Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Superconducting QUantum Interference Devices (SQUIDs) are fairly recent
types of magnetometers that use flux quantization combined with Josephson
tunnelling to detect very faint (< 10¯15 T) magnetic fields. Recent scientific
studies have shown that these highly sensitive magnetometers, located in an
ultra-low-noise environment, are capable of observing Earth-ionosphere couplings,
such as P waves emitted during earthquakes or magnetic storms in
the upper atmosphere, S and T breathing modes of the Earth during quiet
magnetic and seismic periods, signals in time correlating with sprites. Since
SQUIDs are much more sensitive than conventional magnetometers, they are
arguably the best tool for understanding space weather and natural hazards,
whether they are produced from space or within the ionosphere by magnetic
storms for instance, or natural disturbances, including magnetic disturbances
produced by earthquakes or as a result of the dynamics of the earth's core.
A study was conducted at SANSA Space Science in Hermanus, Western
Cape, in 2012, to find the correlation between SQUID and Fluxgate data-sets,
with the aim of validating the use of a SQUID as a reliable instrument for Space
Weather observations. In that study, SQUID data obtained from the Low
Noise Laboratory (LSBB) in France was compared to Fluxgate data-sets from
the three closest magnetic observatories to LSBB, namely Chambon la For êt
(France), Ebro (Spain) and Fürstenfeldbruck (Germany), all further than 500
km from LSBB. As a follow-up study, our aim is to correlate the SANSA Space
Science SQUID data at Hermanus with Fluxgate magnetic data also recorded
on-site (at Hermanus). There are notable di_erences between the previous
study and the current study. In the previous study, the three-axis SQUID
used comprised of three low-Tc devices operated in liquid helium (4.2 K) in an
underground, low noise environment shielded from most human interferences.
The SQUID magnetometer operated at Hermanus for the duration of this
study is a high-Tc two-axis device (measuring the x and z components of the
geomagnetic field). This SQUID magnetometer operates in liquid nitrogen
(77 K), and is completely unshielded in the local geomagnetic field of about
26 uT. The environment is magnetically clean to observatory standards, but
experiences more human interference than that at LSBB. The high-Tc SQUIDs
also experience excessive 1/f noise at low frequencies which the low-Tc SQUIDs
do not suffer from, but the big advantage of the current study is that the
SQUIDs are located within 50 m from the observatory's fluxgate. We thus
expect far better correlation between SQUID and fluxgate data than what
was obtained in the previous study, which should improve the isolation of
signals detected by the SQUID but not by the fluxgate. / AFRIKAANSE OPSOMMING: SQUIDs (supergeleidende kwantuminterferensietoestelle) is redelik onlangse
tipes magnetometers wat vloedkwantisering saam met Josephson-tonneling gebruik
om baie klein (< 10¯15 T) magnetiese velde waar te neem. Onlangse
wetenskaplike studies het getoon dat hierdie hoogs sensitiewe magnetometers
die vermoë het om Aarde-ionosfeerkoppeling waar te neem wanneer dit in 'n
ultra-laeruisomgewing geplaas word. Sodanige koppeling sluit in: P-golwe wat
deur aardbewings or magnetiese storms in die boonste atmosfeer veroorsaak
word; S- en T-asemhalingsmodusse van die Aarde gedurende stil magnetiese en
seismiese periodes; en seine in tyd wat korreleer met weerligeffekte in die boonste
atmosfeer. Aangesien SQUIDs heelwat meer sensistief is as konvensionele
magnetometers, is dit moontlik die beste gereedskap om ruimteweer en geassosieerde
natuurlike gevare mee te analiseer; hetsy sulke toestande veroorsaak
word vanaf die ruimte (deur die son) of binne die ionosfeer deur magnetiese
storms of natuurlike steurings wat deur aardbewings of die dinamika van die
Aardkern veroorsaak word.
'n Studie is in 2012 gedoen by SANSA Space Science in Hermanus in die
Wes-Kaap om die korrelasie tussen SQUID- en vloedhekdatastelle te vind met
die doel om SQUIDs as betroubare instrumente vir ruimteweerwaarneming te
bevestig. In daardie studie is SQUID-data verkry vanaf die Laeruis Ondergrondse
Laboratorium (LSBB) in Frankryk, en is dit vergelyk met vloedhekdatastelle
vanaf die drie naaste magnetiese observatoriums aan LSBB, naamlik:
Chambon la Forêt (Frankryk), Ebro (Spanje) en Fürstenfeldbruck (Duitsland).
Al drie hierdie observatoriums is verder as 500 km vanaf LSBB. As 'n opvolgstudie
is ons doelwit om SQUID- en vloedhekdata wat beide op die terrein
van SANSA Space Science in Hermanus waargeneem word, te korreleer. Daar
is merkbare verskille tussen hierdie en die vorige studies. In die vorige studie is
'n drie-as lae-Tc SQUID-magnetometer in vloeibare helium (4.2 K) in 'n laeruis
ondergrondse laboratorium, afgeskerm teen menslike steurings, gebruik.
Die SQUID-magnetometer wat vir die duur van die huidige studie by Hermanus
gebruik is, is 'n hoë-Tc twee-as toestel (wat die x - en z -komponente
van die geomagnetiese veld meet). Hierdie SQUID-magnetometer opereer in
vloeibare stikstof teen 77 K, sonder enige afskerming in die geomagnetiese veld
van ongeveer 26 uT. Die omgewing is magneties skoon volgens observatoriumstandaarde,
maar ondervind meer menslik-veroorsaakde steurings as LSBB.
Die hoë-Tc SQUIDs tel ook heelwat 1/f ruis op (wat lae-frekwensiemetings
beïnvloed); iets wat nie 'n rol speel by die lae-Tc SQUIDs nie. Die groot
voordeel van die huidige studie is dat die SQUIDs binne 50 meter vanaf die
observatorium vloedhekke geleë is. Ons verwag dus heelwat beter korrelasie
tussen SQUID- en vloedhekdata as wat met die vorige studie verkry is, wat dit
makliker sal maak om die isolasie te verbeter van seine wat deur die SQUIDs
waargeneem is, maar nie deur die vloedhekke nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86627 |
| Date | 04 1900 |
| Creators | Matladi, Thabang-Kingsley |
| Contributors | Fourie, C. J., Gouws, D. J., Saunderson, E. F., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiii, 86 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0028 seconds