nous pouvons admettre que le soleil, en diverses circonstances, lors d'éruptions électriques fréquemment de très courte durée, peut envoyer des rayons qui atteignent la terre et pour lesquels Hp est compris entre un et cent millions.
After this, is seems that we have to admit that the sun, in various circumstances, during electric eruptions often of very short duration, may send out rays that hit the Earth and for which Hp is between one and hundred million.
End of the first part of the paper. There is no mention on why B thinks that positive and negative charges are send out from the sun, but that is not surprising, as that is not what the paper is about. This is mainly to show that Strömer is wrong by assuming that the aurora is created by positive rays.
Okay, that was part one. Part two will come later.
