The Sun Today: Severe geomagnetic storm this September 26, 2011 by Dr. Keith Strong

 

Geomagnetic storm index for the Philippines

by Quirino Sugon Jr.

I am thinking of proposing a geomagnetic storm index for the Philippines using MAGDAS (Magnetic Data Acquisition System) data of Kyushu University’s SERC (Space Environment Research Center).  SERC has 6 stations all over the Philippines: TUG (Tuguegarao), MUN (Muntinlupa), LGZ (Legaspi), CEB (Cebu), CDO (Cagayan de Oro), and DAV (Davao).  SERC provided us with data for 2010 at 1 minute interval.  We shall use this data to identify geomagnetic storms from their magnetic signatures.  But to do this, we need first to make a survey on the magnetic storm indices currently used worldwide.  Note that each place defines its own storm index because geomagnetic storms affect different places differently.  At present, there is still no magnetic storm index for the Philippines.

1.  The ever-reliable Wikipedia has a good article on geomagnetic storms.  Here is one definition in terms of DST:

A geomagnetic storm is defined[4] by changes in the Dst[5] (disturbance – storm time) index. The Dst index estimates the globally averaged change of the horizontal component of the Earth’s magnetic field at the magnetic equator based on measurements from a few magnetometer stations. Dst is computed once per hour and reported in near-real-time.[6] During quiet times, Dst is between +20 and -20 nano-Tesla (nT).

2.  NOAA Space weather prediction Center has made a descriptive scale for geomagnetic storms from G1 to G5.  I need a list of geomagnetic storms for 2010 and how NOAA computes its storm scale from its magnetic data.

3.  Wikipedia says that the K-index is measured from the fluctuations in the horizontal component of magnetic field.  It requires only one magnetometer using data in 3 hours.  In the page is the Boulder Scale.  The Kp index is measured from the average of the K-indices of a network of observatories.  In the A-index, each K-index is rescaled into the equivalent 3 hour range.  The Ap index is the average A index for all the stations.

4. Berkeley has a discussion on the DST index.  This index is made by averaging the horizontal component of the magnetic field from midlatitude to equatorial regions.  A negative DST index corresponds to the ring current.  I think there is a mistake here: it is the horizontal fluctuations that must be averaged and not the horizonotal components themselves.

5.  NOAA has a geomagnetic index bulletin for 2010.  I need this.

Equatorial spread F and plasma bubbles

by Quirino Sugon Jr.

I need some literature survey for the equatorial Spread F and plasma bubbles to see if what we are doing has been done before.

D. L. Hysell, M. F. Larsen, C. M. Swenson, A. Barjatya, T. F. Wheeler, T. W. Bullet, M. F. Sarango, R. F. Woodman, J. L. Chau, D. Sponseller, Onset conditions for equatorial spread F determined during EQUIS II. This is the result of rocket investigations of the equatorial spread F in Kwajalein Atoll on August 7 and 15, 2004. The electron density that they found is not a smooth function of height but jagged.

There another paper by the same authors: Rocket and radar investigation of background electrodynamics
and bottom-type scattering layers at the onset of equatorial
spread
.

J. Krall, J. D. Huba, G. Joyce, and T. Yokoyama, Density enhancements associated with equatorial spread F, Ann. Geophys., 28, 327–337 (2010). The paper uses the following definition:”equatorial spread F as diffuse echoes in the ionosphere received continuously at night in equatorial regions over a wide range of frequencies (Booker and Wells, 1938). They use an ionosphere model SAMI3/ES, which uses certain ion diffusion equations. The electron density obtained in from rocket measurements is also jagged as shown in Fig. 8. But I still have to see its corresponding ionogram.

I need a paper that shows a jagged ionosphere from rocket measurements and its corresponding ionogram.

