Balfour Stewart
Balfour Stewart | |
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Kew Observatory, Owens College, Manchester | |
Doctoral advisor | James David Forbes |
Balfour Stewart (1 November 1828 – 19 December 1887) was a Scottish physicist and meteorologist.
His studies in the field of
Career
Stewart was born on 1 November 1828 at 1 London Row in Leith (north of Edinburgh), the son of William Stewart a tea merchant, and his wife, Jane Clouston.[1] His father was involved in business in Great Britain and Australia.
He was educated at
Radiant heat first claimed his attention, and by 1858 he had completed his first investigations into the subject. These yielded a remarkable extension of
In recognition of this work, he received in 1868 the Rumford Medal of the Royal Society, into which he had been elected six years before. Of other papers in which he dealt with this and kindred branches of physics may be mentioned "Observations with a Rigid Spectroscope," "Heating of a Disc by Rapid Motion in Vacuo," "Thermal Equilibrium in an Enclosure Containing Matter in Visible Motion," and "Internal Radiation in Uniaxal Crystals."
In 1859 he was appointed director of
He was the author of several successful textbooks of science, and also of the article on "Terrestrial Magnetism" in the ninth edition of the Encyclopædia Britannica. In conjunction with Professor P. G. Tait he wrote The Unseen Universe, at first published anonymously, which was intended to combat the common notion of the incompatibility of science and religion.[2][3]
A devoted churchman,
The Great Geomagnetic Storms of September 1859
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Balfour Stewart recorded remarkable
Stewart went on the make the following observation.
I now proceed to notice some of the peculiarities of this magnetic storm.
It appears that we have two distinct well-marked disturbances, each commencing abruptly and ending gradually, the first of which began on the evening of August 28 and the second on the early morning of September 2. These two great disturbances correspond therefore in point of time to the two greatauroraldisplays already alluded to.
The second disturbance resulted from what is now known as the Carrington Event, a large solar flare that Richard Carrington and Richard Hodgson observed telescopically on the morning of 1 September, 1859. The first disturbance had no observed solar activity prior to its onset. This could be because the associated solar eruption was either unobserved by optical telescopes at the time of its occurrence, or because the eruption itself did not produce an optical, or "white light", flare like the Carrington flare and was therefore invisible to the optical telescopes in use at the time.
At the 11 November 1859 meeting of the Royal Astronomical Society, Richard Carrington presented a paper[7] describing his observations of the super flare that occurred on 1 September, at 11:18 GMT and later named in his honor. In what appears to be an editorial addition made after the meeting the following observation was appended in parentheses.
(
Kew, and pointed out that a moderate but very marked disturbance took place at about 11h 20m A.M., Sept. 1st, of short duration; and that towards four hours after midnight there commenced a great magnetic storm, which subsequent accounts established to be considerable in the southern as in the northern hemisphere. While the contemporary occurrence may deserve noting, he would not have it supposed that he even leans towards hastily connecting them. “One swallow does not make a summer.”)
From this addendum, it is clear that Richard Carrington was not willing to commit professionally to connecting the magnetic disturbance with the event he had observed on the surface of the Sun even though they occurred at nearly identical times. He had indeed displayed the magnetographs at the Royal Astronomical Society meeting. The time of 11:20 GMT is good agreement with other reports but the time of 4:00 GMT on 2 September 1859 for the commencement of the magnetic storm is an hour earlier than reported by Stewart.
Stewart also reported[5] on a smaller magnetic disturbance that occurred at the same time as the white light solar flare observed by Richard Carrington:
But, beside these two remarkable disturbances into which it divided itself, this great storm comprehends a minor disturbance, not approaching these two in extent, but yet possessing an interest peculiar to itself, which entitles it to be mentioned.
On September 1, a little before noon, Mr. R.C. Carrington happened to be observing, by means of a telescope, a large spot which might then be seen on the surface of our luminary, when a remarkable appearance presented itself, which he described in communications to the Royal Astronomical Society.
