**Langel, R. A. (1937-2000)**

NASA (U.S.) scientist who served as the Project Scientist for the Magsat
mission. Trained as an applied mathematician and physicist, Langel was
born in Pittsburgh, Pennsylvania. He was a strong advocate of
high-accuracy vector magnetic measurements from satellite. These
measurements were used to demonstrate the break in the power spectra at
about spherical harmonic degree 13 that represents the transition from
core-dominated processes to lithospheric-dominated processes (Figure 1
below and Langel and Estes, 1982). Tantalizing suggestions of such a
break had previously been reported from total field intensity
measurements acquired on an around-the-world magnetic profile (Alldredge
et al., 1963). Langel also made use of the high-accuracy vector
measurements, and magnetic observatory measurements, for the
coestimation of internal (core and lithosphere), external (ionosphere
and magnetosphere), and induced magnetic fields. These comprehensive
models of the geomagnetic field were developed in collaboration with T.
Sabaka (NASA) and N. Olsen (Denmark). Earlier workers had relied on a
sequential approach, beginning with the largest (core) fields. Langel
also pioneered mathematical techniques for the merging of a priori
long-wavelength lithospheric magnetic field information with shorter
wavelength observations (Figure 1 below and Purucker et al., 1998) using
inverse techniques. This is necessary because the longest-wavelength
lithospheric magnetic fields are inaccessible to direct observation as
they overlap with the much-larger magnetic fields originating in the
earth's outer core. Significant earlier developments with forward models
came from Cohen (1989) and Hahn et al. (1984). Langel authored or
coauthored in excess of 94 peer-reviewed publications, and helped train
a generation of geomagnetists by virtue of his work on Magsat and his
teaching at Purdue University (U.S.) and Copenhagen University
(Denmark).

Bob was devoted to his family and church. His religiosity was well known
amongst his colleagues, and he undertook missionary work, lead bible
study groups, and worked with teenagers.

![](media/image1.jpeg){width="2.9298611111111112in" height="3.0in"}

Figure 1. Comparison of the Lowes-Mauersberger spectra at the Earth's
surface for a recent Comprehensive Model (line) of the core and
lithospheric fields by Sabaka et al. (2004) and a lithospheric field
model (symbols) by Fox Maule et al. (2005). ![](media/image2.wmf) is the
mean square amplitude of the magnetic field over a sphere produced by
harmonics of degree n.

# Bibliography 

Alldredge, L.R., Vanvoorhis, G.D., and Davis, T.M., 1963, A magnetic
profile around the world[, J. Geophys. Res]{.underline}., 68, 3679-3692.

Cohen, Y, 1989, Traitements et interpretations de donnees spatiales in
geomagnetisme: etude des variations laterales d'aimantation de la
lithosphere terrestre, [Docteur es sciences physiques
thèse]{.underline}, Paris, 95 pp.

Fox Maule, C, Purucker, M., Olsen, N., and Mosegaard, K., 2005, Heat
flux anomalies in Antarctica revealed by satellite magnetic data,
[Science]{.underline}, 10.1126/science.1106888

Hahn, A., Ahrendt, H., Meyer, J., and Hufen, J.H., 1984, A model of
magnetic sources within the Earth's crust compatible with the field
measured by the satellite Magsat, [Geol. Jb]{.underline}., A75, 125-156.

Langel, R., 1987, The Main Geomagnetic Field, in Jacobs, J. (ed.),
[Geomagnetism.]{.underline} New York; Academic Press, pp. 249-512.

Langel, R.A., and Hinze, W.J., 1998, [The Magnetic Field of the Earth's
Lithosphere]{.underline}, Cambridge, Cambridge University Press.

Langel, R.A., and Estes, R.H., 1982, A geomagnetic field spectrum,
[Geophysical Research Letters]{.underline}, 9, 250-253, 1982.

Lowes, F.J., 1974, Spatial power spectrum of the main geomagnetic field,
and extrapolation to the core, Geophys. [Jour. R. Astr.
Soc]{.underline}., 36, 717-730.

Purucker, M., Langel, R., Rajaram, M., and Raymond, C., 1998, Global
magnetization models with a priori information, [Jour. Geophys.
Res]{.underline}., 103, 2563-2584.

Sabaka, T.J., Olsen, N, and Langel, R., 2002, A comprehensive model of
the quiet-time, near-Earth magnetic field: phase 3, [Geophys. J.
Int.,]{.underline} 151, 32-68.

Sabaka, T.J., Olsen, N., and Purucker, M., 2004, Extending Comprehensive
models of the Earth's magnetic field with Oersted and CHAMP data,
[Geophys. J. Int]{.underline}., 159, 521-547.

Taylor, P., and M. Purucker, 2000, Robert A. Langel III (1937-2000),
[EOS, Transactions of the American Geophysical Union]{.underline}, v.
81, 11 April 2000, p. 159.

Michael E. Purucker

# Cross References

Magsat, Spherical Harmonics, IAGA