K. L. Bowles, Radio Wave Scattering in the Ionosphere, in Advances in Electronics and Electron Physics by L. L. Marton, vol. 19, pp. 55-176 (1964). This is an excellent monograph. Here are some notes:

Bowles said in p. 56 that “the scattering of radio waves arises from fluctuations or irregularities in the otherwise smoothly varying distribution of ionization density in the ionosphere…. The term ‘backscattering’ or simply ‘scattering’ will be used to refer to propagation effects in which a small fraction of the signal intensity reaches the observer because its path has been deviated through a relatively large angle by irregular structures of small scale, usually a few tens of meters.” (p. 56)

Bowles has an excellent treatment of scintillation.

p. 142: “At HF frequencies in the vicinity of the F region plasma frequencies, the phenomenon of spread F is frequently observed in conventional sweep-frequency ionograms. Spread F appears in a number of forms which are relatively distinct, at least as viewed in the ionograms, and one such form has been positively identified with field-aligned irregularities. The difficulties associated with the theory of spread-F for frequencies close to the plasma frequency are great, and the association of spread-F in general with field-aligned irregularities is still mainly conjectural.”

p. 145: The South America observations suggested that the range spread F is associated with a relatively thin layer located near the bottom of the profile of F layer ionization density. The thickness of this layer was often 50 im or less, although much thicker regions were sometimes observed. VHF scatter was not associated with frequency spreading, and when ionogram showed only frequency spreading, no VHF F layer scatter was observed.

p. 146: “The mechanism of frequency spread F is considerably more difficult to understand, because the propagation effects apparently occur in the heigh and frequency region where the radio freqquency approaches the local plasma frequency.” Bowden computed the ionograms for ionospheric holes.

Simulation of equatorial electron density profiles and their corresponding vertical incidence ionograms

by Quirino Sugon Jr.

I am writing an end of project report which I must send tomorrow.  I need some related literature on the simulation of equatorial electron density profiles and their corresponding vertical incidence ionograms.  Here’s what I found from the web:

M. A. Cervera and T. J. Harris, Modelling the eff ects of ionospheric disturbances on quasi-vertically incident ionograms using 3D magneto-ionic raytracing, URSIGASS 2011. This is by DSTO Australia. I need to talk to them regarding their ionosonde at Manila Observatory. The authors use quasiparabolic (QP) method just like others. Our method is via cosine splines.  They use Hamiltonian ray tracing, which makes the ray paths dependent on the gradient of the refractive index.  But this method will only work for oblique incidence and not for vertical incidence.  That is why the authors clarified that the method is actually quasi-vertical incidence.

Ionospheric Physics Program, Report on the U.S. Program for the International Geophysical Year, by National Academy of Sciences–National Research Council (Washington DC, November 1965), pp. 253-314.  In p. 257 it was mentioned that there were plans to place vertical ionosphere in equatorial countries: Western Pacific, Marianas Islands, Line Islands in East Central Pacific, and South America.  It was mentioned in p. 276 that they use the matrix method of Budden to extract the electron density as a function of true height, using the group refractive index expressed as a matrix.  The true height is computed using matrix inversion. The assumption is monotonic variation of the electron density as a function of height (p. 277).  This is the assumption that we wish to avoid.

L.A. McKinnell and A.W.V. Poole, Efforts to produce realistic ionograms from electron density profiles in the F1 region, URSI Proceedings, General Assembly 2002, p 0017.   They are using neural networks.  But they did not show an actual ionogram.

Carlo Scotto, Electron density profile calculation technique for Autoscala ionogram analysis, Advances in Space Research
Volume 44, Issue 6, 15 September 2009, Pages 756-766. I cannot access the article yet.

Reinisch, B., and H. Xueqin (1983), Automatic calculation of electron density profiles from digital ionograms 3. Processing of bottomside ionograms, Radio Sci., 18(3), 477-492. Parabolic profile shapes are assumed for the E region and the valley between the E and the F layer. The F layer is approximated by a single sum of Chebyshev polynomials, and the entire profile is described by a set of 16 numerical values.