(Richard Carrington’s paper is then quoted at length.)
On calling at
sun spots, it is not impossible to suppose that in this case our luminary was taken "in the act".This disturbance occurred as nearly as possible at 11h 15m A.M. Greenwich mean time, on September 1, 1859, affecting all the elements simultaneously, and commencing quite abruptly.
This small, short-duration, disturbance described by Stewart is now understood to be due to a rapid ionization increase and resultant electric currents in the ionosphere due to intense X-ray radiation from the solar flare. Travelling at the speed of light, solar flare X-rays take 8 minutes to travel from the sun to the Earth, and arrive simultaneously with the white light flare photons that Carrington observed. The resulting geomagnetic disturbance from the ionospheric currents occurs nearly simultaneously with the photon arrivals and lasts only for as long as the flare X-ray flux continues to ionize the upper atmosphere. The larger magnetic storm that commenced 17.5 hours after the flare is now understood to be caused by a coronal mass ejection (CME) associated with the eruption that caused the solar flare.
By citing the previous research of
Stewart reported that the first geomagnetic storm began at 22:30 GMT on the evening of 28 August 1859, as recorded by self-recording magnetographs at the Kew Observatory. Assuming that the first large geomagnetic storm was caused by a solar eruption similar in scale to the Carrington Event that is known to have caused the second storm, it is interesting to ask if a SFE is evident in the Kew magnetograph records prior to the onset of the second storm. Given that CME speeds can vary widely between solar eruptions, even those with similar-sized flares, the SFE signal may not be 17 hours earlier than the first storm's onset and could be as much as 24--48 hours prior to the storm onset time.
Writings
- Elementary Treatise on Heat (1866; sixth edition, revised, 1895)
- Lessons in Elementary Physics (1871, 1886)
- Physics (1872, 1884)
- The Unseen Universe (1875)
- Paradoxical Philosophy: A Sequel to the Unseen Universe (1878)
- The Conservation of Energy (1875; ninth edition, 1900)
- Lessons in Practical Physics with W. H. Gee, (volume i, 1885; volume ii, 1887)
- An Elementary Treatise on Heat (1888)
References
- ^ Edinburgh and Leith Post Office Directory 1828
- ^ public domain: Chisholm, Hugh, ed. (1911). "Stewart, Balfour". Encyclopædia Britannica. Vol. 25 (11th ed.). Cambridge University Press. pp. 912–913. One or more of the preceding sentences incorporates text from a publication now in the
- ^ The New International Encyclopedia(1905), vol. 18.
- ^ On the Great Magnetic Disturbance of 28 August to 7 September 1859, as Recorded by Photography at the Kew Observatory. (Abstract) by Balfour Stewart, Proceedings of the Royal Society of London, Vol. 11, (1860–1862), pp. 407–410
- ^ a b On the Great Magnetic Disturbance Which Extended from 28 August to 7 September 1859, as Recorded by Photography at the Kew Observatory by Balfour Stewart, Philosophical Transactions of the Royal Society of London, Vol. 151, (1861), pp. 423–430
- ^ An account of the construction of the self-recording magnetographs at present in operation at the Kew Observatory of the British Association. by Balfour Stewart, 1859; PDF Copy
- ^ Description of a Singular Appearance seen in the Sun on 1 September 1859; Carrington, R.C.; Monthly Notices of the Royal Astronomical Society, Vol. 20, pp. 13–15
- ^ The 1859 Solar–Terrestrial Disturbance and the Current Limits of Extreme Space Weather Activity Archived 11 August 2011 at the Wayback Machine, Solar Physics (2004) 224: 407–422 (2005), E.W. Cliver and L. Svalgaard
External links
- Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900. .
- Works by or about Balfour Stewart at Internet Archive
- Works by Balfour Stewart at Google Books
- Papers by Balfour Stewart at Google Scholar