Xuequin Huang, Uncertainty boundaries of electron density profiles deduced from ionograms, University of Massachusetts Lowell, Center for Atmospheric Research (UML-CAR), XI International Digisonde Forum, 30 April to 3 May 2007. The author is using Chebyshev polynomials for the electron density as a function of real height. The presentation mentions spread (range and frequency). I think this is similar to what we are getting, but I am not sure if this refers to the simulation or to the actual data. Construction of the boundary lines requires matrix inversion. Is this the technique of Budden? Ok, he is not using our method.  He is still trying to invert the ionogram to obtain the electron density profile.

The International Satellite for Ionospheric Studies (ISIS) is digitizing its ionograms in the 1960s and 1970s.  There is a TOPIST software for inverting these ionograms for the topside ionosphere.

Xueqin Huang and Bodo Reinisch, Vertical electron density profiles from digisonde ionograms: the average representative profile,  Annali de Geofisica, 39(4), 1996. Similar to that of Xuequin Huang in the previous paper.

 

Seismology as a Jesuit Science

by Quirino Sugon Jr.

I would like to benchmark what we do at Manila Observatory, with what other Jesuit Observatories do, especially in the fields of Seismology, Geomagnetism, and Ionosphere research. I shall start first with a review of Jesuit involvement in Seismology.

Seismology

This is a good reference:

The Jesuit Contribution to Seismology by
Agustin Udías and William Stauder (from Seismological Research Letters, Vol. 67, No. 3, pp. 10-19; May/June 1996)

This has a table of the Jesuit observatories participating in seismic research, but this era is about to come to a close.

“It may be intriguing to some that a religious order dedicated so much effort to a science like seismology. From the very early years of the its foundation in the 16th century by Ignacio de Loyola, the Society of Jesus dedicated itself primarily to educational work through its many colleges and universities. From the beginning of these institutions science was an important subject in the curriculum. A key figure in this development was Christopher Clavius (1537-1612), Professor of Mathematics in the Collegio Romano. Clavius was instrumental in incorporating a serious program of mathematics, astronomy, and natural sciences not only in his own college but also in all Jesuit colleges and universities (MacDonnell, 1989). Secondly, in the 17th and 18th centuries a number of astronomical observatories were established in these institutions. In a number of these, meteorological observations also were made. Finally, in a particularly notable page of this history, Jesuits were appointed Directors of the Astronomical Observatory in Beijing, China (Udías, 1994). This tradition forms the background of modern Jesuit scientific work. Since the middle of the 19th century, as many as forty geophysical observatories were created by Jesuits around the world and in many of these seismological stations were installed (Udías and Stauder, 1991).”

The article also notes that “From 1868, the approximate date of the installation of the first seismograph by the Jesuits in Manila, to the present many members of this religious order have dedicated their time and efforts to seismology.”

Another good reference is

Seismology, The Jesuit Science: Some Jesuits and Their Geophysical Observatories

“Much of this narration is taken from the work of William Stauder, S.J. of St. Louis University and Augustin Udias. The underlying seismic principles are taken from The Random House Encyclopedia.

“Jesuits have contributed so much to the development of seismology and seismic prospecting that Seismology has been called The Jesuit Science, and prompted by Dr. Turner, once president of the British Seismological Association, the Society has been congratulated for dominating the field of seismology in America. Daily reports from the Jesuit network were teletyped to the US Coast and Geodetic Survey in Washington and were published annually in the Bulletin of the Seismological Society of America under the title “The Report Or the Jesuit Seismological Association.” This Jesuit report was read throughout the world and was highly esteemed even in countries such as Norway where the Jesuits themselves were not allowed. Not only earthquake seismology owes much to Jesuit research, but even more indebted is the field of seismic prospecting, now 60 years old which claims as one of its chief authorities and organizers, Daniel Linehan, S.J. who first put the theories of shallow refraction into practice. Two principal factors contributed to the interest of Jesuits in geophysical phenomena: the educational work of the Jesuits in colleges and universities and their missionary endeavors in remote lands.”

There are historical details presented here about the 54 Jesuit observatories.